The fundamental rule of never holding your breath helps to reduce the likelihood of scuba injuries from inadequate exhalation - especially during a runaway ascent!
This guide contains information about arterial gas embolism (AGE) and how to avoid one of the most common, and serious, medical emergencies in diving.
Learning how to breathe in scuba diving is one of the first principles for beginners to master.
The water pressure that surrounds divers (ambient) decreases as they ascend to the surface.
As a consequence of that, the air inside the lungs increases (expands).
The expanding air escapes through the scuba regulator when the diver breathes normally and continuously.
But, if a diver fails to exhale sufficiently the expanding air can cause a pulmonary barotrauma (rupture in the lung tissue). Furthermore, gas bubbles releasing into the major arteries can lead to a severe embolism (AGE).
The bubbles are not confined to the pleural cavity. In fact, they can also restrict blood flow in the brain (leading to brain damage) and other tissues almost anywhere around the body.
Ascending slowly when you dive is the best technique for reducing pressure-related injuries, especially arterial gas embolisms. In other words, be a SAFE diver (Slowly Ascend From Every dive).
In addition, divers should also use their depth gauge (or dive computers) to monitor their ascent rate. The climb should be slow and controlled. For example, the U.S. Navy dive tables use an ascent rate of thirty (30) feet (nine metres) per minute.
But wait - there's more:
Divers should use a well-maintained buoyancy controller (BCD) and drysuit (where applicable) to avoid ascending too quickly. It's also important to have proper weight distribution and to vent expanding air from these devices on the way up.
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Being able to recognise the typical signs and symptoms of arterial gas embolism (AGE) is important. Look for the following conditions within fifteen (15) minutes of reaching the surface:
If a diver loses consciousness soon after surfacing you should suspect that they have arterial gas embolism. If so, they will need hyperbaric oxygen treatment as an urgent priority. Contact the nearest medical services (EMS) and give emergency oxygen to the injured diver.
In fact, if a diver holds their breath during an ascent in a shallow swimming pool, pulmonary barotrauma can still occur.
But, most compressed-gas scuba diving barotraumas and embolisms are caused by pulmonary overinflation, such as during a breath-hold ascent.
In shallow depths, beginners are often immersed in other tasks, such as taking underwater photos, and sometimes forget the importance of breathing continuously.
This part is important:
Underwater, the greatest pressure change takes place as you get closer to the surface - the final three (3) to five (5) metres. Nonetheless, it only takes a small overpressure to cause barotrauma injuries in diving.
Some lung conditions can increase the likelihood of suffering AGE. They include asthma, chest infections, cysts, scar tissue from surgery, obstructive lung disease (COPD), and tumours.
Even so, the best advice for preventing an arterial embolism in diving is to relax and breathe in a normal manner during the ascent.
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