title: Neural mechanism of the pressor response to obstructive and nonobstructive apnea.
abstract: Obstructive and nonobstructive apneas elicit substantial increases in muscle sympathetic nerve activity and arterial pressure. The time course of change in these variables suggests a causal relationship; however, mechanical influences, such as release of negative intrathoracic pressure and reinflation of the lungs, are potential contributors to the arterial pressure rise. To test the hypothesis that apnea-induced pressor responses are neurally mediated, we measured arterial pressure (photoelectric plethysmography), muscle sympathetic nerve activity (peroneal microneurography), arterial O2 saturation (pulse oximeter), and end-tidal CO2 tension (gas analyzer) during sustained Mueller maneuvers, intermittent Mueller maneuvers, and simple breath holds in six healthy humans before, during, and after ganglionic blockade with trimethaphan (3-4 mg/min, titrated to produce complete disappearance of sympathetic bursts from the neurogram). Ganglionic blockade abolished the pressor responses to sustained and intermittent Mueller maneuvers (-4 +/- 1 vs. +15 +/- 3 and 0 +/- 2 vs. +15 +/- 5 mmHg) and breath holds (0 +/- 3 vs. +11 +/- 3, all P < 0.05). We conclude that the acute pressor response to obstructive and nonobstructive voluntary apnea is sympathetically mediated.
authors.affiliation: Department of Medicine, University of Wisconsin, and Middleton Memorial Veterans Hospital, Madison, Wisconsin 53706, USA.
authors.forename: S
authors.initials: S
authors.lastname: Katragadda
authors.forename: A
authors.initials: A
authors.lastname: Xie
authors.forename: D
authors.initials: D
authors.lastname: Puleo
authors.forename: J B
authors.initials: JB
authors.lastname: Skatrud
authors.forename: B J
authors.initials: BJ
authors.lastname: Morgan
mesh_terms: D000328:Adult; D001049:Apnea / Q000503:physiopathology*; D001341:Autonomic Nervous System / Q000187:drug effects / Q000503:physiopathology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005730:Ganglionic Blockers / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D008297:Male; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology; D012891:Sleep Apnea Syndromes / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology
chemical_list: D005730:Ganglionic Blockers