Obstruction of the upper airway during sleep (OSAS) is widely treated by having patients self-administer nasal continuous positive airway pressure (CPAP). To obtain objective evidence of the patterns of CPAP use, information was gathered from two urban sites on 35 OSAS patients who were prescribed CPAP for a total of 3,743 days. Patients were given CPAP machines that contained a microprocessor and monitor that measured actual pressure at the mask for every minute of each 24-h day for an average of 106 days per patient. They were not aware of the monitor inside the CPAP machines. Monitor output was compared with patients' diagnostic status, pretreatment clinical and demographic characteristics, and follow-up self-reports of CPAP use, problems, side effects, and aspects of daytime fatigue and sleepiness. Patients attempted to use CPAP an average of 66 +/- 37% of the days monitored. When CPAP was used, the mean duration of use was 4.88 +/- 1.97 h. However, patients' reports of the duration of CPAP use overestimated actual use by 69 +/- 110 min (p < 0.002). Both frequency and duration of CPAP use in the first month reliably predicted use in the third month (p < 0.0001). Although the majority (60%) of patients claimed to use CPAP nightly, only 16 of 35 (46%) met criteria for regular use, defined by at least 4 h of CPAP administered on 70% of the days monitored. Relative to less regular users, these 16 patients had more years of education (p = 0.05), and were more likely to work in professional occupations.(ABSTRACT TRUNCATED AT 250 WORDS)

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The purpose of this study was to examine the relationship between night-to-night variability and nightly duration of continuous positive airway pressure (CPAP) therapy over the first 9 weeks of treatment and to determine when patients begin to establish a nonadherent pattern of use. Data were analyzed from a study of daily CPAP use covertly monitored in 32 diagnosed patients with obstructive sleep apnea (OSA) using a microprocessor monitor encased in a CPAP machine. Patterns of CPAP use were bimodal, based on the frequency of nightly use. Approximately half the subjects were consistent users of CPAP, applying it > 90% of the nights for an average of 6.22 +/- 1.21 hours per night, while the other half comprised intermittent users who had a wide range of daily use averaging 3.45 +/- 1.94 hours per night on the nights CPAP was used. The percent of days skipped was significantly correlated with decreased nightly duration (rho = -0.73, p < 0.0001). Analysis of the night-to-night pattern of use revealed that the two groups differed significantly in the nightly duration of CPAP use by the fourth day of treatment (p = 0.001). Exploration of factors that potentially differentiate the two groups revealed no reliable predictors. However, intermittent users continued to report significantly greater OSA symptoms (snoring, snorting, and apnea) posttreatment, suggesting that they continued to experience sleep disordered breathing.

To establish a natural model of sleep-disordered breathing, we investigated respiration during wakefulness and sleep in the English bulldog. This breed is characterized by an abnormal upper airway anatomy, with enlargement of the soft palate and narrowing of the oropharynx. During sleep, the animals had disordered respiration and episodes of O2 desaturation. These were worst in rapid-eye-movement (REM) sleep, with most bulldogs having O2 saturations of less than 90% for prolonged durations. In contrast, control dogs never desaturated. In REM sleep, the bulldogs had episodes of both central and obstructive apnea, the latter being associated with paradoxical movements of the rib cage and abdomen. During wakefulness, the bulldogs were hypersomnolent as evidenced by a shortened sleep latency (mean of 12 min compared with greater than 150 min for controls). This animal model should facilitate studies of the natural history of the sleep apnea syndrome and its complications.

Nasal continuous positive airway pressure (CPAP) has become the nonsurgical treatment of choice for obstructive sleep apnea syndrome (OSAS). Recent evidence suggests that intermittent use of CPAP by patients is more common than nightly compliance. To determine the consequences of intermittent CPAP use, in terms of a return of sleep-disordered breathing and daytime hypersomnolence, 15 OSAS subjects were evaluated at three times: (1) before CPAP treatment (pretreatment), (2) after 30 to 237 days posttreatment during a night of CPAP use (on CPAP), and (3) during a night without CPAP (off CPAP). Evaluations of sleep-disordered breathing and three domains of hypersomnolence, physiologic sleep tendency, subjective sleepiness, and performance, were accomplished with the respiratory disturbance index (RDI), multiple sleep latency test (MSLT), Stanford sleepiness scale (SSS), and psychomotor vigilance task (PVT), respectively. CPAP use was encouraged and monitored from pretreatment to post-treatment by daily diaries for most subjects and an electronic device for a subset of subjects. As expected, CPAP eliminated apneas and hypopneas, and following the on CPAP night, there were statistically significant improvements in objective measures of sleepiness (MSLT and PVT). Subjective measures of sleepiness and fatigue also showed improvement. Sleeping without CPAP for one night reversed virtually all of the sleep and daytime alertness gains derived from sleeping with CPAP. This occurred despite a statistically significant reduction in the RDI on the night off CPAP (M = 36.8, SD = 28.0 events/h) relative to the pretreatment night (M = 56.6, SD = 24.8 events/h), which may be due to a lessening of the edema of the upper airway following CPAP use.(ABSTRACT TRUNCATED AT 250 WORDS)

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Basic mechanisms of sleep-disordered breathing (SDB) during rapid-eye-movement sleep (REMS) have been little investigated, despite the fact that events are often more prolonged and SaO2 nadirs lower during REMS. We predicted that the mechanisms of SDB in REMS would be related to the normal phasic changes in respiratory control in that state, rather than to cyclic arousals or responses to hypoxia as postulated for non-REMS SDB. Recordings of the EMG of the diaphragm (DIA) and the sternohyoid (SH), an upper airway dilating muscle, were made in five English bulldogs during sleep. We found that, as predicted, SDB events were associated with phasic influences rather than with arousals or response to hypoxia. The onset of SDB was significantly related to suppression of drive to both the DIA (p less than 0.01) and the SH (p less than 0.01). The mean drive of the DIA was suppressed to 42% of normal and of the SH to 17% of normal; the suppression of the SH was significantly greater than that of the DIA (p less than 0.05). Events were associated with changes in respiratory muscle EMG patterns typical of phasic REMS (p less than 0.01 for each muscle). The occurrence and duration of events exhibited no clear pattern or relationship to arousal or SaO2. Rather, as would be expected of phenomena associated with phasic REMS, the onset and termination of events were unpredictable. The association of SDB in REMS with phasic REMS influences rather than arousal or hypoxia suggests new directions for therapeutic approaches.

The effect of phasic eye movement activity on ventilation during rapid-eye-movement (REM) sleep was studied in seven healthy young adults by use of the respiratory inductive plethysmograph. Mean ventilation (VE) and ventilatory components during REM sleep were not significantly different from that seen in either stages 1-2 or 3-4 sleep. The percent of rib cage contribution to ventilation in REM sleep, 29.3 +/- 5.1%, was reduced compared with 54.4 +/- 5.8% in stage 1-2 and 52.2 +/- 4.3% in stage 3-4 sleep (P less than 0.005). When one separated breaths by the degree of associated phasic eye movement activity, it became apparent that breathing during REM sleep is very heterogeneous. Increasing eye movement activity was associated with inhibition of ventilation with a reduction in VE from 5.1 +/- 0.3 to 3.8 +/- 0.3 l/min. Tidal volume and frequency both fell, whereas inspiratory duration was unchanged. Compartmental ventilation was also affected, with the fall in the rib cage contribution from 37.8 +/- 6.4 to 15.3 +/- 5.6%. Chest wall and abdominal movement became more asynchronous as phasic-eye-movement activity increased and frank paradoxical breathing was seen.