Pre-adaptation, adaptation and de-adaptation to high altitude in humans: cardio-ventilatory and haematological changes

Abstract

The aim of this study was first to investigate cardio-ventilatory and haematological responses induced by intermittent acclimation and second to study de-adaptation from high altitude observed after descent. To achieve these objectives nine subjects were submitted to intermittent acclimation in a low barometric chamber (8 h daily for 5 days, day 1 at 4500 m, day 5 at 8500 m) before an expedition to the Himalayas. Cardio-ventilatory changes were measured during a hypobaric poikilocapnic hypoxic test (4500 m, barometric pressure = 589 hPa) and haematological changes were studied at sea level. These measurements were performed before and after acclimation, after return to sea level, but also 1 and 2 months after the expedition. In addition, partial pressures of oxygen and carbon dioxide in arterial blood (PaO2, PaCO2) and arterial erythropoietin concentration [EPO] were measured at rest during the hypoxic test. Results suggested the pre-adaptation protocol was efficient since an increased PaO2 (+12%, P < 0.05), a smaller difference in alveolo-arterial PO2 ( -63%, P < 0.05) and a lower PaCO2 ( -11%, P < 0.05), subsequent to ventilatory changes, were observed after acclimation with a significant increase in reticulocytes and in sea level [EPO] (+44% and +62% respectively, P < 0.05). De-adaptation was characterized by a loss of these cardio-ventilatory changes 1 month after descent, whereas the haematological changes (increased red blood cells and packed cell volume, P < 0.05) persisted for 1 month before disappearing 2 months after descent. This study would also suggest that acute hypoxia performed after a sojourn at high altitude could induce significantly depressed EPO responses (P < 0.05).

Live High-Train Low Altitude Training: Responders and Non- Responders

“…The relative increase (compared to non-responders) in the current study in SpO 2 in responders (which corroborates the theory of Chapman et al could be explained in part by increased haemoglobin concentration [30], enhanced erythropoietic response [7,31], which may result in increased red cell volume [4] and subsequently increased arterial oxygen content. Weil et al noted a graded response such that an increase in red cell mass was proportional to oxyhaemoglobin saturation at sea level and altitude [32].…”

Effects of Intermittent Altitude Exposures on Acclimatization of 4,300 M

“…However, this adaptation was accomplished in fewer hours, and thus could be considered a more efficient method of acclimatizing people to altitude. Our results support most of the previous research measuring resting ventilation before and after intermittent exposures to various altitudes (49,51,72,88,92), but differ from a recently published study (80). However, that study (80) only exposed volunteers to altitude for 2 h-d" 1 , and a longer exposure time may be needed to induce the beneficial ventilatory changes we observed.…”

Cold Adaptations

“…But the rise in TSH is inversely related to the intensity of the light, so it is not always retrieved 51) . Last, the biological significance of these changes in the thyroid hormones is unknown 57) and the relationship between this syndrome and one of a type of cold adaptation has yet to be defined 58,59) .…”