RESUMEN
High-altitude (HA) natives have blunted ventilatory sensitivities to hypoxia, and it is uncertain whether this blunting is reversible on migration to sea level (SL). To study this, the ventilatory sensitivities to hypoxia of HA natives residing near SL were compared with those of SL natives. Two studies were performed. In study A, 24 HA subjects who had lived above 3,000 m for an average of 14 yr and had been resident at SL for an average of 23 yr were compared with 23 SL controls. In study B, 25 HA subjects who had lived above 3,500 m for at least 20 yr and had been resident at SL for no more than 5 yr were compared with 25 SL controls. Hypoxic sensitivities were assessed by breathing seven progressively more hypoxic gas mixtures that contained progressively more CO2 in an attempt to maintain isocapnia throughout. The ventilatory sensitivities to hypoxia (l . min-1 . %-1 . m-2) did not differ significantly (by analysis of variance) between HA and SL natives in either study A (-0.51 +/- 0.25, mean +/- SD) or study B (-0.34 +/- 0. 15), but the ventilatory sensitivities did differ significantly between the two studies for reasons which are not entirely clear. We conclude that HA natives residing at SL, even if previously at HA for >20 yr, do not maintain the severely blunted hypoxic responses that have been reported in such individuals.
Asunto(s)
Aclimatación/fisiología , Altitud , Hipoxia/fisiopatología , Mecánica Respiratoria/fisiología , Adulto , Femenino , Humanos , Masculino , Consumo de Oxígeno/fisiología , PerúRESUMEN
This study was designed to determine whether subjects born at high altitude (HA; 2,000 m or above) who subsequently move to near sea level (SL) develop end-tidal PCO2 (PETCO2) and PO2 (PETO2) values that equal those of SL natives living near SL. A total of 108 male HA natives living near SL were identified by survey of a district in Lima, Peru, and a further 108 male SL natives from the same district were identified as control subjects. Of these subjects, satisfactory data for inclusion in the study were obtained from 93 HA and 82 SL subjects. Mean PETCO2 and PETO2 values were 37.7 +/- 2.5 (SD) and 104.7 +/- 3.2 Torr, respectively, in HA subjects and 37.7 +/- 2.2 and 104.8 +/- 3.0 Torr, respectively, in SL subjects. The average difference between SL natives and HA natives for PETCO2 was 0.07 Torr (-0.64 to 0.78; 95% confidence interval) and for PETO2 was 0.05 Torr (-0.89 to 0.99, 95% confidence interval). The average age and weight of the SL and HA subjects did not differ, but the HA subjects were shorter and tended to have larger vital capacities, consistent with their origin at HA. We conclude that the PETCO2 and PETO2 near SL of SL natives and HA natives do not differ.