As air in the diver’s lungs expands on ascent, increasing volume proportionally to keep the pressure equal to the surrounding pressure (Boyle’s law in action), the expanded gas must be able to escape. This is achieved by continuously breathing or breathing out during an ascent. If the maximum volume of the lungs is reached by holding your breath on ascent, the lungs get over-pressurized and may start to tear or rupture.
Arterial gas embolism, abbreviated as AGE, occurs if air escapes through tears in lung alveoli and goes into the bloodstream (pulmonary capillaries). Air can enter tissue or the bloodstream, which may lead to serious injury or death. Over-pressurizing can easily happen: Even ascending 1 to 1.5 meters/3 to 5 feet with full lungs can give rise to lung injuries. Especially in shallow water, the pressure drop (respiratory volume increase) per ascended 1 meter/3 feet is greatest as you get closer to the surface.
The following symptoms are symptoms of AGE:
- Loss of consciousness
Although these symptoms are comparable to those of DCS, AGE symptoms are rapid and dramatic, whereas DCS symptoms are somewhat delayed. Symptoms occur during and immediately after surfacing.
The early management of AGE and DCS is the same. Although a diver with severe DCS or AGE requires urgent re-compression for definitive treatment, it is essential that they be stabilized at the nearest medical facility before transportation to a chamber. Early oxygen first aid is important and may reduce symptoms substantially, but this should not change the treatment plan.
Symptoms of AGE and serious DCS often clear after initial oxygen breathing, but they may reappear later. Because of this, always contact your country's diving emergency services or a dive physician in cases of suspected DCS or AGE—even if the symptoms and signs appear to have resolved.