Postural effects on pharyngeal protective reflex mechanisms.
OBJECTIVE
Pharyngeal muscle dilators are important in obstructive sleep apnea pathogenesis because the failure of protective reflexes involving these muscles yields pharyngeal collapse. Conflicting results exist in the literature regarding the responsiveness of these muscles during stable non-rapid eye movement sleep. However, variations in posture in previous studies may have influenced these findings. We hypothesized that tongue protruder muscles are maximally responsive to negative pressure pulses during supine sleep, when posterior tongue displacement yields pharyngeal occlusion.


METHODS
We studied all subjects in the supine and lateral postures during wakefulness and stable non-rapid eye movement sleep by measuring genioglossus and tensor palatini electromyograms during basal breathing and following negative pressure pulses.


METHODS
Upper-airway physiology laboratory of Sleep Medicine Division, Brigham and Women's Hospital.


METHODS
17 normal subjects.


RESULTS
We observed an increase in genioglossal responsiveness to negative pressure pulses in sleep as compared to wakefulness in supine subjects (3.9 percentage of maximum [%max] +/- 1.1 vs 4.4 %max +/- 1.0) but a decrease in the lateral decubitus position (4.1 %max +/- 1.0 vs 1.5 %max +/- 0.4), the interaction effect being significant. Despite this augmented reflex, collapsibility, as measured during negative pressure pulses, increased more while subjects were in the supine position as compared with the lateral decubitus position. While the interaction between wake-sleep state and position was also significant for the tensor palatini, the effect was weaker than for genioglossus, although, for tensor palatini, baseline activity was markedly reduced during non-rapid eye movement sleep as compared with wakefulness.


CONCLUSIONS
We conclude that body posture does have an important impact on genioglossal responsiveness to negative pressure pulses during non-rapid eye movement sleep. We speculate that this mechanism works to prevent pharyngeal occlusion when the upper airway is most vulnerable to collapse eg, during supine sleep.
Malhotra
Atul
A
Sleep Medicine and Pulmonary/Critical Care Divisions, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. amalhotra1@partners.org
Trinder
John
J
Fogel
Robert
R
Stanchina
Michael
M
Patel
Sanjay R
SR
Schory
Karen
K
Kleverlaan
Darci
D
White
David P
DP
D000328:Adult; D015992:Body Mass Index; D005260:Female; D005683:Gagging / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010609:Pharyngeal Muscles / Q000502:physiology; D011187:Posture / Q000502:physiology*; D011312:Pressure; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis / Q000517:prevention & control*; D012894:Sleep Stages / Q000502:physiology; D014059:Tongue / Q000502:physiology; D014851:Wakefulness / Q000502:physiology