Journal of Applied Physiology, Vol 80, Issue 5 1528-1539, Copyright © 1996 by American Physiological Society

ARTICLES

Negative pressure-induced deformation of the upper airway causes central apnea in awake and sleeping dogs

C. A. Harms, Y. J. Zeng, C. A. Smith, E. H. Vidruk and J. A. Dempsey
John Rankin Laboratory of Pulmonary Medicine, Department of Preventive Medicine, University of Wisconsin, Madison 53705, USA.

We investigated the effects of negative pressure (NP) in the isolated upper airway (UA) in three unanesthetized dogs. The UA was isolated, and the dogs breathed through an endotracheal tube while wearing a fitted fiberglass snout mask. NP (-2 to -32 cmH2O) was applied in a square wave below the larynx or at the snout at end expiration and was held until inspiratory effort during wakefulness, non-rapid-eye-movement (NREM) sleep, and rapid-eye-movement (REM) sleep. During all states of consciousness, NP applied to the UA prolonged expiratory time (TE) 1) below a threshold of -8 to -10 cmH2O, which coincided with closure of the oro- and/or velopharynx; and 2) in a progressive fashion at more negative pressures than threshold, up to a mean apneic length of 324% of the control value (or 13.9 s) at -30 cmH2O. TE prolongation was less during REM sleep at a given NP (P < 0.05). Augmented tonic genioglossal electromyographic activity also occurred with the applied NP during wakefulness and NREM sleep but not with REM sleep. NP (-20 to -32 cmH2O) applied as a brief pulse (300-500 ms) during NREM sleep caused transient airway occlusion, terminated the breath during inspiration, and prolonged TE when applied at end expiration. Central apneas always persisted beyond the termination of the UA closure. TE prolongation in response to NP persisted in the presence of a topical anesthetic nebulized through the UA sufficient to abolish the laryngeal gag reflexes. We conclude that UA closure and deformation will cause significant TE prolongation during all states of consciousness and activation of the genioglossus muscle during wakefulness and NREM sleep but not during REM sleep.

This article has been cited by other articles:

				J. A Dempsey, C. A Smith, T. Przybylowski, B. Chenuel, A. Xie, H. Nakayama, and J. B Skatrud The ventilatory responsiveness to CO2 below eupnoea as a determinant of ventilatory stability in sleep J. Physiol., October 1, 2004; 560(1): 1 - 11. [Abstract] [Full Text] [PDF]

				G. W. Don and K. A. Waters Influence of sleep state on frequency of swallowing, apnea, and arousal in human infants J Appl Physiol, June 1, 2003; 94(6): 2456 - 2464. [Abstract] [Full Text] [PDF]

				T. R. Feroah, H. V. Forster, L. Pan, N. E. Schlick, P. Martino, and T. Rice Negative pressure effects on mechanically opposing pharyngeal muscles in awake and sleeping goats J Appl Physiol, November 1, 2001; 91(5): 2289 - 2297. [Abstract] [Full Text] [PDF]

				P. R. Eastwood, A. K. Curran, C. A. Smith, and J. A. Dempsey Hemodynamic effects of pressures applied to the upper airway during sleep J Appl Physiol, August 1, 2000; 89(2): 537 - 548. [Abstract] [Full Text] [PDF]

				P. R. Eastwood, A. K. Curran, C. A. Smith, and J. A. Dempsey Effect of upper airway negative pressure on inspiratory drive during sleep J Appl Physiol, March 1, 1998; 84(3): 1063 - 1075. [Abstract] [Full Text] [PDF]

				C. A. Smith, K. S. Henderson, L. Xi, C.-M. Chow, P. R. Eastwood, and J. A. Dempsey Neural-mechanical coupling of breathing in REM sleep J Appl Physiol, December 1, 1997; 83(6): 1923 - 1932. [Abstract] [Full Text] [PDF]

				A. K. Curran, P. R. Eastwood, C. A. Harms, C. A. Smith, and J. A. Dempsey Superior laryngeal nerve section alters responses to upper airway distortion in sleeping dogs J Appl Physiol, September 1, 1997; 83(3): 768 - 775. [Abstract] [Full Text] [PDF]