Role of sensory input from the lungs in control of muscle sympathetic nerve activity during and after apnea in humans

• Published in: Journal of applied physiology (1985) Vol. 97; no. 2; pp. 635 - 640
• Main Authors: Khayat, Rami N, Przybylowski, Tadeusz, Meyer, Keith C, Skatrud, James B, Morgan, Barbara J
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.08.2004; American Physiological Society
• Subjects: Adult; Apnea - physiopathology; Biological and medical sciences; Blood Pressure; Chemoreceptor Cells - physiology; Female; Fundamental and applied biological sciences. Psychology; Heart Rate; Humans; Hyperventilation - physiopathology; Lung - innervation; Lung - physiology; Lung Transplantation; Lungs; Male; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Muscular system; Nervous system; Pressoreceptors - physiology; Respiratory Mechanics; Respiratory system; Sympathetic Nervous System - physiology; Human; Sympathetic nerve; Vertebrata; Apnea; Mammalia; baroreflex; Lung; lung transplantation; Striated muscle; chemoreflex; Respiratory system; pulmonary stretch receptors
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00241.2004

Departments of 1 Medicine, 2 Population Health Sciences, and 3 Orthopedics and Rehabilitation, University of Wisconsin-Madison and Middleton Veterans Affairs Hospital, Madison, Wisconsin 53706 Submitted 3 March 2004 ; accepted in final form 2 April 2004 We reasoned that, if the lung inflation reflex contributes importantly to apnea-induced sympathetic activation, such activation would be attenuated in bilateral lung transplant recipients (LTX). We measured muscle sympathetic nerve activity (MSNA; intraneural electrodes), heart rate, mean arterial pressure, tidal volume, end-tidal P CO 2 , and arterial oxygen saturation in seven LTX and seven healthy control subjects (Con) before, during, and after 20-s end-expiratory breath holds. Our evidence for denervation in LTX was 1 ) greatly attenuated respiratory sinus arrhythmia and 2 ) absence of cough reflex below the level of the carina. During apnea, the temporal pattern and the peak increase in MSNA were virtually identical in LTX and Con (347 ± 99 and 359 ± 46% of baseline, respectively; P > 0.05). In contrast, the amount of MSNA present in the first 5 s after resumption of breathing was greater in LTX vs. Con (101 ± 4 vs. 38 ± 7% of baseline, respectively; P < 0.05). There were no between-group differences in apnea-induced hypoxemia or hypercapnia, hemodynamic, or ventilatory responses. Thus cessation of the rhythmic sympathoinhibitory feedback that normally accompanies eupneic breathing does not contribute importantly to sympathetic excitation during apnea. In contrast, vagal afferent input elicited by hyperventilation-induced lung stretch plays an important role in the profound, rapid sympathetic inhibition that occurs after resumption of breathing after apnea. pulmonary stretch receptors; lung transplantation; chemoreflex; baroreflex Address for reprint requests and other correspondence: B. J. Morgan, Dept. of Orthopedics and Rehabilitation, 1300 University Ave., 5173 MSC, University of Wisconsin-Madison, Madison, WI 53706 (E-mail: morgan{at}surgery.wisc.edu ).