Decompression Sickness (DCS) is a medical condition resulting from a rapid reduction in the pressure surrounding the body, most commonly associated with scuba diving. Often referred to as “the bends,” DCS occurs when moving too quickly from a high-pressure environment to a lower-pressure one. Symptoms can range from mild joint discomfort to life-threatening neurological collapse. Understanding how this illness manifests is crucial for those who engage in activities that put them at risk.
How Decompression Sickness Occurs
The human body absorbs inert gases, primarily nitrogen, from the air we breathe. Under increased ambient pressure, such as when a diver descends underwater, more of this gas dissolves into the body’s tissues to maintain equilibrium. This process, called saturation, is normal as long as the pressure remains high.
Problems begin when the surrounding pressure decreases too quickly, such as during a rapid ascent. The dissolved inert gas, no longer held in solution, comes out of the tissues and forms bubbles in the blood and other body structures. Excessive bubble formation can mechanically obstruct blood flow, distort tissues, and trigger inflammatory responses. The location and size of these bubbles directly determine the type and severity of the symptoms experienced.
Type I Symptoms: The Painful Manifestations
Type I Decompression Sickness is the origin of the term “the bends.” The most frequent complaint is pain, typically localized in or around the large joints of the arms and legs, such as the shoulders, elbows, hips, and knees. This pain is often described as deep, aching, throbbing, or a “boring” sensation that can be severe.
The pain does not typically increase with movement of the joint. In addition to joint pain, Type I symptoms can involve the skin, manifesting as intense itching (pruritus) or a rash. A specific skin manifestation, known as cutis marmorata, appears as a mottled, marbled, or net-like discoloration on the skin. General symptoms like unusual fatigue, malaise, and muscle aches are also common.
Type II Symptoms: Neurological and Respiratory Danger
Type II Decompression Sickness involves the central nervous system, respiratory system, or circulatory system. Neurological manifestations are the most common and dangerous feature, resulting from bubbles forming in or traveling to the brain and spinal cord. Symptoms include numbness, tingling, sensory changes, muscle weakness, impaired gait, or full paralysis.
If the bubbles affect the inner ear, a person may experience severe vertigo, unsteadiness (“staggers”), hearing loss, or persistent ringing in the ears (tinnitus). More severe neurological involvement can present as stroke-like symptoms, including confusion, vision loss, severe headache, and loss of consciousness. A rare but grave form is pulmonary DCS, known as “the chokes,” which occurs when bubbles obstruct circulation in the lungs, causing a dry, persistent cough, chest pain, and worsening difficulty breathing.
Immediate Response and Medical Treatment
Recognizing any symptom of Decompression Sickness requires an immediate and decisive response. The first action is to stop all physical activity and immediately administer 100% oxygen via a tight-fitting non-rebreather mask, if available. High-flow oxygen is a crucial first aid measure that helps accelerate the elimination of inert gas from the body.
The affected person should be kept lying flat and warm while emergency medical services are contacted. Rapid transport to a facility with a hyperbaric chamber is the definitive treatment for DCS. Inside the chamber, the patient undergoes recompression, breathing 100% oxygen at increased atmospheric pressure. This pressure reduces the size of the gas bubbles, forcing the gas back into solution so it can be safely eliminated. Timely treatment is paramount.