© 2002 American Thoracic Society
Laryngeal Muscle Activities with Cerebral Hypoxia–Ischemia in Newborn LambsDepartment of Pediatrics, University of Kentucky, Lexington, Kentucky; and Department of Pediatrics, University of Florida, Gainesville, Florida Correspondence and requests for reprints should be addressed to Alastair A. Hutchison, M.B.Ch.B., F.R.A.C.P., Division of Neonatology, Department of Pediatrics, MS-472, 800 Rose Street, Lexington, KY 40536-0298. E-mail: aahutch{at}msn.com This study tested the hypotheses that (1) acute cerebral hypoxia–ischemia changes laryngeal adductor, laryngeal abductor, and diaphragmatic activities, resulting in central apnea with laryngeal closure; and (2) these laryngeal muscle activities act to maintain absolute lung volume. The respiratory pattern was determined in three asphyxiated, awake preterm lambs after cesarean section birth and in 12 awake, term lambs, with normal lung function, after induction of acute cerebral hypoxia–ischemia by occlusion of the brachiocephalic artery. Electrocorticogram activity, flow, volume, electromyograms of laryngeal abductor and adductor muscles and diaphragm, and, in the term lambs, trans-upper airway pressure and carotid blood flow were recorded. With either preterm birth asphyxia or induced acute cerebral hypoxia–ischemia, minute ventilation initially increased, and then hypopnea occurred. During the hypopnea, laryngeal adductor activity was prominent, accompanied by an increased upper airway pressure and a maintained/raised absolute lung volume. Thus, when acute hypoxia–ischemia limited to the upper body is induced in lambs with normal lung function, expiratory laryngeal adduction with closure of the upper airway occurs and likely functions to aid autoresuscitation.
Key Words: birth • posterior cricoarytenoid • resuscitation • thyroarytenoid This article has been cited by other articles:
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