Am. J. Respir. Crit. Care Med., Vol 152, No. 6, 12 1995, 1956-1960.
Is normobaric simulation of hypobaric hypoxia accurate in chronic airflow limitation?
MT Naughton, PD Rochford, JJ Pretto, RJ Pierce, NF Cain and LB Irving
Department of Thoracic Medicine, Heidelberg Hospital, Victoria, Australia.
Hypobaric hypoxemia is experienced by passengers during commercial aircraft
flight. In order to assess the extent of hypoxemia and to test whether
hypobaric hypoxia can be accurately estimated at sea level, the results of
the normobaric hypoxia altitude simulation test (N-HAST) were compared with
those of the hypobaric hypoxia altitude simulation test (H-HAST) in six
normal control subjects and nine patients with chronic airflow limitation
(CAL) at simulated cabin altitudes of 6,000 ft (1,829 m) and both at rest
and during exercise at 8,000 ft (2,438 m). Serial arterial blood samples
were drawn during the breathing of 15.1 and 16.3% inspired oxygen at sea
level (N-HAST) at rest and during light exercise, and during the breathing
of room air at simulated cabin altitudes (H-HAST) of 609 mm Hg (6,000 ft)
and 565 mm Hg (8,000 ft) at rest and during light exercise. As measured
with the H-HAST technique, the mean (+/- SD) PaO2 of the normal group fell
from 96.2 +/- 6.2 mm Hg (sea level) to 70.1 +/- 6.0 mm Hg (6,000 ft), and
to 61.7 +/- 1.6 mm Hg (8,000 ft at rest) and 54.8 +/- 7.1 mm Hg (8,000 ft
during exercise) (p < 0.005 by analysis of variance [ANOVA]). In the CAL
group, the mean (+/- SD) PaO2 fell from 75.8 +/- 8.2 mm Hg (sea level) to
57.0 +/- 6.3 mm Hg (6,000 ft), and 49.5 +/- 6.1 mm Hg (8,000 ft at rest),
and 38.6 +/- 7.5 mm Hg (8,000 ft during exercise) (p < 0.005 by
ANOVA).(ABSTRACT TRUNCATED AT 250 WORDS)
