PADI Divemaster Certification Practice Exam

How does the body respond to breath-hold diving?

1. Oxygen levels drop and CO2 levels drop

2. Oxygen levels increase and CO2 levels increase

3. Oxygen levels drop and CO2 levels rise

4. There is no significant change in gas levels

The correct answer is: Oxygen levels drop and CO2 levels rise

The body's response to breath-hold diving involves a physiological mechanism that significantly affects gas levels in the blood. As a diver holds their breath underwater, the body begins to consume the available oxygen for metabolic processes, leading to a decrease in oxygen levels. Simultaneously, carbon dioxide (CO2) is produced as a by-product of metabolism. This causes CO2 levels to rise in the bloodstream. The increase in CO2 levels is particularly significant because it triggers the urge to breathe. This response is critical for maintaining homeostasis, as rising CO2 levels lead to changes in blood pH and can prompt discomfort and the need to surface for air. Therefore, during breath-hold diving, while oxygen levels drop due to consumption, CO2 levels rise as a result of metabolic processes. Understanding this balance is crucial for divers, as it helps explain the importance of breath control, the limits of breath-holding, and the physiological signals that indicate it’s time to surface and take a breath.