Scuba Diving International (SDI) AFS 270 Practice Test

When decompression sickness is suspected, the top priority is to maximize oxygen delivery to the body and speed up the elimination of dissolved nitrogen. Administering 100% oxygen provides the best first-aid measure because it raises the amount of oxygen in the blood and tissues, while creating a gradient that accelerates nitrogen off-gassing from tissues and any bubbles. This approach helps reduce symptoms and supports tissue perfusion while you arrange for definitive treatment, such as recompression in a hyperbaric chamber. The other options don’t address this essential need. Inflating the buoyancy control device could worsen symptoms by affecting buoyancy and circulation. Verifying the dive computer or checking air tank pressure doesn’t treat the physiological issue at hand and won’t relieve symptoms. After giving oxygen, seek prompt medical treatment and follow established care guidelines (keep warm, avoid exertion, and arrange hyperbaric assessment).