We tested whether higher minute ventilation (Vm) and higher hypoxic ventilatory response (HVR) were necessary prerequisites to climb Everest or K2 without oxygen, in 11 climbers at sea level (SL), on arrival at the Everest base camp (5200m, HA-1), after 15-day acclimatization (HA-2) (2004 Italian Everest-K2 Expedition). We measured resting oxygen saturation (SaO2), Vm, breathing rate (BR), HVR, vital capacity, maximal voluntary ventilation (MVV), ventilatory reserve (RES) at SaO2=70% (defined as 100 x (MVV- Vm )/MVV), ventilatory efficiency (physiological dead space/tidal volume ratio (Vd/Vt) and SaO2/Vm ). Within 61 days from HA-2, 5 climbers (G1) summited Everest or K2 without oxygen support, 6 climbers (G2) did not (4) or used oxygen. G1 and G2 did not differ at SL and HA-1. At HA-2, G1 showed smaller increases in Vm (to 13.3±0.8 vs 19.2±0.6 L/min, p<0.001), BR (to 10.7±1.9 vs 20.2±0.8 br/min, p<0.001), HVR (to -2.14±0.51 vs 5.09±1.03 L/min/% SaO2, p<0.05), and greater RES (66.6±6.3 vs 26.7±8.8%, p<0.01) vs G2. Ventilatory efficiency was higher in G1 (Vd/Vt: 0.09±0.01 vs 0.16±0.02, p<0.05, SaO2/Vm: 6.66±0.39 vs 4.64±0.13 %/L/min, p<0.001). Despite environmental, technical and psychologic factors, successful climbers had smaller responses to hypoxia during acclimatization, but consequently had greater reserve for the summit. Ventilatory efficiency may prevent excessive increases in ventilation, allowing a sustainable ventilation in the extreme hypoxia at the summit.
Climbing Everest and K2 without oxygen: what helps?
POMIDORI, Luca;PAOLUCCI, Elisa;COGO, Annaluisa
2005
Abstract
We tested whether higher minute ventilation (Vm) and higher hypoxic ventilatory response (HVR) were necessary prerequisites to climb Everest or K2 without oxygen, in 11 climbers at sea level (SL), on arrival at the Everest base camp (5200m, HA-1), after 15-day acclimatization (HA-2) (2004 Italian Everest-K2 Expedition). We measured resting oxygen saturation (SaO2), Vm, breathing rate (BR), HVR, vital capacity, maximal voluntary ventilation (MVV), ventilatory reserve (RES) at SaO2=70% (defined as 100 x (MVV- Vm )/MVV), ventilatory efficiency (physiological dead space/tidal volume ratio (Vd/Vt) and SaO2/Vm ). Within 61 days from HA-2, 5 climbers (G1) summited Everest or K2 without oxygen support, 6 climbers (G2) did not (4) or used oxygen. G1 and G2 did not differ at SL and HA-1. At HA-2, G1 showed smaller increases in Vm (to 13.3±0.8 vs 19.2±0.6 L/min, p<0.001), BR (to 10.7±1.9 vs 20.2±0.8 br/min, p<0.001), HVR (to -2.14±0.51 vs 5.09±1.03 L/min/% SaO2, p<0.05), and greater RES (66.6±6.3 vs 26.7±8.8%, p<0.01) vs G2. Ventilatory efficiency was higher in G1 (Vd/Vt: 0.09±0.01 vs 0.16±0.02, p<0.05, SaO2/Vm: 6.66±0.39 vs 4.64±0.13 %/L/min, p<0.001). Despite environmental, technical and psychologic factors, successful climbers had smaller responses to hypoxia during acclimatization, but consequently had greater reserve for the summit. Ventilatory efficiency may prevent excessive increases in ventilation, allowing a sustainable ventilation in the extreme hypoxia at the summit.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
