Sensorimotor function of the upper-airway muscles and respiratory sensory processing in untreated obstructive sleep apnea

Abstract

Numerous studies have demonstrated upper-airway neuromuscular abnormalities during wakefulness in snorers and obstructive sleep apnea (OSA) patients. However, the functional role of sensorimotor impairment in OSA pathogenesis/disease progression and its potential effects on protective upper-airway reflexes, measures of respiratory sensory processing, and force characteristics remain unclear. This study aimed to gain physiological insight into the potential role of sensorimotor impairment in OSA pathogenesis/disease progression by comparing sensory processing properties (respiratory-related evoked potentials; RREP), functionally important protective reflexes (genioglossus and tensor palatini) across a range of negative pressures (brief pulses and entrained iron lung ventilation), and tongue force and time to task failure characteristics between 12 untreated OSA patients and 13 controls. We hypothesized that abnormalities in these measures would be present in OSA patients. Upper-airway reflexes (e.g., genioglossus onset latency, 20 ± 1 vs. 19 ± 2 ms, P = 0.82), early RREP components (e.g., P1 latency 25 ± 2 vs. 25 ± 1 ms, P = 0.78), and the slope of epiglottic pressure vs. genioglossus activity during iron lung ventilation (-0.68 ± 1.0 vs. -0.80 ± 2.0 cmH(2)O/%max, P = 0.59) were not different between patients and controls. Maximal tongue protrusion force was greater in OSA patients vs. controls (35 ± 2 vs. 27 ± 2 N, P < 0.01), but task failure occurred more rapidly (149 ± 24 vs. 254 ± 23 s, P < 0.01). Upper-airway protective reflexes across a range of negative pressures as measured by electromyography and the early P1 component of the RREP are preserved in OSA patients during wakefulness. Consistent with an adaptive training effect, tongue protrusion force is increased, not decreased, in untreated OSA patients. However, OSA patients may be vulnerable to fatigue of upper-airway dilator muscles, which could contribute to disease progression.

Effects of Inhaled Fluticasone on Upper Airway during Sleep and Wakefulness in Asthma: A Pilot Study

“…13 This finding may mirror other UAW muscles alterations in response to our intervention with FP. Interestingly, a more recent study of untreated OSA patients reported a pattern of wakefulness tongue function changes 46 similar to that observed in our study, i.e., these patients, relative to controls, demonstrated greater maximal protrusive force but shorter time to task failure. These functional alterations have as histological substrate a shift from type I (slow twitch-low force, fatigue resistant) to type II (fast twitch-high force, fatigue prone) muscle fibers, 47,48 and are believed to be an adaptive mechanism to the increased contractile demands on the dilator.…”

“…These functional alterations have as histological substrate a shift from type I (slow twitch-low force, fatigue resistant) to type II (fast twitch-high force, fatigue prone) muscle fibers, 47,48 and are believed to be an adaptive mechanism to the increased contractile demands on the dilator. 46 Was a similar pathology involved in our subjects? Further work needs to be done to answer this question.…”

Trazodone Increases the Respiratory Arousal Threshold in Patients with Obstructive Sleep Apnea and a Low Arousal Threshold

“…Raw genioglossus and tensor palatini EMG were rectified, movingtime averaged (100 ms), and expressed as a percentage of maximum activity. 23,24 Peak (maximum during inspiration) and tonic EMG (nadir during expiration), and respiratory parameters were quantified on a breath-by-breath basis using customdesigned semi-automated software as described previously. 25 Upper airway resistance (R UA ) was quantified as the difference in mask versus epiglottic pressure during inspiration at a flow rate of 200 mL/s.…”

“…23,24 Wakefulness upper airway muscle activity and respiratory parameters were acquired during quiet breathing on and off therapeutic CPAP prior to lights out at approximately 10:30. If required, the CPAP level was increased throughout the night to eliminate any sign of inspiratory flow limitation (according to the epiglottic pressure-flow relationship), yielding the holding pressure.…”

Nerve and Muscle Changes in the Upper Airways of Subjects with Obstructive Sleep Apnea: Structural Basis for the Neurogenic Theory

“…The respiratory-related evoked potentials (RREPs) during wakefulness in OSA revealed a reduction in the amplitude but not the latency of the early RREP components [44,47] reflecting sensory processing is reduced in the OSA patients [48]. Other studies revealed no changes [49][50][51].…”