During open water certification, a scuba diver is taught that the most important rule in scuba diving is to breathe continuously and to avoid holding his breath underwater. But why is this rule so important?
Scuba diving is different from snorkeling or free diving. When a snorkeler or freediver takes a breath from the surface and dives down, the air in his lungs compresses due to the pressure of the water.
Steps to Avoid a Pulmonary Barotrauma
A lung over-pressurization injury is known as a pulmonary barotrauma, and can occur at both microscopic and macroscopic levels if a diver holds his breath and ascends. A pulmonary barotrauma is a dangerous injury because it can force air into a divers chest cavity or bloodstream.
The Take-Home Message About the Most Important Rule in Scuba Diving:
The rule to never hold your breath when scuba diving is important both for dive safety and dive efficiency. A diver who holds his breath underwater will not decrease his air consumption or prolong his dive. He merely increases the concentration of carbon dioxide in his lungs which makes him feel starved for air.