Medicine and Health · Shallow Water Blackout and Asthma

Shallow Water Blackout

Asthma

Shallow Water Blackout

The most common types of freediving accidents are caused by oxygen starvation in the tissue. This so called Shallow Water Blackout is a sudden loss of consciousness that strikes during the freediver’s ascent within 10 meters of the surface. If this occurs frequently, irreversible damage to the brain tissue can be caused in the long run.

Before a breath-hold dive, the freediver causes hyper ventilations in order to reduce the partial pressure of carbon dioxide in the organism, which concentration is what activates the stimulants that constitute our natural breathing alarm. During apnea, although the voluntary form of breathing is interrupted, the remaining physiological processes continue, for example the absorption of nitrogen by the tissues, in such a way that the diver can suffer from a decompression attack.

During ascent the oxygen tends to diffuse toward the lungs, causing sudden anoxia in the brain, which in turn causes loss of consciousness and, unless the diver is rescued, death by drowning.

It is recommended never to freedive alone, but in partners and it is even preferable to alternate with other partners waiting on the surface.
Even if hyper ventilation can increase between 40 and 60% during the freedive, it should be done with caution given that it causes dizziness and muscle cramps in arms and legs. It is recommended not to repeat for more than 3 or 4 times.

Asthma

Asthma is a chronic respiratory illness where the airways are sensitive and inflamed (asthmatic bronchitis) due to various causes where the airways are obstructed, letting through less air.
There are certain circumstances which don’t cause the actual asthma itself but can cause an asthmatic crisis. These are the so called triggering factors: cold, humidity, physical exercise, tobacco smoke, infections in the airways, intense emotions and drugs.
There is nothing preventing an asthmatic from diving, however, an extra risk is posed. A diver with asthma can suffer from asthmatic crises underwater, panic attacks and even pulmonary barotraumatism.
These divers are recommended to use regulators with special modifications that allow the air in the tank to be humidified and also to consult with a medical professional before diving.