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1 Departmento De Ciencias Biologicas y Fisiologicas/IIA, Universidad Peruana Cayetano Heredia, Lima 100, Peru; and 2 University Laboratory of Physiology, University of Oxford, Oxford OX1 3PT, United Kingdom
High-altitude (HA) natives have blunted ventilatory responses to
hypoxia (HVR), but studies differ as to whether this blunting is lost
when HA natives migrate to live at sea level (SL), possibly because HVR
has been assessed with different durations of hypoxic exposure (acute
vs. sustained). To investigate this, 50 HA natives (>3,500 m,
for >20 yr) now resident at SL were compared with 50 SL natives as
controls. Isocapnic HVR was assessed by using two protocols:
protocol 1, progressive stepwise induction of hypoxia over
5-6 min; and protocol 2, sustained (20-min) hypoxia
(end-tidal PO2 = 50 Torr). Acute HVR was
assessed from both protocols, and sustained HVR from protocol
2. For HA natives, acute HVR was 79% [95% confidence interval
(CI): 52-106%, P = not significant] of SL
controls for protocol 1 and 74% (95% CI: 52-96%,
P < 0.05) for protocol 2. By contrast,
sustained HVR after 20-min hypoxia was only 30% (95% CI:
7-67%, P < 0.001) of SL control values. The
persistent blunting of HVR of HA natives resident at SL is substantially less to acute than to sustained hypoxia, when hypoxic ventilatory depression can develop.
regulation of ventilation; human; Andean natives; hypoxic ventilatory depression; chemoreflex; blunting
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