Metabolic responses during initial days of altitude acclimatization in the Eastern Himalayas

Abstract

The study was carried out on 16 men (aged 20-30 years) to evaluate daily metabolic responses during the early phase of altitude acclimatization at moderate altitudes between 3100 and 4200 m in the Eastern Himalayas. Resting (R) and submaximal exercise (E) oxygen consumption (IVO2) at 100 W at sea level (SL) were 3.25 (SEM 0.15) and 20.31 (SEM 0.77) ml/kg per min respectively. On day 1 at 3110 m both R and E IVO2 decreased (P < 0.001) and subsequently remained constant. At 3445 m these values tended to increase over the 3110 m values but were lower than the SL values. At 4177 m the decline in IVO2 was significantly greater (P < 0.01) than at the preceding altitudes. Pulmonary ventilation (IVE) increased consistently (P < 0.001) with increase in altitude. The arterial oxygen saturation (SaO2) at different altitudes was lower (P < 0.001) than SL values. The cardiac frequency (fC) at R and E was higher (P < 0.001) at altitude; the values at 3110 and 3445 m were significantly lower (P < 0.001) than at 4177 m. Blood pressure (BP) increased (P < 0.001) on the first day at each altitude. The systolic BP tended to decline towards SL values but the diastolic BP remained high (P < 0.001) throughout. The resting blood lactic acid concentration, [la-]bl, showed a decline (P < 0.001) only at 4177 m. The [la-]bl at E was similar at 3110 and 3445 m but was higher (P < 0.01) at 4177 m. These observations suggest that acclimatization to a mid-altitude of 3445 m can be safely avoided where rapid ascent to higher altitude is required.

Ophthalmological Effects of High Altitude

“…A small rise in blood pressure [21] and an increase in the heart rate are observed [22]. Increased sympathetic and catecholamine activity was also suggested as the cause of these changes [23] despite some conflicting studies [24,25]. Respiratory effects are also investigated in decompression chambers in detail.…”

Physical activity at moderate and high altitudes. Cardiovascular and respiratory morbidit

“…Pulmonary ventilation increases and, inversely, saturation of oxygen (SaO 2 ) drops with an increase in altitude 2,5,20 .…”

“…Some investigators have found an increase in BP [1][2][3][4][5] , others a slight reduction [6][7] , and others no change at all 8,9 . The tendency observed in most of the studies, however, is an increase in blood pressure levels on the first day of exposure to a significant altitude and, later, a decline of the values to those found at sea level, mainly in regard to the systolic blood pressure (SBP) 3,5 .…”

“…Oxygen uptake (VO 2 ) -Several studies show a reduction in VO 2 at rest and/or at certain level of exercise at moderate and high altitudes 5,22,23 .…”

“…Acute exposure to hypobaric hypoxia increases HR at rest [2][3][4][5]11 . It also increases the component of low frequency and reduces that of high frequency in the spectral analysis 3,8 .…”