Decompression sickness, commonly known as “the bends,” is a condition affecting individuals exposed to rapid pressure changes, like scuba divers. It occurs when gases dissolved in the body form bubbles as external pressure decreases too quickly. This article explains the mechanisms behind decompression sickness, its risk factors, and essential prevention and response steps.
What are the Bends?
The human body absorbs gases from the air we breathe, primarily nitrogen and oxygen. During a dive, increased pressure underwater causes more of these gases, especially nitrogen, to dissolve into the body’s tissues and blood. This occurs because air under high pressure contains more gas molecules per breath. The body continuously uses oxygen, but nitrogen, being an inert gas, accumulates in the tissues.
If pressure is reduced too quickly, such as during a rapid ascent from a dive, the accumulated nitrogen comes out of solution and forms gas bubbles within the blood and tissues. These bubbles can expand, injure tissues, or block blood vessels, leading to various symptoms.
Depth and Pressure’s Influence
There is no single “magic depth” at which decompression sickness (DCS) automatically occurs; rather, the risk significantly increases with both depth and the duration spent at that depth. As a diver descends, pressure increases, causing gases to compress and more nitrogen to dissolve into the body. For instance, at 33 feet of seawater, the pressure doubles compared to the surface, and pressure continues to increase by one atmosphere for every additional 33 feet of depth.
This relationship is partly explained by Henry’s Law, which states that the amount of gas dissolved in a liquid is proportional to the partial pressure of that gas above the liquid. Deeper dives mean higher partial pressures of nitrogen, leading to more nitrogen dissolving into tissues. Boyle’s Law also plays a role, as it describes how gas volume decreases with increasing pressure and expands with decreasing pressure. Even relatively shallow dives can lead to DCS if ascent procedures are not followed correctly, or if other risk factors are present.
Other Factors Increasing Risk
While depth and dive duration are primary considerations, several other factors can increase susceptibility to decompression sickness. Rapid ascent rates are a major contributor, as they do not allow sufficient time for nitrogen to safely leave the body. Extended bottom times and repetitive dives can lead to a buildup of residual nitrogen.
Physiological factors also play a role, including dehydration, which can slow circulation and hinder efficient nitrogen off-gassing. Being cold during a dive, experiencing fatigue, or engaging in strenuous exertion immediately after a dive can also elevate risk. Individual health conditions, such as higher body fat content and age, can further increase a diver’s risk.
Preventing Decompression Sickness
Preventing decompression sickness involves adhering to established safety protocols. Divers should always follow dive tables or dive computer limits, which provide guidelines for safe depth and time exposures.
Maintaining a slow and controlled ascent rate, typically no faster than 30 feet per minute, is crucial. Performing safety stops, usually for 3 to 5 minutes at a depth of 15 to 20 feet, provides extra time for dissolved nitrogen to escape before surfacing. Avoiding “yo-yo” diving, which involves multiple rapid ascents and descents, helps prevent excessive bubble formation. Proper hydration before and after dives is important. Additionally, avoiding strenuous exercise and heavy alcohol consumption immediately after diving can help reduce risk.
Recognizing and Responding
Recognizing the signs and symptoms of decompression sickness is vital for timely intervention. Common symptoms include joint pain and skin manifestations like rashes or itching. More severe symptoms may involve neurological issues like numbness, tingling, muscle weakness, unsteadiness, or vertigo. Individuals may also experience fatigue, difficulty breathing, or chest pain.
If decompression sickness is suspected, immediate medical attention is necessary. The affected individual should be kept lying flat, and 100% oxygen should be administered if available. Transport to a recompression chamber, where the individual is placed in a high-pressure environment to reduce bubble size and allow for gradual off-gassing, is the definitive treatment. Delaying treatment can negatively affect the outcome and potentially lead to long-term complications.