What is svt in medical terms: Supraventricular tachycardia – Symptoms and causes
Supraventricular tachycardia – Illnesses & conditions
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About supraventricular tachycardia
Symptoms of supraventricular tachycardia
Causes of supraventricular tachycardia
Diagnosing supraventricular tachycardia
Treating supraventricular tachycardia
About supraventricular tachycardia
Supraventricular tachycardia (SVT) is a heart condition featuring episodes of an abnormally fast heart rate.
The heart will suddenly start racing, then stop racing or slow down abruptly.
Episodes can last for seconds, minutes, hours or (in rare cases) days. They may occur regularly, several times a day, or very infrequently, once or twice a year.
The heart rate may be as high as 250 beats per minute, but is usually between 140 and 180 (a normal heartbeat should be 60-100 beats per minute at rest).
What it means
- ‘Supraventricular’ means that the problem occurs in the upper chambers (atria) of the heart.
- ‘Tachycardia’ means an abnormally rapid heart rhythm.
When the heart beats normally, its muscular walls contract (tighten and squeeze) to force blood out and around the body. They then relax, so the heart can fill with blood again. This process is repeated for every heartbeat.
In SVT, the heart muscle is contracting so fast that it cannot relax between contractions. This reduces the amount of blood being pumped around the body, which can make you feel dizzy and short of breath.
You usually feel heart palpitations (noticeable heartbeats) and a fast pulse.
Why it happens
SVT is caused by abnormal electrical impulses that start suddenly in the upper chambers of your heart (the atria). These impulses override your heart’s natural rhythm.
It is often a short circuit in the electrical system of your heart that causes these spontaneous impulses. The short circuit causes an electrical signal to travel continuously around in a circle. Each time the signal completes the circuit, the impulse spreads out to the rest of your heart, forcing it to beat rapidly.
SVT attacks often happen for no obvious reason. However, they may be triggered by a change in posture, exertion, emotional upset, coffee or alcohol.
Who is affected
SVT can occur in anyone at any age, but it often occurs for the first time in children or young adults.
In the vast majority of cases, attacks of SVT are harmless, do not last long and settle on their own without treatment.
If necessary, SVT can be treated with drugs that correct the abnormal heart rate. It can also be permanently treated with a very effective surgical procedure called catheter ablation, which interrupts the abnormal electrical circuits.
Symptoms of supraventricular tachycardia
If you have supraventricular tachycardia (SVT) you’ll usually feel your heart racing in your chest or throat and a very fast pulse (140-180 beats per minute).
You may also feel:
- chest pain
- fatigue (tiredness)
On rare occasions, you may faint because of a drop in blood pressure.
How long do symptoms last?
Symptoms of SVT can last for seconds, minutes, hours, or (in rare cases) days.
They may occur regularly, several times a day, or very infrequently, once or twice a year.
How is it different from atrial fibrillation?
SVT features a fast, regular heart rate whereas atrial fibrillation features a fast but irregular heart rate (‘flutters’)
Read more on atrial fibrillation
Causes of supraventricular tachycardia
An episode of supraventricular tachycardia (SVT) occurs when abnormal electrical impulses suddenly start in the upper chambers of the heart, and override the heart’s natural rhythm.
SVT is sometimes called paroxysmal supraventricular tachycardia (PSVT). Paroxysm means a sudden temporary disturbance of heart rhythm.
PSVT is usually caused by a short circuit in the electrical system of the heart, which causes an electrical signal to travel rapidly and continuously around in a circle, forcing the heart to beat each time it completes the circuit.
Another type of SVT is called Wolff-Parkinson-White syndrome, where an abnormal electrical connection occurs between the atria (upper heart chambers) and ventricles (lower heart chambers). People with Wolff-Parkinson-White syndrome are born with a strand of extra muscle tissue between these chambers. This produces a short circuit, which causes the fast heartbeat.
SVT is usually triggered by extra heartbeats (ectopic beats), which occur in all of us but may also be triggered by:
- some medications, including asthma medications, herbal supplements and cold remedies
- drinking large amounts of caffeine or alcohol
- stress or emotional upset
- a change in posture
- smoking lots of cigarettes
How the heart works
The heart has two upper chambers (the left and right atria) and two lower chambers (the left and right ventricles).
The atria and ventricles have walls of muscle. A heartbeat happens when this muscle suddenly contracts (tightens) so that the chambers become smaller and the blood inside is squeezed out.
The control of the heartbeat starts with a small clump of cells in the right atrium, called the sinoatrial node (the heart’s natural pacemaker). This sends out electrical impulses through the atrial muscle to another clump of cells called the atrioventricular (AV) node, found between the atria and ventricles. The impulse then continues through the AV node down fibres that conduct the impulse into the muscle of the ventricles.
The AV node determines the rate of contraction of the ventricles. The pulse felt at the wrist is due to the contraction of the ventricles.
Diagnosing supraventricular tachycardia
If your GP suspects that you have supraventricular tachycardia (SVT), they may ask you to have an electrocardiogram and refer you to a heart specialist.
An electrocardiogram (ECG) is a test that records the rhythm and electrical activity of your heart.
Small stickers (electrodes) are stuck to your arms, legs and chest, and connected via wires to an ECG machine.
Every time your heart beats, it produces tiny electrical signals. An ECG machine traces these signals onto paper. Your heart rate during SVT may be as high as 250 beats per minute, but is usually between 140 and 180.
ECGs are usually done in hospital or in your GP’s surgery. It takes about five minutes and is painless.
If you manage to have the test done during an attack of SVT, the ECG will record your abnormal heart rate. The diagnosis of SVT can then be confirmed (and other conditions ruled out).
However, it may be difficult to capture an attack. So your doctor may ask you to wear a small, portable electrocardiogram monitor that will record your heart rate either continuously over 24 hours, or when you switch it on (at the start of an attack).
Further tests may be done once episodes of SVT are confirmed. These aim to determine the exact location within the heart that is triggering the episodes of SVT.
For example, you may be asked to take part in a electrophysiology study done under sedation, in which doctors pass electrodes (soft flexible wires) up through a vein in your leg to your heart. These electrodes measure the electrical signals in your heart and enable doctors to determine where the abnormal signals are coming from.
Treating supraventricular tachycardia
In many cases, the symptoms of supraventricular tachycardia (SVT) stop quickly and no treatment is needed.
If treatment is needed, you will have to go to hospital. Treatment for SVT cannot be given until your diagnosis has been confirmed from an electrocardiogram (ECG).
If symptoms last for a long time or are severe, a medicine – usually adenosine – can be injected into your vein, which blocks the abnormal electrical impulses in your heart.
When adenosine is not recommended – for example, if you have asthma – an injection of verapamil can be given instead.
Medication may be also prescribed to prevent further episodes of SVT. This includes:
- beta blockers, which slow the electrical impulses in the heart
Electric shock treatment
Electric shock treatment (called cardioversion) is occasionally used to stop an episode of SVT. A machine called a defibrillator applies an electrical current to your chest. This is usually done under general anaesthetic (you are put to sleep).
Catheter ablation is an extremely effective procedure that produces small scars in your heart that block the electrical signal travelling around the abnormal electrical circuit. It prevents further episodes of SVT.
A catheter (a thin, soft wire) is guided through one of your veins into your heart, where it records electrical activity. When the precise position of the circuit is found, either heat generated by an electric current or cold (cryoablation) is transmitted to the catheter tip to destroy a small mass of muscle, producing a small scar.
This procedure is usually done under a local anaesthetic (the area is numbed), with some sedation.
The following non-drug methods may be tried to stop SVT:
- Hold your nose, close your mouth and try to blow out hard (called the Valsalva manoeuvre). This should feel like straining on the toilet.
- A health professional can massage an area in your neck called the carotid sinus.
- Dip your face into cold water during an attack.
Supraventricular tachycardia (SVT) – NHS
Supraventricular tachycardia (SVT) is a condition where your heart suddenly beats much faster than normal. It’s not usually serious, but some people may need treatment.
Causes of supraventricular tachycardia (SVT)
SVT happens when the electrical system that controls your heart rhythm is not working properly.
This causes your heart to suddenly beat much faster. It can then slow down abruptly.
A normal resting heart rate is 60 to 100 beats per minute (bpm). But with SVT your heart rate suddenly goes above 100bpm. This can happen when you’re resting or doing exercise.
Symptoms of supraventricular tachycardia (SVT)
Having SVT means your heart suddenly beats faster.
- usually lasts for a few minutes, but can sometimes last for several hours
- can happen several times a day or once a year – it varies
- can be triggered by tiredness, caffeine, alcohol or drugs – but often there’s no obvious trigger
- can happen at any age, but often starts for the first time in children and young adults – many people have their first symptoms between 25 and 40
You may get no other symptoms, but sometimes people also:
- have chest pain
- feel weak, breathless or lightheaded
- feel tired
- feel sick or are sick
Non-urgent advice: See a GP if you keep getting a fast heartbeat
It’s important to get it checked out. You might need a test, such as an electrocardiogram (ECG), to find out what’s going on.
Immediate action required: Call 999 or go to A&E if:
- you have been diagnosed with SVT and your episode has lasted longer than 30 minutes
- you have sudden shortness of breath with chest pain
You need to go to hospital for treatment immediately.
Things you can do to help with supraventricular tachycardia (SVT)
If your episodes of SVT only last a few minutes and do not bother you, you may not need treatment.
You can make changes to your lifestyle to reduce your chances of having episodes, such as:
- cutting down on the amount of caffeine or alcohol you drink
- stopping or cutting back on smoking
- making sure you get enough rest
Your doctor may also be able to recommend some simple techniques to help stop episodes when they happen.
Treating supraventricular tachycardia (SVT) in hospital
SVT is rarely life threatening. But you may need treatment in hospital if you keep having long episodes.
This may include:
- medicines to control the episodes of SVT – given as tablets or through a vein
- cardioversion – a small electric shock to the heart to help it get back to a normal rhythm
- catheter ablation – a treatment where thin tubes are placed through a vein or artery into your heart to correct the problem with the electrical system; this permanently cures the problem in most patients
Find out more about:
- cardioversion: British Heart Foundation
- catheter ablation: British Heart Foundation
Page last reviewed: 27 April 2021
Next review due: 27 April 2024
clinical death from the point of view of medicine – Moscow 24, 06/09/2015
Photo: M24. ru/Mikhail Sipko
Woland’s mouth, perfectly describe the feelings of most people. Probably, there is no person who would not be afraid of death. But along with the big death, there is a small death – clinical. What is it, why people who have experienced clinical death often see the divine light and is it not a delayed path to paradise – in the material M24.ru.
Clinical death from the point of view of medicine
The problems of studying clinical death as a borderline state between life and death remain among the most important in modern medicine. Unraveling many of its mysteries is also difficult because many people who have experienced clinical death do not fully recover, and more than half of patients with a similar condition cannot be resuscitated, and they die for real – biologically.
So, clinical death is a condition accompanied by cardiac arrest, or asystole (a condition in which various parts of the heart stop contracting first, and then cardiac arrest occurs), respiratory arrest and deep, or beyond, cerebral coma. With the first two points, everything is clear, but about whom it is worth explaining in more detail. Usually doctors in Russia use the so-called Glasgow scale. According to the 15-point system, the reaction of opening the eyes, as well as motor and speech reactions, is evaluated. 15 points on this scale correspond to clear consciousness, and the minimum score – 3, when the brain does not respond to any kind of external influence, corresponds to transcendental coma.
After stopping breathing and cardiac activity, a person does not die immediately. Almost instantly, consciousness is turned off, because the brain does not receive oxygen and its oxygen starvation sets in. But nevertheless, in a short period of time, from three to six minutes, he can still be saved. Approximately three minutes after breathing stops, cell death begins in the cerebral cortex, the so-called decortication. The cerebral cortex is responsible for higher nervous activity and, after decortication, resuscitation measures, although they can be successful, a person can be doomed to a vegetative existence.
Photo: TASS/Sergey Bobylev
A few minutes later, cells of other parts of the brain begin to die – in the thalamus, hippocampus, cerebral hemispheres. The state in which all parts of the brain have lost functional neurons is called decerebration and actually corresponds to the concept of biological death. That is, the revival of people after decerebration is in principle possible, but a person will be doomed for the rest of his life to be on artificial lung ventilation and other life-sustaining procedures for a long time.
The fact is that the vital (vital – M24.ru) centers are located in the medulla oblongata, which regulates breathing, heartbeat, cardiovascular tone, as well as unconditioned reflexes like sneezing. With oxygen starvation, the medulla oblongata, which is actually a continuation of the spinal cord, dies one of the last sections of the brain. However, although the vital centers may not be damaged, by then decortication will have set in, making it impossible to return to normal life.
Other human organs such as the heart, lungs, liver and kidneys can survive much longer without oxygen. Therefore, one should not be surprised at the transplantation, for example, of kidneys taken from a patient with an already brain dead. Despite the death of the brain, the kidneys are still in working condition for some time. And the muscles and cells of the intestine live without oxygen for six hours.
Currently, methods have been developed that can increase the duration of clinical death up to two hours. This effect is achieved with the help of hypothermia, that is, artificial cooling of the body.
Photo: TASS/Vladimir Smirnov
As a rule (unless, of course, it happens in a clinic under the supervision of doctors), it is rather difficult to determine exactly when the cardiac arrest occurred. According to current regulations, doctors are required to carry out resuscitation measures: heart massage, artificial respiration for 30 minutes from the start. If during this time it was not possible to resuscitate the patient, then biological death is stated.
However, there are several signs of biological death that appear as early as 10–15 minutes after brain death. First, Beloglazov’s symptom appears (when pressing on the eyeball, the pupil becomes similar to a cat’s), and then the cornea of the eyes dries up. If these symptoms are present, resuscitation is not carried out.
How many people survive clinical death safely
It may seem that most people who find themselves in a state of near death come out of it safely. However, this is not the case, only three to four percent of patients can be resuscitated, after which they return to normal life and do not suffer from any mental disorders or loss of body functions.
Another six to seven percent of patients, being resuscitated, nevertheless do not fully recover, suffer from various brain lesions. The vast majority of patients die.
Such sad statistics are largely due to two reasons. The first of them – clinical death can occur not under the supervision of doctors, but, for example, in the country, from where the nearest hospital is at least half an hour away. In this case, the doctors will come when it will be impossible to save the person. Sometimes it is impossible to timely defibrillate when ventricular fibrillation occurs.
“Special Report”: Beyond the Boundaries
The second reason is the nature of the damage to the body during clinical death. When it comes to massive blood loss, resuscitation is almost always unsuccessful. The same applies to critical myocardial damage in a heart attack.
For example, if more than 40 percent of the myocardium is affected as a result of blockage of one of the coronary arteries, death is inevitable, because the body cannot live without heart muscles, no matter what resuscitation measures are taken.
Thus, it is possible to increase the survival rate in case of clinical death mainly by equipping crowded places with defibrillators, as well as by organizing flying ambulance crews in hard-to-reach areas.
Clinical death for patients
If clinical death for doctors is an emergency, in which it is necessary to urgently resort to resuscitation, then for patients it often seems like a path to the bright world. Many near-death survivors have reported seeing light at the end of a tunnel, some meeting their long-dead relatives, others looking at the earth from a bird’s eye view.
“I had a light (yes, I know how it sounds), and I seemed to see everything from the outside. It was bliss, or something. No pain for the first time in so much time. “someone else’s life and now I’m just slipping back into my skin, my life – the only one in which I’m comfortable. It’s a little tight, but it’s a pleasant tightness, like a frayed pair of jeans that you’ve been wearing for years,” says Lydia, one of the patients, who suffered clinical death.
Photo: M24.ru/Mikhail Sipko
It is this feature of clinical death, its ability to evoke vivid images, that is still the subject of much controversy. From a purely scientific point of view, what is happening is described quite simply: brain hypoxia occurs, which leads to hallucinations in the actual absence of consciousness. What kind of images arise in a person in this state is a strictly individual question. The mechanism of occurrence of hallucinations has not yet been fully elucidated.
At one time the endorphin theory was very popular. According to her, much of what people experience near death can be attributed to the release of endorphins due to extreme stress. Since endorphins are responsible for getting pleasure, and in particular even for orgasm, it is easy to guess that many people who survived clinical death considered ordinary life after it to be only a burdensome routine. However, in recent years, this theory has been debunked because researchers have found no evidence that endorphins are released during clinical death.
There is also a religious point of view. As, however, in any cases that are inexplicable from the standpoint of modern science. Many people (there are scientists among them) tend to believe that after death a person goes to heaven or hell, and the hallucinations that survivors of near-death experience saw are only proof that hell or heaven exists, like the afterlife in general. It is extremely difficult to give any assessment to these views.
Nevertheless, not all people experienced heavenly bliss at clinical death.
“I suffered clinical death twice in less than one month. I didn’t see anything. When they returned, I realized that I was nowhere, in non-existence. I didn’t have anything there. I concluded that there you get rid of everything by completely losing yourself , probably, together with the soul. Now death does not really bother me, but I enjoy life, “accountant Andrey cites his experience.
In general, studies have shown that at the time of human death, the body loses little in weight (literally a few grams). Adherents of religions hastened to assure mankind that at this moment the soul is separated from the human body. However, the scientific approach says that the weight of the human body changes due to chemical processes occurring in the brain at the time of death.
Current standards require resuscitation within 30 minutes of the last heartbeat. Resuscitation stops when the human brain dies, namely on registration on the EEG. I have personally resuscitated a patient once who went into cardiac arrest. In my opinion, the stories of people who have experienced clinical death are, in most cases, a myth or fiction. I have never heard such stories from patients of our medical institution. As well as there were no such stories from colleagues.
Moreover, people tend to call clinical death completely different conditions. It is possible that the people who allegedly had it did not actually die, they just had a syncopal state, that is, fainting.
Cardiovascular diseases remain the main cause that leads to clinical death (as well as to death in general). Generally speaking, such statistics are not kept, but it must be clearly understood that clinical death occurs first, and then biological. Since the first place in mortality in Russia is occupied by diseases of the heart and blood vessels, it is logical to assume that they most often lead to clinical death.
One way or another, the phenomenon of near-death experience deserves careful study. And it is quite difficult for scientists, because in addition to the fact that it is necessary to establish which chemical processes in the brain lead to the appearance of certain hallucinations, it is also necessary to distinguish truth from fiction.
science coma patients scientific issues clinical death
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How light and darkness control our biological rhythms 3
Magazine “Schrödinger’s Cat” (Polina Ogorodnikova)
Domestic cats for some reason ask to eat from early morning, while office workers get hungry in the afternoon. Owls get food at night, and many residents of St. Petersburg dislike white nights because of insomnia. In each of us, the biological clock is ticking, but what exactly are the processes behind the movement of their arrows?
Where the clock is hidden
The biological clock is one of the body’s systems, like the immune system or the cardiovascular system. All living beings need these clocks to synchronize with the rhythms of nature – to adapt to the change of day and night or the change of seasons. Many functions of the body are subject to the biological clock, including thermoregulation, blood pressure, and hormone production.
The clock that controls our body works on three levels. The first is a tiny clockwork hidden in every cage. For its discovery, American researchers Jeffrey Hall, Michael Rosbash and Michael Young received the 2017 Nobel Prize in Physiology or Medicine.
The main role in it is played by special clock proteins, which are synthesized in all cells with a nucleus – in animals, plants, and fungi. Part of the clock proteins is formed in the morning, activating the metabolism in the cell, the other – in the evening, inhibiting metabolism. This is how the daily, or circadian (from the Latin circa – about and dies – day), the rhythm of the work of an individual cell is set. And if one of the genes that synthesize clock proteins mutates, various rhythms of the body can be disturbed: sleep and wakefulness, motor activity, digestion. All these rhythms are connected – if a person does not sleep at night, this can lead not only to insomnia or depression, but also to diabetes, even to cancer.
Clocks are needed not only for every cell, but also for the organism as a whole. The rhythms of all cells are synchronized by a special hormonal gland of the brain called the pineal gland, or the pineal gland, which produces melatonin and serotonin – hormones that regulate our sleep and wakefulness, as well as appetite and mood. During daylight hours, the pineal gland produces the “happiness hormone” serotonin, and during the dark, serotonin is converted into the “sleep hormone” melatonin – it makes sleep deeper and more fulfilling.
In sufficient quantities, melatonin is produced only in the dark, even dim light reduces its production – turn off all the lamps and curtain the windows! And serotonin, on the contrary, needs light: the more light, the better the mood and the higher the performance.
Now let’s move on to the third level. The highest control center for all the rhythmic functions of the body is the suprachiasmatic nuclei of the hypothalamus. It is this group of nerve cells that receives a direct signal from the retina of the eye, which tells the clock what is now on the street: day or night. This small area in the diencephalon is the main generator of circadian rhythms, its neurons adjust to external light signals and control the pineal gland.
Everything has its time
02:00 – Deepest sleep
03:00 – Lowest blood pressure
04:30 – Lowest body temperature
06:45 – Most dramatic increase in blood pressure
07:30 – Stops secretion of melatonin
08:30 – Possible urge to defecate
10:00 – Highest readiness for action
14:30 – Maximum coordination
15:30 – Fastest reaction time
17:00 – Most active blood circulation and maximum muscle strength
18:30 – Highest blood pressure
19:00 – Highest body temperature
21:00 – Melatonin secretion begins
22:30 – Intestinal motility is suppressed
The source of this “schedule” is a book “Biohacking. A Guide to Unleashing the Body’s Full Potential” by Finnish researchers Sovijärvi Olli, Teemu Arin and Halmetoja Jaakko. But the time here is approximate – do not be discouraged if your “highest readiness for action” comes much later than ten in the morning!
How not to break your watch
What about owls and larks – do they have clocks set differently? Actually we don’t know. Maybe there are also “pigeons” – people who are active during the day, but sleepy in the morning and evening. But it is known for sure that, no matter what bird you are, you need to sleep at night and stay awake during the day. This is how we are genetically programmed, to live differently means to shorten life.
It is especially harmful to constantly change your routine. For example, scientists from the University of Michigan studied the database of the Nurses Health Study project – a long-term study of the health of more than 120,000 American nurses – and found that shift work (either day or night) increases the risk of ischemic stroke by 4% every five years. Other studies based on the same data have shown that working night shifts at least three nights a month for 15 years or more can increase the risk of colorectal cancer as well as breast cancer.
The reason is desynchronosis, that is, a mismatch of biological rhythms, which is a risk factor for the development of cardiovascular and oncological diseases. Desynchronosis is accompanied by prolonged increased fatigue, decreased performance and sleep disturbances.
One-time desynchronosis is known to anyone who has experienced jet lag – a syndrome that occurs when a person changes time zones abruptly, when a person crosses more than three or four time zones. After it comes the stage of resynchronization – when the biological rhythms of the body adjust to the new conditions. Interestingly, if the flight was from east to west, the average recovery speed will be 92 minutes a day, and if from west to east – it will be one and a half times lower, 57 minutes a day. It turns out that it is more difficult to adapt when flying to the east.
Our body also feels out of sync when we while away the time with a smartphone. It is the blue, short-wavelength part of the color spectrum that suppresses the production of melatonin. The melanopsin photopigment in the cells of the retina of the eye reacts to blue light – the opinion of the brain about whether it is night or day depends on it. When the light is red, the brain does not understand that it is daytime outside. But the screens of gadgets just emit a bright and cold blue light, in vain cheering the brain in the middle of the night.
For biohackers: mobile applications for taking care of circadian rhythms
Name: My circadian clock
What it works on: Android and IOS
What it can: helps norms analyze the rhythms of sleep, eating and physical activity
How it works. The course of the biological clock depends not only on light, but also on the time of training and eating. Moreover, the more predictable the daily routine is, the more successfully biorhythms will regulate important processes in the body: digestion, immune response, sleep, and much more. View your schedule in graph form, get recommendations, and help scientists at the Salk Institute for Biological Research in the United States learn more about the circadian rhythms of different people using the mobile application. For the first two weeks, it will carefully collect information about the subject, and then it will begin to instill good habits – for example, do not skip lunch at work and go to bed on time.
What is it called: Twilight
What it works on: Android
What it can do: prevents gadgets from spoiling sleep
How it works. From a medical point of view, life in pink glasses can be quite useful. But it is even better to build a red or orange filter between the eyes and gadget screens. It is useful to observe such a regimen in the evenings so that the blue spectrum does not once again lead to the production of melanopsin, which signals the biological clock that it is daytime – time to be awake. To reduce the harmful effects of blue screens, a mobile application will help, which will make the colors of the display warmer in the evening. By the way, in many modern smartphones this function is included in the standard settings.
What it’s called: Lux Light Meter Free
What it works on: Android
What it can do: measures light levels
How it works. If you go on a safari to some African country, then the retina of the eye will receive at least 1000 lux every day (these are the units in which the level of illumination is measured). But in an office space with the lights on, the indicators will turn out to be completely different – about 500 lux if the employee is sitting near the window without curtains.