Physiological mechanisms of upper airway hypotonia during REM sleep

David G McSharry; Julian P Saboisky; Pam Deyoung; Amy S Jordan; John Trinder; Erik Smales; Lauren Hess; Nancy L Chamberlin; Atul Malhotra

doi:10.5665/sleep.3498

Physiological mechanisms of upper airway hypotonia during REM sleep

Sleep. 2014 Mar 1;37(3):561-9. doi: 10.5665/sleep.3498.

Authors

David G McSharry¹, Julian P Saboisky², Pam Deyoung³, Amy S Jordan⁴, John Trinder⁴, Erik Smales³, Lauren Hess³, Nancy L Chamberlin⁵, Atul Malhotra⁶

Affiliations

¹ Sleep Disorders Research Laboratory, Brigham and Women's Hospital and Harvard Medical School, Boston, MA ; Letterkenny General Hospital, Co. Donegal, Ireland.
² Neuroscience Research Australia and University of New South Wales, Randwick, Sydney, NSW, Australia.
³ Sleep Disorders Research Laboratory, Brigham and Women's Hospital and Harvard Medical School, Boston, MA.
⁴ Sleep Laboratory, Psychological Sciences, The University of Melbourne, Parkville, Victoria, Australia.
⁵ Dept. of Neurology, Harvard Medical School, Boston, MA.
⁶ Sleep Disorders Research Laboratory, Brigham and Women's Hospital and Harvard Medical School, Boston, MA ; Division of Pulmonary and Critical Care, University of California, San Diego, CA.

Abstract

Study objectives: Rapid eye movement (REM)-induced hypotonia of the major upper airway dilating muscle (genioglossus) potentially contributes to the worsening of obstructive sleep apnea that occurs during this stage. No prior human single motor unit (SMU) study of genioglossus has examined this possibility to our knowledge. We hypothesized that genioglossus SMUs would reduce their activity during stable breathing in both tonic and phasic REM compared to stage N2 sleep. Further, we hypothesized that hypopneas occurring in REM would be associated with coincident reductions in genioglossus SMU activity.

Design: The activity of genioglossus SMUs was studied in (1) neighboring epochs of stage N2, and tonic and phasic REM; and (2) during hypopneas occurring in REM.

Setting: Sleep laboratory.

Participants: 29 subjects (38 ± 13 y) (17 male).

Intervention: Natural sleep, including REM sleep and REM hypopneas.

Measurement and results: Subjects slept overnight with genioglossus fine-wire intramuscular electrodes and full polysomnography. Forty-two SMUs firing during one or more of stage N2, tonic REM, or phasic REM were sorted. Twenty inspiratory phasic (IP), 17 inspiratory tonic (IT), and five expiratory tonic (ET) SMUs were characterized. Fewer units were active during phasic REM (23) compared to tonic REM (30) and stage N2 (33). During phasic REM sleep, genioglossus IP and IT SMUs discharged at slower rates and for shorter durations than during stage N2. For example, the SMU peak frequency during phasic REM 5.7 ± 6.6 Hz (mean ± standard deviation) was less than both tonic REM 12.3 ± 9.7 Hz and stage N2 16.1 ± 10.0 Hz (P < 0.001). The peak firing frequencies of IP/IT SMUs decreased from the last breath before to the first breath of a REM hypopnea (11.8 ± 10.9 Hz versus 5.7 ± 9.4 Hz; P = 0.001).

Conclusion: Genioglossus single motor unit activity is significantly reduced in REM sleep, particularly phasic REM. Single motor unit activity decreases abruptly at the onset of REM hypopneas.

Keywords: Obstructive sleep apnea; genioglossus; rapid eye movement sleep; single motor unit; upper airway hypotonia.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Adult
Electromyography
Female
Humans
Male
Muscle Hypotonia / physiopathology*
Muscle, Skeletal / physiopathology
Polysomnography
Respiration
Sleep Apnea, Obstructive / physiopathology*
Sleep, REM*
Tongue / physiopathology

Abstract

Publication types

MeSH terms

Grants and funding