Reduction in Gas Density
A reduction in gas density results in lower breathing resistance.
Varene and associates[261]
examined the effect
of ambient pressure from 0.5 to 5 ATA on airway resistance in normal subjects. Their
data can be summarized by either of the following equations:
RP
/R0
= 0.57 + 0.44 ·
PATA
(11)
or
RP
/R0
= PATA
0.59
(12)
where PATA
is ambient pressure in ATA, RP
is airway resistance
at ambient pressure, and R0
is airways resistance at 1 ATA. For example,
at an ambient pressure of 0.5 ATA (5486 m), airway resistance is reduced by approximately
20%. Under resting conditions, differences in breathing pattern during exposure
to high altitude are minor when compared with a similar degree of hypoxia at sea
leve.[262]
