Type 2 Decompression Sickness symptoms are most accurately attributed to which mechanism?

• A. Air embolism in the pulmonary artery
• B. Non-cardiogenic pulmonary edema from activation of the inflammatory cascade
• C. Small air emboli in the alveolar-capillary membranes
• D. Air emboli in the CSF altering the responses of central chemoreceptors

Answer: (B)

The main concept is how Type 2 decompression sickness causes lung symptoms. In Type 2 DCS, inert-gas bubbles trigger an inflammatory response that activates white blood cells and inflammatory mediators, which makes the pulmonary capillaries more permeable. This capillary leak leads to non-cardiogenic pulmonary edema, producing dyspnea and hypoxemia without the heart actually failing or large airway blockages. That inflammatory edema pattern fits Type 2 DCS best, explaining why the pulmonary symptoms arise from edema driven by inflammation rather than simply from a bubble obstructing a vessel.

Air embolism in the pulmonary artery would imply a focal vascular blockage causing abrupt hemodynamic effects, not the diffuse edema driven by inflammation. Small air emboli at the alveolar-capillary membranes could impair gas exchange, but the dominant mechanism for Type 2’s pulmonary involvement is the inflammatory cascade causing edema rather than discrete emboli. Air emboli in the CSF would produce neurologic effects related to central nervous system signaling, not the pulmonary edema pattern.