Exposure to elevated barometric pressure during hyperbaric oxygen therapy can directly affect a number of physiologic parameters, including which of the following?

1. Arterial and alveolar partial pressure for oxygen
2. Temperature of the gases being breathed
3. Work of breathing
4. Lung volumes
a. 1 and 2 c. 2, 3, and 4
b. 1 and 4 d. 1, 2, 3, and 4

ANS: D
The effect of increased ambient pressure on the partial pressure of alveolar oxygen (PAO2) can be explained by Dalton's law, which states that the total pressure of a gas mixture, such as air, equals the sum of the partial pressures of each of the constituent gases in the mixture. According to Gay-Lussac's law, if the volume of a gas remains constant, there is a direct relationship be-tween the absolute pressure of a gas and its temperature. It is reasonable to suggest that if the volume of a hyperbaric chamber remains constant, then increasing the pressure would raise the temperature inside of the chamber.