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

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 99/5/2036    most recent 01040.2004v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science 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 ISI Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Thomson, S. Articles by Semple, S. J. Search for Related Content PubMed PubMed Citation Articles by Thomson, S. Articles by Semple, S. J.

HIGHLIGHTED TOPICS
Physiology and Pathophysiology of Sleep Apnea

Ventilation is unstable during drowsiness before sleep onset

¹Department of Respiratory Medicine, Charing Cross Hospital Campus, and ²Clinical and Academic Unit of Sleep and Breathing, Royal Brompton Hospital, National Heart and Lung Institute, Imperial College, London, United Kingdom

Submitted 24 September 2004 ; accepted in final form 20 June 2005

Ventilation is unstable during drowsiness before sleep onset. We have studied the effects of transitory changes in cerebral state during drowsiness on breath duration and lung volume in eight healthy subjects in the absence of changes in airway resistance and fluctuations of ventilation and CO₂ tension, characteristic of the onset of non-rapid eye movement sleep. A volume-cycled ventilator in the assist control mode was used to maintain CO₂ tension close to that when awake. Changes in cerebral state were determined by the EEG on a breath-by-breath basis and classified as alpha or theta breaths. Breath duration and the pause in gas flow between the end of expiratory airflow and the next breath were computed for two alpha breaths which preceded a theta breath and for the theta breath itself. The group mean (SD) results for this alpha-to-theta transition was associated with a prolongation in breath duration from 5.2 (SD 1.3) to 13.0 s (SD 2.1) and expiratory pause from 0.7 (SD 0.4) to 7.5 s (SD 2.2). Because the changes in arterial CO₂ tension (Pa_CO2) are unknown during the theta breaths, we made in two subjects a continuous record of Pa_CO2 in the radial artery. Pa_CO2 remained constant from the alpha breaths through to the expiratory period of the theta breath by which time the duration of breath was already prolonged, representing an immediate and altered ventilatory response to the prevailing Pa_CO2. In the eight subjects, the CO₂ tension awake was 39.6 Torr (SD 2.3) and on assisted ventilation 38.0 Torr (1.4). We conclude that the ventilatory instability recorded in the present experiments is due to the apneic threshold for CO₂ being at or just below that when awake.

apneic threshold for CO₂; sleep-related rise in PCO₂; arterial to end-tidal PCO₂ gradient

This article has been cited by other articles:

				L. H. Ibrahim, S. R. Patel, M. Modarres, N. L. Johnson, R. Mehra, H. L. Kirchner, and S. Redline A Measure of Ventilatory Variability at Wake-Sleep Transition Predicts Sleep Apnea Severity Chest, July 1, 2008; 134(1): 73 - 78. [Abstract] [Full Text] [PDF]

				Y.-L. Lo, A. S Jordan, A. Malhotra, A. Wellman, R. A Heinzer, M. Eikermann, K. Schory, L. Dover, and D. P White Influence of wakefulness on pharyngeal airway muscle activity Thorax, September 1, 2007; 62(9): 799 - 805. [Abstract] [Full Text] [PDF]

				K. R. Casey, K. O. Cantillo, and L. K. Brown Sleep-Related Hypoventilation/Hypoxemic Syndromes Chest, June 1, 2007; 131(6): 1936 - 1948. [Abstract] [Full Text] [PDF]