Source: Annual Congress 2012 - Various issues in clinical physiology
Disease area: Respiratory critical care

Abstract

Background
We investigated breathing patterns and oxygenation in mountaineers climbing to extreme altitude to evaluate effects of hypoxemia and acclimatization.
Methods
In 34 mountaineers (mean age 45y, 7 women) portable recordings of respiratory inductive plethysmography, pulse oximetry and ECG were performed during a climb to the summit of Muztagh Ata, China (7546m). Breath by breath ventilation was analyzed and periodic breathing quantified by spectral analysis.
Results
Repeated recordings during 2 climbs from 4497-5533m within 5-8 days revealed an increase in oxygen saturation and periodic breathing and a decrease in heart rate (table). During the climb from 6865-7546m hypoxemia was pronounced.
Conclusions
Mountaineers were able to climb to extreme altitude despite severe hypoxemia. The heart rate reserve was utilized to a greater extent than the ventilatory reserve. With acclimatization, periodic breathing increased despite a higher oxygen saturation, consistent with a persistently high ventilatory drive while the heart rate reduction suggested a decrease in sympathetic tone.

Physiologic adaptation during ascent to 7546m

	Climbs from 4497-5533m		Climb from 6865-7546m
	day 4 n=33	days 9-12 n=32	days 17-19 n=19
Oxygen saturation, %	73±4	77±4*	68±3**
Minute ventilation, L/min	33.1±8.1	35.3±7.5	31.1±9.6
Minute ventilation, %MVV	25±11	24±11	22±8
Mean inspiratory flow, L/min	1.1±0.3	1.2±0.3*	1.1±0.3
Power of periodic breathing, arbitrary units	0.6±0.1	0.7±0.1*	0.6±0.1
heart rate, 1/min	122±15	112±14	122±11**
Heart rate, %HRmax	85±13	80±12*	86±9**

Means±SD during 6-8h climbs;*P<0.05 vs day 4;**P<0.05 vs 4497m, day 9-12; MVV=40*FEV1 at corresponding altitude; %HRmax=% of heart rate during maximal exercise at 5533m (Latshang 2011)

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T.D. Latshang, A. Garde, A.J. Turk, T. Hess, M.M. Bosch, D. Barthelmes, J. Pichler Hefti, M. Maggiorini, U. Hefti, T.M. Merz, O.D. Schoch, K.E. Bloch (Zurich, Winterthur, Aarau, Berne, St. Gallen, Switzerland; Barcelona, Spain). Breathing patterns in mountaineers climbing to extreme altitude (7546m). Eur Respir J 2012; 40: Suppl. 56, 3796

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