Aviat Space Envir Md
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Aviat Space Envir Md · Oct 1993
Seven-day pyridostigmine administration and thermoregulation during rest and exercise in dry heat.
Seven men participated in a double-blind study of effects of multiple-dose oral pyridostigmine bromide (PB) on physiological responses to 4-h heat stress tests (HST's) in a hot dry environment, 42 degrees C, 20% relative humidity. Subjects underwent 2 7-d series of tests, separated by 72 h, taking 30 mg PB every 8 h in one series, and placebo in the other. Each HST began right after the 0800 dose of PB or placebo. ⋯ PB increased sweating and evaporative water loss by about 4%, and lowered chest skin temperature during exercise by 0.7 degrees C; but it had no significant effect on rectal temperature, other skin temperatures, O2 uptake, or fluid balance. PB alone had no significant effect on heart rate (HR), but had a significant interaction with day: although PB had essentially no effect on HR in the 1st HST, its effect increased progressively so that HR during exercise in the 4th HST was 8 beats.min-1 lower with PB. Multiple-dose PB had only slight effects on responses to moderate exercise-heat stress beyond those described after single-dose PB, and we found no adverse effects of multiple-dose PB administration.
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Numerous cases of acute mountain sickness (AMS) during trekking were reported to have been successfully treated with portable pressure chambers. The effect of early pressurization during acute altitude exposure in the Alps had not been previously studied. In order to test the hypothesis that an early pressurization of unacclimatized subjects for 3 h could prevent or delay the appearance of symptoms of AMS, 51 previously healthy subjects climbed from 1,030 to 4,360 m within 12 h. ⋯ S.). The next morning, however, AMS score, HR, and SaO2 were similar for both groups. It is concluded that during acute ascent in the Alps, an early 3-h pressurization of unacclimatized subjects does slightly delay the onset of AMS but does not prevent the illness nor does it attenuate its severity upon appearance.