Journal of Applied Physiology, Vol 70, Issue 2 590-593, Copyright © 1991 by American Physiological Society
Evidence for hypoxic depression of CO2-ventilation response in carotid body-resected humans
Y. Honda and I. Hashizume
Department of Physiology, School of Medicine, Chiba University, Japan.
Steady-state CO2-ventilation response curves with hyperoxia (end-tidal PO2
greater than 200 Torr) and mild hypoxia (end-tidal PO2 approximately equal
to 60 Torr) were compared in five carotid body-resected (BR) patients and
five control patients. The data were analyzed by fitting a linear equation,
V = S(PETCO2-B), where V is minute ventilation S is the response curve
slope. PETCO2 is end-tidal PCO2, and B is the response curve threshold. S
slightly increased from hyperoxia to hypoxia in both BR and control groups.
On the other hand, B moderately increased with hypoxia in BR patients,
whereas it slightly decreased in controls. These changes were all not
significant. However, in accordance with the change in B, the response
curve to hypoxia at V of 10 1/min was significantly shifted in opposite
directions in the two groups, i.e., rightward and leftward shift in BR and
control groups, respectively. Thus the average magnitude of V calculated at
PETCO2 of 40 Torr in hypoxia was significantly lower in BR patients than in
controls (P less than 0.01). We conclude that this hypoxic depression of
the CO2-ventilation response found in BR patients may have resulted, at
least in part, from modulation of the brain stem neural mechanisms that
were elicited by loss of afferent discharges from the carotid body.
