Physiological and genomic consequences of intermittent hypoxia - Selected Contribution: Chemoreflex responses to CO2 before and after an 8-h exposureto hypoxia in humans
M. Fatemian et Pa. Robbins, Physiological and genomic consequences of intermittent hypoxia - Selected Contribution: Chemoreflex responses to CO2 before and after an 8-h exposureto hypoxia in humans, J APP PHYSL, 90(4), 2001, pp. 1607-1614
The ventilatory sensitivity to CO2, in hyperoxia, is increased after an 8-h
exposure to hypoxia. The purpose of the present study was to determine whe
ther this increase arises through an increase in peripheral or central chem
osensitivity. Ten healthy volunteers each underwent 8-h exposures to 1) iso
capnic hypoxia, with end-tidal P-O2 (PETO2) = 55 Torr and end-tidal PCO2 (P
ETCO2) = eucapnia; 2) poikilocapnic hypoxia, with PETO2 = 55 Torr and PETCO
2 uncontrolled; and 3) air-breathing control. The ventilatory response to C
O2 was measured before and after each exposure with the use of a multifrequ
ency binary sequence with two levels of PETCO2: 1.5 and 10 Torr above the n
ormal resting value. PETO2 was held at 250 Torr. The peripheral (Gp) and th
e central (Gc) sensitivities were calculated by fitting the ventilatory dat
a to a two-compartment model. There were increases in combined Gp + Cc (26%
, P < 0.05), Gp (33%, P < 0.01), and Gc (23%, P = not significant) after ex
posure to hypoxia. There were no significant differences between isocapnic
and poikilocapnic hypoxia. We conclude that sustained hypoxia induces a sig
nificant increase in chemosensitivity to CO2 within the peripheral chemoref
lex.