1191 Development of a Clinically-Validated Questionnaire and Scoring Algorithm Designed to Identify Common Sleep Problems Among Adults

Introduction

Although sleep is critical to maintaining health and quality of life, inadequate sleep duration and/or quality is common. It can be difficult to distinguish sleep problems that may be addressed through adjustments to lifestyle versus issues that may represent a more serious condition requiring medical intervention. SmartSleep Analyzer is a cloud-based questionnaire and scoring algorithm designed to categorize respondents according to likely sleep problems as follows: obstructive sleep apnea (OSA), snoring, trouble falling asleep or staying asleep, delayed sleep phase disorder (DSPD), shift work disorder (SWD), chronic sleep restriction (CSR), or no sleep problem. Primary, secondary, and tertiary categorizations are provided, where applicable. The objective of this study was to validate the questionnaire scoring algorithm categorization/s against a sleep physician assessment.

Methods

From 2,316 available records, 90 complete questionnaires were randomly selected for this analysis. The questionnaire scoring algorithm categorization was compared against the consensus assessment of three independent sleep physicians who each reviewed the answers to all questions before arriving at a diagnosis.

Results

The questionnaire respondents (70% female) were aged 42.2±14.5 years, had a mean BMI of 32.0±7.7 kg/m2, and self-reported sleep duration of 6.5±1.4 hours/night. The primary, secondary, or tertiary categorization of the questionnaire scoring algorithm matched the primary consensus categorization of the physicians 90.6% of the time (95% confidence interval (CI): 82.6 to 95.7). When OSA and snoring were grouped, agreement increased to 98.9% (95% CI: 94.0 to 100). In all analyses undertaken, the accuracy of questionnaire scoring algorithm against the physicians exceeded the accuracy of the physicians when compared to each other.

Conclusion

These results demonstrate that our questionnaire and scoring algorithm performs well in identifying sleep problems that may impact adult respondents, using physician-review as the comparison standard.

Support

Philips

Trazodone increases arousal threshold in obstructive sleep apnoea

A low arousal threshold is believed to predispose to breathing instability during sleep. The present authors hypothesised that trazodone, a nonmyorelaxant sleep-promoting agent, would increase the effort-related arousal threshold in obstructive sleep apnoea (OSA) patients. In total, nine OSA patients, mean+/-sd age 49+/-9 yrs, apnoea/hypopnoea index 52+/-32 events.h(-1), were studied on 2 nights, one with trazodone at 100 mg and one with a placebo, in a double blind randomised fashion. While receiving continuous positive airway pressure (CPAP), repeated arousals were induced: 1) by increasing inspired CO(2) and 2) by stepwise decreases in CPAP level. Respiratory effort was measured with an oesophageal balloon. End-tidal CO(2 )tension (P(ET,CO(2))) was monitored with a nasal catheter. During trazodone nights, compared with placebo nights, the arousals occurred at a higher P(ET,CO(2)) level (mean+/-sd 7.30+/-0.57 versus 6.62+/-0.64 kPa (54.9+/-4.3 versus 49.8+/-4.8 mmHg), respectively). When arousals were triggered by increasing inspired CO(2) level, the maximal oesophageal pressure swing was greater (19.4+/-4.0 versus 13.1+/-4.9 cm H(2)O) and the oesophageal pressure nadir before the arousals was lower (-5.1+/-4.7 versus -0.38+/-4.2 cm H(2)O) with trazodone. When arousals were induced by stepwise CPAP drops, the maximal oesophageal pressure swings before the arousals did not differ. Trazodone at 100 mg increased the effort-related arousal threshold in response to hypercapnia in obstructive sleep apnoea patients and allowed them to tolerate higher CO(2) levels.

Heart rate chaos in obstructive sleep apnea in children

Obstructive sleep apnea syndrome (OSAS) in children is associated with a bradytachyarrhythmia during an obstructive event. Polysomnographic recordings were obtained from 15 children; 9 had OSAS (apnea/hypopnea index = 13.6 +/- 8.2/hr, mean +/- SD) and 6 normal controls. Heart rate variability was analyzed for the presence of chaotic dynamics. Using a 5-minute sliding window, chaos was detected using numerical titration technique. In both groups, REM had a higher chaotic intensity than NREM sleep (p < 0.05). Furthermore, chaos was significantly increased during periods with apneic events compared to stable breathing. These data indicate that sleep state and disordered breathing are important determinants of the autonomic control of heart rate chaos in children.

Effect of increased lung volume on sleep disordered breathing in patients with sleep apnoea

BACKGROUND

Previous studies have shown that changes in lung volume influence upper airway size and resistance, particularly in patients with obstructive sleep apnoea (OSA), and that continuous positive airway pressure (CPAP) requirements decrease when the lung volume is increased. We sought to determine the effect of a constant lung volume increase on sleep disordered breathing during non-REM sleep.

METHODS

Twelve subjects with OSA were studied during non-REM sleep in a rigid head-out shell equipped with a positive/negative pressure attachment for manipulation of extrathoracic pressure. The increase in lung volume due to CPAP (at a therapeutic level) was determined with four magnetometer coils placed on the chest wall and abdomen. CPAP was then stopped and the subjects were studied for 1 hour in three conditions (in random order): (1) no treatment (baseline); (2) at "CPAP lung volume", with the increased lung volume being reproduced by negative extrathoracic pressure alone (lung volume 1, LV1); and (3) 500 ml above the CPAP lung volume(lung volume 2, LV2).

RESULTS

The mean (SE) apnoea/hypopnoea index (AHI) for baseline, LV1, and LV2, respectively, was 62.3 (10.2), 37.2 (5.0), and 31.2 (6.7) events per hour (p = 0.009); the 3% oxygen desaturation index was 43.0 (10.1), 16.1 (5.4), and 12.3 (5.3) events per hour (p = 0.002); and the mean oxygen saturation was 95.4 (0.3)%, 96.0 (0.2)%, 96.3 (0.3)%, respectively (p = 0.001).

CONCLUSION

An increase in lung volume causes a substantial decrease in sleep disordered breathing in patients with OSA during non-REM sleep.

Sleep. 2: pathophysiology of obstructive sleep apnoea/hypopnoea syndrome

The pathogenesis of airway obstruction in patients with obstructive sleep apnoea/hypopnoea syndrome is reviewed. The primary defect is probably an anatomically small or collapsible pharyngeal airway, in combination with a sleep induced fall in upper airway muscle activity.

Genioglossal activation in patients with obstructive sleep apnea versus control subjects. Mechanisms of muscle control

Pharyngeal dilator muscle activation (GGEMG) during wakefulness is greater in patients with obstructive sleep apnea (OSA) than in healthy control subjects, representing a neuromuscular compensatory mechanism for a more collapsible airway. As previous work from our laboratory has demonstrated a close relationship between GGEMG and epiglottic pressure, we examined the relationship between genioglossal activity and epiglottic pressure in patients with apnea and in control subjects across a wide range of epiglottic pressures during basal breathing, negative-pressure (iron-lung) ventilation, heliox breathing, and inspiratory resistive loading. GGEMG was greater in the patients with apnea under all conditions (p < 0.05 for all comparisons), including tonic, phasic, and peak phasic GGEMG. In addition, patients with apnea generated a greater peak epiglottic pressure on a breath-by-breath basis. Although the relationship between GGEMG and epiglottic negative pressure was tight across all conditions in both groups (all R values > = 0.69), there were no significant differences in the slope of this relationship between the two groups (all p values > 0.30) under any condition. Thus, the increased GGEMG seen in the patient with apnea during wakefulness appears to be a product of an increased tonic activation of the muscle, combined with increased negative-pressure generation during inspiration.

Upper-airway collapsibility: measurements and sleep effects

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is characterized by repetitive pharyngeal collapse during sleep. Several techniques have been proposed to assess the collapsibility of the upper airway in awake humans, but sleep-wake comparisons have rarely been attempted and there are few studies comparing OSA patients to control subjects. We sought to compare two collapsibility measurement techniques between normal and apneic subjects, and between wakefulness and sleep.

DESIGN

We conducted three studies. First, we examined whether collapsibility assessed by negative pressure pulses (NPPs) during wakefulness reflected values during sleep in 21 normal subjects. Second, we determined in these normal subjects whether collapsibility during sleep assessed by NPPs was predictive of collapsibility measured by inspiratory resistive loading (IRL). Finally, we compared upper-airway collapsibility between apnea patients (n = 22) and normal volunteers (n = 38) during wakefulness by NPPs.

SETTING

Clinical and research laboratories at the Brigham and Women's Hospital.

PARTICIPANTS

Two populations of normal subjects (n = 21 and n = 38) and OSA patients (n = 22).

MEASUREMENTS AND RESULTS

Collapsibility during wakefulness, as measured by NPPs, correlated significantly with collapsibility during sleep (r = 0.62; p = 0.003). There was also a significant correlation between the two measures of collapsibility (IRL and NPP) during sleep (r = 0.53; p = 0.04). Both measures revealed a significant increase in pharyngeal collapsibility during sleep as compared to wakefulness. Finally, apnea patients had significantly greater pharyngeal collapsibility than control subjects during wakefulness (p = 0.017).

CONCLUSIONS

These data suggest that upper-airway collapsibility measured during wakefulness does provide useful physiologic information about pharyngeal mechanics during sleep and demonstrates clear differences between individuals with and without sleep apnea.

Phasic mechanoreceptor stimuli can induce phasic activation of upper airway muscles in humans

1. Upper airway dilator muscles are phasically activated throughout breathing by respiratory pattern generator neurons. Studies have shown that non-physiological upper airway mechanoreceptive stimuli (e.g. rapidly imposed pulses of negative pressure) also activate these muscles. Such reflexes may become activated during conditions that alter airway resistance in order to stabilise airway patency. 2. To determine the contribution of ongoing mechanoreceptive reflexes to phasic activity of airway dilators, we assessed genioglossal electromyogram (GG EMG: rectified with moving time average of 100 ms) during slow (physiological) oscillations in negative pressure generated spontaneously and passively (negative pressure ventilator). 3. Nineteen healthy adults were studied while awake, during passive mechanical ventilation across normal physiological ranges of breathing rates (13-19 breaths min-1) and volumes (0.5-1.0 l) and during spontaneous breathing across the physiological range of end-tidal carbon dioxide (PET,CO2; 32-45 mmHg). 4. Within-breath phasic changes in airway mechanoreceptor stimuli (negative pressure or flow) were highly correlated with within-breath phasic genioglossal activation, probably representing a robust mechanoreceptive reflex. These reflex relationships were largely unchanged by alterations in central drive to respiratory pump muscles or the rate of mechanical ventilation within the ranges studied. A multivariate model revealed that tonic GG EMG, PET,CO2 and breath duration provided no significant independent information in the prediction of inspiratory peak GG EMG beyond that provided by epiglottic pressure, which alone explained 93 % of the variation in peak GG EMG across all conditions. The overall relationship was: Peak GG EMG = 79.7 - (11.3 X Peak epiglottic pressure), where GG EMG is measured as percentage of baseline, and epiglottic pressure is in cmH2O. 5. These data provide strong evidence that upper airway dilator muscles can be activated throughout inspiration via ongoing mechanoreceptor reflexes. Such a feedback mechanism is likely to be active on a within-breath basis to protect upper airway patency in awake humans. This mechanism could mediate the increased genioglossal activity observed in patients with obstructive sleep apnoea (i.e. reflex compensation for an anatomically smaller airway).

Increased prevalence of obstructive sleep apnea syndrome in obese women with polycystic ovary syndrome

Obstructive Sleep Apnea (OSA) is considerably more common in men than women. Preliminary data suggest that androgens may play a role in the male predominance of apnea. Polycystic Ovary Syndrome (PCOS) is characterized by menstrual disturbances, androgen excess, and frequently obesity. These features suggest that women with PCOS may be at increased risk for OSA. To determine whether obese women with PCOS have an increased prevalence of sleep apnea compared with age and weight-matched reproductively normal women, we performed overnight polysomnography for determination of the apnea-hypopnea index (AHI) in 18 obese women with PCOS and age and weight-matched control women. Additional measurements included waist, hip, and neck circumferences, serum total testosterone, unbound testosterone, and DHEAS. Women with PCOS had a higher AHI than controls (22.5 +/- 6.0, vs. 6.7 +/- 1.0, P = 0.008). Women with PCOS were also more likely to suffer from symptomatic OSA syndrome (44.4% vs. 5.5%, P = 0.008). AHI correlated with waist-hip ratio (r = 0.51, P < 0.03), serum testosterone (r = 0.52, P < 0.03) and unbound testosterone (r = 0.50, P < 0.05) in women with PCOS. We conclude that obese women with PCOS are at increased risk of OSA when compared with matched reproductively normal women. Women with PCOS should be carefully questioned regarding symptoms of sleep apnea.

Airway mechanics and ventilation in response to resistive loading during sleep: influence of gender

The male predominance in obstructive sleep apnea (OSA) is currently poorly understood although differences in pharyngeal airway anatomy and physiology have been proposed. As the response to inspiratory resistive loading (IRL) provides important information on both airway collapsibility (mechanics) and ventilatory control, we compared this respiratory response in eight normal women and eight age and body mass index (BMI)-matched men, during stable nonrapid eye movement (NREM) sleep. Upper airway mechanics, ventilation, plus activation of two dilator muscles (genioglossus [GG] and tensor palatini [TP]) were monitored during basal breathing (BL), followed by four sequentially applied loads (5, 10, 15, 25 cm H(2)O/L/s) for three breaths each. Men developed more severe hypopnea in response to identical applied external loads than did women. At a resistance of 25 cm H(2)O/L/s, VT decreased by 26 +/- 1% in women compared with 44 +/- 1% in men (differences between sexes p < 0.05). Pharyngeal resistance (Rpha) in response to IRL increased significantly more in men than women (37.3 +/- 11.2 cm H(2)O/L/s in men at maximal load, compared with an increase of 6.6 +/- 3.9 cm H(2)O/L/s in women, p < 0.05). Men and women had near identical minute ventilation responses to total load (applied extrinsic plus measured intrinsic), implying no differences in central drive or load response. There were no significant increases in GG or TP activation in response to IRL in either sex. We conclude that normal men are more vulnerable to load-induced hypoventilation than women, due to increased upper airway collapse, which could not be explained by differences in dilator muscle activation. This implies a fundamental difference in the upper airway anatomy and/or tissue characteristics between the two sexes.

Upper airway muscle responsiveness to rising PCO(2) during NREM sleep

Although pharyngeal muscles respond robustly to increasing PCO(2) during wakefulness, the effect of hypercapnia on upper airway muscle activation during sleep has not been carefully assessed. This may be important, because it has been hypothesized that CO(2)-driven muscle activation may importantly stabilize the upper airway during stages 3 and 4 sleep. To test this hypothesis, we measured ventilation, airway resistance, genioglossus (GG) and tensor palatini (TP) electromyogram (EMG), plus end-tidal PCO(2) (PET(CO(2))) in 18 subjects during wakefulness, stage 2, and slow-wave sleep (SWS). Responses of ventilation and muscle EMG to administered CO(2) (PET(CO(2)) = 6 Torr above the eupneic level) were also assessed during SWS (n = 9) or stage 2 sleep (n = 7). PET(CO(2)) increased spontaneously by 0.8 +/- 0.1 Torr from stage 2 to SWS (from 43.3 +/- 0.6 to 44.1 +/- 0.5 Torr, P < 0.05), with no significant change in GG or TP EMG. Despite a significant increase in minute ventilation with induced hypercapnia (from 8.3 +/- 0.1 to 11.9 +/- 0.3 l/min in stage 2 and 8.6 +/- 0.4 to 12.7 +/- 0.4 l/min in SWS, P < 0.05 for both), there was no significant change in the GG or TP EMG. These data indicate that supraphysiological levels of PET(CO(2)) (50.4 +/- 1.6 Torr in stage 2, and 50.4 +/- 0.9 Torr in SWS) are not a major independent stimulus to pharyngeal dilator muscle activation during either SWS or stage 2 sleep. Thus hypercapnia-induced pharyngeal dilator muscle activation alone is unlikely to explain the paucity of sleep-disordered breathing events during SWS.

Genioglossal but not palatal muscle activity relates closely to pharyngeal pressure

The stimuli controlling pharyngeal dilator muscles are poorly defined. Local mechanoreceptors are a leading possibility. To address this, we assessed the relationship between two dilator muscle electromyograms (EMGs, i.e., genioglossus [GG-an inspiratory phasic muscle], tensor palatini [TP-a tonically active muscle]) and potential stimuli (i.e., epiglottic pressure [Pepi], airflow [V], and pharyngeal resistance [Rpha]). Fifteen normal subjects were studied, during wakefulness and stable non-rapid eye movement (NREM) sleep. The GGEMG and TPEMG were assessed during basal breathing and during inspiratory resistive loading (four loads, done in triplicate), while quantifying Pepi and choanal pressures (Pcho, Millar catheters) plus V. There was a strong correlation between Pepi and GGEMG during wakefulness in most subjects (9 of 15 had absolute R > 0.7 [p < 0.05], group mean R = -0.62, p < 0.05). These correlations were less robust during NREM sleep (8 of 15 absolute R > 0.6 [p < 0.05], group mean R = -0.39, ns). The slope of the Pepi versus GGEMG relationship was greater during wakefulness than sleep (-0.67 versus -0.39% max/ cm H(2)O, p < 0.05). No significant correlations were observed between TPEMG and any of the measured potential stimuli. We conclude that intrapharyngeal pressure may modulate genioglossus activity during wakefulness, with a fall in muscle responsiveness during sleep. The activity of the TP was not clearly influenced by any measured local stimulus either awake or asleep.

Influence of chemoreceptor stimuli on genioglossal response to negative pressure in humans

Genioglossal muscle (GG) activity is modulated by both chemoreceptive and mechanoreceptive reflexes that help stabilize airway patency. We assessed the effects of blood gas changes, within the range encountered during mild obstructive apnea-arousal cycles, on GG activity and the GG reflex to upper airway negative pressure. Eighteen healthy adults were studied while awake under 5 conditions: (1) baseline (PET(CO(2)) = 40 mm Hg, Sa(O(2)) = 99%); (2) hypercapnia (PET(CO(2)) = 45 mm Hg); (3) hypocapnia (PET(CO(2)) = 35 mm Hg, induced via hyperventilation with an iron lung ventilator); (4) hypoxia (Sa(O(2)) = 87%); and (5) hypercapnia plus hypoxia (PET(CO(2)) = 45 mm Hg, Sa(O(2)) = 87%). Measurements included airflow, choanal and epiglottic pressures (Pchoa and Pepi), upper airway resistance, phasic and tonic GG EMG, and the GG reflex to negative pressure (Pchoa = -12.5 cm H(2)O). Ventilation increased from a baseline of 10.7 up to 22.7 L. min(-1) under conditions of altered blood gases. Peak inspiratory phasic GG EMG increased from 6. 5 to 11.1% of maximal contraction but there were no significant changes in either tonic GG EMG (range, 4.3 to 5.8% of maximum) or magnitude of the GG reflex (range, 4.1 to 5.5% of maximum). Among conditions there was a high correlation between upper airway pressures and peak phasic GG EMG (Pchoa, r = 0.97, p < 0.01; Pepi, r = 0.87; p = 0.06). We conclude that in this range of blood gases: (1) the GG reflex to negative pressure is unchanged; (2) slow airway pressure changes throughout inspiration, generated either actively or passively, influence GG EMG activity; and (3) mechanoreceptive control of GG EMG can fully explain all changes in GG activity, suggesting that chemoreceptive inputs to GG are minimal, or are not simply summated with mechanoreceptor inputs.

The influence of a transmucosal cholinergic agonist on pharyngeal muscle activity

STUDY OBJECTIVE

To assess the effect of high local oral nicotine administration on the upper airway (UA) of normal males during wakefulness.

DESIGN

Nonrandomized study.

SETTING

Brigham & Women's Hospital General Clinical Research Center.

PARTICIPANTS

Two groups of 13 and 12 normal male subjects were evaluated.

INTERVENTIONS

A "Fast acting" or "Intermediate acting" 2 mg transmucosal nicotine patch was attached to an upper molar tooth of study participants during wakefulness.

MEASUREMENTS

All data were collected prior to, and at several time points after, patch placement. Data measured included serum nicotine levels, genioglossal EMG, and pharyngeal resistance during basal breathing as well as the UA muscle response and UA collapsibility during negative UA pressure pulses.

RESULTS

None of the variables measured showed a statistically significant change with either nicotine patch despite a significant rise (p<0.05) in nicotine serum levels post patch placement in both groups. In several subjects, muscle activity and responsiveness to negative pressure increased after application of both patches and returned to near baseline levels at the last time point measured, a response consistent with the time course of nicotine release in both patches.

CONCLUSIONS

Oral nicotine administration failed to consistently increase GG muscle activation which may be a problem of local bioavailability of nicotine in the muscle.

Local mechanisms drive genioglossus activation in obstructive sleep apnea

Individuals with obstructive sleep apnea (OSA) require increased pharyngeal muscle dilator activation during wakefulness to maintain upper airway patency. Negative pressure is one potential stimulus for this neuromuscular compensation. Individuals with OSA who have previously undergone tracheostomy provide an opportunity to study upper airway physiology in both the presence and absence of upper airway respiratory stimuli. If negative pressure (or another local airway stimulus) were important in driving pharyngeal dilator muscle activation, one would predict that during nasal breathing, the pharynx of a tracheostomized patient would be exposed to negative pressure, and that high levels of muscle activation would therefore be measured. Conversely, during breathing by the patient through the tracheal stoma, one would expect low levels of muscle activation in the absence of local stimuli. We measured a number of respiratory variables, including genioglossus activation under both nasal and tracheal stomal breathing conditions, in five patients. In all five patients there was a significant and substantial decrease in both peak phasic (100 +/- 0 to 53.4 +/- 9.2 arbitrary units [mean +/- SEM], p < 0.01) and tonic genioglossus activation (36.3 +/- 5.3 to 20.7 +/- 3.9 arbitrary units, p < 0.05) during stomal breathing as compared with nasal breathing. We conclude that local upper airway respiratory stimuli, possibly negative pressure, are important in mediating the increased pharyngeal dilator muscle activation seen in sleep apnea patients during wakefulness.

Reduced genioglossal activity with upper airway anesthesia in awake patients with OSA

We examined whether topical upper airway anesthesia leads to a reduction in genioglossal (GG) electromyogram (EMG) in patients with obstructive sleep apnea (OSA). Airway mechanics were also evaluated. In 13 patients with OSA, we monitored GG EMG during tidal breathing and during the application of pulses of negative airway pressure (-10 to -12 cmH(2)O). Airflow resistance and airway collapsibility were determined. All measurements were performed with and without topical anesthesia (lidocaine). Anesthesia led to a significant fall in the peak GG EMG response to negative pressure from 36.1 +/- 4.7 to 24.8 +/- 5.3% (SE) of maximum (P < 0.01). This was associated with a fall in phasic and tonic EMG during tidal breathing (phasic from 24.4 +/- 4.1 to 16.4 +/- 3.4% of maximum and tonic from 10.9 +/- 1.6 to 8.0 +/- 1.3% of maximum, P < 0.01). A significant rise in pharyngeal airflow resistance was also observed. Our results demonstrate that topical receptor mechanisms in the nasopharynx importantly influence dilator muscle activity and are likely important in driving the augmented dilator muscle activity seen in the apnea patient.

Effect of wake-sleep transitions and rapid eye movement sleep on pharyngeal muscle response to negative pressure in humans

1. Genioglossus (GG) activation in response to upper airway negative pressure may be an important mechanism in the maintenance of airway patency. This reflex occurs during wakefulness but is diminished during stable non-rapid eye movement (NREM) sleep. Since obstructive events occur more commonly at wake-sleep transitions and during rapid eye movement (REM) sleep than during stable NREM sleep, we assessed the GG reflex during these two vulnerable states. 2. Seventeen healthy adults were studied throughout one evening and overnight. Electroencephalograms (EEGs), electro-oculograms (EOGs), submental electromyogram (EMG), GG EMG (intramuscular electrodes), and choanal plus epiglottic pressures were recorded. The GG reflex response to pulses of -8 cmH2O choanal pressure applied via nose mask during early inspiration was quantified repeatedly during relaxed wakefulness, within five breaths of wake-sleep transition (EEG alpha-theta transition) and during REM sleep. Only trials without EEG arousal were analysed, resulting in data from 14 subjects during sleep onset and 10 subjects during REM sleep (overall, 174-491 trials per state). 3. During wakefulness there was brisk GG reflex activation in response to negative pressure (amplitude: +78.5 +/- 28.3 % baseline (mean +/- s.e.m.); latency to maximal response: 177 +/- 16 ms). 4. At sleep onset, although there was marked variability among individuals, there was no significant reduction in the magnitude of the GG reflex for the group as a whole (amplitude: +33.2 +/- 8.2 % baseline; latency: 159 +/- 15 ms). 5. In contrast, during REM sleep there was a reduction of GG reflex (amplitude: -12.6 +/- 8.3 % baseline (P = 0.017 vs. awake); latency: 160 +/- 10 ms (n.s. vs. awake)) and greater airway collapsibility during the applied pressures (P = 0.043 vs. awake). 6. We conclude that there was no systematic reduction in the GG reflex to negative pressure at sleep onset. Nonetheless, it remains possible that sleep-deprived normal subjects and patients with sleep apnoea could react differently. 7. The apparent inhibition of the GG reflex during REM sleep may help explain why the upper airway is vulnerable to collapse during this state.

A look toward the future

There will be many changes in the sleep field in the next 5 to 10 years. These will include increments in our knowledge of basic neurobiologic mechanisms driving sleep and the impact of sleep loss on general health. The technology used in the sleep laboratory will likely change as well, leading to a larger range of available tests and new ways to conduct standard ones. Finally, as the knowledge base in sleep increases, the expertise required to practice sleep medicine will rise, leading to a better trained, more focused practitioner.

Indications for positive airway pressure treatment of adult obstructive sleep apnea patients: a consensus statement

We developed a short-length document that clearly delineates a prudent approach to and criteria for reimbursement of positive airway pressure (PAP) costs for the treatment of obstructive sleep apnea (OSA). Treatment modalities for OSA with PAP include continuous positive airway pressure, bilevel or variable PAP, and autotitrating PAP. This guidance on the appropriate criteria for PAP use in OSA is based on widely acknowledged peer-reviewed studies and widely accepted clinical practice. These criteria reflect current opinion on the appropriate clinical management of OSA in lieu of data pending from the Sleep Heart Health Study and upcoming outcome studies. This document is not intended to provide a complete review and analysis of the OSA clinical literature. The key to the success of this document is to foster consensus within and outside the clinical sleep community by providing a common sense and easily understood approach to the treatment of OSA with PAP.

Local reflex mechanisms: influence on basal genioglossal muscle activation in normal subjects

STUDY OBJECTIVES

To define the influence of topical nasopharyngeal anesthesia on genioglossal EMG responsiveness to both negative pressure and basal muscle activity. The effects on airway mechanics (resistance and collapsibility) were also determined.

PARTICIPANTS

18 normal adult subjects (9 males and 9 premenopausal females)

DESIGN AND MEASUREMENTS

Genioglossal EMG (GG EMG) was measured with intramuscular electrodes. Basal phasic and tonic GG EMG were defined, in addition to the muscle response to multiple brief applications of negative airway pressure (-10 to 12 cm H2O). Airflow resistance (at 0.2 L/second and peak flow) plus airway collapsibility were also determined. All measurements were completed with and without dense nasopharyngeal anesthesia (lidocaine).

RESULTS

Following nasopharyngeal anesthesia, peak GG EMG response to negative pressure fell from 28.1+/-4.3 (SE) to 19.6+/-3.4% of maximum (p<0.01). This was associated with a significant fall in both peak phasic and tonic GG EMG under basal conditions (phasic: 20.2+/-3.2 to 15.9+/-2.7% of maximum, tonic: 13.9+/-2.5 to 9.8+/-1.8% of maximum). Falling muscle activity led to a trend of rising airflow resistance and increasing airway collapsibility.

CONCLUSIONS

Local, topical receptor mechanisms located in the nasopharynx importantly modulate upper airway dilator muscle activity in humans during normal tidal breathing. Therefore, the mechanisms exist for the airway to respond to local events which would tend to compromise airway patency.

Evaluation of a computerized polysomnographic system

Computerized polysomnographic systems have came into common use in sleep laboratories around the world. Despite potential advantages over standard paper polysomnography, these computerized systems have been minimally evaluated as to accuracy, analysis time, or cost effectiveness when compared to paper. We evaluated the Healthdyne ALICE 3 system for comparability to paper polysomnography in sleep quantification and technician analysis time. Fifty patients were recorded simultaneously both on paper and on the ALICE 3 system and analyzed blindly with summary data from these records being quantified and compared. Five additional patients were studied for epoch-by-epoch analysis. Score-rescore assessments were accomplished for both groups. The results indicate that when allowed to autoscore, this computerized system produced substantial errors in sleep staging (REM sleep time 56.4 + 4.9 minutes vs 73.2 + 8.4 minutes for paper versus computer). This was the case for respiratory (AHI of 26.5 + 4.3 vs 15.3 + 2.6 for paper vs computer) and arousal assessment as well. However, with editing, similar results to those obtained with paper were achieved (REM sleep time -56.4 + 4.9 vs 59.0 + 4.6; AHI -26.5 + 4.3 vs 26.1 + 4.7 for paper and computer respectively), with differences rarely exceeding score-rescore discrepancies. Analysis time was substantially reduced by use of the computer (172.6 + 9.9 vs 79.7 + 4.8 minutes for paper vs computer). Epoch-by-epoch analysis revealed a trend to score toward wakefulness or lighter sleep on computer compared to paper although the differences were small. Respiratory, arousal and PLM scoring were quite similar. In conclusion, this study suggests that the ALICE 3 system with editing can produce results similar to those obtained with paper.

Evaluation of the Healthdyne NightWatch system to titrate CPAP in the home

Although a number of devices have been developed to monitor sleep and breathing in the home, there are few publications on methodologies by which CPAP can be titrated in the home setting. This study was conducted to determine the outcome of CPAP titration in the home using the Healthdyne NightWatch (NW) system. This home sleep-evaluation system was used to diagnose sleep apnea in 30 patients using a previously described methodology. These patients subsequently underwent CPAP titration in the home using the NW system, with modem technology allowing the transfer of data from the home to the laboratory. This group was compared with 30 patients who were diagnosed with sleep apnea using standard in-lab polysomnography and had CPAP titrated on a full night in the laboratory. Both groups were subsequently placed on CPAP at the appropriate pressure for 6-8 weeks, after which a full in-lab study was completed to assess CPAP efficacy at the prescribed pressure. Compliance was also determined using a pressure-activated monitor. No differences in any variable assessed could be found between the two groups. Mean compliance was 4.6 + 0.5 (SEM) and 4.3 + 0.5 hours of CPAP use per night for the home and in-lab groups respectively. Mean AHIs on the follow-up study were 7.4 + 1.2 and 7.6 + 1.6 events per hour for the home versus in-lab groups. Sleep stage distribution was also quite comparable between groups. As a result, this study suggests that sleep apnea can be diagnosed and CPAP titrated in the home with a similar outcome, at least at 6 to 8 weeks, to standard in-laboratory testing.

A look toward the future

There will be many changes in the sleep field in the next 5 to 10 years. These will include increments in our knowledge of the basic neurobiologic mechanisms driving sleep and the impact of sleep loss on general health. The technology used in the sleep laboratory will likely change as well, leading to a larger range of available tests and new ways to conduct standard ones. Finally, as the knowledge base in sleep increases, the expertise required to practice sleep medicine will rise, leading to a better-trained, more focused practitioner.

Upper airway muscle activity in normal women: influence of hormonal status

Obstructive sleep apnea is a disorder with a strong male predominance. One possible explanation could be an effect of female hormones on pharyngeal dilator muscle activity. Therefore, we determined the level of awake genioglossus electromyogram (EMGgg) and upper airway resistance in 12 pre- and 12 postmenopausal women under basal conditions and during the application of an inspiratory resistive load (25 cmH2O . l-1 . s). In addition, a subgroup of eight postmenopausal women were studied a second time after 2 wk of combined estrogen and progesterone replacement in standard doses. Peak phasic and tonic genioglossus activity, expressed as a percentage of maximum, were highest in the luteal phase of the menstrual cycle (phasic 23.9 +/- 3.8%, tonic 10.2 +/- 1.0%), followed by the follicular phase (phasic 15.5 +/- 2.2%, tonic 7.3 +/- 0.8%), and were lowest in the postmenopausal group (phasic 11.3 +/- 1.6%, tonic of 5.0 +/- 0.6), whereas upper airway resistance did not differ. There was a weak but significant positive correlation between progesterone levels and both peak phasic (P < 0.05) and tonic (P < 0.01) EMGgg. Finally, there was a significant increase in EMGgg in the postmenopausal group restudied after hormone therapy. In conclusion, female hormones (possibly progesterone) have a substantial impact on upper airway dilator muscle activity.

Ventilatory responses to sustained eucapnic hypoxia in healthy males during wakefulness and NREM sleep

The effects of sustained eucapnic hypoxia (SEH, 20 minutes SaO2, approximately 80%) on ventilation and supraglottic airflow resistance (Rua) plus genioglossal (gg) and diaphragmatic (di) electromyograms (EMGs) were compared during wakefulness and nonrapid eye movement (NREM) sleep in six healthy normal male subjects. Early augmentation of ventilation was followed by decline or roll-off in both states. The augmentation of ventilation was less in sleep than wakefulness (e.g., after 5 minutes hypoxia, 140% and 167% of baseline, respectively, p < 0.05). This appeared to be due to three factors: 1) sleep-related increases in Rua [the ventilatory responses to SEH (sleep vs. awake) were inversely related to changes in Rua (sleep vs. awake) (p < 0.05)], 2. reduced central neural drive (inspiratory phasic EMG di after 5 minutes SEH, 111% and 121% of baseline, p < 0.05), and 3) failure to increase respiratory frequency during SEH sleep. There was also a nonsignificant trend to a biphasic response in EMG gg and a small increase in Rua during SEH.

Complex home monitoring

As the demand for sleep evaluations rises, one response has been to conduct such studies in the home. In this brief review, complex home sleep monitoring systems (those recording at least four channels of physiologic data) on which there is peer-reviewed data are assessed. Four currently available systems met these criteria and are discussed. Each such system has clear strengths and weaknesses. These overall data suggest that home monitoring systems are becoming increasingly complex and more successful in monitoring, the desired variables. This trend is likely to continue.

Effects of sustained and repetitive isocapnic hypoxia on ventilation and genioglossal and diaphragmatic EMGs

We compared the effects of sustained isocapnic hypoxia (SIH; 20 min) and repetitive isocapnic hypoxia (RIH; 10 2-min episodes) on ventilation (VI), genioglossal (EMGgg) and diaphragmatic electromyographic (EMGdi) activities, and supraglottic airway resistance in 11 normal supine male subjects (36.6 +/- 2.2 yr) during wakefulness. Seven of the subjects had control measurements on a separate day. Desaturation was similar (arterial O2 saturation 80-84%) in the SIH and RIH protocols. SIH and RIH caused a biphasic ventilatory response: early augmentation of VI (169.5 +/- 6.9 and 168.9 +/- 4.3% of baseline, respectively; not significant) followed by a significant roll-off (VI after 20 min of cumulative hypoxia 153 +/- 4.0 and 150.8 +/- 10.2% respectively; not significant). Moving-time-average EMGdi signals (peak inspiratory and phasic) demonstrated a similar biphasic response in the two protocols. Mean EMGgg responses, however, differed. During SIH, peak inspiratory EMGgg increased early and remained elevated. Phasic and tonic EMGgg signals showed a similar trend. During RIH, early augmentation of peak inspiratory and phasic EMGgg signals was followed by a marked roll-off in activity such that by the 10th hypoxic episode neither value increased above baseline. In the 2-min periods between hypoxic episodes, there was a progressive suppression of peak inspiratory and phasic EMGgg values below baseline. Supraglottic airway resistance did not change significantly during either SIH or RIH. VI and phasic EMGs did not change during control experiments. We conclude that in awake normal male subjects SIH and RIH cause similar biphasic responses in VI and EMGdi activity. Phasic EMGgg activity responses differ between SIH and RIH: EMGgg remains augmented during SIH, whereas during RIH early augmentation is followed by marked suppression.

Serotonergic effects on hypoglossal neural activity and reflex responses

We determined the effects of serotonin (5HT; 6 concentrations ranging from 0.005 to 500 microM) pressure microinjection into the hypoglossal (XII) motor nucleus (100-500 nl; pH = 7.2-7.4) on XII whole nerve activity and reflex response to upper airway negative pressure in 15 decerebrated, vagotomized, paralyzed and artificially ventilated cats. Increasing 5HT concentration resulted in a concentration dependent increase in ipsilateral tonic XII activity, with no change in phasic XII activity. Threshold concentrations ranged from 0.005 to 0.5 microM, with the maximal response reached at 5 microM. Increasing 5HT concentration also increased the duration of the XII response. This ranged from 50 s with 0.5 microM, to over 10 min with 500 microM 5HT. However, 5HT did not significantly change the XII whole nerve reflex response to upper airway negative pressure (-20 cm H2O) at any 5HT concentration (n = 5). All 5HT effects were reversed by microinjection of 1.0 mM methysergide. We conclude that XII responses to 5HT are elicited at low concentrations of 5HT, which have a relatively short duration of effect, but that 5HT at the XII motor nucleus has no effect on the XII reflex response to upper airway negative pressure.

Influence of sleep onset on upper-airway muscle activity in apnea patients versus normal controls

Current evidence suggests that patients with obstructive sleep apnea (OSA) may have augmented pharyngeal dilator muscle activity during wakefulness, to compensate for deficient anatomy. However, the isolated effect of sleep on the activity of these muscles (comparing OSA patients with controls) has not been studied. We therefore determined waking levels of genioglossus (GG) and tensor palatini (TP) muscle activity (% of maximum electromyographic [EMG] activity) in 10 OSA patients and eight controls, and then assessed the impact of the first two breaths of sleep (theta electroencephalographic [EEG] activity) following a period of stable wakefulness. Apnea patients demonstrated greater genioglossal (27.4 +/- 4.0 versus 10.7 +/- 2.1%) and tensor palatini (31.9 +/- 6.5 versus 10.6 +/- 1.9%) EMG activity than did controls during wakefulness. This augmented muscle activity in apnea patients could be reduced to near control levels during wakefulness with the application of continuous positive airway pressure (CPAP) to the upper airway. At sleep onset, control subjects demonstrated small but consistent decrements in the activity of both the TP and GG muscles. On the other hand, apnea patients demonstrated large, significantly greater decrements in TP EMG at sleep onset than did the control subjects. The effect of sleep on GG EMG in apnea patients was inconsistent, with most (n = 7) demonstrating large (significantly larger than controls) decrements in genioglossal activity. However, three OSA patients demonstrated small increments in GG EMG at sleep onset despite falling TP EMG and obstructive apnea or hypopnea. We conclude that sleep onset is associated with significantly larger decrements in TP muscle EMG activity in OSA patients than in controls, which may represent a loss of neuromuscular compensation that is present during wakefulness. However, our results for the GG muscle were more variable, and did not always support this hypothesis.

Influence of gender on waking genioglossal electromyogram and upper airway resistance

Obstructive sleep apnea is generally recognized as more common in men than in women. This could relate to gender differences in either ventilatory control mechanisms or the structure and function of the pharyngeal airway. Most studies suggest that women have a structurally smaller pharyngeal airway than men, which would likely predispose rather than protect them from airway collapse. However, pharyngeal airway patency is actually a dynamic interaction between anatomy and pharyngeal muscle activity. We therefore hypothesized that females may have increased pharyngeal dilator muscle activity, thereby protecting them from airway collapse during sleep. To test this hypothesis, we compared genioglossal EMG (GG-EMG, measured as a percentage of maximal muscle activity) and upper airway resistance in 22 healthy subjects, 11 males and 11 females, during wakefulness. No significant difference in pharyngeal resistance could be found between the genders. However, inspiratory peak phasic and expiratory tonic GG-EMG activity were both significantly greater in females (GG-EMG peak phasic; 24.3 +/- 3.8 versus 13.1 +/- 4.5% of maximum, p < 0.02; GG-EMG tonic; 12.2 +/- 2.8 versus 4.7 +/- 1.2% of maximum, p < 0.01). In addition, females demonstrated a significant EMG response to inspiratory loading that was not observed in men. We conclude that women have, under basal conditions during wakefulness, augmented genioglossal muscle activity compared with men. To the extent that this augmented muscle activity is maintained across states, the female airway may be more stable and less collapsible.

Influences of NREM sleep on activity of palatoglossus and levator palatini muscles in normal men

Most evidence indicates that palatal position has an important influence on respiration during sleep. We have previously demonstrated during wakefulness that the levator palatini (LP) and the palatoglossus (PG) muscles function in an integrated manner in determining the route of respiration. In this study we first determined the effect of non-rapid-eye-movement (NREM) sleep on LP and PG electromyograms (EMGs) and then assessed if subjects could switch from nasal (NR) to oral (OR) respiration during NREM sleep without arousal. Six normal males subjects were studied using intramuscular EMG recording electrodes (LP and PG) and a divided mask to separate NR and OR. Peak inspiratory and end-expiratory EMGs of the LP fell significantly during NREM sleep [3.7 +/- 0.4 (SE), 1.9 +/- 0.4, and 2.4 +/- 0.7 arbitrary units for LP peak inspiratory awake, stage 2, and stage 3/4, respectively; 2.7 +/- 0.2, 1.5 +/- 0.2, and 1.8 +/- 0.5 arbitrary units for LP end-expiratory awake, stage 2, and stage 3/4, respectively; P < 0.05]. In a similar manner, the peak inspiratory EMG of the PG fell from wakefulness to stage 2 NREM sleep [5.1 +/- 0.5 and 3.9 +/- 0.5 arbitrary units for PG peak inspiratory awake and stage 2, respectively]. On the other hand, the PG peak inspiratory activity returned to near waking levels during stage 3/4 sleep, with the PG end-expiratory activity never falling during sleep. A total of 14 nasal occlusions were performed during NREM sleep. In all cases except one, an arousal was required to institute a change to OR.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of accuracy and analysis time of a novel device to monitor sleep and breathing in the home

Obstructive sleep apnea is increasingly recognized as a common and debilitating disorder. As a result, a variety of diagnostic technologies have evolved to potentially decrease cost and improve access and ease of assessment. In this study we compared the Healthdyne NightWatch (NW) System (a home sleep diagnostic methodology) to standard polysomnography (PSG) in two sleep centers. Two separate studies were completed. NW was compared to a simultaneously obtained PSG in 30 patients (IN-LAB study). Seventy additional patients were studied in both the home with NW and in the laboratory with PSG (HOME-LAB study). The NW system records eye movement, leg movement, SaO2, nasal-oral airflow, chest and abdominal wall motion, body position and heart rate on a solid state recorder, which permits sleep staging based on body and eye movement and standard respiratory assessment. For the PSG, standard paper recording techniques were used. The IN-LAB study revealed a correlation between NW and PSG for total sleep time of r = 0.72, with NW tending to score some awake time as nonrapid eye movement sleep. The correlation for apnea-hypopnea index (AHI) was r = 0.94 between systems, with a sensitivity of 100% and specificity of 63.6% at an AHI threshold of 10. The HOME-LAB study demonstrated understandably poor correlations between NW and PSG for most measures of sleep, which is likely a product of night-to-night variability in sleep, home versus laboratory effects and the differences in sleep staging methodology. However, the correlation for AHI was r = 0.92, with a sensitivity of 90.7% and a specificity of 70.4% at an AHI threshold of 10. Using a new methodology to assess agreement between diagnostic systems, we observed 78.6% diagnostic agreement between NW and PSG in the HOME-LAB study, with NW underestimating AHI 4.3% of the time and overestimating it in 17.1% of cases. This may relate to night-to-night variability in AHI or greater NW computer sensitivity to subtle hypopneas. We conclude that NW provides an accurate determination of AHI in both the home and laboratory, using limited instrumentation. The analysis time for NW is also reduced compared to PSG, and patients generally prefer the NW evaluation.

Respiratory-related control of palatoglossus and levator palatini muscle activity

Route of respiration [nasal (NR) vs. oral (OR)] is determined by the position of the soft palate. Despite this, little is known about the respiratory-related activity of palatal muscles. We investigated the activity of two palatal muscles: palatoglossus (PG) and levator palatini (LP). Eight normal male subjects were studied during wakefulness with intramuscular electrodes placed in the PG and LP. The electromyograms (EMGs) of the PG and LP were measured during both NR and OR under 1) quiet basal respiration, 2) inspiratory resistive loading (25 cmH2O.l-1.s), and 3) progressive hypercapnia. The PG consistently demonstrated inspiratory phasic activity during NR with greater inspiratory and expiratory EMGs (P < 0.05) during basal NR compared with basal OR [3.3 +/- 0.2 (SE), 1.1 +/- 0.1, 2.3 +/- 0.4, and 1.0 +/- 0.2 arbitrary units for PG nasal inspiratory, PG oral inspiratory, PG nasal expiratory, and PG oral expiratory, respectively]. During OR, the LP was inspiratory phasic in 4 subjects and expiratory phasic in 4 subjects, with greater inspiratory and expiratory EMGs during basal OR compared with basal NR (5.5 +/- 1.1, 2.1 +/- 0.4, 6.8 +/- 1.5, and 1.8 +/- 0.4 arbitrary units for LP oral inspiratory, LP nasal inspiratory, PG oral expiratory, and PG nasal expiratory, respectively). Both muscles demonstrated significantly increased activity during both inspiratory resistive loading and hypercapnia. However, their route-specific activation pattern continued during such stimulated breathing. We conclude that 1) the route of respiration is influenced by the complex interaction of the PG and LP and 2) the response of these muscles to respiratory stimuli is dependent on the route of respiration.

Nocturnal nasal continuous positive airway pressure in patients with chronic obstructive pulmonary disease. Influence on waking respiratory muscle function

Patients with COPD often have reduced inspiratory muscle strength and endurance as well as poor exercise tolerance. Increased inspiratory work during sleep (probably due to increased upper airway resistance) may further strain these compromised respiratory muscles in COPD patients. We hypothesized that nasal continuous positive airway pressure (CPAP) might reduce respiratory work during sleep in COPD patients and thereby improve waking inspiratory muscle function. To test this hypothesis, eight male COPD patients were treated with sustained nocturnal nasal CPAP. Inspiratory muscle strength (maximum inspiratory pressure) and endurance (sustained inspiratory pressure) as well as clinical performance (12-min walk) were assessed before and after therapy. We observed that compared with matched controls, COPD patients treated with nocturnal nasal CPAP had significant and substantial improvement in inspiratory muscle strength and endurance as well as functional ability as assessed by the 12-min walk. In addition, CPAP did not significantly alter sleep quality or oxygenation in the patients studied. We conclude that nocturnal nasal CPAP improves inspiratory muscle performance during wakefulness in COPD patients, which is very likely a product of the reduced work of breathing during sleep while these individuals received CPAP.

Iron status, movement disorders, and acute phase response in elderly psychiatric patients

The previously reported relation between iron deficiency and movement disorders was studied in a population with a high prevalence of both problems. There was no evidence of a direct statistical relation between iron deficiency and movement disorders. Significant associations were, however, found between movement disorders and features of the acute phase response to physiological stress. Indices of iron status are known to be affected by the acute phase response and it is suggested that the previously reported abnormalities in iron status may be secondary to this.

Influence of sleep on response to negative airway pressure of tensor palatini muscle and retropalatal airway

Increased retropalatal airway resistance may be caused by a sleep-induced loss of palatal muscle activity and a diminished ability of these muscles to respond to the increasing intrapharyngeal negative pressure that develops during sleep. To investigate these possibilities, in six normal subjects, we determined the effect of non-rapid-eye-movement sleep on 1) the tensor palatini (TP) electromyogram (EMG) response to rapid-onset negative-pressure generations (NPG) in the upper airway and 2) the collapsibility of the retropalatal airway during these NPGs. During wakefulness, the change in TP EMG from basal to peak levels (during NPG) was 19.8 +/- 3.2 arbitrary units (P < 0.005). This was markedly reduced during sleep (3.6 +/- 1.5 arbitrary units; P < 0.001). The latency of the TP EMG response was 48.5 +/- 5.6 ms during wakefulness but was prolonged during sleep (105.0 +/- 12.2 ms; P < 0.02). The peak transpalatal pressure during NPG (a measure of airway collapse) was 2.1 +/- 0.7 cmH2O during wakefulness and increased to 5.3 +/- 0.8 cmH2O during sleep (P < 0.05). We conclude that the brisk reflex response of the TP muscle to negative pressure during wakefulness is markedly reduced during non-rapid-eye-movement sleep, in association with a more collapsible retropalatal airway. We speculate that the reduction in this TP reflex response contributes to retropalatal airway narrowing during sleep in normal subjects.

Influence of sleep on genioglossus muscle activation by negative pressure in normal men

An important mechanism controlling genioglossus (GG) muscle activity is the reflex response to negative airway pressure. We hypothesize that this reflex response may be lost during sleep and believe that this loss may be important in the pathogenesis of airway collapse during sleep. Thus, we determined the effect of non-rapid eye movement (NREM) sleep on the GG electromyogram (EMG) response to brief (0.2 to 0.6 s) episodes of negative pressure generation (NPG) in the upper airway of six normal subjects. Up to 100 NPGs (mean 58 +/- 12) were recorded both awake and during stable NREM sleep. During wakefulness, the change in GG moving time average EMG from basal to peak levels (during NPG) was 17.1 +/- 2.5 au (a 154 +/- 22% increase above basal levels). This response was markedly reduced during NREM sleep (2.7 +/- 1.2 au; p < 0.01). The latency of the GG EMG response was 53.8 +/- 11.5 ms during wakefulness (n = 6), but much longer during sleep (132.7 +/- 24.5 ms; n = 3; p < 0.03). We conclude that in normal subjects (1) the GG muscle responds to negative airway pressure by reflex activation during wakefulness, and (2) this reflex activation is reduced or lost during NREM sleep. We speculate that loss of this mechanism during sleep may contribute to pharyngeal collapse in obstructive apnea patients.

Influence of sleep on alae nasi EMG and nasal resistance in normal men

The influence of sleep on the upper airway musculature varies considerably, with some muscles maintaining their activity at waking levels and others falling substantially. The influence of sleep on the alae nasi (AN), a dilator muscle of the nasal airway, has been minimally studied to date. Thus we determined the effect of non-rapid-eye-movement (NREM) sleep on the AN electromyogram and its relationship to nasal resistance (Rn) in nine normal supine males. Phasic inspiratory AN activity decreased from 20 +/- 6 arbitrary units during wakefulness to 5 +/- 1 arbitrary units (P < 0.001) at the onset of stage 2 NREM sleep and remained unchanged for two subsequent hours of NREM sleep. However, the Rn at the onset of NREM sleep remained similar to awake values (5.7 +/- 0.9 cmH2O.l-1 x s) and increased only after 1 h of NREM sleep (8.6 +/- 1.7 cmH2O.l-1 x s, P < 0.05), thus demonstrating little relationship to AN activity. We conclude that Rn increases slightly after 1 h of sleep, whereas AN activity decreases at stage 2 sleep onset. Thus AN activity has little influence on Rn during sleep.

Influence of NREM sleep on respiratory-related cortical evoked potentials in normal humans

Sleep substantially alters respiratory system responses to a variety of ventilatory stimuli. This could, to some extent, be a product of a sleep-induced decrement in respiratory afferent traffic to the cortex or cortical influences on central respiratory neurons. To investigate this, we determined the effect of non-rapid-eye-movement (NREM) sleep on cortical evoked potentials produced by rapid-onset inspiratory negative-pressure generations in the airway of seven normal subjects. Mean electroencephalographic activity at Cz-C3 and Cz-C4 for each subject was obtained by signal averaging. For Cz-C3, four respiratory-related cortical evoked potentials (P1, N1, P2, N2) occurred during wakefulness with latencies of 72 +/- 8, 128 +/- 9, 231 +/- 12, and 340 +/- 15 ms and amplitudes of 2.7 +/- 1.1, -3.2 +/- 1.1, 3.0 +/- 0.9, and -2.1 +/- 1.0 microV, respectively. During sleep, amplitudes of N1 and P2 were much greater (-9.4 +/- 1.3 and 14.1 +/- 1.7 microV, respectively; P < 0.05) and the latencies of P1, N1, and P2 (116 +/- 16, 244 +/- 24, and 664 +/- 75 ms, respectively) were substantially prolonged (P < 0.05). We conclude that respiratory-related cortical evoked potentials produced by negative-pressure generations in the airway during wakefulness are profoundly altered by NREM sleep. Their latencies are prolonged, magnitudes are increased, and the waveform is altered to resemble a K-complex. This altered sensory processing may impair respiratory responses during NREM sleep.

Influence of non-REM sleep on inspiratory muscle activity and lung volume in asthmatic patients

To determine the effect of non-REM (NREM) sleep on inspiratory muscle electromyographic (EMG) activity in asthmatic patients and the subsequent effect of such changes on FRC, 12 asthmatic patients with nocturnal worsening were monitored overnight in a horizontal volume-displacement body plethysmograph. During studies FRC was monitored using the single inspiratory occlusion technique, whereas EMG activities of the diaphragm (DI), intercostal (IC), and sternocleidomastoid (SCM) muscles were monitored using surface electrodes. FRC decreased progressively, from 3.63 +/- 0.27 L while awake prior to "lights out" to 3.15 +/- 0.27 L after 60 min of NREM sleep (p < 0.005). With awakening at the end of the study FRC increased to 4.69 +/- 0.48 L (p < 0.01). Onset of NREM sleep was also associated with significant (p < 0.05) reductions in EMG tonic activities of all three inspiratory muscles. These levels of tonic activity returned and were further augmented (p < 0.001) with awakening at the conclusion of the study. Linear relationships were demonstrated between sleep-state dependent changes in FRC and EMG tonic activity for each of the three inspiratory muscles (r = 0.98, 0.93, and 0.97 for DI, IC, and SCM, respectively, p < 0.01). NREM sleep did not significantly alter mean inspiratory phasic activities of these muscles, although there was considerable heterogeneity between individual subjects in the effects of NREM sleep.(ABSTRACT TRUNCATED AT 250 WORDS)

Influences of NREM sleep on the activity of tonic vs. inspiratory phasic muscles in normal men

Studies of sleep influences on human pharyngeal and other respiratory muscles suggest that the activity of these muscles may be affected by non-rapid-eye-movement (NREM) sleep in a nonuniform manner. This variable sleep response may relate to the pattern of activation of the muscle (inspiratory phasic vs. tonic) and peripheral events occurring in the airway. Furthermore, the ability of these muscles to respond to respiratory stimuli during NREM sleep may also differ. To systematically investigate the effect of NREM sleep on respiratory muscle activity, we studied two tonic muscles [tensor palatini (TP), masseter (M)] and two inspiratory phasic ones [genioglossus (GG), diaphragm (D)], also measuring the response of these muscles to inspiratory resistive loading (12 cmH2O.l-1.s) during wakefulness and NREM sleep. Seven normal male subjects were studied on a single night with intramuscular electrodes placed in the TP and GG and surface electrodes placed over the D and M. Sleep stage, inspiratory airflow, and moving time average electromyograph (EMG) of the above four muscles were continuously recorded. The EMG of both tonic muscles fell significantly (P less than 0.05) during NREM sleep [TP awake, 4.3 +/- 0.05 (SE) arbitrary units, stage 2, 1.1 +/- 0.2; stage 3/4, 1.0 +/- 0.2. Masseter awake, 4.8 +/- 0.6; stage 2, 3.3 +/- 0.5; stage 3/4, 3.1 +/- 0.5]. On the other hand, the peak phasic EMG of both inspiratory phasic muscles (GG and D) was well maintained.(ABSTRACT TRUNCATED AT 250 WORDS)

Waking genioglossal electromyogram in sleep apnea patients versus normal controls (a neuromuscular compensatory mechanism)

Pharyngeal collapse in obstructive sleep apnea patients is likely a product of a sleep-related decrement in pharyngeal dilator muscle activity superimposed upon abnormal airway anatomy. We postulate that during wakefulness, increased pharyngeal dilator muscle activity in apnea patients compensates for diminished airway size thus maintaining patency. We studied the waking genioglossus (GG) electromyogram (EMG) activity in 11 OSA patients and 14 age-matched controls to determine if GG activity is higher in the awake state in apnea patients than controls. To make this determination, we developed a reproducible methodology whereby true maximal GG EMG could be defined and thus basal activity quantitated as a percentage of this maximal value. Therefore, direct comparisons of basal activity between individuals was possible. We observed apnea patients to have significantly greater basal genioglossal activity compared to controls (40.6 +/- 5.6% vs. 12.7 +/- 1.7% of maximum). This difference persisted when size-matched subsets were compared. This augmented GG activity in apnea patients could be reduced with positive airway pressure. We speculate that this neuromuscular compensation present during wakefulness in apnea patients may be lost during sleep leading to airway collapse.