UK SPORT DIVING MEDICAL COMMITTEE |
RESPIRATORY SYSTEM
PNEUMOTHORAX AND DIVING
An individual who suffers pulmonary barotrauma whilst diving is at risk of developing a pneumothorax (which will often become a tension pneumothorax on ascent as ambient pressure is reduced) and/or surgical emphysema and/or arterial gas embolism. It is therefore recommended that individuals who are believed to be at significantly increased risk of pulmonary barotrauma compared with the general population should not dive. Lung disease which might be expected to cause gas trapping during ascent is particularly likely to predispose to pulmonary barotrauma. However, there is little objective evidence to date that obstructive lung disease per se increase the risk of pulmonary barotrauma in divers. There is some evidence to suggest that pulmonary barotrauma does occur more frequently in divers whose lungs are small and stiff.
Special consideration needs to be given to individuals who have previously suffered pneumothorax or pulmonary barotrauma. Three situations must be considered:
1.
Spontaneous pneumothorax. A
spontaneous pneumothorax is one
which occurs without precipitating
trauma.
a. It may occur in (generally
older) individuals with severe
underlying lung disease (e.g.
chronic airways disease) when it
is clear that the nature of the
lung disease would prevent diving.
They are numerically equal to the
numbers that occur in young
persons (see below) but are more
serious due to the lack of
pulmonary reserve.
b. It may also occur in fit and
healthy young adults who might
otherwise be good candidates for
diving. They are more frequent in
young men than young women (7:1)
and they are more common in
smothers than non-smokers. In
young men, "light"
smoking increases the risk seven
fold, moderate smoking raises the
risk to 20-fold and heavy smoking
raises it to 100-fold. Some
spontaneous pneumothoraces are
associated with forced inspiratory
manoeuvres such as hiccuping or
the completion of functional tests
of total lung capacity or peak
inspiratory pressures. Such cases
suggest that voluntary high
inflations can stretch some parts
of healthy lungs beyond their
elastic limits. 60% of the
spontaneous pneumothoraces are
noted in the first 3 hours of the
waking day. Almost all are
unilateral and affect the right
and left lungs with equal
frequency, but some 2% are
bilateral, probably betraying a
defect in the mesothelial barrier
separating the two pleural spaces
in the antero-superior
mediastinum. They rarely occur
after the age of 40 years.
Recurrence rates after recovery
from a first spontaneous
pneumothorax are high (-50%), are
more commonly ipsilateral than
contralateral but are very
infrequent after intervals of two
years or more. The medical
committee has therefore adopted
the pragmatic approach of
accepting that in individuals with
a history of spontaneous
pneumothorax who have had a
bilateral pleurectomy or who are
unoperated upon but had no
pneumothorax for five years the
risk of pulmonary barotrauma is
small and not significantly
greater than for many in the
general population e.g. smokers.
Such individuals may dive provided
that a CT scan of the chest and
lung function tests, including
flow-volume loops, show no reason
to suggest that there is
significant residual lung disease.
2. Traumatic pneumothorax. Traumatic pneumothorax may follow blunt or penetrating trauma, including iatrogenic. This will include pneumothorax occurring as a result of positive-pressure ventilation (over-pressure pulmonary barotrauma). In all these situations there are good reasons for the individuals to have sustained their pneumothorax and there is no reason to suppose that such individuals will be at increased risk of pulmonary barotrauma when diving, provided that there has been complete resolution of associated lung pathology. Resolution should be assessed by CT scan of the chest and lung function tests, including a flow-volume loop.
3. Pulmonary barotrauma when ascending from a dive (see also the medical standard on "Dysbaric illness and diving"). Pulmonary barotrauma on ascent more frequently leads to air embolism in divers possibly due to the fact that divers are resisting the air expansion which results in the lung bursting on the inside leading to air escape into the arterial circulation. Lung rupture is commonly asymptomatic and is likely to occur frequently in normobaric life as a result of manoeuvres such as couching, sneezing or taking and holding a deep breath. A technique commonly employed by divers is so-called "skip" breathing in which the normal ventilatory pattern of; inhale, exhale, pause is replaced by: inhale, pause, exhale. It is likely that such a breathing pattern may predispose to lung rupture because the lung is repeatedly taken close to, and maintained at, its elastic limit. Under normobaric conditions such a rupture may provoke the leakage of only small, asymptomatic amounts of gas into the mediastinum. However, if this were to occur at depth and the diver was then to surface. Boyle's Law would cause the volume to increase in proportion to the depth at which the leakage occurred. In all the most shallow of dives, such an expansion may be sufficient to provoke symptoms. Divers should therefore be taught to avoid "skip" breathing techniques and also to avoid taking deep breaths to total lung capacity. Individuals who have had pulmonary barotrauma during ascent must be fully investigated for any evidence of underlying lung pathology.
Referral of the case to the medical committee is recommended.
References
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