title: Active upper airway closure during induced central apneas in lambs is complete at the laryngeal level only.
abstract: We tested the hypotheses that active upper airway closure during induced central apneas in nonsedated lambs 1). is complete and occurs at the laryngeal level and 2). is not due to stimulation of the superior laryngeal nerves (SLN). Five newborn lambs were surgically instrumented to record thyroarytenoid (TA) muscle (glottal constrictor) electromyographic (EMG) activity with supra- and subglottal pressures. Hypocapnic and nonhypocapnic central apneas were induced before and after SLN sectioning in the five lambs. A total of 174 apneas were induced, 116 before and 58 after sectioning of the internal branch of the SLN (iSLN). Continuous TA EMG activity was observed in 88% of apneas before iSLN section and in 87% of apneas after iSLN section. A transglottal pressure different from zero was observed in all apneas with TA EMG activity, with a mean subglottal pressure of 4.3 +/- 0.8 cmH2O before and 4.7 +/- 0.7 cmH2O after iSLN section. Supraglottal pressure was consistently atmospheric. Sectioning of both iSLNs had no effects on the results. We conclude that upper airway closure during induced central apneas in lambs is active, complete, and occurs at the glottal level only. Consequently, a positive subglottal pressure is maintained throughout the apnea. Finally, this complete active glottal closure is independent from laryngeal afferent innervation.
authors.affiliation: Department of Surgery, University of Sherbrooke, Quebec, Canada J1H 5N4.
authors.forename: Pierre-Hugues
authors.initials: PH
authors.lastname: Fortier
authors.forename: Philippe
authors.initials: P
authors.lastname: Reix
authors.forename: Julie
authors.initials: J
authors.lastname: Arsenault
authors.forename: Dominique
authors.initials: D
authors.lastname: Dorion
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Praud
mesh_terms: D000402:Airway Obstruction / Q000503:physiopathology*; D000818:Animals; D000831:Animals, Newborn; D001049:Apnea / Q000503:physiopathology*; D001193:Arytenoid Cartilage / Q000503:physiopathology; D002211:Capsaicin / Q000008:administration & dosage / Q000494:pharmacology; D004298:Dopamine / Q000008:administration & dosage / Q000494:pharmacology; D004576:Electromyography; D005931:Glottis / Q000503:physiopathology; D007275:Injections, Intravenous; D007823:Laryngeal Nerves / Q000187:drug effects / Q000503:physiopathology; D007830:Larynx / Q000187:drug effects / Q000503:physiopathology*; D012132:Respiratory Muscles / Q000503:physiopathology; D012756:Sheep; D013268:Stimulation, Chemical
chemical_list: D002211:Capsaicin; D004298:Dopamine