What is the primary mechanism behind decompression sickness (DCS) when moving from high to low ambient pressure?

What is the primary mechanism behind decompression sickness (DCS) when moving from high to low ambient pressure?

• A. Increased ambient pressure causing compression of tissues and gas dissolution.
• B. Reduction in ambient pressure causing formation of gas bubbles from dissolved inert gases in tissues, with inadequate elimination after ascent.
• C. Microorganisms producing gas within tissues.
• D. Thermal injury to lipid membranes causing bubble formation.

Answer: (B)

Rapid ascent into lower ambient pressure allows nitrogen dissolved in body tissues to come out of solution and form gas bubbles. Under high pressure, more nitrogen is dissolved in tissues; when the pressure drops, the dissolved nitrogen becomes supersaturated and exsolves as bubbles in tissues and blood. If the rate of ascent is too fast or the body cannot eliminate the gas quickly enough, these bubbles obstruct microcirculation and trigger inflammatory and tissue injury, producing the symptoms of decompression sickness. This is why the mechanism involves formation of gas bubbles from dissolved inert gas due to reduced pressure after ascent. The other options describe processes that don’t match this mechanism: increased pressure dissolves gas rather than forming bubbles, microorganisms aren’t the cause, and thermal injury isn’t involved in DCS.

Rapid ascent into lower ambient pressure allows nitrogen dissolved in body tissues to come out of solution and form gas bubbles. Under high pressure, more nitrogen is dissolved in tissues; when the pressure drops, the dissolved nitrogen becomes supersaturated and exsolves as bubbles in tissues and blood. If the rate of ascent is too fast or the body cannot eliminate the gas quickly enough, these bubbles obstruct microcirculation and trigger inflammatory and tissue injury, producing the symptoms of decompression sickness. This is why the mechanism involves formation of gas bubbles from dissolved inert gas due to reduced pressure after ascent. The other options describe processes that don’t match this mechanism: increased pressure dissolves gas rather than forming bubbles, microorganisms aren’t the cause, and thermal injury isn’t involved in DCS.