Dynamic response of the peripheral chemoreflex loop to changes in end-tidal O2.
We studied the peripheral ventilatory response dynamics to changes in end-tidal O2 tension (PETO2) in 13 cats anesthetized with alpha-chloralose-urethan. The arterial O2 tension in the medulla oblongata was kept constant using the technique of artificial perfusion of the brain stem. At constant end-tidal CO2 tension, 72 ventilatory on-responses due to stepwise changes in PETO2 from hyperoxia (45-55 kPa) to hypoxia (4.7-9.0 kPa) and 62 ventilatory off-responses due to changes from hypoxia to hyperoxia were assessed. We fitted two exponential functions with the same time delay to the breath-by-breath ventilation and found a fast and a slow component in 85% of the ventilatory on-responses and in 76% of the off-responses. The time constant of the fast component of the ventilatory on-response was 1.6 +/- 1.5 (SD) s, and that of the off-response was 2.4 +/- 1.3 s; the gain of the on-response was smaller than that of the off-response (P = 0.020). For the slow component, the time constant of the on-response (72.6 +/- 36.4 s) was larger (P = 0.028) than that of the off-response (43.7 +/- 28.3 s), whereas the gain of the on-response exceeded that of the off-response (P = 0.031). We conclude that the ventilatory response of the peripheral chemoreflex loop to stepwise changes in PETO2 contains a fast and a slow component.
Berkenbosch
A
A
Department of Physiology and Physiological Physics, University of Leiden, The Netherlands.
DeGoede
J
J
Ward
D S
DS
Olievier
C N
CN
VanHartevelt
J
J
D000818:Animals; D001933:Brain Stem / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D002415:Cats; D002628:Chemoreceptor Cells / Q000502:physiology*; D000860:Hypoxia / Q000378:metabolism; D008526:Medulla Oblongata / Q000378:metabolism; D008954:Models, Biological; D010101:Oxygen Consumption / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D012129:Respiratory Function Tests; D013990:Tidal Volume; D014132:Trachea / Q000502:physiology
D002245:Carbon Dioxide