Ventilatory and Cardiovascular Responses to Hypoxia and Exercise in Andean Natives Living at Sea Level

Gamboa, Alfredo, Léon-Velarde, Fabiola, Rivera-Ch.,María, Vargas, Manuel, Palacios, José-Antonio, and Monge-C, Carlos. Ventilatory and Cardiovascular Responses to Hypoxia and Exercise in Andean Natives Living at Sea Level. High Alt Med Biol 2:341-347, 2001.-This study was designed to determine in subjects born at high altitude who move to sea level (HA-SL: born at 3500 m or above; n = 25) whether their cardiorespiratory responses to hypoxia and exercise are similar to those of sea level natives (SL, n = 25). The average age (39 ± 7.3 yr), weight (72 ± 7.3 kg), and height (1.71 ± 0.01 m) did not differ between the SL and HA-SL subjects. All subjects were studied at rest or during exercise (60 W on cycle ergometer) while breathing room air (F_IO2 = 0.21 and P_B = 760) or hypoxia (F_IO2 = 0.115 and PB = 760) in the following order: (1) normoxia at rest (NX-Rs), (2) hypoxia at rest (HX-Rs, 11.5% O₂), hypoxia at exercise (HX-Ex), and normoxia at exercise (NX-Ex). Each period lasted 5 min. In absolute values, HA-SL showed significantly higher ventilation (V_E, L/ min) during exercise in both normoxia and hypoxia and higher oxygen saturation (Sa_O2, %) during hypoxia both at rest and in exercise. They also had lower end-tidal CO₂ values (P_ETCO2, torr) at rest in both normoxia and hypoxia, but a higher P_ETCO2 in hypoxic exercise. Heart rate (HR, beats/ min) was lower at rest in both normoxia and hypoxia, but higher in exercise. With acute hypoxia, Sa_O2 decreased less in the HA-SL than in the SL at rest (HA-SL, 9.2 ± 0.8; SL, 12.0 ± 0.82) and during exercise (HA-SL, 18.3 ± 1.1; SL, 21.2 ± 1.2). In conclusion, this study shows that HA-SL natives have increased ventilation and heart rate during exercise once their lifelong hypoxia is relieved.