A STUDY OF CARDIOPULMONARY FUNCTION AND WORKING CAPACITY OF SOJOURNERS ACUTELY EXPOSED TO DIFFERENT ALTITUDE LEVELS IN ETHIOPIA

Abstract

Forced vital capacity (FVC, L/sec), forced expiratory
volume (FEV1, L/ sec), FEVl %, forced expiratory flow rate (FEF 200~1200 ml,.
L/sec), forced mid~expiratory flow rate (FMF 25-75 %, L/sec), peak
expiratory flow rate (PEFR, L/ min), minute ventilation (VE, L/ min),
oxygen saturation of arterial blood (Sa02%), working capacity
(Kgm/min/m2 body surface area), pulse rate (beats/min) and arterial
blood pressure (mmHg) were studied in eight male sojourners
descending to 137P-490 m and ascending to 2550-3300 m from their
altitude of residence (2440 m). Of the lung function indices, mean FEF 200-
1200 ml increased from 6.54 L/ sec at 2440 m to 7.18 L/ sec and 8.33 LI sec,
respectively, at 2550 m and 3100 m. It was not m~asured at 3300 m for
lack of electric/ower supply. Mean values of FEF 200-1200 ml were found
to be correlate to the altitudes of investigation significantly (r=0.7316),
The increase in FEF 200-1200 mt probably reflects that large airways tend to
open up more widely perhaps concomitant with enlargement of alveolar
spaces at 2550 m and above to compensate for the reduced PA02 and
reduced en uptake, Mean VE showed a 4-5-fold increase with exercise
essentially at all levels of altitude. Acute altitudinal effect became quite
evident at 3300 m. At rest, VE increased from 5,62 L/min at 2440 m to
7.78 L/min at 3300 m. During exercise, increase in VE with ascent
apparently protects the low 02 saturation (91.9% at rest and 86.9% in
this study). Although the mean of exercise VE was markedly increased
only at 3300 m, its overall correlation with altitude (r=0.6698) and mean
working capacity (r=-0.6426) was quite significant (two-tailed P=0.0236).
Sa02% was found to be correlated with mean (r=0.7955) and individual
measurements (r=0.7628) of working capacity. Mean working capacity
was reduced by about 20% with ascent and increased by about 9% with
descent. It was negatively correlated with ascent (r=-0.9101). This
signifies that physical performance is quite limited by hypoxia with
ascent. Mean pulse rate, which was 75 beats 1 min at 2440 m increased to
82 beats/min at 490 m. It decreased to 72 beats/min at 3300 m. This is
probably attributable to the decrease in ambient temperature and
relative humidity with ascent and to the increase with descent. Arterial
blood pressure (mean sx.stolicl diastolic) was found to be 100.1. / 62.13
mmHg at 2440 m, 93.1/59,4 mm Hg at 490 m, 99.6/59.4 at 1370 m and
101.46-102.5/62.5-63.1 mmHg at 2550-3300 m. This pattern of change
seems to be attributable to changes in peripheral vascular resistance
which is apparently secondary to changes in ambient temperature and
relative humidity. One of the sojourners experienced only generalised
fatigue .. This suggests that physiological alterations occurring at 3300 m
cannot apparently induce acute mountain sickness in residents of
medium altitude.