Which factor increases the likelihood of CNS O2 toxicity?

Which factor increases the likelihood of CNS O2 toxicity?

• A. Longer dive duration
• B. Lower oxygen concentration
• C. High oxygen partial pressure
• D. Slower ascent

Answer: (C)

Oxygen partial pressure in the breathing gas is the key determinant of CNS O2 toxicity. The brain is sensitive to how much oxygen is being delivered in a hyperoxic environment, so higher partial pressures of O2 increase the risk of central nervous system symptoms, including dizziness, vision changes, twitching, and seizures. In closed-circuit diving, the partial pressure of O2 you breathe equals the O2 fraction times the ambient pressure; as you go deeper or use oxygen-rich mixes, that partial pressure rises, raising the danger of CNS toxicity. The longer you stay exposed to high pO2, the greater the chance of reaching toxic levels, but the essential factor is the actual pO2 value, not just time. Reducing the oxygen concentration lowers pO2 and lowers risk, while slower ascent mainly affects other issues like decompression and surface-to-depth pressure changes rather than CNS O2 toxicity directly.

Oxygen partial pressure in the breathing gas is the key determinant of CNS O2 toxicity. The brain is sensitive to how much oxygen is being delivered in a hyperoxic environment, so higher partial pressures of O2 increase the risk of central nervous system symptoms, including dizziness, vision changes, twitching, and seizures. In closed-circuit diving, the partial pressure of O2 you breathe equals the O2 fraction times the ambient pressure; as you go deeper or use oxygen-rich mixes, that partial pressure rises, raising the danger of CNS toxicity. The longer you stay exposed to high pO2, the greater the chance of reaching toxic levels, but the essential factor is the actual pO2 value, not just time. Reducing the oxygen concentration lowers pO2 and lowers risk, while slower ascent mainly affects other issues like decompression and surface-to-depth pressure changes rather than CNS O2 toxicity directly.