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This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 104/5/1426    most recent 01056.2007v1 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 Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Eckert, D. J. Articles by Catcheside, P. G. Search for Related Content PubMed PubMed Citation Articles by Eckert, D. J. Articles by Catcheside, P. G.

Effects of hypoxia on genioglossus and scalene reflex responses to brief pulses of negative upper-airway pressure during wakefulness and sleep in healthy men

¹Adelaide Institute for Sleep Health, Repatriation General Hospital, Daw Park; ²School of Molecular and Biomedical Science, Discipline of Physiology, The University of Adelaide, Adelaide; and ³Department of Medicine, Flinders University, Bedford Park, South Australia, Australia

Submitted 2 October 2007 ; accepted in final form 15 February 2008

Hypoxia can depress ventilation, respiratory load sensation, and the cough reflex, and potentially other protective respiratory reflexes such as respiratory muscle responses to increased respiratory load. In sleep-disordered breathing, increased respiratory load and hypoxia frequently coexist. This study aimed to examine the effects of hypoxia on the reflex responses of 1) the genioglossus (the largest upper airway dilator muscle) and 2) the scalene muscle (an obligatory inspiratory muscle) to negative-pressure pulse stimuli during wakefulness and sleep. We hypothesized that hypoxia would impair these reflex responses. Fourteen healthy men, 19–42 yr old, were studied on two separate occasions, 1 wk apart. Bipolar fine-wire electrodes were inserted orally into the genioglossus muscle, and surface electrodes were placed overlying the left scalene muscle to record EMG activity. In random order, participants were exposed to mild overnight hypoxia (arterial oxygen saturation 85%) or medical air. Respiratory muscle reflex responses were elicited via negative-pressure pulse stimuli (approximately –10 cmH₂O at the mask, 250-ms duration) delivered in early inspiration during wakefulness and sleep. Negative-pressure pulse stimuli resulted in a short-latency activation followed by a suppression of the genioglossus EMG that did not alter with hypoxia. Conversely, the predominant response of the scalene EMG to negative-pressure pulse stimuli was suppression followed by activation with more pronounced suppression during hypoxia compared with normoxia (mean ± SE suppression duration 64 ± 6 vs. 38 ± 6 ms, P = 0.006). These results indicate differential sensitivity to the depressive effects of hypoxia in the reflex responsiveness to sudden respiratory loads to breathing between these two respiratory muscles.

respiratory reflexes; suppression; sleep-disordered breathing