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Chapter 11
7
Occasionally a valve effect allows air to pass from the air passages into the pneumothorax
but prevents its return. As more and more air collects in the pneumothorax, the pressure in
the thoracic cavity rises and forces the contents of the chest (including the heart and lungs)
to the opposite side. This is called a
tension pneumothorax
and its effect on cardiac
function is catastrophic and rapidly fatal if the air is not released.
If the lung rupture occurs at depth, the air in the chest cavity expands with ascent (Boyles
Law) and this may also cause a tension pneumothorax
Bleeding may take place into the pneumothorax, leading to a
haemo-pneumothorax.
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Clinical features.
A pneumothorax is usually heralded by
chest pain
, often made worse by breathing, and
causes
shortness of breath
. Respiration becomes rapid and the heart rate increases.
With a
tension pneumothorax,
as the mediastinum is pushed to the opposite side, the
trachea can be felt to be displaced to that side. The patient becomes increasingly short of
breath and may become cyanotic (blue) and shocked. The pulse is difficult to feel as the
blood pressure falls.
With severe cases of burst lung, a pneumothorax will be evident very soon after the diver
reaches the surface, but in milder cases, the symptoms of pneumothorax may be delayed for
many hours. Symptoms may be brought on by coughing or altitude exposure (e.g. mountain
range, travel in aircraft, more diving).
Fig. 11.5
X–ray of diver's chest after suffering pulmonary barotrauma of ascent with a
right sided pneumothorax. The right chest cavity appears "black" due to its being
filled with air and the collapsed lung (white) can be seen low, near the midline.
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