Certified Hyperbaric Technologist Practice Test 2026 – Comprehensive Exam Prep

The partial pressure of oxygen (PO2) in the lungs of a person breathing air at sea level is approximately 100 mmHg. This value is derived from the composition of air, which is about 21% oxygen. At sea level, the atmospheric pressure is around 760 mmHg. To calculate the PO2, you multiply the total atmospheric pressure by the fractional concentration of oxygen in the air.

So, 21% of 760 mmHg is about 160 mmHg. However, the PO2 in the alveoli, where gas exchange occurs, is lower due to the presence of water vapor and the mixing of fresh air with residual air in the lungs. This gas exchange process leads to the alveolar PO2 being around 100 mmHg, which allows sufficient oxygen to be available for diffusion into the blood.

Understanding this context is crucial for anyone working in hyperbaric medicine, as it highlights the relationships between altitude, pressure, and gas exchange in the lungs.