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

Abstract

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% O(2)), 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 CO(2) 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.

Structural Modulation of Brain Development by Oxygen: Evidence on Adolescents Migrating from High Altitude to Sea Level Environment

“…After residing at SL for a long period of time, they redevelop an adaption to high concentration of oxygen environment. For example, HA adult residents had a decrease in resting heart rate after continuous residence at SL for 2 years [31], [32]. HA residents who descended to SL over a three-month period showed a slow disappearance of electrocardiographic signs of right ventricular hypertrophy [30].…”

“…HA natives have developed adaptations in respiratory and cardiovascular function [38]–[40]. After residing at SL for a long period of time, they redeveloped an adaption to high concentration of oxygen environment [29]–[32], [41], [42]. In the present study, pulmonary function and cardiovascular function were also examined.…”

“…In some brain regions, neuronal activities can be enhanced by transient inhalation of high concentration of oxygen [25]–[28]. In HA residents who have immigrated to lowlands for a long period of time, peripheral physiological systems typically employ adaptive mechanisms such as alterations in respiratory and circulatory function [29]–[32] and hemoglobin concentration [33]. Such alterations change oxygen transport in the cerebral blood flow, and then lead to cumulative changes in brain structure.…”

Aclimatação em altitude simulada: efeitos sobre a frequência cardíaca e saturação de oxigênio da hemoglobina em jogadores de futebol

“…Entre as estratégias compensatórias à manutenção do equilíbrio homeostático em repouso e exercício na altitude, encontram-se o aumento da FC (GAMBOA et al, 2001;BÄRTSCH;GIBBS, 2007). No presente estudo, tal alteração é observada na primeira sessão, na qual houve aumento da FC de repouso quando comparado à situação de normoxia.…”

O desafio da altitude. Uma perspectiva fisiológica

“…Um dos mecanismos de adaptação fisiológica mais característicos, inerente à exposição aguda a elevadas altitudes, é o incremento acentuado da frequência respiratória e do volume corrente (27,45,72,84). Esta resposta ventilatória à hipóxia induzida, essencialmente, pela estimulação de químio-receptores periféricos (11,43) sensíveis às variações do conteú-do arterial de oxigénio, possibilita o incremento da Fisiologia de altitude ventilação de 2 a 5 vezes relativamente aos valores obtidos ao nível do mar e, com isso, o aumento da pressão alveolar parcial de oxigénio alveolar (38,73).…”