Which of the following is defined by nitrogen bubbles in the bloodstream?

• A. Drowning
• B. Barotrauma
• C. Decompression Sickness
• D. Air Embolism

Answer: (C)

When ambient pressure drops rapidly, dissolved nitrogen comes out of solution and forms gas bubbles in the blood and tissues. This is why this condition is called decompression sickness: the inert nitrogen bubbles disrupt microcirculation and provoke tissue injury and inflammation as they expand and block vessels. In divers or pilots who ascend too quickly, these bubbles can affect joints (causing pain known as “the bends”), the skin, lungs, and especially the brain, leading to dizziness, confusion, weakness, or chest symptoms.

This differs from drowning, which is the result of water entering the airways and causing hypoxia; barotrauma, which is tissue injury from pressure changes in air-filled spaces like the ears or lungs; and air embolism, which involves gas bubbles entering the bloodstream from external air sources or trauma rather than nitrogen coming out of solution due to rapid decompression. In decompression sickness the hallmark is nitrogen bubbles formed in the bloodstream and tissues after a rapid decrease in pressure, rather than air entering the circulation from outside.