Geniohyoid muscle function in awake canines

• Published in: Journal of applied physiology (1985) Vol. 95; no. 2; pp. 810 - 817
• Main Authors: Yokoba, M, Hawes, H. G, Easton, P. A
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.08.2003; American Physiological Society
• Subjects: Air breathing; Airway Resistance; Animals; Biological and medical sciences; Carbon Dioxide - pharmacology; Deglutition - physiology; Dogs; Dogs - physiology; Electromyography; Fundamental and applied biological sciences. Psychology; Head - physiology; Inhalation; Muscular system; Neck Muscles - physiology; Posture - physiology; Respiration - drug effects; Respiratory Physiological Phenomena; Respiratory system; Respiratory system: anatomy, metabolism, gas exchange, ventilatory mechanics, respiratory hemodynamics; Rest; Vertebrates: respiratory system; Fissipedia; Carnivora; Upper respiratory tract; Shortening; Electrophysiology; Striated muscle; Swallowing; Respiratory system; Muscle contraction; Vertebrata; Mammalia; Electromyography; Genioglossus muscle; Dog
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00332.2002

Department of Critical Care, University of Calgary, Calgary, Alberta, Canada T2N 4N1 Submitted 15 April 2002 ; accepted in final form 24 March 2003 The geniohyoid (Genio) upper airway muscle shows phasic, inspiratory electrical activity in awake humans but no activity and lengthening in anesthetized cats. There is no information about the mechanical action of the Genio, including length and shortening, in any awake, nonanesthetized mammal during respiration (or swallowing). Therefore, we studied four canines, mean weight 28.8 kg, 1.5 days after Genio implantation with sonomicrometry transducers and bipolar electromyogram (EMG) electrodes. Awake recordings of breathing pattern, muscle length and shortening, and EMG activity were made with the animal in the right lateral decubitus position during quiet resting, CO 2 -stimulated breathing, inspiratory-resisted breathing (80 cmH 2 O · l -1 · s), and airway occlusion. Genio length and activity were also measured during swallowing, when it shortened, showing a 9.31% change from resting length, and its EMG activity increased 6.44 V. During resting breathing, there was no phasic Genio EMG activity at all, and Genio showed virtually no movement during inspiration. During CO 2 -stimulated breathing, Genio showed minimal lengthening of only 0.07% change from resting length, whereas phasic EMG activity was still absent. During inspiratory-resisted breathing and airway occlusion, Genio showed phasic EMG activity but still lengthened. We conclude that the Genio in awake, nonanesthetized canines shows active contraction and EMG activity only during swallowing. During quiet or stimulated breathing, Genio is electrically inactive with passive lengthening. Even against resistance, Genio is electrically active but still lengthens during inspiration. upper airway; swallowing; shortening; muscle contraction; electromyogram Address for reprint requests and other correspondence: P. A. Easton, Dept. of Medicine, Rm. 223 Heritage Bldg., Univ. of Calgary, 3330 Hospital Dr. NW, Calgary, AB, Canada T2N 4N1.