Which statement best describes the mechanism underlying decompression sickness?

• A. Oxygen toxicity
• B. Infectious agents
• C. Formation of inert gas bubbles in tissues and blood during rapid decompression
• D. Barotrauma

Answer: (C)

Rapid decompression causes inert gas, mainly nitrogen, to come out of solution and form bubbles in the blood and tissues. At depth, nitrogen dissolves in fats and liquids under the increased pressure; when ascent happens quickly, the ambient pressure drops and those dissolved amounts become supersaturated, nucleating into gas bubbles. These bubbles can block small vessels and injure tissue, producing symptoms that depend on where the bubbles form—joint pain from bubbles in joints, neurologic signs from bubbles in the brain or spinal cord, or chest symptoms from bubbles in the lungs. This mechanism is distinct from oxygen toxicity (driven by high oxygen partial pressure), infectious disease, or barotrauma (tissue injury from pressure change rather than bubble formation). Hyperbaric oxygen therapy treats decompression sickness by recompressing to shrink and dissolve the bubbles while delivering high-percentage oxygen.