PADI Divemaster Certification Practice Exam

What effect do dissolved gases in the body have on tissues beneath the surface?

1. They create a vacuum

2. They exert pressure

3. They dissolve completely

4. They are harmless

The correct answer is: They exert pressure

Dissolved gases in the body, such as nitrogen and oxygen, exert pressure on tissues at depths during a dive. As a diver descends, the pressure increases, and this adjustment affects how gases behave in the body. The gases are under increased pressure, which influences their solubility in the body's fluids and tissues according to Henry's Law, stating that the amount of gas that dissolves in a liquid is directly proportional to the pressure of that gas. When a diver ascends, the surrounding pressure decreases, which can lead to the formation of bubbles if the dissolved gases come out of solution too quickly. This process exemplifies why understanding the effects of dissolved gases is crucial to preventing decompression sickness. The other options suggest concepts that do not accurately represent the physiological changes occurring in the body under increased pressure, such as the misconception that gases create a vacuum, dissolve completely, or are harmless when, in fact, their management is vital for safe diving practices.