L-Tryptophan does not influence acute ventilatory response at moderate altitude.

Altitude induced insomnia is a very common symptom in mountaineering. Conventional hypnotics such as benzodiazepines potentially can be associated with untoward side effects because they can impair ventilatory adaptation to hypoxia at altitude. The objective of our study was to evaluate the effect of a alternative potentially sedative drug, L-tryptophan on ventilation at moderate altitude. STUDY DESIGN, METHODS AND RELEVANT RESULTS: Randomised, double blind, placebo controlled crossover trial. Blood gas analysis of 8 healthy subjects was performed before and one hour after oral administration of 500 mg L-tryptophan or placebo at altitudes of 171 m and at 3,000 m. PaO2 and PaCO2 before and after L-Tryptophan or placebo medication did not change significantly at neither level of altitude investigated. CONCLUSION: L-tryptophan does not impair ventilatory adaptation to mild hypoxia at moderate altitude.

[Physical exercise impairs the acute stage of adaptation to moderate altitude]. / Körperliche Belastung beeinträchtigt die akute Anpassung in mittlerer Höhenlage.

UNLABELLED: A recent study has reported the impairment of high altitude adaptation capacity by physical exercise in a decompression chamber. The aim of our protocol was to evaluate if physical exercise at moderate altitude in the Alps would show a similar effect. 8 alpinists were examined in a randomised cross-over trial at 171 m and at 3000 m altitude under sedentary and under exercise condition (50% maximal workload on the bicycle ergometer four times 30 minutes during the first 6 hours of an 8 hour observation period at each altitude). At the beginning and at the end of each observation period AMS scores and arterial oxygen saturation SaO2 were measured. The differences of the AMS scores and the differences of SaO2 at both test conditions were compared at both altitudes. RESULTS: In comparison to sedentary condition, the differences between initial and final AMS scores at 3000 m altitude were significantly higher (-0.38 +/- 0.52 vs. -1.25 +/- 0.46, diff 0.88, 95% CI 0.58 to 1.17, p < 0.01), as well as the difference between initial and final SaO2 (-0.25 +/- 0.71% vs. 2.25 +/- 1.04%, diff. -2.5%, 95% CI for the diff. -3.59 to -1.41, p < 0.01). AMS score and SaO2 did not change after exercise at 171 m altitude. CONCLUSION: Physical exercise impairs the acute stage of adaptation to moderate altitude. This is mainly due to the exercise-induced exaggeration of arterial hypoxaemia.

Correlation between raised body temperature and acute mountain sickness score at moderate altitude.

UNLABELLED: In high altitude mountaineering, a rise in body temperature has long been associated with acute mountain sickness. No data exist on the situation at moderate altitudes in the Austrian Alps. The objective of this study was to investigate a potential relationship between an increase in body temperature and acute mountain sickness (AMS) and hypoxemia at moderate altitude. Body temperature and arterial oxygen saturation (SaO2) were measured in 40 alpinists at 1000 m altitude and after ascent to 3100 m altitude, and the AMS score was measured at 3100 m altitude. At 3100 m altitude, 3 alpinists with AMS (score 3) experienced a 0.87 +/- 0.12 degree C rise in body temperature and a 10.67 +/- 1.15% reduction in SaO2. In 8 moderately affected alpinists, temperature increased by 0.49 +/- 0.16 degree C and SaO2 was reduced by 6.75 +/- 1.75%. In 29 alpinists without signs of AMS, temperature did not change (difference 0.02 +/- 0.14 degree C) and SaO2 decreased by 4.59 +/- 0.82%. The difference between temperatures at the two altitudes correlated significantly with the SaO2 difference between the two altitudes (rs = 0.408, p < 0.01) and with the AMS scores (rs = 0.814, p < 0.01). CONCLUSION: Comparable with maximal forms of AMS at high altitude, our data provide reason to speculate that systemic inflammatory disease could also be causal in less severe forms of acute mountain sickness. Therefore, in cases of fever at moderate altitude, the differential diagnosis must include acute mountain sickness.