Diving Gas Embolism

Excerpt

Diving using an underwater breathing apparatus (UBA) of any type involves inspiration of compressed gas by the diver at pressures above normal surface pressure. Seawater is sufficiently denser than air such that the pressure exerted by one atmosphere (atm) of air is equivalent to the pressure at 33 feet of seawater (fsw), meaning that ambient pressure on a diver will double in the first 33 feet of descent. During any dive, a diver is subject to the limitations imposed by Boyle's Law, which states that pressure and volume are inversely related. As pressure decreases, the volume will increase proportionally, which means that the same diver holding his breath and ascending from 33 fsw would double his lung volume on return to the surface if that were anatomically possible without structural damage to the lungs. Acute exacerbation of reactive airway disease, anatomic anomalies such as bullae or blebs, or holding the breath can entrap air in the lungs of a diver. Subsequent ascent of as little as 1 meter (approximately 3 feet) may cause an overpressurization sufficient to rupture lung alveoli and introduce gas into the surrounding tissues and/or blood vessels. This is referred to as pulmonary overinflation syndrome and results in one or more overexpansion injuries: pneumomediastinum, pneumothorax, subcutaneous emphysema, or arterial gas embolism.