How does ambient pressure influence PPO2 during a dive?

The relationship between ambient pressure and partial pressure of oxygen (PPO2) during a dive is rooted in the principles of gas behavior under pressure. As a diver descends, the ambient pressure increases because of the water column above them. According to Dalton's Law, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each gas in that mixture.

When a diver goes deeper, not only does the ambient pressure increase, but so does the partial pressure of the gases inhaled—particularly oxygen in this context. Since the air we breathe at the surface is composed of approximately 21% oxygen, the PPO2 can be calculated using the formula:

PPO2 = (percentage of oxygen in the mixture) × (ambient pressure)

As depth increases, the ambient pressure increases, and since the percentage of oxygen stays constant in air, the PPO2 directly increases as well. This rise in PPO2 has significant implications for divers, especially regarding the risk of oxygen toxicity when diving at greater depths.

This understanding emphasizes the importance of monitoring the depth and associated PPO2 levels to enhance safety and effectively manage dive profiles. The other options imply that PPO2 either decreases, remains constant, or is unrelated to depth, which