A diver with joint pain, pruritus, paralysis, hypoxemia, dyspnea, wheezing, and AMS after ascent most likely has which diagnosis and pathophysiology?

• A. Pulmonary embolism; blood clot
• B. Decompression sickness; tissues release gas
• C. Fat embolism; lipid emboli
• D. Arterial gas embolism; air in arteries

Answer: (B)

Nitrogen coming out of solution during ascent forms gas bubbles in tissues and blood, disrupting microcirculation and triggering a cascade of symptoms. In divers this creates the bends—joint and muscle pain—from bubbles in synovial spaces and tissues; pruritus from cutaneous bubbles; neurologic symptoms such as weakness, paralysis, or altered consciousness when bubbles affect the brain or spinal cord; and pulmonary signs like hypoxemia and dyspnea with wheezing from bubbles in the lungs causing ventilation-perfusion mismatch and airway irritation. The overall picture after ascent is classic for decompression sickness due to inert gas bubbles obstructing vessels and provoking inflammation. This differs from arterial gas embolism, which stems from barotrauma causing air to enter arterial circulation, or from fat embolism or a thromboembolic pulmonary event, which have different initiating events and symptom patterns. Hyperbaric oxygen therapy is the key treatment to shrink bubbles and promote nitrogen washout.