Diving medicine

When a diver suffers from inadequate decompression or gas embolism, he/she must first be returned to a pressurized environment, where the gases will be recompressed. This should normally relieve localized pain caused by gas bubbles, restore normal blood flow, and will frequently relieve the patient of many, if not all, of the subjective symptoms.

The administration of 100% oxygen to the patient is essential for the inert gases to dissolve. Research and field experience have proven the therapeutic value of 100% oxygen in recompression treatments. Once this treatment is underway, other treatments can also be performed.

Divers who require recompression in a hyperbaric chamber may or may not require additional emergency medical attention.

Three general classes of diving medical emergencies require recompression treatment:

• a. Arterial Gas Embolism (AGE);
• b. Decompression Sickness; and
• c. Omitted decompression.

Arterial Gas Embolism (AGE) is the most dangerous of the three, requires immediate attention. It can occur during a brief dive in shallow waters, or even during a dive performed in a swimming pool using breathing equipment. It develops rapidly, and must be treated without delay.

Decompression sickness can be just as serious, but may develop more slowly, up to 24 hours after the completion of a seemingly routine and uneventful dive. However, statistics indicate that most cases will occur less than 6 hours after surfacing.

Omitted decompression results from a failure to observe the appropriate schedule of decompression, possibly due to a serious injury to the diver in the water or an emergency at the dive station. In some cases, decompression sickness may be prevented by using one of the Surface Decompression Tables. Otherwise, a therapeutic treatment table must be used. Omitted decompression includes minor to major decompression deficits. In both cases, symptoms may vary from a mild tingling sensation to a loss of consciousness. If you or your diving partner have any doubts about your condition, contact the Centre de médecine de plongée du Québec.

Pulmonary barotrauma is a general term used to describe the condition caused by  the expansion of gases in the lungs as pressure drops, normally during the ascent. These gases might have been retained in the lungs by choice (voluntary breath holding) or by accident (blocked air passages). The diver, panicking because of a difficult situation, may hold his/her breath without even realizing it. Gases can also be trapped in parts of the lung as a result of damage from previous diseases or accidents, active infection (pneumonia, bronchitis), or asthma.

When the lungs are overinflated and the alveoli rupture, gases can cause four types of traumas:

• a. Arterial gas embolism (A.G.E.)-gases enter the capillaries surrounding the alveoli, travel back to the heart through the pulmonary veins, and are carried throughout the body by the arteries;
• b. Pneumothorax- gases reach the space between the lung and the chest wall, causing the lung to collapse. This is rare in healthy individuals, as the membrane covering the lung (also called pleura) is very tough and rarely ruptures;
• c. Mediastinal emphysema- gases travel along the veins, arteries and bronchioles from the site of the rupture, in the periphery of the lung, to reach the heart, major vessels and primary bronchi in the centre of the thorax (mediastinum); and
• d. Subcutaneous emphysema- gases travel up from the mediastinum and are trapped under the skin, in the area above the clavicles at the base of the neck.

In AGEs, the gas bubbles located in the bloodstream may become trapped in the arteries irrigating the spinal cord or the brain, cutting off circulation and thereby causing paralysis, unconsciousness, or death. The term Cerebral Gas Embolism will be used if the brain is affected.
Pneumothorax and Mediastinal/Subcutaneous Emphysema usually is not life threatening, unlike AGEs, but require prompt attention nevertheless. Recompression is not recommended for Pneumothorax and Mediastinal/Subcutaneous Emphysema. If you have any doubts about your condition, contact the Centre de médecine de plongée du Québec.