Decompression Sickness (The Bends)

Decompression sickness, commonly known as “the bends,” is a multisystem disorder caused by the sudden and irregular release of dissolved inert gases (primarily nitrogen or helium) from tissues when exposed to pressure changes, leading to the formation of gas bubbles. This condition typically occurs when rapidly ascending from pressurized environments, such as during scuba diving. Bubbles may form within blood vessels, outside blood vessels, or in intracellular and intercellular spaces.

Physical Basis

Decompression sickness is physiologically explained by Henry’s Law. According to this law, at constant temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas. During diving, as ambient pressure increases, the amount of inhaled gases dissolved in tissues also increases. If the ambient pressure drops rapidly during ascent, these dissolved gases may form bubbles. The quantity of gas in tissues depends not only on depth but also on the duration of exposure at that depth. Inappropriate ascents increase the likelihood of bubble formation.

Image of a Diver (Generated by Artificial Intelligence)

Pathophysiology

Intravascular bubbles can obstruct blood vessels, leading to ischemia, hypoxia, and edema. Extravascular bubbles cause cellular damage by exerting mechanical pressure on tissues. These physical effects trigger inflammatory responses. Events such as endothelial injury, platelet activation, neutrophil accumulation, and coagulation system stimulation increase vascular permeability and disrupt blood flow. Biochemical processes contribute to secondary pathological mechanisms that exacerbate disease severity.

Epidemiology and Risk Factors

Decompression sickness most commonly affects divers but can also occur in astronauts, individuals working in pressurized environments, and aviators who ascend rapidly to high altitudes. Risk factors include depth, duration of dive, rapid ascent, inadequate decompression, dehydration, obesity, advanced age, cold water exposure, physical exertion, and repetitive dives. The relationship between gender, menstruation, and oral contraceptive use remains unclear.

Classification and Clinical Features

Type 1 Decompression Sickness:

It primarily affects the skin, musculoskeletal system, and lymphatic system. Typical manifestations include joint pain (especially in the shoulders, elbows, hips, and knees), itching, marbled skin lesions (cutis marmorata), and lymphedema.

Type 2 Decompression Sickness:

Characterized by neurological, cardiopulmonary, and inner ear symptoms. Spinal cord involvement may result in paraplegia, sensory loss, and sphincter dysfunction. Cardiopulmonary manifestations include chest pain, dyspnea, and frothy sputum. Inner ear symptoms include vertigo, hearing loss, and tinnitus.

Diagnosis and Evaluation

Diagnosis is based on history and physical examination. Depth, duration, and rate of ascent must be assessed. Laboratory tests (complete blood count, creatine kinase, etc.) and imaging modalities (chest X-ray, CT, MRI) may provide supportive information. However, these tests have limited sensitivity for diagnosis and are primarily used for differential diagnosis.

Treatment

Initial Management:

Administration of 100% oxygen is essential. Oxygen therapy reduces tissue hypoxia, shrinks bubbles, and accelerates elimination of inert gases. Conscious patients should receive oral isotonic fluids; others should receive intravenous isotonic fluids. Fluids containing glucose or hypotonic solutions should be avoided.

Recompression Therapy (Hyperbaric Oxygen):

The most effective treatment for decompression sickness is hyperbaric oxygen therapy (HBOT). It reduces bubble volume, enhances oxygenation, and suppresses inflammation. Early application yields high success rates, but HBOT can still be effective in delayed cases. Severe cases may require multiple sessions.

Differential Diagnosis

Decompression sickness may be confused with air embolism and pulmonary barotrauma. Air embolism typically occurs after uncontrolled, rapid ascent and presents with neurological symptoms affecting the brain. Decompression sickness, by contrast, often involves spinal cord pathology. The timing of symptom onset, dive profile, and pattern of symptom distribution aid in differential diagnosis.

Prevention

Proper training before diving, adherence to dive tables, slow and controlled ascent, adequate surface intervals, and medical evaluation are fundamental preventive measures. It is recommended to avoid air travel within the first 24 hours after diving.

Decompression sickness is a multisystem disorder that occurs in environments exposed to pressure, such as scuba diving, and is characterized by gas bubbles formed by inert gases in tissues. Clinical manifestations range from mild joint pain to severe neurological deficits. Diagnosis relies primarily on history and physical examination; treatment is based on oxygen support and hyperbaric oxygen therapy. Prevention depends critically on adherence to diving protocols, education, regular health assessments, and compliance with ascent procedures. With early diagnosis and timely treatment, most patients achieve full recovery.

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