Why is an AED not authorized at depth?

• A. The shock from an AED presents an electrical hazard when surrounded by compressed 100% O2
• B. AEDs are too sensitive to pressure changes
• C. AEDs cannot function underwater
• D. AEDs require a direct electrical connection to the patient

Answer: (A)

AED use at depth is avoided because the electrical shock can ignite an oxygen-rich environment. In diving scenarios, breathing gas can be highly enriched with oxygen, especially when cylinders or supplemental oxygen are involved. The defibrillator’s electrical discharge can produce heat or sparks that, in the presence of compressed 100% oxygen, raise the risk of ignition and fire. That fire/explosion hazard outweighs any potential benefit of delivering a shock underwater, so these devices aren’t authorized at depth. In water, other practical issues would also complicate use, but the primary safety concern is the danger of ignition in an oxygen-rich atmosphere.