Rationale. We tested whether higher ventilation and higher ventilatory responses to hypoxia were necessary prerequisites to climb Everest or K2 without oxygen. Methods. We studied elite 11 climbers of the 2004 Italian Expedition to Everest and K2 - at sea level (SL), after arriving at the Everest base camp (5200m, HA-1), and after 15 days of acclimatization (HA-2). We measured resting oxygen saturation (SaO2) minute ventilation (Vm), breathing rate (BR), hypoxic ventilatory response (HVR), vital capacity, maximal voluntary ventilation (MVV), ventilatory reserve (RESERVE) at SaO2=70% (defined as 100 x (MVV- Vm )/MVV), and 2 markers of ventilatory efficiency (physiological dead space/tidal volume ratio (Vd/Vt) and SaO2 / Vm ). Results. The summits of Everest or K2 were reached 29 and 61 days after HA-2, respectively. five climbers (Group1) summited without oxygen support, 6 (Group2) did not summit (4 subjects) or used oxygen. At SL and HA-1, all variables were similar in the 2 groups. At HA-2, Group1 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 so had greater RESERVE (66.6±6.3 vs 26.7±8.8%, p<0.01) as compared to Group2. Ventilatory efficiency was higher in Group1 (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). Conclusions. Despite the undoubted role of environmental, technical and psychologic factors, successful climbers had smaller increases in their responses to hypoxia during acclimatization, but consequently had greater available reserve for the summit. Ventilatory efficiency may be important in preventing excessive increases in ventilation, thus allowing a sustainable ventilation even in the extreme hypoxia at the summit.
Reduced Ventilation Response during Acclimatization May Help in Reaching the Summit of Mt. Everest or K2 without Oxygen
POMIDORI, Luca;PAOLUCCI, Elisa;COGO, Annaluisa
2005
Abstract
Rationale. We tested whether higher ventilation and higher ventilatory responses to hypoxia were necessary prerequisites to climb Everest or K2 without oxygen. Methods. We studied elite 11 climbers of the 2004 Italian Expedition to Everest and K2 - at sea level (SL), after arriving at the Everest base camp (5200m, HA-1), and after 15 days of acclimatization (HA-2). We measured resting oxygen saturation (SaO2) minute ventilation (Vm), breathing rate (BR), hypoxic ventilatory response (HVR), vital capacity, maximal voluntary ventilation (MVV), ventilatory reserve (RESERVE) at SaO2=70% (defined as 100 x (MVV- Vm )/MVV), and 2 markers of ventilatory efficiency (physiological dead space/tidal volume ratio (Vd/Vt) and SaO2 / Vm ). Results. The summits of Everest or K2 were reached 29 and 61 days after HA-2, respectively. five climbers (Group1) summited without oxygen support, 6 (Group2) did not summit (4 subjects) or used oxygen. At SL and HA-1, all variables were similar in the 2 groups. At HA-2, Group1 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 so had greater RESERVE (66.6±6.3 vs 26.7±8.8%, p<0.01) as compared to Group2. Ventilatory efficiency was higher in Group1 (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). Conclusions. Despite the undoubted role of environmental, technical and psychologic factors, successful climbers had smaller increases in their responses to hypoxia during acclimatization, but consequently had greater available reserve for the summit. Ventilatory efficiency may be important in preventing excessive increases in ventilation, thus allowing a sustainable ventilation even in the extreme hypoxia at the summit.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
