Which physical effect is described as due to nitrogen bubbles expanding in the blood during rapid decompression?

• A. Chest and joint pain caused by nitrogen bubbles in the blood expanding
• B. Severe ear and sinus pain
• C. Forced expulsion of air
• D. You will feel very cold

Answer: (A)

Rapid decompression lowers the ambient pressure, causing dissolved nitrogen in the blood to come out of solution and form bubbles. These bubbles can irritate or obstruct tissues and vessels, especially in joints and the chest, leading to chest and joint pain—the classic presentation of decompression illness. Ear and sinus pain results from pressure changes in air-filled spaces, not primarily from nitrogen bubbles in the blood. Forced expulsion of air is a different barotrauma effect, and feeling very cold isn’t the main consequence of nitrogen bubble expansion in the bloodstream.