HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Xi, L Articles by Dempsey, J A Search for Related Content PubMed PubMed Citation Articles by Xi, L Articles by Dempsey, J A

John Rankin Laboratory of Pulmonary Medicine, Department of Preventive Medicine, University of Wisconsin, Madison 53705-2368.

1. We assessed short-term potentiation of ventilation in response to brief systemic normocapnic hypoxaemia in conscious dogs. Four recumbent dogs were exposed to Pa, O2 35-55 mmHg with Pa, CO2 maintained normocapnic for forty to fifty seconds and then abruptly returned to normoxia. Minute ventilation (VI) increased 4- to 5-fold during hypoxia due to both increased tidal volume (VT) and frequency (f). Several trials of hypoxic exposure with normoxic restoration were conducted with animals intact and following bilateral cold blockade of the cervical vagus nerves sufficient to block completely the Hering-Breuer reflex. 2. In the vagally intact dog, when normoxia was restored immediately following normocapnic hypoxia (PET, O2 = 40 Torr), expiratory time (TE) was prolonged to 190 +/- 68% of control (mean +/- S.E.M., range 53-350%) on the second or third breath and then returned slowly to control values on subsequent breaths. The prolongation of TE following removal of the hypoxic stimulus was positively correlated with the magnitude of the peak VT reached during hypoxic exposure. However, VT and VI remained significantly greater than control over a twenty second or four-breath period following hypoxia. 3. In the vagally blocked dog, no prolongation of TE was observed following isocapnic hypoxia; nor was TE following hypoxia correlated with the magnitude of the VT during hypoxia. The time constants of decay of VI, VT and f back to control, following hypoxia averaged 16, 19 and 9 s, respectively. 4. We conclude that short-term potentiation of ventilatory output following peripheral chemoreceptor hypoxic stimulation does exist in the awake dog, but the stimulatory after-effect is masked and TE is prolonged by a 'memory' of inhibitory vagal feedback. The magnitude of this inhibitory after-effect on TE prolongation increases in proportion to the increase in tidal volume achieved during the hypoxaemia. 5. This inhibitory effect of vagal memory may contribute to instability of breathing pattern and apnoea following transient disturbances in ventilatory output.

This article has been cited by other articles:

				E. F. Bailey and R. F. Fregosi Modulation of upper airway muscle activities by bronchopulmonary afferents J Appl Physiol, August 1, 2006; 101(2): 609 - 617. [Abstract] [Full Text] [PDF]

				I. Mitrouska, E. Kondili, G. Prinianakis, N. Siafakas, and D. Georgopoulos Effects of Theophylline on Ventilatory Poststimulus Potentiation in Patients with Brain Damage Am. J. Respir. Crit. Care Med., April 15, 2003; 167(8): 1124 - 1130. [Abstract] [Full Text] [PDF]

				F. Han, S. Subramanian, T. E. Dick, I. A. Dreshaj, and K. P. Strohl Ventilatory behavior after hypoxia in C57BL/6J and A/J mice J Appl Physiol, November 1, 2001; 91(5): 1962 - 1970. [Abstract] [Full Text] [PDF]

				P. L. Janssen, J. S. Williams, and R. F. Fregosi Consequences of periodic augmented breaths on tongue muscle activities in hypoxic rats J Appl Physiol, May 1, 2000; 88(5): 1915 - 1923. [Abstract] [Full Text] [PDF]

				J. H. Mateika and R. F. Fregosi Long-term facilitation of upper airway muscle activities in vagotomized and vagally intact cats J Appl Physiol, February 1, 1997; 82(2): 419 - 425. [Abstract] [Full Text] [PDF]