Treatment procedures eg rupture of an aortic balloon pump 24 Gas Embolism In Diving Accidents

Two principle mechanisms are involved when neurological manifestations occur in direct relation to diving activities77 :

- Lung barotrauma is relatively rare but a very serious cause. It is observed during the expansion of voluntary or pathological air trapping during decompression (ascent). Following Boyle-Mariotte's law, the air in the lungs increases in volume as pressure decreases, enlarges the alveoli and breaks into the pulmonary circulation.

These accidents are not related to the duration or depth of the diving activities and are observed mainly in inexperienced divers or in the case of "blow up" (i.e, very rapid) ascents.

- Decompression sickness is caused by the formation of inert gas bubbles within the body - usually nitrogen or helium contained in the breathing gas mixture, depending on the mixture inhaled). The bubbles may form within tissues but frequently access the venous circulation and are detectible with via ultrasonography (i.e., Doppler or echocardiography). VGE caused by decompression are not always symptomatic, but if the volumes exceed a certain threshold biological injury occurs as detailed in the preceding sections. Usually decompression sickeness is the result of violations of decompression tables that control the duration and depth of diving activities. In summary, the most common causes of GE are (Table 1):

• - vascular access and perfusion in the central veins,

• - pleural or pulmonary exploration procedures,

• - vascular catheterisation with injection,

These are therefore predominantly iatrogenic and could be reduced by effective preventative measures.

Table 2.2.2-1. Personal series of 95 cases of GE collected in a 20 year period

Origin of bubble

Nb

%

Central venous access

38

40

Coelioscopy

14

15

Pleural puncture

10

11

Haemodialysis

9

10

Angiography (coronary / cerebral)

7

7

Trans-thoracic and trans-bronchial biopsy

6

6

Heart surgery

5

5

Neuro-surgery

3

3

Swan Ganz catheterisation

3

3

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