Barotrauma during ascent is due to expansion of gas in body cavities. Which of the following is the correct mechanism?

Barotrauma during ascent is due to expansion of gas in body cavities. Which of the following is the correct mechanism?

• A. Contraction of gas in body cavities
• B. Increased ambient pressure
• C. Infection
• D. Expansion of gas in body cavities

Answer: (D)

Barotrauma during ascent occurs because gas trapped in body cavities expands when external pressure falls. Gas volume increases as pressure decreases (Boyle’s law), so air in closed spaces like the middle ear, sinuses, or any gas-filled compartments can overexpand. If that gas cannot escape quickly enough, the expanding volume raises pressure on surrounding tissues, leading to membrane rupture or tissue injury—the hallmark of barotrauma. This is why expansion of gas in body cavities is the correct mechanism. Contraction of gas would require higher external pressure, which isn’t happening during ascent. Infection isn’t driven by these pressure changes, and increased ambient pressure isn’t what occurs during ascent (it happens with descent).

Barotrauma during ascent occurs because gas trapped in body cavities expands when external pressure falls. Gas volume increases as pressure decreases (Boyle’s law), so air in closed spaces like the middle ear, sinuses, or any gas-filled compartments can overexpand. If that gas cannot escape quickly enough, the expanding volume raises pressure on surrounding tissues, leading to membrane rupture or tissue injury—the hallmark of barotrauma.

This is why expansion of gas in body cavities is the correct mechanism. Contraction of gas would require higher external pressure, which isn’t happening during ascent. Infection isn’t driven by these pressure changes, and increased ambient pressure isn’t what occurs during ascent (it happens with descent).