The bends from scuba diving: Symptoms and Signs of The Bends (Decompression Sickness): Treatment
What Are The Bends (Decompression Sickness) When Diving?
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SCUBA diving is a relatively safe sport. However, there is always a small chance of getting the bends. What are the bends and how can divers avoid getting them?
What Are the Bends in SCUBA Diving?
You may have heard the term before on TV or movies, but what exactly are the bends? The bends is the common term for what divers call decompression sickness. Decompression sickness, or DCS for short, is improper decompression after exposure to increased pressure. In diving, it is when small nitrogen bubbles become trapped inside the blood and body tissues due to a subsequent decrease in pressure.
What Is Decompression Sickness
In SCUBA diving, there are pressure changes that affect the gases a diver breathes. In most recreational diving circumstances, air is the source of gas that is inside a SCUBA tank. When you descend, the pressure increases and you absorb the oxygen and nitrogen inside the SCUBA tank. Oxygen is able to be used for metabolism, but nitrogen stays in your tissues and loads them with nitrogen that is unusable by your body.
The amount of nitrogen you can hold inside your tissues without getting the bends, is termed ‘no decompression limit’. If you exceed these time limits, the chance of getting the bends increases. Thus, longer and deeper dives have the greatest chance of getting decompression sickness. However, it is never 100% that you will or will not get the bends.
How Do Divers Get the Bends?
Besides absorbing more and more nitrogen while underwater, when you ascend from a dive, as the pressure begins to decrease, the nitrogen bubbles slowly dissipate out of your blood and tissues. It is very important to do a safe, slow ascent to help the nitrogen off-load properly. A rapid ascent increases the risk of getting the bends.
Lastly, doing a safety stop at 15 feet for 3 minutes will allow more time for nitrogen to leave your body and reduce your risk of getting the bends. Of course, there are technical divers, and divers that dive below 100 feet, that can dive safely by making several stops on the way up to allow nitrogen to escape the body.
What Are the Symptoms?
Symptoms of decompression sickness typically occur between 6-24 hours after diving. There can be several types of symptoms that arise from decompression sickness. Some of the main symptoms include:
- Loss of appetite
- Feeling ill
- Pain in the joints
When decompression sickness is severe (Type II), paralysis and death can occur.
How to Avoid the Bends
Complete avoidance of getting decompression sickness while diving is not possible. Most dive tables leave a 1% risk of getting the bends while diving. However, divers can mostly avoid the bends if they follow a couple of general rules:
1) Stay hydrated. Dehydration is a major cause of what causes decompression sickness when diving.
2) Never push your limits. Do not stay at a given depth for the maximum allowable bottom time. Instead, start to come shallower before there is less than 5 minutes remaining of no stop time.
3) Stay warm. Cold exposure is a significant source of decompression sickness risk because nitrogen does not release as quickly.
4) Ascend slowly. Ascending slowly from a dive will allow nitrogen to more easily come out of your tissues.
5) Make a safety stop. Safety stops allow for excess nitrogen to leave your body.
There are many risk factors for what causes decompression sickness in SCUBA divers.
1) Dehydration. As mentioned above, dehydration is one of the main causes of the bends.
2) Illness. If you are sick, not only will it be hard to clear your ears, but it also adds stress to your body and increases the risk of decompression sickness.
3) Being overweight. Nitrogen dissolves very readily in fatty tissues. So the more fat a diver has, the greater the amount of nitrogen that can be potentially absorbed.
4) Tired. Being tired puts extra stress on your body which increases the risk of getting decompression sickness.
5) Alcohol. Alcohol that is usually still in the body from the night before can increase the risk of decompression sickness. Most often, it is the dehydrating effect of alcohol that causes this.
6) Over exertion. When you do strenuous exercise while diving, like swimming hard against a current, you can absorb more nitrogen.
7) Cold. Being cold on a dive can increase nitrogen absorption. Proper thermal protection is important to keep you warm while diving.
8) Injury. If you have an injury, blood flow tends to be altered slightly to allow perfusion of blood to the site of injury. This altered blood flow can increase risk of decompression sickness.
9) Heart Defects like patent foramen ovale.
10) Flying or going to altitude after diving. Follow the rules! After diving, it takes more time to get rid of the nitrogen still in your body. Researchers have found that after 1 single dive, you must wait 12 hours to fly and after more than 1 dive and several days of diving, you must wait at least 18 hours before flying. Even increases in altitude such as driving up a mountain can increase your chances of getting the bends.
11) Age. We can’t really doing anything about our age. It is always best to seek a doctor’s advice on whether it is safe to go diving. Usually, in older age, divers tend to make shorter, shallower dives.
Treatment for the Bends
Depending on the severity of decompression sickness, 100% oxygen can be all that is needed to help symptoms subside. However, oxygen therapy inside of a hyperbaric chamber is often what is needed. Anyone that experiences symptoms of decompression sickness after diving is advised to seek immediate medical help. More often than not, the chances of surviving decompression sickness with medical treatment are very high.
What are the bends and how do we avoid it are common questions in the dive community, especially for those just learning to dive. Most divers will never experience decompression sickness and will have safe dives throughout their careers. Just remember to follow the appropriate dive plans for your certification level, always stay well within your limits, and stay hydrated!
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Scuba Diving: Decompression Illness & Other Dive-Related Injuries
Arterial Gas Embolism
Gas entering the arterial blood through ruptured pulmonary vessels can distribute bubbles into the body tissues, including the heart and brain, where they can disrupt circulation or damage vessel walls. The clinical presentation of arterial gas embolism (AGE) ranges from minimal neurologic findings to dramatic symptoms requiring urgent and aggressive treatment.
In general, suspect AGE in any scuba diver who surfaces unconscious or loses consciousness within 10 minutes after surfacing. Initiate basic life support, including administration of the highest fraction of oxygen. Because relapses can and do occur, divers suffering AGE should be rapidly evacuated to a hyperbaric oxygen treatment facility even if they appear to have recovered fully.
Decompression Sickness (“The Bends”)
Breathing air under pressure causes excess inert gas (usually nitrogen) to dissolve in and saturate body tissues. The amount of gas dissolved is proportional to, and increases with, the total depth and time a diver is below the surface. As the diver ascends, the excess dissolved gas must be cleared through respiration. Depending on the amount of gas dissolved and the rate of ascent, some gas can supersaturate tissues, where it separates from solution to form bubbles, interfering with blood flow and tissue oxygenation.
Other Conditions Related to Diving
Any incapacitation while underwater can result in drowning (see Sec. 4, Ch. 12, Injury & Trauma).
Hazardous Marine Life
Oceans and waterways are filled with marine animals, most of which are generally harmless unless threatened. Most injuries among divers are the result of chance encounters or defensive maneuvers of marine life. Wounds from marine life have many common characteristics, including bacterial contamination, foreign bodies, bleeding, and occasionally venom. See Sec. 4, Ch. 7, Zoonotic Exposures: Bites, Stings, Scratches & Other Hazards, for prevention and injury management recommendations.
Immersion (Induced) Pulmonary Edema
The normal hemodynamic effects of water immersion account for a shift of fluid from peripheral to central circulation that can result in higher pressures within the pulmonary capillary bed, forcing excess fluid into the lungs. Cold water can cause peripheral vasoconstriction and augment this central fluid shift. Symptoms and signs of immersion (induced) pulmonary edema (IPE) generally begin on descent or at depth and include chest pain, dyspnea, wheezing, and productive cough with frothy, sometimes pink-tinged sputum. Although not entirely well understood, age, overhydration, overexertion, negative inspiratory pressure, and left ventricular hypertrophy are believed to increase IPE risk in otherwise healthy divers. Anyone experiencing acute pulmonary edema while diving requires a work-up to rule out myocardial ischemia, evaluation of left ventricular function, hypertrophy, and valvular integrity.
At increasing depths, generally >100 ft (≈30 m), the partial pressure of nitrogen within the breathing gas increases, causing narcosis in all recreational divers. Nitrogen narcosis can be life threatening when it impairs a diver’s ability to make appropriate and proper decisions while under water. This narcosis quickly clears on ascent and is not seen on the surface after a dive, which helps differentiate this condition from AGE.
At increasing partial pressures of oxygen, levels in the blood become high enough to cause seizures. This condition is not seen when diving on compressed air within recreational depth limits.
Diving & Air Travel
Flying after Diving
The risk of developing decompression sickness increases when divers go to increased altitude too soon after a dive. Commercial aircraft cabins are generally pressurized to the equivalent of 6,000–8,000 ft (≈1,830–2,440 m) above sea level. Instruct asymptomatic divers to wait before flying at an altitude or cabin pressure >2,000 ft (610 m) for
- ≥12 hours after surfacing from a single no-decompression dive;
- ≥18 hours after multiple dives or multiple days of diving; or
- 24–48 hours after a dive that required decompression stops.
These recommended preflight surface intervals reduce, but do not eliminate, risk for DCS. Longer surface intervals further reduce this risk.
Diving after Flying
There are no guidelines for diving after flying. Divers should wait a sufficient period to acclimate mentally and physically to their new location to focus solely on the dive.
Preventing Diving Disorders
Recreational divers should dive conservatively and well within the no-decompression limits of their dive tables or computers. When multiple dives are planned, strict guidelines, known as surface intervals, are prescribed to allow adequate time for dissolved inert gas to drop to acceptable levels before the next dive. Tables derived from man-tested algorithms have traditionally been used by divers to manually calculate dive times and surface intervals. Dive computers possess the reliability and computing power to use the same algorithms and compute individual guidance based on real-time depth and time inputs. Dive computers have largely replaced the use of tables for the manual process of dive planning.
Risk factors for DCI are primarily dive depth, dive time, and rates of ascent. Additional factors, such as altitude exposure soon after a dive, difficult diving conditions (e.g., colder water, currents, decreased visibility, wave action), dives to depths >60 ft (18 m), multiple consecutive days of diving or repetitive dives, overhead situations (e. g., diving in underwater caves or wrecks), strenuous exercise, and certain physiologic variables (e.g., dehydration), also increase risk. Caution divers to stay well hydrated and rested and dive within the limits of their training. Diving is a skill that requires training and certification and should be done with a well-trained, attentive companion (dive buddy).
Treatment of Diving Disorders
Definitive treatment of DCI begins with early recognition of symptoms, followed by recompression with hyperbaric oxygen. Be suspicious of any unusual symptoms occurring soon after a dive, especially neurological symptoms, and evaluate these properly. Provide a high concentration (100%) of supplemental oxygen; surface-level oxygen given for first aid might relieve the signs and symptoms of DCI and should be administered as soon as possible.
Because of either incidental causes, immersion, or DCI itself, which can cause capillary leakage, divers often are dehydrated. In most cases, treatment includes administering isotonic glucose-free intravenous fluids. Oral rehydration fluids also can be helpful, provided they can be administered safely (i.e., if the diver is conscious and can maintain their airway).
The definitive treatment of DCI is recompression and oxygen administration in a hyperbaric chamber. Stable or remitting symptoms of mild DCI (e.g., constitutional symptoms, some cutaneous sensory changes, limb pain, or rash) in divers reporting from remote locations without a hyperbaric facility might not require recompression. Medical management decisions made with the assistance of a qualified dive medicine physician also should account for the prevailing circumstances, logistics and hazards of evacuation, and the implications of failing to recompress. Serial neurologic exams are essential to the decision-making process.
Divers Alert Network (DAN) maintains 24-hour emergency consultation and evacuation assistance at +1-919-684-9111 (collect calls accepted). DAN can help with the medical management of injured divers by deciding if recompression is needed, providing the location of the closest recompression facility, and arranging patient transport. Divers and health care providers also can contact DAN for routine, nonemergency consultation by telephone at 919-684-2948, extension 6222, or by accessing the DAN.
Travelers who plan to scuba dive might want to ascertain whether recompression facilities are available at their destination before embarking on their trip.
The following authors contributed to the previous version of this chapter: Daniel A. Nord, Gregory A. Raczniak, James M. Chimiak
Brubakk AO, Neuman TS, Bennett PB, Elliott DH. Bennett and Elliott’s physiology and medicine of diving, 5th edition. London: Saunders; 2003.
Chapter 6: Pulmonary and Venous Disorders. In: J. Chimiak, editor. The heart & diving. Durham (NC): Divers Alert Network. Available from: https://dan.org/wp-content/uploads/2020/07/the-heart-and-diving-dan-dive-medical-reference.pdf.
Dear G, Pollock NW. DAN America dive and travel medical guide, 5th edition. Durham, NC: Divers Alert Network; 2009.
Divers Alert Network. Flying after diving. 2003. Available from: https://dan.org/research-reports/research-studies/flying-after-diving.
Mitchell SJ, Doolette DJ, Wachholz, CJ, Vann RD, editors. Management of mild or marginal decompression illness in remote locations. Sydney, Australia: Undersea and Hyperbaric Medical Society; 2004.
Moon RE. Treatment of decompression illness. In: Bove AA, Davis JC, editors. Bove and Davis’ diving medicine, 4th edition. Philadelphia: WB Saunders; 2004. pp. 195–223.
Neuman TS, Thom SR. Physiology and medicine of hyperbaric oxygen therapy. Philadelphia, PA: Saunders; 2008.
US Navy. The Navy diving manual revision 7. USA: Carlisle Military Library; 2018.
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