Scuba Diving International (SDI) Computer Nitrox Practice Exam

Which factor does NOT increase susceptibility to oxygen toxicity?

1. Scar tissue in the sinuses

2. High oxygen partial pressure

3. Duration of exposure to oxygen

4. High physical activity levels

The correct answer is: Scar tissue in the sinuses

Scar tissue in the sinuses does not increase susceptibility to oxygen toxicity. Oxygen toxicity generally arises from environmental conditions that expose the body to high levels of oxygen, particularly at higher pressures, which increase the partial pressure of oxygen in the tissues. High partial pressure of oxygen, which can occur during deep dives or when utilizing oxygen-enriched air, significantly increases the risk of toxicity because higher pressures drive more oxygen into the body's tissues. Similarly, the duration of exposure plays a crucial role; the longer one is exposed to elevated oxygen levels, the greater the potential for toxic effects to develop. High physical activity levels also contribute because exertion can elevate oxygen consumption, leading to increased metabolic rates and potential for toxicity under elevated pressure conditions. On the other hand, while scar tissue in the sinuses can influence normal respiratory function, it does not directly affect the body's response to oxygen at pressure. The presence of scar tissue does not increase the likelihood or severity of oxygen toxicity in the same manner that elevated partial pressures, prolonged exposure, or strenuous activity can.