What ppO2 level is associated with the occurrence of blackout and death in the human body?

The partial pressure of oxygen (ppO2) is a critical factor in diving physiology and can have serious implications for divers. The correct answer reflects the level at which the risks become life-threatening. Specifically, a ppO2 level of 1.6 ata is associated with harmful effects, including the potential for hyperoxia, which can lead to symptoms such as convulsions or a loss of consciousness, commonly referred to as blackout.

At this elevated pressure, the body experiences an increase in oxygen toxicity, which can affect the central nervous system. This is particularly relevant in the context of deep diving and the use of enriched air or nitrox, where divers are exposed to higher levels of oxygen than what is present in breathable air. Understanding this threshold is crucial for safety in diving practices.

The other options reflect significantly lower partial pressures of oxygen, which generally do not lead to acute toxic effects or immediate risks of blackout. Thus, recognizing that 1.6 ata is the threshold for severe complications in the context of oxygen exposure helps divers maintain greater awareness of the risks involved in their activities.