What is Maximal Voluntary Ventilation. How is MVV measured. What factors affect MVV results. Why is MVV important in clinical settings. How does MVV relate to respiratory health. What are the limitations of MVV testing. How can MVV be used to assess exercise tolerance.

The Fundamentals of Maximal Voluntary Ventilation (MVV)

Maximal Voluntary Ventilation (MVV) is a crucial pulmonary function test that measures the maximum volume of air an individual can voluntarily move in and out of their lungs within one minute. This test provides valuable insights into respiratory muscle strength, endurance, and overall lung function.

To perform an MVV test, subjects are instructed to breathe as rapidly and deeply as possible for a duration of 15 to 30 seconds. The ventilatory volumes are recorded, and the maximum volume achieved over 15 consecutive seconds is then extrapolated to express the result in liters per minute.

Key Points of MVV Measurement

• Typically performed for 15-30 seconds
• Results expressed in liters per minute
• Reported at body temperature (37°C)
• Measured at standard pressure, fully saturated with water vapor (760 mm Hg)

How does respiratory frequency affect MVV results? While the respiratory frequency used during the test is noted and recorded as a subscript (e.g., MVV90 or MVV110), it’s important to understand that the choice of frequency does not significantly impact the test outcome. Maximal levels are usually achieved between 70 and 120 breaths per minute.

Factors Influencing MVV Performance

Several factors can influence an individual’s MVV performance, making it a complex yet informative test. Understanding these factors is crucial for accurate interpretation of results.

Physiological Factors

• Respiratory muscle coordination
• Chest wall musculoskeletal health
• Neurological conditions
• Overall physical conditioning
• Presence of ventilatory defects

How do these factors affect MVV results? Conditions such as loss of respiratory muscle coordination, musculoskeletal diseases of the chest wall, neurological disorders, and deconditioning from chronic illnesses can all lead to decreased MVV values. This multifactorial nature makes the test non-specific but valuable in assessing overall respiratory health and function.

Pathological Conditions

MVV is particularly sensitive to airway obstruction, showing significant decreases in patients with this condition. Interestingly, mild to moderate restrictive defects may have less impact on MVV results, as rapid, shallow breathing can effectively compensate for decreased lung volume.

Clinical Applications of MVV Testing

Despite its limitations, MVV testing has several important clinical applications that make it a valuable tool in respiratory medicine.

Exercise Tolerance Evaluation

How does MVV relate to exercise capacity? MVV correlates well with subjective dyspnea and proves useful in evaluating exercise tolerance. This relationship makes it an important parameter in cardiopulmonary exercise testing, providing crucial information for determining ventilatory reserve.

Preoperative Risk Assessment

Why is MVV valuable in preoperative evaluations? MVV appears to have prognostic value in preoperative assessments. This is likely because the extrapulmonary factors to which it is sensitive are also important for recovery from surgical procedures.

Respiratory Muscle Endurance Assessment

MVV provides a measure of respiratory muscle endurance, which is particularly important in evaluating respiratory muscle fatigue. This application extends to various conditions, including:

• Obstructive ventilatory defects
• Restrictive ventilatory defects
• Specific neuromuscular diseases

MVV in Neuromuscular Disorders: The Case of Myasthenia Gravis

Myasthenia gravis presents a unique challenge in MVV testing, highlighting both the test’s potential utility and its limitations in certain conditions.

How does MVV behave in myasthenia gravis patients? In this condition, patients can often produce maximal efforts for a short time, resulting in normal Forced Vital Capacity (FVC) and maximal inspiratory and expiratory pressures. However, they cannot sustain this effort, leading to decreased MVV or repeated FVC values, even within 12 to 15 seconds.

What precautions should be taken when performing MVV in myasthenia gravis patients? Due to the risk of rapid respiratory crisis and potential respiratory failure, some experts suggest that MVV should never be measured in myasthenia gravis patients, except under carefully controlled circumstances where it may be useful in evaluating treatment effectiveness.

Limitations and Considerations in MVV Testing

While MVV testing provides valuable insights, it’s crucial to understand its limitations for proper interpretation and application.

Subject Dependence

How does subject cooperation affect MVV results? MVV is heavily dependent on subject cooperation and effort. This reliance on patient participation can introduce variability in results and may limit its applicability in certain populations or clinical scenarios.

Non-Specificity

Why is MVV considered a non-specific test? The multitude of factors that can influence MVV results, including extrapulmonary conditions, makes it a non-specific test. This characteristic necessitates careful interpretation in conjunction with other clinical and diagnostic information.

MVV and Exercise Testing: Ventilatory Reserve Assessment

MVV plays a crucial role in cardiopulmonary exercise testing, particularly in the assessment of ventilatory reserve.

How is MVV used in exercise testing? MVV is used for the indirect calculation of ventilatory reserve through its relationship with minute volume during a maximum exercise test. This application provides valuable insights into an individual’s capacity to increase ventilation during physical exertion.

Importance in Cardiopulmonary Exercise Testing

• Helps determine ventilatory reserve
• Provides context for interpreting exercise limitations
• Aids in differentiating between cardiac and pulmonary exercise limitations

MVV in Respiratory Muscle Training

Beyond its diagnostic applications, MVV also finds use in therapeutic contexts, particularly in respiratory muscle training.

How is MVV utilized in respiratory muscle training? MVV is often used as a target for respiratory muscle training, especially in the normocapnic hyperpnea modality. This application helps in designing and monitoring the effectiveness of respiratory muscle strengthening programs.

Benefits of MVV-Guided Respiratory Training

• Provides a quantifiable target for improvement
• Allows for individualized training programs
• Helps track progress over time

What populations can benefit from MVV-guided respiratory training? This approach can be particularly beneficial for:
– Athletes looking to improve respiratory endurance
– Patients with chronic respiratory conditions
– Individuals recovering from respiratory muscle weakness

Estimating MVV: Challenges and Considerations

While direct measurement of MVV provides the most accurate results, there have been attempts to estimate MVV values using other pulmonary function parameters.

Can MVV be accurately estimated from other pulmonary function tests? Historically, several equations have been proposed to estimate MVV, with many based on the Forced Expiratory Volume in the first second (FEV1). However, recent research suggests that this approach may not be reliable for all populations.

Limitations of MVV Estimation

• May not account for individual variations in respiratory muscle strength and endurance
• Potentially inaccurate in patients with certain respiratory conditions
• Does not capture the dynamic nature of the MVV maneuver

Why is direct measurement of MVV preferred? Direct measurement of MVV, despite its challenges, provides a more accurate representation of an individual’s maximum voluntary ventilatory capacity. It captures the complex interplay of respiratory muscle strength, endurance, and coordination that estimates based on static measures like FEV1 may miss.

Future Directions in MVV Research and Application

As our understanding of respiratory physiology and the factors influencing MVV continues to evolve, several areas of research and potential applications are emerging.

Emerging Research Areas

• Development of more accurate estimation methods for MVV
• Investigation of MVV’s role in predicting outcomes in various respiratory conditions
• Exploration of MVV’s potential in personalized respiratory rehabilitation programs

How might technological advancements improve MVV testing? Future developments in respiratory function testing equipment may lead to more standardized and less effort-dependent methods of assessing maximum voluntary ventilation. This could potentially increase the test’s reliability and broaden its clinical applications.

Potential Clinical Applications

What new clinical applications might emerge for MVV testing? Some potential areas include:
– Enhanced preoperative risk stratification
– More precise tailoring of respiratory muscle training programs
– Improved assessment of respiratory function in neuromuscular disorders
– Better prediction of weaning outcomes in mechanically ventilated patients

As research in these areas progresses, the role of MVV in clinical practice may continue to evolve, potentially leading to more targeted and effective respiratory care strategies.

Conclusion: The Enduring Value of MVV in Respiratory Assessment

Maximal Voluntary Ventilation (MVV) remains a valuable tool in the arsenal of respiratory function tests, offering unique insights into an individual’s respiratory capacity and limitations. While it has its challenges and limitations, MVV provides information that complements other pulmonary function tests and contributes to a comprehensive understanding of respiratory health.

Key Takeaways

• MVV offers a dynamic assessment of respiratory function
• It provides valuable information for exercise testing and preoperative evaluation
• MVV results must be interpreted in the context of other clinical information
• Direct measurement is preferred over estimation for accuracy
• Future research may expand MVV’s clinical applications and improve testing methodologies

As we continue to refine our understanding of respiratory physiology and pathology, the role of MVV in clinical practice and research is likely to evolve. Its unique ability to assess the integrated function of the respiratory system ensures its continued relevance in pulmonary medicine and related fields.

Maximal Voluntary Ventilation – an overview

Maximal Voluntary Ventilation.

The maximal voluntary ventilation (MVV) measurement is defined as the maximal volume of air that can be moved by voluntary effort in 1 minute. Subjects are instructed to breathe rapidly and deeply for 15 to 30 seconds, ventilatory volumes are recorded, and the maximal volume achieved over 15 consecutive seconds is expressed in liters per minute. Lung volumes are reported at the largest size possible within the chest and at body temperature (37° C) and standard pressure fully saturated with water vapor (760 mm Hg).

The observer should demonstrate the test; then the subject should choose his or her own respiratory rate and perform several practice runs. The respiratory frequency used in the MVV should be noted and recorded as a subscript (e.g., MVV₉₀ or MVV₁₁₀). Maximal levels are usually achieved between 70 and 120 breaths/min, but the choice of frequency does not greatly affect the test. ²³

This test is heavily dependent on subject cooperation and effort. Loss of coordination of respiratory muscles, musculoskeletal disease of the chest wall, neurologic disease, and deconditioning from any chronic illness, as well as ventilatory defects, decrease MVV, so the test is nonspecific. The MVV is decreased in patients with airway obstruction, but less so with mild or moderate restrictive defects because rapid, shallow breathing can compensate effectively for the decreased lung volume.

Despite these caveats, MVV can be useful in special circumstances. It correlates well with subjective dyspnea and is useful in evaluating exercise tolerance. It appears to have prognostic value in preoperative evaluation, possibly because the extrapulmonary factors to which it is sensitive are also important for recovery from a surgical procedure.²⁴ It also provides a measure of respiratory muscle endurance that may be important in the evaluation of respiratory muscle fatigue, whether from obstructive or restrictive ventilatory defects or from specific neuromuscular diseases. ²⁵ In myasthenia gravis, for example, the patient can often produce maximal efforts for a short time, so that FVC and maximal inspiratory and expiratory pressures are normal. However, the effort cannot be sustained, so the MVV or repeated FVC values decrease, even within 12 to 15 seconds. The respiratory crisis of myasthenia gravis may happen rapidly and lead to respiratory failure. As a result, some investigators have suggested that MVV should never be measured in patients with myasthenia gravis, except under carefully controlled circumstances when it may be useful in evaluating treatment.⁶

Frontiers | Maximal Voluntary Ventilation Should Not Be Estimated From the Forced Expiratory Volume in the First Second in Healthy People and COPD Patients

Introduction

The maximal voluntary ventilation (MVV) is the largest amount of air that a person can inhale and then exhale during a 12- to 15-s interval with maximal voluntary effort (Neder et al., 1999). This maneuver was used to provide information about the functioning of the inspiratory pump and chest wall and is used to evaluate maximum ventilatory capacity (Colwell and Bhatia, 2017) and respiratory muscle endurance, but the last ERS statement on respiratory muscle tests does not recommend its use for these purposes because mechanical aspects of the chest wall and lung tissue can affect the MVV value (Laveneziana et al., 2019). It is used for indirect calculation of the ventilatory reserve through a relationship with minute volume during a maximum exercise test (ATS/ACCP, 2003). The performance of this test can be modified by factors such as strength and endurance of the respiratory muscles and/or airways as well as chest wall biomechanics (Barreiro and Perillo, 2004; Pellegrino et al., 2005; Suh and Lee, 2017). From a technical point of view, the mobilized volume is extrapolated to the volume of air that would be moved in 60 s in order to avoid prolonged hyperventilation (Neufeld et al. , 2018), and the result is expressed in liters/minute with an accuracy of ±10% (±15 L/min; ATS/ACCP, 2003).

Evaluation through this maneuver, together with other evaluations of lung function, was used for the follow-up of neuromuscular diseases (Rochester and Esau, 1994), and the prediction of the risk of postoperative complications (Bevacqua, 2015). Another important use is in cardiopulmonary exercise testing because it provides useful information for determining the ventilatory reserve (Ferrazza et al., 2009; Arena and Sietsema, 2011). The assessment of MVV is also used as a target for respiratory muscle training with normocapnic hyperpnea modality (Markov et al., 2001). In the past years, several equations have been described in the literature to estimate the MVV value, and the majority of these studies use the multiplication of the forced expiratory volume in the first second (FEV₁) values by a constant (Cara, 1953; Gandevia and Hugh-Jones, 1957; Miller et al., 1959; Simonsson, 1963; Campbell, 1982). These predictive equations were developed to avoid the use of expensive equipment and patients’ intense ventilatory effort (Carter et al., 1987; Stein et al., 2003). Recently, the new publication of the Statement on Respiratory Muscle Testing of the European Respiratory Society (ERS) recommends estimating the MVV value as the FEV₁ × 30 or 40 (Laveneziana et al., 2019). It is possible that these formulas were developed in a different historical context, where the availability of spirometry equipment that also evaluated MVV was scarce.

Additionally, the majority of the prediction formulas were developed by linear regression analysis and were validated based on good correlation values. However, the correlation coefficient is a measure of strength of the relationship between two variables and does not allow the evaluation of agreement nor accuracy between instruments (Carter et al., 1987). Thus, there is a lack of evidence based on concordance analysis between the values obtained from MVV and the estimated values obtained through the formulas.

In this context, the objective of this study was to evaluate the agreement between the direct MVV measure values and those obtained through equations based on FEV₁ values in healthy people and chronic obstructive pulmonary disease (COPD) patients. Given the complexity of the respiratory system and the various factors that interact in the MVV test, we hypothesized that both direct and estimated values did not have an acceptable agreement in healthy people and COPD patients.

Materials and Methods

A retrospective study was conducted with healthy subjects and patients with COPD. Data obtained from two previously conducted studies were analyzed (Araújo et al., 2012; Farias et al., 2014). These studies are approved by the Research Ethics Committee of Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN, Brazil, under protocols 260/08 and 449/2010 (Brazilian Clinical Trials Registry RBR-7bqxm2) and done according to the Declaration of Helsinki of 1975. The evaluations of the healthy population were carried out between April 2009 and March 2010. COPD patients were evaluated between May 2011 and April 2012. Self-reported healthy subjects recruited from the university community with ages between 20 and 80 years, non-athletes, and with no history of smoking or pulmonary or neurological diseases composed the healthy group. The healthy ones with spirometric values below predicted (<80% of forced vital capacity, FVC, and/or FEV₁, and below the lower limit of normality) were excluded. The patients with COPD were recruited in the respiratory outpatient clinic of the Onofre Lopes University Hospital (Natal, Brazil). Inclusion criteria were clinically stable patients, following the GOLD guidelines, with a post-bronchodilator spirometry value of FEV₁/FVC less than 70%, PaO₂ > 55 mmHg at rest with no recommendation for prescribing home oxygen therapy, and no other significant diseases that could prevent patient evaluation (Singh et al. , 2019). Those with psychiatric disturbances, heart disease, or neurological or neuromuscular diseases associated were excluded. All patients gave informed consent.

Measurements

Spirometry was used to perform the pulmonary function tests using a DATOSPIR-120 spirometer (SibelMed^®, Barcelona, Spain) according to the recommendations of the ATS/ERS guidelines (Miller et al., 2005). Three technically acceptable and reproducible forced expiratory curves were obtained for each participant. Variability between them was <5%, and only the curve with the best performance was considered for analysis. The predictive reference values for the Brazilian population were calculated according to de Castro Pereira et al. (2007), and the FVC, FEV₁, and FEV₁/FVC in their absolute and relative values were considered for analysis. For the MVV, the participants were instructed to maximize ventilation by inhaling and exhaling as quickly and deeply as possible for 15 s (Miller et al. , 2005), and values were expressed in liters per minute. The estimated MVV values based on the predictive formulas were determined by multiplying the FEV₁, acquired during spirometry, by a constant (Table 1; Cara, 1953; Gandevia and Hugh-Jones, 1957; Miller et al., 1959; Simonsson, 1963; Campbell, 1982). Five equations were included. Two of the five included equations (Equations 2 and 3) are theoretical mathematical models, clinically not tested.

Table 1. Prediction equations.

Statistical Analysis

Data were expressed as mean ± SD, otherwise stated. Estimated MVV values were compared with the direct measure of MVV using Student’s t test for paired samples with a significance level of p < 0.05. Pearson coefficients of correlation were also performed between direct and estimated MVV values. The following classification was used to interpret the values found: negligible correlation (r < 0.10), weak correlation (r ≥ 0. 1 to 0.39), moderate correlation (r ≥ 0.40 to 69), strong correlation (r ≥ 0.70 to 0.89), and very strong correlation (r = 0.90 to 1; Schober et al., 2018).

Agreements were evaluated using Bland–Altman plots (Bland and Altman, 1986), and the results were presented as bias (percentage of the difference between measured and estimated MVV values) and limits of agreement (± 1.96 SD). The 95% confidence intervals for both the bias and the limits of agreement were also added (Giavarina, 2015). Acceptable limits to the value of the equations would be accepted given a mean bias ≤5%, limits of agreement ≤10% (ATS/ACCP, 2003), and a 95% confidence interval of the mean bias within the line of equity of the Bland–Altman plot (i.e., 0% difference; Giavarina, 2015). Subgroup analysis was also conducted for healthy individuals (male and female) and for COPD patients (GOLD II, GOLD III, and GOLD IV).

Data were analyzed using GraphPad Prism 6 (GraphPad Software Inc., San Diego, CA, United States) software, and the level of significance was set at p < 0. 05 with a two-tailed approach.

Results

Healthy Subjects

Data on 207 healthy people (47 ± 17 years, 102 male, and 105 female) were included. Anthropometric characteristics, spirometry, and data from MVV are shown in Table 2. For Student’s t test, only Equation 4 showed no significant differences with the direct measured MVV value. Regarding subgroup analysis, measured MVV values were not statistically different from Equations 4 and 5 in males. All equations were statistically different in females (Table 3).

Table 2. Anthropometric and spirometric values of healthy and COPD subjects.

Table 3. Mean MVV values measured directly and predicted MVV values.

The results of all equations were significantly correlated with the measured MVV values (all rs = 0.86, ps < 0.0001). Similar results were also found for both male (r = 0.75, p < 0.0001) and female (r = 0. 82, p < 0.0001) subgroups. As shown in Table 4, the mean bias of all equations varied from –3.9% (Equation 5) to 27% (Equation 1), and only Equations 3–5 presented a mean bias ≤5%. For males, this variation was between –1.7% and 29.1% and, for females, between –6.2 and 24.7% (Figure 1).

Table 4. Bland–Altman analysis between measured MVV and prediction equations.

Figure 1. Bland–Altman analysis in Healthy group. Bland–Altman plots of those equations that presented a mean bias of ≤5% between MVV values measured directly and estimated for the healthy people. Bias is the average of the differences in percentage. Upper and lower limits of agreement are mean bias ±1.96 times its SD. The continuous lines represent the bias value, the dashed lines represent the limits of agreement, and the dotted lines represent the confidence intervals.

COPD Patients

Data of 83 COPD patients (65.5 ± 6.4 years, 29 GOLD II, 30 GOLD III, and 24 GOLD IV) were included. Equations 3–5 showed no significant differences from measured MVV values (Table 3). All equations were also significantly correlated with measured MVV values (all rs = 0.76, ps < 0.0001). When analyzing subgroups, significant correlations were found only for GOLD III (r = 0.38, p = 0.04), and GOLD IV (r = 0.49, p = 0.02).

Poor agreements were also found between measured MVV values and those predicted from equations. For all patients, the mean bias varied from –4.4% (Equation 5) to 26.3% (Equation 1; Table 4). Despite Equations 3–5 presenting a mean bias of ≤5%, the limits of agreement were always greater than 40% (Figure 2).

Figure 2. Bland–Altman analysis in COPD group. Bland–Altman plots of those equations that presented a mean bias of ≤5 between MVV values measured directly and estimated for the COPD patients. Bias is the average of the differences in percentage. Upper and lower limits of agreement are mean bias ±1. 96 times its SD. The continuous lines represent the bias value, the dashed lines represent the limits of agreement, and the dotted lines represent the confidence intervals.

Discussion

Several studies use the estimation of MVV value from a prediction equation with the FEV₁ value, usually multiplying the FEV₁ by 35 or 40 (Callens et al., 2009; Werkman et al., 2011; Stevens et al., 2013). The main finding of this study was that, apart from strong correlations, a poor concordance was observed between measured MVV values and those estimated from equations. Although most of the formulas have statistically significant correlations, it is not possible to establish that both evaluation methods are equivalent through these statistical tests. When analyzing Bland–Altman plots, a poor agreement was observed. In the case of healthy subjects, the mean bias of all equations varied from –3.9% (Equation 5) to 27% (Equation 1), and only Equations 3–5 presented a mean bias ≤5%. For males, this variation was between –1.7 and 29.1% and, for females, between –6.2 and 24.7%. Nevertheless, as observed in Figure 1, the prediction equations not only overestimated (Equation 3) or underestimated (Equations 4 and 5) the measured MVV values, but also the limits of agreement were greater than that 10% recommended by scientific societies (Miller et al., 2005). All the equations presented a poor agreement. The limit of agreement analysis revealed a wide variation among equations. Although mean differences (bias) of Equations 2 and 3 in healthy individuals may be within the limits of acceptability of the test, its limits of agreement present a large dispersion, which does not allow validating the estimated value of MVV as a real value. These equations are based on a linear mathematical model, but possibly, the behavior of the respiratory system does not respond to a linear model. Therefore, it is complex to predict real physiological values using prediction formulas based on linear mathematical models.

We have found a wide average discrepancy between methods. This important discrepancy between the real and the estimated value could generate an underestimation or overestimation when an assessment test or isocapnic training about a percentage of the MVV value is established. Also, some formulas have differences close to 30% compared to the real value, which could generate important errors in the clinical interpretation if we only estimate the MVV value. The limits of the agreement and the bias value are quite wide, so it is not possible to establish that both methods are equivalent. There is no clear trend regarding the behavior of differences with the different equations. The dispersion of the points was always greater than the acceptable validity limits for this test.

On the other hand, these equations include parameters as FEV₁ in healthy subjects, but the patients with chronic respiratory diseases may have abnormalities in the pulmonary function test that may change the accuracy of the measured MVV. Additionally, we analyze the equations in COPD patients to explore if the agreement presents the same behavior in both normal and pathological conditions.

The behavior was the same; poor agreements were also found between the measured MVV values and the ones predicted from equations. The mean bias varied from -4.4% (Equation 5) to 26.3% (Equation 1) with the greater variation observed in the GOLD III subgroup (from -2.9.0% with Equation 5 to 27.8% with Equation 1). Despite Equations 3–5 presenting a mean bias of ≤5%, the limits of agreement were always greater than 40%.

Maximal voluntary ventilation has poor specificity, is highly effort dependent, and can be uncomfortable for the patients. MVV depends on motivation and can be tiring for some patients (Laveneziana et al., 2019). It is reported that MVV depends on inspiratory and expiratory breathing effort in all type of subjects. The inspiratory airflow depends mainly on inspiratory muscle power in overcoming static elastic recoil of the respiratory system and resistive forces of the lung, and the expiratory airflow relies mainly on lung recoil (Lavietes et al. , 1979; Milic-Emili and Orzalesi, 1998). Respiratory work is affected by respiratory rate, presenting a decrease in tidal volume and breathing power as the respiratory rate increases, and expiratory muscles have less time to harness the potential chemical energy for their action. This could affect the validity of the MVV estimation by means of equations because the expiratory technique during spirometry differs greatly from how it is performed in the MVV (Milic-Emili and Orzalesi, 1998). In normal subjects, lung recoil is known to be the major determinant of expiratory airflow in MVV performance. The use of equations of prediction based on FEV₁ fails to take into account some physical characteristics that influence MVV (Neufeld et al., 2018), such as height, sex, and age. The literature has shown that individuals who smoke or are pregnant and people with cystic fibrosis had MVV values that deviate from sex, height, and age-matched controls (Stein et al., 2003; Hasan et al., 2013; Tell et al. , 2014; Neufeld et al., 2018). The MVV execution involves repeated, rapid, and maximum ventilation, generating an increase in inspiratory and expiratory volumes in comparison with the tidal volume. COPD patients frequently present a phenomenon of hyperinflation, which generates a progressive decrease in inspiratory capacity (Gagnon et al., 2014). MVV is an assessment test that could be affected by hyperinflation, and this is the principal reason why we argue that it’s impossible to estimate the MVV value through a single expiratory parameter as the FEV₁. This can be confirmed by the evidence of increases in the MVV value after lung volume reduction surgery in COPD patients (Benditt et al., 1997; Martinez et al., 1997).

Our results are in line with Nunes et al. (2016), who carried out a concordance study between the measured and estimated MVV value in 119 patients with pulmonary hypertension. The result showed that there was an overestimation of estimated values of lower measured MVV and underestimation at higher values. These findings confirm that it is not possible to predict the MVV value only through a multiple of the FEV₁ value. This study only analyzes healthy subjects and COPD patients, so it is relevant to evaluate the concordance of these formulas in pathologies that present a restrictive ventilatory alteration. Our results confirm that, in order to know the value of the MVV, it is necessary to evaluate it not using a formula with the FEV₁ value. The time when the spirometry teams did not evaluate the MVV is behind, and practically, most of the spirometry equipment allows this ventilatory test. The measurement of the MVV is considered an easily realizable test, and it is currently possible to perform it with most of the equipment available in the market, so it would not be advisable to replace its value by an estimate from the value of FEV₁.

The MVV assessment provided complementary information and has clinical implications not only in healthy subjects and obstructive patients, but also in patients with restrictive diseases, as in the case of neuromuscular disease, given that they also perform MVV in the midrange of vital capacity. In this sense, MVV reflects the efficiency of lung recoil. The breathing pattern has a wide range of irregularities during the entire breathing period, and the calculation can conduct a mistake (Suh et al., 2019).

On the other hand, there are assessments that use the MVV, for example, the analysis of cardiopulmonary exercise testing, a routine evaluation of physical capacity. This outcome is useful for measuring the ventilatory reserve in patients with respiratory and cardiovascular disease (Guazzi et al., 2017). Taking this into account, the healthcare professional can distinguish between a cardiovascular and respiratory profile in the case of exercise intolerance (Nathan et al., 2019). However, we need to know the ventilatory reserve for this analysis, and the calculation of MVV provides an error risk.

In spite of having good levels of correlation and that some do not present significant differences with the real value of the MVV, when evaluating the agreement of these values, it is shown that it is not possible to consider these MVV evaluation formulas as valid due to presenting limits of agreement with a substantial dispersion.

Our study has some limitations. The number of patients diagnosed with COPD classified by GOLD categories is small. This only allows a global analysis of COPD patients that does not consider the severity of the disease. On the other hand, we did not analyze the hyperinflation. This parameter provides essential information because the efficiency of the movement of the diaphragm muscle depends on its correct biomechanical position, and the hyperinflation can influence the measure of MVV.

Conclusion

In conclusion, MVV values estimated from equations are scattered and may underestimate or overestimate the real MVV value in healthy people and COPD patients. For this reason, a direct MVV measurement is suggested in this population instead of estimations through prediction equations. In consequence, we should not use the estimated results as a replacement for the real value of MVV.

Data Availability Statement

The datasets generated for this study are available on request to the corresponding author.

Ethics Statement

The studies involving human participants were reviewed and approved by Research Ethics Committee of Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN, Brazil, under protocol 260/08 and 449/2010. The patients/participants provided their written informed consent to participate in this study.

Author Contributions

GF, VR, CC, and AD contributed to design the study. PA, CC, and GF conducted assessments. MO-Y, AS, and GF analyzed, interpreted all experimental data, and were major contributors in writing the manuscript. All authors revised the manuscript.

Funding

GF received a grant from CNPq number 312876/2018-1, and VR received a grant from CNPq number 315580/2018-6. This study was financed in part by the Coordinação de Aperfeiçoamento de Pessoal de Nível Superior – Brazil (CAPES) – Finance Code 001.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

The researchers would like to thank the to all the people who voluntarily participated in this investigation.

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Pulmonary Function Tests | Asthma Doctors Triangle

Lung function tests (also called pulmonary function tests, or PFTs) check how well your lungs work. The tests determine how much air your lungs can hold, how quickly you can move air in and out of your lungs, and how well your lungs put oxygen into and remove carbon dioxide from your blood.

Spirometry is the first and most commonly performed lung function test. It measures how much and how quickly you can move air out of your lungs. For this test, you breathe into a mouthpiece attached to a recording device (spirometer). The information collected by the spirometer may be printed out on a chart called a spirogram.

Common lung function values measured with spirometry:

• Forced vital capacity (FVC). This measures the amount of air you can exhale with force after you inhale as deeply as possible.
• Forced expiratory volume (FEV). This measures the amount of air you can exhale with force in one breath. The amount of air you exhale may be measured at 1 second (FEV1), 2 seconds (FEV2), or 3 seconds (FEV3). FEV1 divided by FVC can also be determined.
• Forced expiratory flow 25% to 75%. This measures the air flow halfway through an exhale.
• Peak expiratory flow (PEF). This measures how much air you can exhale when you try your hardest. It is usually measured at the same time as your forced vital capacity (FVC).
• Maximum voluntary ventilation (MVV). This measures the greatest amount of air you can breathe in and out during 1 minute.
• Slow vital capacity (SVC). This measures the amount of air you can slowly exhale after you inhale as deeply as possible.
• Total lung capacity (TLC). This measures the amount of air in your lungs after you inhale as deeply as possible.
• Functional residual capacity (FRC). This measures the amount of air in your lungs at the end of a normal exhaled breath.
• Residual volume (RV). This measures the amount of air in your lungs after you have exhaled completely. It can be done by breathing in helium or nitrogen gas and seeing how much is exhaled.
• Expiratory reserve volume (ERV). This measures the difference between the amount of air in your lungs after a normal exhale (FRC) and the amount after you exhale with force (RV).

Pulmonary Function Testing – ppt video online download

Presentation on theme: “Pulmonary Function Testing”— Presentation transcript:

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1

Pulmonary Function Testing
Chapter 8

2

Pulmonary Function Testing
Which of the following is the true pulmonary function test? Spirometry Lung volumes Diffusion capacity ABG

3

Pulmonary Function Testing
Process of having the patient perform specific inspiratory and expiratory maneuvers Important to be familiar with these tests and values even if you do not work in a PFT lab Used for the following: Medical diagnosis Surgery related evaluation Disability evaluation Public Health/Research Studying the effects of exercise on the lungs

4

Contraindications Recent abdominal, thoracic, or eye surgery
Hemodynamic instability Symptoms of acute severe illness Chest pain, nausea, vomiting, high fever, dyspnea Recent hemoptysis Pneumothorax Recent history of abdominal, thoracic, or cerebral aneurysm

5

Normal Values Height Weight Age Gender Race Effort dependent

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Patient Instructions Prior to Testing
Should not drink alcohol for four hours prior to test Should not smoke at least one hour before test Do not eat a large meal two hours prior to test No vigorous exercise 30 minutes before test Do not wear tight form fitting clothes May need to remove loose dentures for test Should wait at least one month post MI, consider impact of problems that may affect results (chest/abdominal pain, oral or facial pain, stress incontinence, dementia, physical deformities or medical conditions) Bring a list of all medications – potentially withhold bronchodilators, corticosteroids

7

Equipment Spirometer Respirometer Pneumotachometer
Body Plethysmograph – body box Diffusion System Gas Analysis

8

ATPS vs BTPS Ambient Temperature and Pressure Saturated
Ambient temp is less than body temp Volume of air measured by spirometer is slightly less than the volume actually exhaled Measurements made by system must be converted Body Temperature and Pressure Saturated Requires knowing the ambient temperature, barometric pressure and humidity level ATPS is multiplied by the correction factor to obtain the higher BTPS values

9

Conversion from ATPS to BTPS conditions
Temp. ºC Corr.factor

10

Classification of Lung Defects
OBSTRUCTIVE RESTRICTIVE Expiratory flow is below normal Anatomic site can be identified Diseases: Cystic fibrosis Bronchitis Asthma Bronchiectasis Emphysema Lung volumes are reduced Diseases: Neuromuscular Cardiovascular Pulmonary Trauma/chest wall dysfunction Obesity

11

NORMAL SPIROGRAM

12

Spirogram Volumes Capacities Tidal Volume Minute Volume
Residual Volume Inspiratory Reserve Volume Expiratory Reserve Volume Vital Capacity Total Lung Capacity Function Residual Capacity Inspiratory Capacity

13

Vital Capacity Forced (FVC) Slow (SVC) Requires proper coaching
Three distinct phases Decreased in both obstructive and restrictive diseases Slow (SVC) Helps avoid air trapping

14

Slow Vital Capacity

15

Total Lung Capacity Increased with obstructive disease
Decreased with restrictive disorders Sum of the vital capacity and residual volume Obtain RV by: Body plethysmography Nitrogen washout Helium dilution

16

Body Plethysmography Uses the “body box” Boyles Law
Unknown lung gas vol = Gas pressure of the box Known box gas vol Gas pressure of the lungs

17

In body plethysmography, the patient sits inside an airtight box, inhales or exhales to a particular volume (usually FRC), and then a shutter drops across their breathing valve. The subject makes respiratory efforts against the closed shutter causing their chest volume to expand and decompressing the air in their lungs. The increase in their chest volume slightly reduces the box volume and thus increases the pressure in the box. This method of measuring FRC actually measures all the conducting pathways including abdominal gas; the actual measurement made is VTG (Volume of Thoracic gas).

18

Nitrogen Washout Open circuit method Patient breathes
100% oxygen while the nitrogen washed out of the lungs is measured Assumes 79% of lung volume is nitrogen Several “problems” with this test

19

Helium Dilution Closed system
Known volume and concentration of He added and it will be diluted in proportion to the size of the lung volume

20

Helium Dilution

21

Flow Measurements FEV1 FEV3 FEF FEF 25-75% PEFR

22

FEV1 Maximal volume exhaled during the first second of expiration
Best indicator of obstructive lung disease Flow characteristics of the larger airways Best expressed as a percentage of the FVC (FEV1/FVC) Should be able to exhale 70% of the vital capacity in the first second Decreased in obstructive disorders

23

FEV3 Evaluates flow 3 seconds into expiration
Indicates flow in the smaller airways

24

Forced Expiratory Flow
FEF 25-75% Examines the middle 50% of the exhaled curve Reflects degree of airway patency/condition of the medium to small airways Early indicator of obstructive dysfunction Normal value is 4-5 L/sec

25

Forced Expiratory Flow
FEF Average flow after the first 200ml is exhaled Good indicator of the integrity of large airway funtioning Decreased in obstructive disorders Normal value is 6-7L/se

26

Peak Expiratory Flow Rate
Maximum flow rate achieved during an FVC Used in asthmatics to identify the severity of airway obstruction and guide therapy Dependent on patient effort Normal value is 10L/sec (600L/min), decreases with age and obstruction

27

Maximum Voluntary Ventilation
MVV – patient breathes as fast and deep as possible for seconds Tests for overall lung function, ventilatory reserve capacity and air trapping Normal = 170L/min Decreased in obstructive disorders

28

Flow Volume Loops Identify inspiratory and expiratory components – opposite from ventilator waveforms! Reveals a pattern typical for certain diseases

29

Graphic Representation of Values

30

Flow Volume Loops Restrictive Obstructive

31

Figure 08-07. Flow volume loop
Figure    Flow volume loop. These flow volume loops are typical patterns seen with (A) normal, (B) restrictive lung diseases, (C) upper airway obstruction, and (D) severe chronic obstructive lung disease

32

33

Flow-volume loops of (a) fixed upper airway obstruction, (b) variable extrathoracic upper airway obstruction, and (c) variable intrathoracic upper airway obstruction.

34

35

Identify these loops!

36

37

Bronchodilators Test before and after to assess the degree of reversibility of the airway obstruction Medication is not standardized A positive response is demonstrated by: FVC increase >10% FEV1 increase of 200ml or 15% over baseline FEF25-75% 20%-30% increase Often given a trial even if no response is seen

38

Diffusion Capacity (DL)
Represents the gas exchange capabilities of the lungs Measures the ability of gas to diffuse across the alveolar-capillary membrane using carbon monoxide: DLCO

39

DLCO Diseases that reduce surface area – DL
emphysema Interstitial altering of the membrane integrity – DL Pulmonary fibrosis, Asbestosis, Sarcoidosis

40

Other Studies Airway Resistance Compliance Studies Nitrogen Washout
Quantifying allows understanding of the severity of the disease Measured using plethysomograph Compliance Studies Identifies the relative stiffness of the lung Esophageal balloon catheter Nitrogen Washout Determines if there is gross maldistribution of ventilation Closing Volume Used for diagnosis of small airway obstruction Respiratory Quotient Determines the amount of carbon dioxide produced and oxygen consumed

41

Exercise Testing 6 minute walk test Anaerobic threshold
Exercise challenge Ventilatory Capacity

42

Bronchoprovocation Testing
Used to diagnose “occult” asthma Challenge the patient with an inhaled bronchoconstrictor – Methacholine (also can use cold air or exercise) Object is to determine the minimum level that elicits a 20% decrease in FEV1 Requires bronchodilator ready for use as well as resuscitation equipment!

43

ATS Guidelines General Considerations for Lung Function Testing
Standardization of Spirometry Standardization of the Measurements of Lung Volumes Standardization of the single breath determination of carbon monoxide uptake in the lung Interpretive Strategies for Lung Function Tests Cardiopulmonary Exercise Testing Guidelines for the Six-minute Walk Test Guidelines for Methacholine and Exercise Challenge Testing

44

ATS (American Thoracic Society) STANDARDS
1. No coughing: especially during first second of FVC 2. Good start of test: <5% of FVC exhaled prior to a max expiratory effort. (<5% extrapolation) 3. No early termination of expiration: exhalation time of six seconds or a plateau of 2 seconds 4. No variable flows: flow rate should be consistent and as fast as possible throughout exhaled VC 5. Good reproducibility or consistency of efforts: 2 best FVC’s and 2 best FEV1’s should agree within 5% or 100 ml (whichever is greatest)

45

Evaluation/Interpretation of PFT’s
INTERPRETATION CRITERIA TEST NORMAL MILD MODERATE SEVERE FVC >80% 61-80% 50-60% <50% Restriction FEV1 >80% 61-80% 50-60% <50% Obstruction PEFR >80% 61-80% 50-60% <50% FEF25-75 >80% 61-80% 50-60% <50% Small Airway Disease FEV1/FVC 70-75% 60-69% 50-59% <50% Obstruction POSITIVE RESPONSE TO BRONCHODILATOR 1. FVC: increase greater than 10% 2. FEV1: increase of 200cc or 15% over baseline 3. FEF25-75: 20% increase 4. 2 out of 3 should improve to indicate a positive response

46

Evaluation of Results Evaluation of the Vital Capacity
can be reduced in obstructive and restrictive disease if VC is reduced, evaluate the TLC if the TLC is increased = obstruction if the TLC is decreased = restriction if VC is normal, evaluate the TLC if the FVC is greater than 90% of the SVC = normal if the FVC is less than 90% of the SVC = obstruction Evaluation of the FEV1/FVC if the FEV1/FVC is normal then the lungs are normal or restrictive if the FEV1/FVC is reduced = obstruction

47

Evaluation of Results Evaluation of the Total Lung Capacity: % pred.
increased =hyperinflation present evaluate the FEV1 Normal = normal lungs Decreased = obstruction Decreased Normal = restrictive Decreased = obstructive and restrictive Evaluation of FEF 25-75% if normal then normal lungs or possible restriction if reduced = peripheral obstruction

48

Evaluation of Results To differentiate between obstructive and restrictive diseases utilize the DLCO as well

49

50

Summary RESTRICTIVE PATTERN
1. Defined on the basis of a reduction in both the vital capacity and total lung capacity. 2. Residual volume and other volumes and capacities may be variably reduced. 3. Flow rates are normal unless restrictive process is severe. 4. FEV1 is reduced, but the FEV1/FVC will be normal. OBSTRUCTIVE PATTERN 1. Defined on the basis of a reduction in one or more pulmonary flow tests. 2. Vital capacity tends to decrease and the residual volume tends to rise with increasing severity of the disease process causing the obstructive pattern.

51

Critical Thinking FVC and FEV1 are reduced in both obstructive and restrictive disorders for different reasons. With restrictive disease, lung expansion is reduced and all lung volumes are smaller than normal. With obstructive disease there is airway obstruction which slows expiratory flow. FEV1 is reduced because of the increased airway resistance, which decreases expiratory flow rates. FVC is reduced because airway obstruction in the bronchioles causes air trapping in the lungs. To differentiate between obstructive and restrictive patterns, compare the FEV1 with the FVC using the FEV1/FVC ratio. Those with airway obstructions will exhale less than 70% of their FVC in the 1st second. Those with restrictive disease and/or healthy lungs will be able to exhale more than 70% of their FVC in one second. Both obstructive and restrictive diseases may exhibit decreased FVC and FEV1. How can the two kinds of patterns be differentiated?

52

Critical Thinking THE DLCO! Chronic bronchitis involves mostly airways and is characterized by chronic inflammation of the mucosa, excessive mucus, and bronchospasm; all of which narrow the airways. Pulmonary emphysema primarily involves alveolar structures and is characterized by destruction of alveolar architecture, elastic fibers, and the alveolar capillary membrane. Emphysema decreases gas exchange surface area. Chronic bronchitis does not involve alveoli and therefore does not change surface area for gas exchange. A decreased diffusion capacity is associated with emphysema A patient has spirometry and lung volumes typical of the obstructive pattern. The FEV1, FEV1/FVC and FEF’s are significantly reduced and the FRC and TLC are increased. Two common obstructive diseases are chronic bronchitis and pulmonary emphysema. How can pulmonary function data differentiate between these two diseases?

53

Critical Thinking Emphysema is characterized by a destruction of elastic tissue in the lung, which causes a lower lung recoil force. When lung recoil forces decrease, as in emphysema, chest wall expansion forces predominate, the chest wall expands outward pulling the lung with it. A new equilibrium occurs at increased lung volume so the FRC is increased. The RV is increased in emphysema because the VC is decreased because of small airway obstruction. When a person with emphysema tries to exhale completely, his or her bronchioles collapse, trapping air in the lungs. Increased FRC = hyperinflation; Increased RV = air trapping In the advanced stages of pulmonary emphysema, the FRC and the RV are increased; in addition the VC is often decreased. Why do these changes occur?

Spirometry – Spirometry – abcdef.wiki

Pulmonary function test

maneuver

TLC	Total lung capacity: lung volume at maximum inflation, sum of VC and RV.
TV	Tidal volume: The volume of air entering or from the lungs during quiet breathing (TV indicates a subdivision of the lung; when accurately measuring tidal volume, as in calculating gas exchange, the symbol TV or V is used T ).
RV	Residual Volume: The volume of air remaining in the lungs after maximum expiration.
ERV	Expiratory Reserve Volume: The maximum volume of air that can be exhaled from the end-expiratory position.
IRV	Inspiratory reserve volume: The maximum volume that can be inhaled from the end-inspiratory level.
IC	Inspiratory capacity: sum of IRV and TV.
IVC	Lung vital capacity: the maximum volume of air inhaled from the point of maximum expiration.
VK	Vital capacity: The volume of expired air after the deepest inhalation.
V T	Tidal volume: The volume of air entering or from the lungs during quiet breathing (VT indicates the division of the lung; when accurately measuring tidal volume, as in calculating gas exchange, the symbol TV or V is used T ).
FRC	Functional Residual Capacity: End-expiratory volume of the lungs.
RV / TLC%	Residual volume expressed as a percentage of TLC.
V A	Alveolar gas volume
V L	Actual volume of the lung, including the volume of the conducting airways.
FVC	Forced vital capacity of the lungs: Determination of the vital capacity of the lungs by the maximum forced expiration.
OFV t	Forced expiratory volume (time): General term for the volume of air exhaled under forced conditions during the first t seconds.
OFV 1	Expiratory volume at the end of the first second of forced expiration
FEF x	Forced expiration associated with some part of the FVC curve; modifiers refer to the amount of FVC already exhaled
FEF max.	Maximum instantaneous flow rate achieved during the FVC
FIF	Forced inspiratory flow: (A specific measurement of a forced expiratory curve is designated by a nomenclature similar to the nomenclature for a forced expiratory curve. For example, the maximum inspiratory flow is designated FIF max . Unless otherwise noted, volume qualifiers indicate the volume inhaled from the RV at the measuring point.)
PEF	Peak Expiratory Flow: Highest forced expiratory flow measured with a peak flow meter.
MVV	Maximum Random Ventilation: The volume of air exhaled over a specified period during repetitive maximum effort.

Spirometry (which means breath measurement ) is the most common of the lung function tests (PFT). It measures lung function, specifically the amount (volume) and / or speed (flow) of air that can be inhaled and exhaled. Spirometry is useful in assessing breathing patterns that determine conditions such as asthma, pulmonary fibrosis, cystic fibrosis, and COPD. It is also useful as part of a health surveillance system in which breathing patterns are measured over time.

In spirometry, pneumotachographs are created, which are charts showing the volume and flow of air entering and leaving the lungs during one inhalation and one exhalation.

Readings

Spirometry is indicated for the following reasons:

Contraindications.

Forced expiratory maneuvers can aggravate some diseases. Spirometry should not be performed if the patient:

• Hemoptysis of unknown origin
• Pneumothorax
• Unstable cardiovascular status (angina pectoris, recent myocardial infarction, etc.)D.)
• Aneurysms of the chest, abdomen or brain
• Cataract or recent eye surgery
• Recent thoracic or abdominal surgery
• Nausea, vomiting or acute illness
• Recent or current viral infection
• Undiagnosed hypertension

Spirometry testing

Modern USB-PC based spirometer.

Spirometry device. The patient presses his lips against the blue mouthpiece. The teeth pass between the projections and the shield, and the lips pass through the shield. The nose clip ensures that breathing only passes through the mouth.

Screen for spirometry readings on the right. The camera can also be used for body plethysmography.

Spirometer

A spirometry test is performed using a device called a spirometer, which comes in several different types. Most spirometers display the following graphs, called spirograms:

• time volume curve showing volume (l) along the y-axis and time (seconds) along the x-axis
• flow-volume loop , which graphically depicts the air flow rate on the Y-axis, and the total volume inspired or expired on the X-axis

Procedure

The Basic Forced Vital Capacity (FVC) test varies slightly depending on the equipment used, whether closed or open circuit, but should comply with the ATS / ERS spirometry standardization.

Typically, the patient is asked to inhale as deeply as possible and then exhale as hard as possible through the transducer for as long as possible, preferably at least 6 seconds. Sometimes a rapid inhalation (inhalation) follows immediately, especially when assessing possible obstruction of the upper airways. Sometimes the test is preceded by a period of quiet inhalation and exhalation through the transducer (tidal volume), or a rapid inhalation (part of the forced inhalation) will precede the forced exhalation.

Soft nose clips can be used during the test to prevent air from escaping through the nose.Filter mouthpieces can be used to prevent the spread of microorganisms.

Test Limitations

The maneuver is highly dependent on the cooperation and effort of the patient and is usually repeated at least three times to ensure reproducibility. Because results depend on collaboration with patients, FVC can only be underestimated but never overestimated.

Due to the need to cooperate with the patient, spirometry can only be used on children who are old enough to understand and follow these instructions (6 years of age or older), and only on patients who are able to understand and follow the instructions – thus, this test is not is suitable. suitable for patients who are unconscious, under strong sedation or with limitations that may interfere with intense breathing efforts. Other types of lung function tests are available for infants and unconscious individuals.

Another major limitation is the fact that in many patients with intermittent or mild asthma between exacerbations, spirometry is normal, which limits the usefulness of spirometry as a diagnosis. It is more useful as a monitoring tool: a sudden drop in FEV1 or other spirometric value in the same patient can signal poor control, even if the baseline value is still normal.Patients are encouraged to record their personal best scores.

An example of a printout of a modern PC-based spirometer.

Related tests

Spirometry can also be part of a bronchial challenge test used to measure bronchial hypersensitivity to strenuous exercise, inhalation of cold / dry air, or to pharmaceuticals such as methacholine or histamine.

Sometimes a bronchodilator is given before another round of comparison tests is given to assess the reversibility of a condition. This is commonly referred to as the test for the reversibility of the or post-bronchodilator test (Post BD) and is an important part of the diagnosis of asthma versus COPD.

Other additional lung function tests include plethysmography and nitrogen washout.

Parameters

The most common parameters measured by spirometry are vital lung capacity (VC), forced vital capacity (FVC), forced expiratory volume (FEV) at set intervals of 0.5, 1.0 (FEV1), 2.0 and 3, 0 seconds, forced expiratory flow 25–75% (FEF 25–75) and maximum voluntary ventilation (MVV), also known as maximum respiratory capacity.In certain situations, other tests may be performed.

Results are usually presented as raw data (liters, liters per second) and as predicted percentages – the test result as a percentage of “predicted values” for patients with similar characteristics (height, age, gender, and sometimes race and weight). … Interpretation of results may vary depending on the clinician and the source of the predicted values. Generally speaking, results close to 100% predicted are the most normal, and results over 80% are often considered normal.Several publications have published predictive values ​​that can be calculated based on age, gender, weight, and ethnicity. However, a doctor’s examination is necessary to accurately diagnose any individual situation.

Under certain circumstances, a bronchodilator is also prescribed and a comparison of the pre- and post-treatment schedule is made to assess the effectiveness of the bronchodilator. See Sample Printout.

Functional Residual Capacity (FRC) cannot be measured with spirometry, but can be measured with plethysmograph or dilution tests (eg helium dilution test).

The mean values ​​of forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and forced expiratory flow 25–75% (FEF25–75%), according to a 2007 US study of 3600 subjects aged from 4 to 80 years old. years. The Y-axis is expressed in liters for FVC and FEV1 and in liters / second for FEF25–75%.

Forced vital capacity (FVC)

Forced vital capacity (FVC) is the volume of air that can be forcibly released after a full inhalation, measured in liters.FVC is the simplest method for spirometry tests.

Forced expiratory volume in 1 second (FEV1)

FEV1 is the volume of air that can be forcibly released in the first 1 second after a full inspiration. According to the diagram, the average FEV1 values ​​in healthy people depend mainly on gender and age. Values ​​between 80% and 120% of the average are considered normal. Predicted normal FEV1 values ​​can be calculated and depend on age, gender, height, weight and ethnicity, and the study on which they are based.

FEV1 / FVC ratio

FEV1 / FVC is the ratio of FEV1 to FVC. In healthy adults, this figure should be approximately 70-80% (decreases with age). In obstructive diseases (asthma, COPD, chronic bronchitis, emphysema) FEV1 decreases due to the increased resistance of the airways to the expiratory flow; FVC can also decrease due to premature expiratory closure of the airway, but not in the same proportion as FEV1 (for example, both FEV1 and FVC decrease, but the former suffers more due to increased airway resistance). This leads to a decrease in the value (<70%, often ~ 45%). In restrictive diseases (eg, pulmonary fibrosis) FEV1 and FVC are proportionally reduced, and the value may be normal or even increase as a result of decreased lung elasticity.

The derived FEV1 value is the predicted FEV1% (FEV1%), which is defined as the patient’s FEV1 divided by the mean population FEV1 for any person of the same age, height, sex, and race.

Forced expiration (FEF)

Forced expiration (FEF) is the flow (or velocity) of air exiting the lungs during the middle of a forced expiration.It can be administered at discrete times, usually determined by how much of the forced vital capacity (FVC) is exhaled. Typical discrete intervals are 25%, 50% and 75% (FEF25, FEF50, and FEF75) or 25% and 50% of the exhaled FVC. It can also be expressed as the mean of the flow over an interval, also usually limited to when certain FVC fractions remain, usually 25–75% (FEF25–75%). The average ranges in the healthy population depend mainly on gender and age, with an FEF of 25–75% shown in the diagram on the left. Values ​​from 50-60% to 130% of the average are considered normal. Predicted normal values ​​for FEF can be calculated and depend on age, gender, height, weight and ethnicity, as well as the study on which they are based.

MMEF or MEF stands for maximum (average) expiratory flow and is the peak expiratory flow taken from the flow-volume curve and measured in liters per second. In theory, it should be identical to the Peak Expiratory Flow (PEF), which, however, is usually measured by a peak flow meter and is expressed in liters per minute.

Recent studies indicate that FEF25-75% or FEF25-50% may be more sensitive than FEV1 in detecting obstructive small airway disease. However, in the absence of concomitant changes in standard markers, discrepancies in mean expiratory flow may not be specific enough to be useful, and current practice guidelines recommend continuing to use FEV1, VC, and FEV1 / VC as indicators of obstructive disease….

Less commonly, forced expiration can be performed at intervals determined by the remaining total lung capacity. In such cases, it is usually referred to as, for example, FEF70% TLC, FEF60% TLC, and FEF50% TLC.

Forced inspiratory flow 25–75% or 25–50%

Forced inspiratory flow 25–75% or 25–50% (FIF 25–75% or 25–50%) is the same as FEF 25–75% or 25–50%, except that the measurement is taken during inspiration.

Peak expiratory flow (PEF)

Normal peak expiratory flow (PEF) values ​​shown on the EU scale.

Peak expiratory flow (PEF) is the maximum flow (or velocity) achieved during the maximum forced expiration initiated with a full inspiration, measured in liters per minute or liters per second.

Tidal volume (TV)

Tidal volume is the amount of air normally inhaled or exhaled at rest.

Total lung capacity (TLC)

Total lung capacity (TLC) is the maximum volume of air present in the lungs.

Dissipation ability (DLCO)

Diffusion capacity (or DLCO) is the absorption of carbon monoxide in one breath over a standard time (usually 10 seconds). During the test, a person inhales a test gas mixture of less than one percent of normal air containing an inert tracer gas and CO. Since hemoglobin has a greater affinity for CO than for oxygen, the breath holding time can be as little as 10 seconds, which is enough time for this CO transfer.Since the inhaled amount of CO is known, the exhaled CO is subtracted to determine the amount carried during the breath hold. Tracer gas is analyzed simultaneously with CO to determine the distribution of the test gas mixture. This test detects diffuse abnormalities, such as pulmonary fibrosis. This should be corrected for anemia (low hemoglobin concentration decreases DLCO) and pulmonary hemorrhage (excess red blood cells in the interstitium or alveoli can absorb CO and artificially increase DLCO capacity).Atmospheric pressure and / or altitude will also affect the measured DLCO, so a correction factor is needed to correct the standard pressure.

Maximum random ventilation (MVV)

Maximum Random Ventilation (MVV) is a measure of the maximum amount of air that can be inhaled and exhaled in one minute. For patient convenience, this is done over a 15-second period of time, after which it is extrapolated to a value within one minute, expressed in liters / min.Average values ​​for men and women are 140-180 and 80-120 liters per minute, respectively.

Static lung compliance (C

_st )

When assessing static lung compliance, volume measurements with a spirometer should be supplemented with pressure transducers in order to simultaneously measure transpulmonary pressure. When plotting the relationship between changes in volume and changes in transpulmonary pressure, C _st represents the slope of the curve for any given volume, or, mathematically, ΔV / ΔP.Static lung compliance is perhaps the most sensitive parameter for detecting abnormal lung mechanics. It is considered normal if it is between 60% and 140% of the population average for any person of similar age, sex, and body composition.

In ventilated patients with acute respiratory failure, “static compliance of the entire respiratory system is usually achieved by dividing the tidal volume by the difference between the plateau pressure measured at the airway opening (PaO) during occlusion at the end of surgery. inhalation and positive end-expiratory pressure (PEEP) set by the ventilator. ”

Others

Forced Expiration Time (FET)
Forced Expiration Time (FET) measures the expiration time in seconds.

Slow vital capacity (SVC)
Slow vital capacity (SVC) is the maximum volume of air that can be exhaled slowly after a slow maximal inhalation.

Maximum pressure (P _max and P _i )

P _max is the asymptotically maximum pressure that can be generated by the respiratory muscles at any lung volume, and P _i is the maximum inspiratory pressure that can be created at certain lung volumes. For this measurement, additional pressure sensors are required. It is considered normal if it is between 60% and 140% of the population average for any person of similar age, sex, and body composition. The derived parameter is retraction ratio (CR), which is equal to P _max / TLC.

Average transit time (MTT)
Average transit time is the area under the flow-volume curve divided by the forced vital capacity.

Maximum Inspiratory Pressure (MIP)
MIP, also known as Negative Inspiratory Force (NIF) , is the maximum pressure that can be generated against a blocked airway, starting at functional residual capacity (FRC). It is a marker of respiratory muscle function and strength. Water pressure in centimeters (cmh3O) is measured with a pressure gauge. Maximum inspiratory pressure is an important and non-invasive indicator of diaphragm strength and an independent tool for the diagnosis of many diseases.Typical maximum inspiratory pressure in adult males can be estimated from the equation, M _IP = 142 – (1. 03 x century) CMH ₂ O, where age is in years.

Technologies used in spirometers

• Volumetric spirometer
• Spirometer for flow measurement
  • Pneumatic flush
  • Lilly (screen) pneumotach
  • Turbine / stator rotor (commonly incorrectly referred to as a turbine. Actually, a rotating blade that spins due to the airflow generated by an object.Blade revolutions are counted as they interrupt the light beam)
  • Pitot tube
  • Hot-wire anemometer
  • ultrasound

See also

Recommendations

Further reading

• Miller M.R., Krapo R., Hankinson J., Brusasco V., Burgos F., Kasaburi R., Coates A., Enright P., Van der Greenten S.P., Gustafsson P., Jensen R. , Johnson, DC, McIntyre N., McKay R., Navahas D., Pedersen O. Pellegrino R, Viegi G, Wanger J (July 2005). “General guidelines for testing lung function.” European Respiratory Journal . 26 (1): 153-161. DOI: 10.1183 / 0

  36.05.00034505. PMID 15994402. S2CID 5626417.

External Links

Spirography and spirometry: interpretation, preparation, results, norm

Methods for the study of respiration spirometry and spirography

The main methods for studying external respiration in humans include:

1.Spirometry is a method for determining the vital capacity of the lungs (VC) and its constituent air volumes.

2. Spirography is a method of graphic registration of indicators of the function of the external link of the respiratory system.

3. Pneumotachometry – a method of measuring the maximum speed of inspiration and expiration during forced breathing.

4. Pneumography – a method of registering respiratory movements of the chest.

5. Peak fluorometry is a simple way of self-assessment and constant monitoring of bronchial patency.The device – peak flow meter allows you to measure the volume of passing air during exhalation per unit of time (peak expiratory flow rate).

6. Functional tests (Stange and Genche).

1. Spirometry

The functional state of the lungs depends on age, gender, physical development and a number of other factors. The most common characteristic of the lung condition is the measurement of lung volumes, which indicate the development of the respiratory organs and functional reserves of the respiratory system.

The volume of inhaled and exhaled air can be measured with a spirometer. The most common water spirometer. A dry air spirometer is also used.

Spirometry is the most important way to assess the function of external respiration.

This method is used to determine the vital capacity of the lungs, lung volumes, as well as the volumetric air flow rate. During spirometry, the person breathes in and out with maximum force.

The most important data is provided by the analysis of expiratory maneuver – exhalation.Pulmonary volumes and capacities are called static (basic) respiratory rates. There are 4 primary lung volumes and 4 containers.

○ The vital capacity of the lungs (VC) is the maximum amount of air that can be exhaled after the maximum inhalation.

Spirometry

In the study, the actual VC is determined, which is compared with the proper VC (VC). In an adult, the JEL is 3-5 liters of average height. In men, its value is about 15% higher than in women.Schoolchildren aged 11-12 have a JEL of about 2 liters; children under 4 years old – 1 liter; newborns – 150 ml. VC = TO + ROVD + ROVD. JEL can be calculated using the formula: JEL (L) = 2.5 × Height (m).

○ Tidal volume (TO), or depth of breathing, is the volume of air inhaled and exhaled at rest.

In adults, DO = 400-500 ml, in children 11-12 years old – about 200 ml, in newborns – 20-30 ml.

○ Expiratory reserve volume (Routine) – the maximum volume that can be exhaled with effort after a calm exhalation.Rovyd = 800-1500 ml.

○ Inspiratory reserve volume (RVD) – the maximum volume of air that can be additionally inhaled after a quiet inhalation.

The inspiratory reserve volume can be determined in two ways: calculated or measured with a spirometer. To calculate, it is necessary to subtract the sum of the tidal and reserve expiratory volumes from the VC value. To determine the reserve inspiratory volume using a spirometer, it is necessary to draw in the spirometer from 4 to 6 liters of air and, after a calm breath from the atmosphere, take the maximum breath from the spirometer.The difference between the initial air volume in the spirometer and the volume remaining in the spirometer after a deep breath corresponds to the inspiratory reserve volume.

ROVD = 1500-2000 ml.

○ Residual volume (RO ) – the volume of air remaining in the lungs even after maximum exhalation. Measured by indirect methods only. The principle of one of them is that a foreign gas such as helium is injected into the lungs (dilution method) and the volume of the lungs is calculated from the change in its concentration.The residual volume is 25-30% of the VC value.

Accept RO = 500-1000 ml.

○ Total lung capacity (TLC) – the amount of air in the lungs after maximum inspiration. OEL = ZEL + OO. OEL = 4500-7000 ml.

○ Functional residual lung capacity (FOC) – the amount of air remaining in the lungs after a calm exhalation. FOEL = ROVD.

○ Inspiratory capacity (EVC) – the maximum volume of air that can be inhaled after a calm exhalation. UVD = DO + ROVD.

In addition to static indicators characterizing the degree of physical development of the respiratory apparatus, there are additional – dynamic indicators , which provide information on the efficiency of lung ventilation and the functional state of the respiratory tract.

○ Forced vital capacity (FVC) – the amount of air that can be exhaled during forced exhalation after maximum inhalation.

Normally, the difference between VC and FVC is 100-300 ml.An increase in this difference to 1500 ml or more indicates resistance to air flow due to narrowing of the lumen of small bronchi. FVC = 3000-7000 ml.

○ Anatomical dead space (DMP) – the volume in which gas exchange does not occur (nasopharynx, trachea, large bronchi) – cannot be directly determined.

DMP = 150 ml.

○ Respiratory rate (RR) – the number of breaths per minute. BH = 16-18 d.ts./min.

○ Respiratory minute volume (MRV) – the amount of air ventilated in the lungs in 1 minute.MOD = DO + BH. MOD = 8-12 liters.

○ Alveolar ventilation (AV) – the volume of exhaled air entering the alveoli.

AB = 66 – 80% of the MOD. AB = 0.8 l / min.

○ Breathing reserve (RB) – an indicator characterizing the possibility of increasing ventilation.

Normally, the RD is 85% of the maximum ventilation (MVV). MVL = 70-100 l / min.

2. Spirography

Spirography is a method of graphic registration of tidal volumes, which can be used to determine all of the above parameters of pulmonary ventilation.

Currently, electronic devices and computer programs are used that allow graphically recording and processing volumes, flows and rates of respiratory maneuvers in a variety of modes.

3. Functional tests

The time during which a person can hold their breath, overcoming the desire to breathe, individually.

It depends on the excitability of the central nervous system, the state of the external respiration apparatus, the cardiovascular system and the blood system.The duration of an arbitrary maximum breath holding is used as a functional test that characterizes several body systems. As you know, the main stimulant of respiration is carbon dioxide. In healthy people, the time of maximum breath holding after a deep (but not maximum) inhalation ( Shtange test ) is 40-60 seconds, after a calm exhalation ( Genche test ) it is less than 30-40 seconds.

These indicators change with forced breathing.

Research: Spirography and Spirometry

This information cannot be used for self-medication! Consultation with a specialist is imperative!

What is spirometry?

Spirometry is a research method that allows you to assess the function of external respiration and includes the measurement of volumetric and velocity parameters. With the help of spirometry, the following indicators are usually measured: respiratory rate, tidal volume, vital capacity of the lungs, forced expiratory volume, and so on.

The term “spirography” refers to the graphical recording of measurements.

How is spirometry performed?

Spirometry is now usually performed with a computer spirometer, which converts the sensor readings into digital format and automatically performs all the necessary calculations.

The subject’s nose is clamped with a special clamp. He has to breathe exclusively through his mouth through a special nozzle-mouthpiece.

Begin the procedure by measuring the breathing characteristics at rest.Next, breathing is studied with forced expiration. The patient then breathes very quickly and deeply to examine the highest possible ventilation.

Often, at the end of the study, functional tests are performed, for example, a test with drugs that dilate the bronchi.

In 3-5 minutes after their application, a second study is carried out. If the indicators of external respiration improve or recover completely, they speak of reversible bronchospasm.

Another functional test is called provocative.The patient is inhaled with histamine, which can lead to bronchospasm and thereby confirm or deny the diagnosis of bronchial asthma.

Where is spirometry done?

This examination can be done on an outpatient basis.

Spirometry is performed by a nurse or functional diagnostics doctor in a polyclinic, diagnostic center or in any other medical facility that has a spirograph.

What diseases does spirometry detect?

Spirometry detects diseases that are accompanied by bronchial obstruction (violation of the patency of the bronchial tree), namely: bronchial asthma, chronic obstructive pulmonary disease, bronchiectasis.

Deviations from the norm of the indicators obtained as a result of the examination make it possible to judge the absence or presence of a disease of the respiratory system in a person, the degree of its severity and the reversibility of the condition.

Who needs spirometry?

Spirometry is necessary for patients with bronchial asthma, obstructive bronchitis, bronchiectasis, and long-term smokers. The study is recommended not only for detecting these diseases, but also for evaluating the effectiveness of treatment.

Preparation for examination

The study should be carried out strictly on an empty stomach, it is advisable not to consume a lot of fluids.

It is worth refraining from smoking. If the patient uses inhalers, he must inform the doctor about it. The method is absolutely painless and does not cause any discomfort.

Contraindications to the procedure

There are no absolute contraindications to spirometry.

What is spirography and how is it done

To one degree or another, the following conditions may interfere with the study: a serious condition of the patient (hypertensive crisis, myocardial infarction, etc.)etc. ), the second half of pregnancy in women (the high position of the diaphragm interferes with deep breathing).

Interpretation of results

Normal values ​​of indicators are individual. Analyzing the results obtained, the doctor draws conclusions taking into account the gender, age, height and weight of the patient.

Most of the results are given by the spirograph, the rest is calculated manually by the specialist, which usually takes no more than an hour. With the conclusion received, the patient needs to contact the doctor who sent him for spirometry.

Interpretation of normal values ​​

Tidal volume (TO) – the volume of air that enters the lungs in one breath with calm breathing (the norm is 500-800 ml).

VC – vital capacity of the lungs (the norm is more than 90%). FVC is the difference between the volume of air in the lungs at the beginning and at the end of expiration, calculated during forced expiration. FEV1 – forced expiratory volume in 1 second (norm – 75%). Tiffeneau’s index – the ratio of FEV1 to FVC as a percentage (the norm is more than 75%).

To study external respiration (ventilation of the lungs), gas exchange in the lungs and tissues, as well as the transport of gases by blood, various methods are used to assess the respiratory function at rest, during physical exertion and various effects on the body.

Pneumography

Pneumography is a registration of respiratory movements. It allows you to determine the frequency and depth of breathing, as well as the ratio of the duration of inhalation and exhalation.

Pneumography is widely used in experimental and clinical and physiological studies to obtain information about the nature of respiratory movements, regulation of external respiration and its disorders in various diseases and pathological conditions.

The equipment used has 3 main elements: a sensor that directly senses respiratory movements; a device that amplifies and transmits sensor readings to a recording apparatus; registration system.

Record respiratory movements at rest, while inhalation is usually somewhat shorter than exhalation, their ratio is approximately 1: 1.3 (Fig.

25a). Then, a change in the nature of breathing during physical activity is recorded (increased frequency and depth of breathing) (Fig. 25b). After an arbitrary holding of breath, breathing is observed to increase (Fig. 25b).

(a) state of rest

(b) during physical activity

(c) after voluntary breath holding

Pneumography does not quantify ventilation of the lungs, therefore it is usually supplemented with spirometry or
spirography , which provides registration of the main lung volumes.

Spirometry allows you to assess the state of external respiration by measuring lung volumes using a spirometer.

Since the functional state of the lungs depends on age, sex, height and other factors, the values ​​obtained must be compared with the proper values ​​for this category of the population. The spirometer can be dry or water. After the maximum inspiration, the subject makes the maximum exhalation into the spirometer, while the VC is fixed. To determine the tidal volume, the subject makes several calm exhalations into the spirometer, then the spirometer reading is divided by the number of exhalations.To determine ROS, the subject after the next calm exhalation makes the maximum exhalation into the spirometer.

Inspiratory reserve volume is calculated by the formula: RVD = VC – (TO + ROVD).

Oxyhemometry and oxygenhemography allow you to determine the content of oxyhemoglobin in the blood at a given time.

The work of an oximeter and an oximeter is based on the photoelectric principle of action. The intensity of the light flux incident on the photocell of the sensor depends on the degree of saturation of hemoglobin with oxygen.

Spirography is a method of graphical registration of changes in lung volumes during natural respiratory movements and volitional forced respiratory maneuvers. Spirography allows you to obtain a number of indicators that describe the ventilation of the lungs.

First of all, these are static volumes and capacities, which characterize the elastic properties of the lungs and chest wall, as well as dynamic indicators that determine the amount of air ventilated through the respiratory tract during inhalation and exhalation per unit of time.

Spirographs are divided into open and closed devices.

In open-type devices, the examinee inhales atmospheric air through the valve box, and the exhaled air enters the Douglas bag or the Tiso spirometer (with a capacity of 100-200 liters), sometimes to the gas meter, which continuously determines its volume. In the collected air, the values ​​of oxygen absorption and carbon dioxide emission are determined per unit time. Closed-type apparatus uses the apparatus bell air circulating in a closed circuit without communication with the atmosphere.

The exhaled carbon dioxide is absorbed by a special absorber (fig. ).

Fig. Schematic of a closed-type spirograph

DIGESTION

For the normal functioning of the human body, a constant supply of food is necessary – proteins, fats, carbohydrates, mineral salts, vitamins, water.

Nutrients (proteins, fats, carbohydrates) are building materials and a source of energy in the body.

Food in the form in which it enters the body cannot be absorbed into the blood and lymph and be used for various functions.Only water, mineral salts, vitamins are assimilated in their natural form. All other food components in the organs of the digestive system undergo mechanical and chemical processing.

Mechanical and chemical processing of food, its transformation into substances assimilated by the body is called digestion . The basis of chemical processing of food is formed by the reactions of hydrolytic cleavage of proteins, fats, carbohydrates under the action of enzymes with the formation of amino acids, fatty acids, glycerol, monosaccharides (mainly glucose), respectively.

Hydrolysis proceeds stepwise depending on the conditions in a particular part of the gastrointestinal tract.

Ventilation in educational institutions: a design feature

Usually, inside schools, colleges, vocational schools, boarding schools, kindergartens, there are many rooms for completely different purposes. Therefore, ventilation in educational institutions requires special design. Air conditioning of laboratories, gyms, swimming pools, kitchens, bathrooms, classrooms and rooms should be done according to completely different criteria.

How air conditioning works in different rooms

Nowadays, it is quite rare to see the construction of a new school or other educational institution. Most often, already existing buildings are allocated for them, subjecting them, if not major, then at least cosmetic repairs.

Although there are several types of premises in the presence of this kind of buildings, in spite of everything, they are obliged to provide students and teachers with a sufficiently clean environment, with all the necessary parameters of temperature and humidity.

When installing ventilation in educational institutions, specialists are required to comply with all SNiP and GOST standards. For example, in a school, in accordance with all the rules and regulations, the following indicators should be:

Study room

• Air inflow – 2.5 m3 per hour;
• Air exhaust – 1.5 m3 per hour;
• Air temperature: minimum – 21 degrees, maximum – 23 degrees;
• The noise tolerance is 110 acoustic decibels.

Also, in establishments of this type, ventilation for fire-prevention purposes must be available (in case of an accident).It is usually equipped with an anti-smoke protection device and a smoke extraction system.

Air conditioning in rooms such as the food block and the gym requires special solutions. Since these rooms are most problematic, they have elevated temperatures and humidity indicators, it is recommended to install industrial ventilation in them. In parallel with them, supply and exhaust installations are installed. It is best to install a central air exchange system in an assembly hall or a dining room in which various kinds of events are held.

Corridor spaces and classrooms usually have vents, so ventilation occurs by self-circulation.

Basic criteria for good ventilation

If there is good ventilation and a well-installed ventilation system, any educational institution will have the following indicators:

1. Air quality. If the air is clean, then it will be much easier to concentrate in it, and this is very important in the conditions of the educational process;

   Auditorium at the university

2. Comfortable conditions.Since almost the entire audience is in a state of inactivity for a long time, they should be comfortable and not stuffy;
3. Silence. All ventilation systems must provide not only clean air, but also the conditions in which you can work.

In administrative premises, such as the teacher’s room, people appear periodically. That is why systems with the effect of responding to different situations must be present here.

A filtration system is used to clean the supply air.In winter, this air requires warming up to an acceptable temperature.

Why ventilation and ventilation is needed

Even people who have special knowledge in the field of air conditioning do not doubt the need to ventilate classrooms, rooms, playrooms and bedrooms. Now there are more cases of replacing old wooden windows with plastic ones, which are more airtight. Sometimes, for greater savings, double-glazed windows are installed without a window. It is strictly forbidden to do this, since children can faint from stuffiness.

Ventilation system device

If the vent is still present, then it is unlikely to be enough for such a large room and carbon dioxide harmful to the body will still remain. Therefore, it is imperative to create air exchange using ventilation for this.

When building a new school or other institution at the design stage, you can easily lay a ventilation device. But what to do in those buildings where financial or other technical reasons do not allow installing the necessary ventilation? Some see the solution in the installation of wall and glass valves that serve as a conduit for the flow of clean air.

How the supply valve works

Having acquired supply valves, you also need to understand their principle of operation in order to get air in the right amount and the right temperature.

Indoor activities

Such a device works as follows. The incoming cold air streams from the upper window part are directed into the space under the ceiling. Since warm internal currents are concentrated there, the temperature is gradually redistributed. As a result, you will get a normal air exchange without creating unnecessary noise and drafts.This equipment is quite profitable, since clean air is supplied all the time, whether it is lesson, sleep, games or classes. You also don’t have to worry about the possibility of a child getting sick – this is out of the question.

The advantages of the inflow valve include:

• Automatic air inflow control;
• Possibility of changing the passage sections for air intake into the building;
• The air flow is circulated if the natural or forced draft device is operating.

Organization of “educational” ventilation

In order to calculate the ventilation device in an educational institution, you need to rely on temperature indicators, as well as the characteristics of air exchange. The following is taken into account:

• When developing supply ventilation with mechanical induction, it is necessary to provide for a separate natural air conditioning system, which will be responsible for removing the waste stream from the premises;
• In any air-conditioned system, it should be taken into account that air flows from classrooms are discharged through corridor spaces, loosely closed windows and a bathroom;
• In the case of training in an institution of less than two hundred people, you can install the system without mechanical impact on the air flow;
• When using air heating in a training room, which is combined with a ventilation unit, it is necessary to provide for automatic control. She will be able to maintain the temperature calculated by you and the optimum humidity;
• When using a stream recirculation system in an educational institution, it is used only after the end of working hours;
• You cannot design exhaust ducts in classrooms. And if there are enough vents, they may not be provided at all.

To ensure an optimal climate in the entire establishment, it is necessary to design a ventilation system separately in each specific room.Particularly much attention needs to be paid to existing laboratories. Hoods with mechanics are usually installed in them. The air supply to such rooms is also special and should be 90% of the room itself and 10% of the adjacent corridors and rooms.

Good ventilation – increased comfort!

The main components of a comfortable stay of people in any room are: acceptable temperature, optimal humidity and air flow rate. Let’s briefly describe each component.

In winter, when the temperature is below zero, air exchange is difficult. This is because the air must be preheated. In this case, random ventilation will create a draft that will definitely negatively affect comfort.

If there are no devices for the regeneration of a warm flow, then the air from the outside should be gradually blown in the direction opposite to where people are. It is possible to install hygro-adjustable valves and thereby optimize the dispersion of the newly supplied air flow in the under-ceiling space, where the temperature is several degrees higher.

For people, the most optimal humidity is 35-65%. Such an indicator will also be able to prevent the destruction of materials that were involved in the construction and decoration of the building. It is this relative humidity that is recommended to be maintained in all rooms.

To select the most suitable equipment, you need to take into account some parameters: the amount of energy consumed, the amount of heat lost, the price of equipment, the cost of installing the ventilation system, maintenance costs during operation.

If you are retrofitting an old plant, the solution does not have to be expensive. There are devices that provide an inflow of a fresh stream and an outflow of waste, which work automatically. They are relatively inexpensive and have a special indicator that reacts to any changes. Such devices will be the most optimal way out of any difficult situation with a ventilation system.

10.3. Research methods and indicators of external respiration

Some
methods of studying external respiration. Spirometry Method for measuring expiratory volumes
air using a spirometer device.
Spirometers of different
type with a turbimetric sensor, and
also aquatic, in which the exhaled
the air is collected under the bell of the spirometer,
placed in water, and by raising the bell
the volume of exhaled is determined
air. Lately, it’s getting wider
sensors are used that are sensitive
to a change in the volumetric air velocity
stream connected to a computer
system. In particular, on this principle
the computer system is working,
called “Spirometer MAC-1”
This system is produced in Minsk. She
allows you to carry out not only spirometry,
but also spirography, as well as pneumo-
choography.

Spirography Continuous recording technique
volumes inhaled and exhaled
air. The resulting graphic
the curve is called a spirogram (Fig.
Yu-2). By spirogram you can determine
not only lung capacity and tidal volumes,
but also the frequency of de- ^Ha Niya, as well as
arbitrary maximum ventilation ^Le gkikh.

Fig.
10.2.
Histogram of lung volumes and capacities
from spirogram } | ry.
Explanation
in the text.

Fig.
10.3.
The flow curve is the volume of healthy and
sick person (dotted line) with
obstructive disorders in small
bronchus

Pneumotachography – Continuous recording technique
volumetric flow rate of inhaled
and exhaled air.

Exist
also many other research methods
respiratory system.Among them:
chest plethysmography,
listening to the sounds of the chest,
fluoroscopy and radiography,
determination of oxygen content and
carbon dioxide in the exhaled stream
air, etc. Some of these
methods will be discussed below.

Volumetric
and flow rates of external respiration.
These indicators
are calculated using special formulas.

Pulmonary
volumes and capacities. The ratio of pulmonary volumes
and containers is shown in Fig.10.3.

At
external respiration study
the following indicators are used
and their abbreviations:

General
lung capacity (OEL) – the volume of air, finding in the lungs after the deepest
inhalation.

Vital
lung capacity (VC) – air volume, which is _t which a person can exhale at a maximum
deep, slow exhalation, made
after maximum inspiration, g
recently in connection with the introduction
pneumotachographic techniques are increasingly defined as
called forsiro bathroom vital capacity of the lungs (FVC). At
the definition of FVC, the patient should
after the deepest breath make the deepest forced
exhalation.In this case, exhalation should be carried out
with an effort to achieve
maximum displacement rate
exhaled air flow to
throughout the entire exhalation. Computer
analysis of such a forced expiration
allows you to calculate up to 30 indicators
external respiration.

Individual
the norm of VC is called due
vital capacity of the lungs (JEL). Her
calculated on the basis of growth,
body weight, age, gender according to the formulas
and tables. For women aged 18-25
age calculation can be carried out by
formula

JEL
= 3. 8 P + 0.029 B-3.190;

for
males of the same age: 9.0003 9.0002
JEL
= 5.8 • P + 0.085 V – 6.908,

where
P – height in meters, B – age in years,
JEL – volume in liters.Depending on
from the listed factors limits
indicators of the proper VC are close to 3-6 liters.
The value of the measured VC is considered
reduced if this decrease is
not less than 20% of the JEL level.

Functional
residual capacity (FRU) – air- Spirit remaining in the lungs
after a calm exhalation. This capacity
consists of residual lung volume
(OOL) and reserve expiratory volume
(PO _{Bb] D} ).

If
for the indicator of external respiration
use the name container, then this
means that the composition of such a container
includes smaller units,
called volumes.For example, OEL
consists of 4 volumes, VC – of 3 volumes.

Respiratory
volume (DO) –
is the volume of air entering
lungs or removed from them in one
Respiratory Cycle. This indicator
also referred to as
deep breathing.

IN
resting state in an adult
DO is 300-800 ml (15-20% of the
VC). For a month-old baby, up to 30 ml, for
one-year-old – 70 ml, for a ten-year-old –
230 ml. If the depth of breathing is greater than normal,
then this breath is called
hyperpnea – excessive, deep breathing, if
TO is less than the norm, then the name is used
oligopnea –
insufficient, shallow breathing.At normal depth and breathing rate
they call him
eupnea – normal, adequate breathing.
The normal respiratory rate of at rest in adults is 8-20
respiratory cycles per minute, at the monthly
a child – about 50, a one-year-old – 35,
ten-year – 20 cycles per minute.

Reserved
inhalation volume (PO _vd ) – the volume of air that
a person can inhale at the maximum
deep breath after
calm breath. The value of PO _wd is normally 50-60% of the value
VC (2-3 l).

Reserved
expiratory volume (PO _vyd ) – maximum volume
air that a person can breathe out
with the deepest exhalation,
taken after a calm exhalation. IN
Normally, the value of PO _Bb1D is
20-35% of VC (1-1.5 liters).

Residual
lung volume (OOL) – air remaining in the respiratory
pathways and lungs after maximum
deep exhalation. Its value is
1 – 1.5 liters (20-35% of the OEL). In elderly persons
age, the value of OOL increases due to
decrease in elastic traction of the lungs,
patency of the bronchi, decrease in strength
respiratory muscles and chest mobility
cells.

IN
not all of the gas exchange takes part
atmospheric air entering
the respiratory system when inhaling, but only
the one that reaches the alveoli having
sufficient blood flow in
surrounding capillaries. In connection with
this distinguishes the so-called dead
space.

Anatomical
dead space
(AMP) is
the volume of air in the respiratory
pathways to the level of respiratory bronchioles
(on these bronchioles there are already
there are alveoli
and is possible
gas exchange). Magnitude
AMP
is 140-260
ml
and depends on
features of the constitution
person (at
solving problems in which it is necessary
use AMP, and its value is not indicated, accept
AMP
equal to 150 90 191
ml).

Physiological
dead space (FMP) volume of atmospheric air,
entering the respiratory tract and
lungs and not taking part in
gas exchange. FMP is more anatomical
dead space, as it includes
it as an integral part.Except for the air
located in the respiratory tract, in
the composition of the FMP includes air entering
into the pulmonary alveoli, but not exchanging
gas with blood due to the absence or
disturbances of blood flow in these alveoli
(for this air is sometimes used
name alveolar
dead space). Normal value of functional
dead space is
20-35% of the tidal volume.
An increase in this value over 35%
may indicate a number of dangerous
diseases.

IN
medical practice is important to consider
dead space factor at
breathing apparatus design
(high-altitude flights, scuba diving,
gas masks), holding a number
diagnostic and resuscitation
activities. Breathing through the tubes
masks, hoses to the respiratory system
an additional person is connected
dead space and large
its volume, despite the increase
breathing depth, ventilation of the alveoli
atmospheric air can become
insufficient.

Minute
breathing volume (MOD) – the volume of air passing
through the lungs in 1 min. For determining
MOD it is enough to know the depth (DO) and
respiratory rate (RR):

MAUD
= DOCHD.

IN
rest rate is 4-6 l / min. This
indicator is often referred to as
ventilation of the lungs (should be distinguished from alveolar
ventilation).

Alveolar
ventilation (AB) – the volume of atmospheric air,
entering the pulmonary alveoli in 1
min.To calculate the alveolar
ventilation need to know the amount of dead
space (MP). If it is not defined
experimentally, then to calculate
take MP = 150 ml. To calculate the alveolar
ventilation you can use the formula

AB
= (DO – MP) BH.

For example,
if the depth of breathing in a person is 650 ml,
and hour – ^t ° and breathing 12 in 1 min, then
AB = (650 – 150) 12 = 6000 ml.

Maximum
lung ventilation (MVL) – maximum air volume,
which can be ventilated
through the lungs of a person in 1 min.MBJ1
can be determined for an arbitrary
hyperventilation at rest (breathe
as deeply and often as possible at rest
permissible no more than 15 s). With the help of
special technique can be determined
MVL while performing intensive
physical work. Depending on
constitution and age of a person norm
MVL is in the range of 40-170 l / min.

Streaming
indicators of external respiration. Except for lung volumes and capacities, and
also ventilation indicators
in assessing the state of the respiratory system
so-called matter
flow rates of external respiration.The simplest method
determination of one of them – peak
expiratory flow rate (POS), is
peak flow measurement. Peak flow meters – simple
and quite affordable
devices. Many patients with diseases
respiratory tract acquire them
for home use.

Peak
expiratory volumetric flow rate (POS) – maximum volumetric flow rate
exhaled air flow achieved
in the process of exhalation forced
vital capacity of the lungs.

IN
conditions of a medical hospital all
are becoming more widespread
pneumotachographs with computer
processing the information received.Devices of this type allow
based on continuous registration
volumetric air flow rate
during the expiration of the forced vital
capacity to calculate up to 30 indicators
external respiration. Most often determined:
POS, maximum displacement rates
air flow at the moment of vshchoh, 25,
50, 75% FVC, called accordingly
indicators MOS25, MOS50, MOS75.

Popular
also determine the volume of forced
expiration in a time equal to 1 s – FVC1.
Based on this indicator
the test is calculated
Tiffno – expressed as a percentage
FVC1 ratio
To
YEL.A curve is also recorded
reflecting the change in volumetric
air speed
flow during forced expiration
(Fig. Yu.Z). In this case, vertically
the volumetric velocity (l / s) is displayed,
horizontally – the percentage of exhaled
FZHEL. On such a graph, the top of the curve
indicates the magnitude of the PIC, the projection of the moment
expiratory flow 25% FVC per curve characterizes
MOS25, projection 50% and 75% FVC
corresponds to
values ​​MOC50 and
MOS75.

have diagnostic value
only
individual points, but also the entire course of the curve.Its part corresponding to 0-25%
exhaled FVC, reflects patency
for air _to rupees
bronchi, trachea and upper respiratory
tracks, section from 50 to 85% FZHEL –
patency of the distal bronchi and
bronchioles. Deflection at _N
section of the curve in the area of ​​exhalation 75-85%
FVC (Figure 10.3) indicates
to reduce the patency of small bronchi
and bronchioles.

The listed
volumetric and flow rates
are used to make a conclusion about the condition
external respiration systems.In diagnostic
systems use four options
primary characteristics of the state
external respiration systems: norm,
obstructive disorders, restrictive
violations, mixed violations (combination
obstructive and restrictive
violations).

For
most streaming and bulk
indicators of external respiration
deviations of their value from the due
(calculated) value by more than 20%
are considered to be outside the normal range.

Obstructive
violations
Is an increase in aerodynamic
airway resistance for
air flow.Instead of this
definitions, the interpretation is often used:
obstructive disorders are a decrease
patency of the respiratory tract. Such
violations can occur due to
increasing the tone of the smooth muscles of the lower
respiratory tract, presence of hypertrophy
mucous membranes, accumulations of mucus,
pus, presence of tumors, abnormalities
regulation of the patency of the upper
respiratory tract and other factors.

O
the presence of obstructive changes in the system
external respiration is judged by a decrease in:
POS, FZHEL ,, MOS ₂₅ ,
MOS ₅₀ ,
MOS ₇₅ ,
MOS ₂₅ _75,
MOS ₇ 5_ ₈ 5,
values ​​of the Tiffno test and MVL.Index
Tiffno’s test is normally 70-85%,
reducing it to 60% is regarded as
moderate violation, and up to 40% – as sharply
severe obstruction
bronchi. In addition, with obstructive
violations are increasing
indicators such as residual volume,
functional residual capacity and
total lung capacity.

Restrictive
violations –
it is a decrease in lung expansion
when inhaling, decreased respiratory excursions
lungs. This may be due to
decrease in lung compliance, the presence
adhesions, congestion in the pleural
cavities of fluid, pus, blood.

Availability
restrictive system changes
external respiration is determined by
decrease in VC (at least 20% of the due
value) and Decrease in MVL (nonspecific
indicator), as well as to decrease
Lung compliance and (in some cases)
ascending (more than 85%) indicator
the Tiffeneau index. With restrictive
violations decrease – ^Xia
total lung capacity, functional
residual capacity and residual ^Point
volume.

Conclusion
about mixed (obstructive and restrictive)
disorders of the external respiration system
done with the simultaneous presence
reduction of the above streaming
and volumetric indicators.

Work
breathing. For
ventilation of the lungs
it is necessary to expend the work. She
performed by the force of contraction
muscles and is spent on overcoming: 1)
elastic resistance of the lungs
and chest – 60-80% of all costs,
2) dynamic (viscous) resistance
(up to 80% of these resistances are created
airway resistance
air flow and up to 20% – viscous
tissue resistance associated with
their deformation), 3) inertial
resistances (energy consumption for
acceleration
chest tissue
and
organs abdominal
cavities – 1
-3% of all energy costs).

Expenses
oxygen for calm breathing make up
2-5% of the total oxygen consumption.
With increased breathing, these costs
can increase up to 30%, and in people with
lung and respiratory disease
paths – up to 60%.