Modulation of respiratory responses to carotid sinus nerve stimulation by brain hypoxia.
This study examines the effect of progressive isocapnic CO hypoxemia on respiratory afterdischarge and the phrenic neurogram response to supramaximal carotid sinus nerve (CSN) stimulation. Twelve anesthetized, vagotomized, peripherally chemodenervated, ventilated cats with blood pressure controlled were studied. During isocapnic hypoxemia, the amplitude of the phrenic neurogram was progressively depressed. In contrast, the increase in peak phrenic amplitude produced by CSN stimulation was unchanged, suggesting that the central respiratory response to CSN stimulation is unaffected by progressive hypoxemia. The time constant of respiratory afterdischarge (tau) was calculated from best-fit plots of phrenic amplitude vs. time after cessation of CSN stimulation. Under control conditions the value of tau was 57.7 +/- 3 (SE) s (n = 12). During progressive isocapnic hypoxemia, tau decreased as a linear function of arterial O2 content (CaO2) such that a 40% reduction of CaO2 resulted in a 48% reduction in tau. This reduction of respiratory afterdischarge may contribute to the genesis of periodic breathing during hypoxia.
Melton
J E
JE
Department of Medicine, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick 08903-0019.
Yu
Q P
QP
Neubauer
J A
JA
Edelman
N H
NH
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism; D002248:Carbon Monoxide; D002346:Carotid Sinus / Q000503:physiopathology*; D002415:Cats; D004558:Electric Stimulation; D005260:Female; D002534:Hypoxia, Brain / Q000503:physiopathology*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010791:Phrenic Nerve / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology*; D012890:Sleep / Q000502:physiology; D013238:Stereotaxic Techniques; D014628:Vagotomy
D002245:Carbon Dioxide; D002248:Carbon Monoxide