How does increased depth affect the PPO2 of a Nitrox mix?

The choice that asserts PPO2 increases with depth is correct because as a diver descends, the pressure surrounding them increases. The partial pressure of oxygen (PPO2) in a gas mixture is influenced by the total pressure exerted on it. According to Dalton's Law, the partial pressure is directly proportional to the total pressure.

For instance, at sea level, the atmospheric pressure is about 1 atmosphere (ATA), and if a diver is using a Nitrox mix consisting of a higher percentage of oxygen, this increased pressure at greater depths causes the PPO2 to rise. For every 10 meters (or approximately 33 feet) of sea water, the overall pressure increases by about 1 ATA. This results in the PPO2 proportionally increasing, since it's based on both the concentration of oxygen in the mix and the surrounding pressure.

In scenarios where divers are using Nitrox, it is essential to monitor PPO2 to prevent oxygen toxicity, which can occur at higher partial pressures. As a diver goes deeper, even with the same Nitrox mixture, the PPO2 will continue to increase due to the higher ambient pressure. This is critical knowledge for safe diving practices and understanding the implications of depth on gas mixtures.