PADI Divemaster Certification Practice Exam

How do the lungs respond to pressure changes during ascent?

1. Increased pressure compresses the lungs

2. Expansion of air occurs within the lungs

3. The lungs become unbalanced with ambient pressure

4. Pressure changes directly affect lung volume

The correct answer is: Expansion of air occurs within the lungs

The option indicating that expansion of air occurs within the lungs accurately describes the physiological response to pressure changes during an ascent. As a diver ascends, the ambient pressure decreases. According to Boyle’s Law, which states that the volume of a gas is inversely proportional to pressure, the decrease in external pressure allows the air trapped in the lungs to expand. As the volume of the gas increases, measures must be taken to equalize the pressure within the lungs to avoid issues such as overexpansion or barotrauma. Therefore, it's crucial that divers exhale during ascent to release air and maintain balanced pressures within and outside of their lungs, preventing any harmful consequences associated with sudden expansions of gas. The other choices relate to different aspects of pressure dynamics but do not capture the direct response of the lungs during ascent as accurately.