PULMONARY FUNCTION
Most divers tend towards an increase in vital
capacity
with age but the general conclusion, that divers tend to have larger
vital
capacities than nondivers, was not confirmed by a study of 126
saturation
divers by Thorsem et al (1989). They suggest that the increase is
transient
and that there is a greater, but belated, diminution. Any change of
vital
capacity probably has little effect upon the divers general health
though
recent studies have shown that divers do develop some degree of air
flow
obstruction due to airway narrowing(Elliott et al, 1990).
Pulmonary diffusion capacity is another
physiological
function which deteriorates with age. At the present time the work to
assess
a possible acceleration in divers is incomplete. Early studies have
been
confined to deep diving, where a diminution of pulmonary diffusion
post-dive
from a particular dive may not be clinically significant and tends to
improve
during the next few weeks. This change is also associated with
diminution
of exercise tolerance (Thrones et al, 1990) but only to a degree that
is
functional rather than clinically significant.
In contrast, a study of 8 divers in a German deep
dive
(Lehnigk et al) showed no significant diminution of total lung carbon
monoxide
diffusion (TLCO) though there were a number of other variables, a
conclusion
also reached from a 450m dive at the National Hyperbaric Center in
Aberdeen.
However, there may be a possible cumulative effect and the most favored
explanation is in association with a cumulative dose of oxygen at
tensions
greater than 0.3 bar.
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