Decompression syndrome (DCS) is a medical condition that arises from rapid changes in ambient pressure, most commonly associated with scuba diving. It occurs when dissolved gases, primarily nitrogen, form bubbles within the body’s tissues and bloodstream as pressure decreases too quickly. DCS can range from mild discomfort to severe, life-threatening complications, making it a serious concern for individuals exposed to significant pressure variations.
How Decompression Syndrome Develops
Under increased pressure, such as during a dive, inert gases like nitrogen from the breathing gas dissolve into the body’s tissues and fluids. The deeper and longer the exposure to pressure, the more gas dissolves into the body. As a person ascends and the surrounding pressure decreases, these dissolved gases begin to come out of solution.
If the ascent is too rapid, the dissolved gas cannot be eliminated quickly enough through normal respiration, leading to supersaturation in the tissues. This supersaturation causes gas to form bubbles within the blood vessels and tissues. These bubbles can then block blood flow (embolism) or directly compress nerves and distort tissues, leading to pain and dysfunction.
Decompression syndrome is categorized into two main types. Type I DCS is less severe, typically affecting the musculoskeletal system and skin. Type II DCS is more serious, often involving the neurological, cardiopulmonary, or inner ear systems.
Recognizing the Signs
The symptoms of decompression syndrome can vary significantly, ranging from subtle discomfort to severe neurological impairment. While symptoms can manifest immediately after surfacing, about 50% of individuals experience them within one hour, and 90% within six hours. In rare instances, symptoms may appear as late as 24 to 48 hours after exposure, particularly with subsequent altitude exposure like air travel.
Common manifestations of Type I DCS include localized deep pain in the joints, particularly in the arms or legs. Skin symptoms like itching, mottling, or rashes can occur. Fatigue and a general feeling of malaise are also reported.
Type II DCS presents with more severe symptoms, often impacting the nervous system. These can include numbness, tingling, and weakness in the limbs, potentially progressing to paralysis. Neurological signs include dizziness, vertigo, unsteadiness, difficulty with urination or bowel control, headaches, and visual disturbances. Respiratory symptoms, known as “the chokes,” are a grave manifestation, characterized by shortness of breath, chest pain, and a cough resulting from pulmonary edema.
Factors Increasing Risk
Several factors can increase an individual’s susceptibility to decompression syndrome. Environmental factors play a role, with deeper and longer dives increasing the amount of inert gas dissolved in tissues. A rapid ascent rate is a primary trigger, as it prevents safe off-gassing through the lungs. Repeated dives within a short period also heighten risk because excess nitrogen can remain dissolved in tissues.
Physiological factors also contribute to DCS risk. Dehydration can increase nitrogen concentration in the blood, increasing bubble formation. Older age can increase risk. Obesity is a factor, as nitrogen dissolves readily in fat.
Cold water exposure, exertion, and fatigue also contribute. Pre-existing medical conditions, such as a patent foramen ovale (a small opening between the heart’s upper chambers), can allow bubbles to bypass the lungs and enter the arterial circulation, increasing the risk of severe DCS.
Emergency Response and Treatment
Immediate action is important if decompression syndrome is suspected. First steps involve basic life support: remove the person from water if submerged, keep them lying flat and still, and keep them warm. Administering 100% oxygen through a non-rebreather mask is a primary first aid measure, as high oxygen concentrations can help reduce symptoms and facilitate gas elimination. Prompt transportation to the nearest hyperbaric facility is necessary.
The definitive medical treatment for DCS is recompression therapy in a hyperbaric chamber. This therapy involves placing the patient in a pressurized chamber and administering pure oxygen at pressures equivalent to 60 feet (18 meters) of seawater. The increased pressure helps to reduce the size of the gas bubbles in the body, forcing them back into a dissolved state. As the patient breathes pure oxygen, it creates a larger gradient for inert gases to diffuse out of tissues and be eliminated. The pressure is then gradually reduced to normal atmospheric pressure over several hours, allowing for safe off-gassing.
Preventive Measures
Preventing decompression syndrome requires careful planning. Divers should carefully plan their dives, considering depth, duration, and ascent rates. Using a dive computer is recommended, as these devices provide real-time data on depth, time, and no-decompression limits, calculating safe ascent profiles. Dive tables also provide schedules for safe ascent.
Making slow and controlled ascents is a primary way to prevent bubble formation, with a recommended rate of no faster than 60 feet (18 meters) per minute. Performing a safety stop, a pause at 15 feet (5 meters) below the surface, allows additional time for nitrogen to off-gas safely before surfacing. Maintaining proper hydration by drinking plenty of water before and after dives is important, while avoiding alcohol and caffeine, as they contribute to dehydration. Allowing adequate surface intervals between dives is also important, with recommendations for flying after diving typically 12 to 18 hours or more.