Response time and sensitivity of the ventilatory response to CO2 in unanesthetized intact dogs: central vs. peripheral chemoreceptors

• Published in: Journal of applied physiology (1985) Vol. 100; no. 1; pp. 13 - 19
• Main Authors: Smith, C. A, Rodman, J. R, Chenuel, B. J. A, Henderson, K. S, Dempsey, J. A
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.01.2006; American Physiological Society
• Subjects: Acid-Base Equilibrium - physiology; Anesthesia; Animals; Biological and medical sciences; Brain - blood supply; Brain - physiology; Carbon dioxide; Carbon Dioxide - administration & dosage; Carbon Dioxide - metabolism; Central Nervous System - physiology; Cerebrovascular Circulation - physiology; Chemoreceptor Cells - physiology; Dogs; Feedback - physiology; Female; Fundamental and applied biological sciences. Psychology; Humans; Hydrogen-Ion Concentration; Lung - innervation; Lung - physiology; Oxygen - metabolism; Peripheral Nervous System - physiology; Pulmonary Ventilation - physiology; Reaction Time - physiology; Reproducibility of Results; Respiratory Mechanics - physiology; Respiratory system; Response time; Sensitivity and Specificity; Fissipedia; Carnivora; Nervous system diseases; Sleep apnea syndrome; Respiratory disease; Chemoreceptor; Vertebrata; Sensitivity; Mammalia; Ventilatory response; Chemosensitivity; Carotid body; Respiration; Dog; sleep apnea; control of breathing
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00926.2005

John Rankin Laboratory of Pulmonary Medicine, Department of Population Health Sciences, School of Medicine, University of Wisconsin, Madison, Wisconsin Submitted 29 July 2005 ; accepted in final form 7 September 2005 We assessed the speed of the ventilatory response to square-wave changes in alveolar P CO 2 and the relative gains of the steady-state ventilatory response to CO 2 of the central chemoreceptors vs. the carotid body chemoreceptors in intact, unanesthetized dogs. We used extracorporeal perfusion of the reversibly isolated carotid sinus to maintain normal tonic activity of the carotid body chemoreceptor while preventing it from sensing systemic changes in CO 2 , thereby allowing us to determine the response of the central chemoreceptors alone. We found the following. 1 ) The ventilatory response of the central chemoreceptors alone is 11.2 (SD = 3.6) s slower than when carotid bodies are allowed to sense CO 2 changes. 2 ) On average, the central chemoreceptors contribute 63% of the gain to steady-state increases in CO 2 . There was wide dog-to-dog variability in the relative contributions of central vs. carotid body chemoreceptors; the central exceeded the carotid body gain in four of six dogs, but in two dogs carotid body gain exceeded central CO 2 gain. If humans respond similarly to dogs, we propose that the slower response of the central chemoreceptors vs. the carotid chemoreceptors prevents the central chemoreceptors from contributing significantly to ventilatory responses to rapid, transient changes in arterial P CO 2 such as those after periods of hypoventilation or hyperventilation ("ventilatory undershoots or overshoots") observed during sleep-disordered breathing. However, the greater average responsiveness of the central chemoreceptors to brain hypercapnia in the steady-state suggests that these receptors may contribute significantly to ventilatory overshoots once unstable/periodic breathing is fully established. carotid body; chemosensitivity; control of breathing; sleep apnea Address for reprint requests and other correspondence: C. A. Smith, Rm. 4245 MSC, Univ. of Wisconsin, 1300 Univ. Ave., Madison, WI 53706 (e-mail: casmith4{at}wisc.edu )