title: Dynamics of ventilatory response to step changes in PCO2 of blood perfusing the brain stem.
abstract: The technique of artificial brain stem perfusion was used to assess the ventilatory response to step changes in PCO2 of the blood perfusing the brain stem of the cat. A two-channel roller pump and a four-way valve allow switching the gas exchanger into and out of the extracorporeal circuit, which controlled the perfusion to the brain stem. Seven alpha-chloralose-urethan-anesthetized cats were studied, and 25 steps of increasing and 23 steps of decreasing PCO2 were analyzed. A model consisting of a single-exponential function with time delay best described the ventilatory response. The time delays 11.7 +/- 8.1 and 6.4 +/- 6.8 (SD) s (obtained from mean values per cat) for the step into and out of hypercapnia, respectively, were not significantly different (P = 0.10) and were of the order of the transit time of the tubing from valve to brain stem. The steady-state CO2 sensitivities obtained from the on- and off-responses were also not significantly different (P = 0.10). The time constants 87 +/- 25 and 150 +/- 51 s, respectively, were significantly different (P = 0.0002). We conclude that the central chemoreflex is adequately modeled by a single component with a different time constant for on- and off-responses.
authors.affiliation: Department of Physiology, University of Leiden, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Berkenbosch
authors.forename: D S
authors.initials: DS
authors.lastname: Ward
authors.forename: C N
authors.initials: CN
authors.lastname: Olievier
authors.forename: J
authors.initials: J
authors.lastname: DeGoede
authors.forename: J
authors.initials: J
authors.lastname: VanHartevelt
mesh_terms: D000818:Animals; D001933:Brain Stem / Q000098:blood supply*; D002245:Carbon Dioxide / Q000097:blood*; D002415:Cats; D005260:Female; D001239:Inhalation; D008297:Male; D010313:Partial Pressure; D010477:Perfusion; D012039:Regional Blood Flow; D012119:Respiration
chemical_list: D002245:Carbon Dioxide