Certified Hyperbaric Technologist Practice Test 2025 – Comprehensive Exam Prep

To determine the partial pressure of oxygen (PO2) in the lungs of a person breathing pure oxygen at a depth of 33 feet of seawater, it is essential to understand the relationship between pressure, oxygen concentration, and the depth of water.

At sea level, atmospheric pressure is approximately 760 mmHg. When diving, for every 33 feet of seawater, the pressure increases by about one atmosphere (760 mmHg). Thus, at a depth of 33 feet, the total pressure is:

- Atmospheric pressure at sea level: 760 mmHg

- Additional pressure from 33 feet of seawater: 760 mmHg

Calculating this gives us a total pressure at 33 feet of approximately 1520 mmHg (760 mmHg + 760 mmHg).

Since the person is breathing pure oxygen, the entire inspired gas is composed of oxygen. Therefore, the partial pressure of oxygen can be calculated by simply taking the total pressure at that depth, which is 1520 mmHg.

This calculation underlines why the answer reflecting a PO2 of 1520 mmHg is accurate, as it aligns with the gas laws governing partial pressures under hyperbaric conditions.