Certified Hyperbaric Technologist Practice Test

What happens to air volume in the body during ascent after diving due to decreasing pressure?

1. It increases

2. It decreases

3. It remains the same

4. It becomes negative

The correct answer is: It increases

During ascent after diving, the pressure surrounding the body decreases. According to Boyle's Law, which states that the volume of a gas is inversely proportional to its pressure at a constant temperature, a decrease in external pressure will lead to an increase in the volume of gas within the body. As a diver ascends, the nitrogen and other gases dissolved in the tissues and those present in body cavities (such as the lungs and sinuses) expand because the surrounding pressure is less than it was at a greater depth. This increase in volume can lead to various physiological effects, such as the potential for barotrauma if proper ascent protocols are not followed, as well as the risk of decompression sickness if the dissolved gases come out of solution too quickly. Understanding this principle is crucial for the safety and health of divers during ascent.