Ventilatory pattern and oxygen saturation(SpO2) in Lowlanders (LL) and Highlanders (HL) during exercise at high altitude (HA)

Ventilatory response is a hallmark of HA acclimatization. We aimed to compare ventilation in LL and HL at rest and during a standardized exercise. Methods: 2 groups of healthy subjects were studied at Shigatse (4200m, Tibet) : 6 HL, M (age 17-19yrs); 6 acclimatized LL (3M,3F) (age 26-35 yrs). All were monitored by means of portable respiratory inductive plethysmography (LifeShirt, VivoMetrics, CA, USA) both at rest and during strenuous walking on a slope with a 50m difference in height. Results: Ventilatory parameters at rest, at 50% and 80% of the predicted maximal heart rate(HRmax) are reported. In HL the breathing rate( RR) was 22.4(1.3), 36.0 (2.6)*°, 47.2(3.2)* br/min; the tidal volume (TV) was 381(56), 703(104)*°, 1264(122) * mL; the ventilation (VE) was 10.1(1.2), 24.2(2.4)*° , 58.4(4.2) * L/min; SaO2% was 85.3(1.1) , 85.3(1.5) °, 81.0(1.4) *. In LL , RR was 18.4 (1,7), 24.3(2.4)*°, 35.1(1.9) * br/min; TV was 445(67), 778(129)*°, 1316(127)* mL; VE was 7.6(0.6), 17.3(2.9)*°, 44.5(3.0)* L/min; SaO2% was 83.3(0.8) ,79.9(1.1)*°, 74.6(1.5)*. HL vs LL show a significantly higher RR at each point [22.4(1.3) vs 18.4 (1,7); 36.0 (2.6) vs 24.3(2.4); 47.2(3.2) vs 35.1(1.9) p<0.01], a significantly higher VE at 80%HRmax [58.4(4.2) vs 44.5(3.0) p=0.02] and a significantly higher SaO2% during exercise (at 50% and 80% HRmax ): [ 85.3(1.5) vs 79.9(1.1); 81.0(1.4) vs 74.6(1.5) p<0.05]. The % increase in VE, RR and TV was not different in the 2 groups. We conclude that acclimatized LL and HL have the same increase in ventilation during exercise at HA but highlanders’ ventilation is characterized by higher RR in all condition and a higher VE during strenuous exercise. This different ventilatory pattern in the HL is accompanied by lower oxygen desaturation during exercise. This fact suggests the adaptation of body’s ability to cope with strenuous exercise and hypoxic stress.