Initial use of portable monitoring versus polysomnography to confirm obstructive sleep apnea in symptomatic patients: an economic decision model.

BACKGROUND: When using portable (level III and level IV) studies to "rule in" obstructive sleep apnea (OSA) in symptomatic patients, the pre-test probability (P) needs to be sufficiently high to minimize patients with negative tests who require full polysomnography. METHODS: We used a theoretical decision analysis model to assess the pre-test probability above which it would be appropriate to use portable studies to rule in disease in symptomatic patients with suspected OSA. For the base case, we considered a symptomatically sleepy patient referred with a probability of OSA of P. We determined the lower threshold of P appropriate for a clinical algorithm based upon an initial ambulatory study compared to initial diagnosis with PSG by comparing costs using the PSG algorithm with a diagnostic algorithm involving initial assessment with a portable study. RESULTS: In our base case, the pre-test probability above which portable testing would be less costly than initial diagnostic PSG would be 0.47. When an initial split night study was compared to portable testing, the pre-test probability above which portable testing was more economically attractive was greater (0.68). Values of P, however, varied considerably depending on values of many variables, including costs of diagnostic testing and CPAP compliance. CONCLUSIONS: Using a decision model, we have developed a theoretical framework to ascertain the pre-test disease probability above which portable studies would be economically attractive as an initial test in the assessment of patients with suspected OSA.

Cost-effectiveness of continuous positive airway pressure therapy in patients with obstructive sleep apnea-hypopnea in British Columbia.

BACKGROUND: Obstructive sleep apnea-hypopnea (OSAH) is a common disorder characterized by recurrent collapse of the upper airway during sleep. Patients experience a reduced quality of life and an increased risk of motor vehicle crashes (MVCs). Continuous positive airway pressure (CPAP), which is the first-line therapy for OSAH, improves sleepiness, vigilance and quality of life. OBJECTIVE: To assess the cost-effectiveness of CPAP therapy versus no treatment for OSAH patients who are drivers. METHODS: A Markov decision analytical model with a five-year time horizon was used. The study population consisted of male and female patients, between 30 and 59 years of age, who were newly diagnosed with moderate to severe OSAH. The model evaluated the cost-effectiveness of CPAP therapy in reducing rates of MVCs and improving quality of life. Utility values were obtained from previously published studies. Rates of MVCs under the CPAP and no CPAP scenarios were calculated from Insurance Corporation of British Columbia data and a systematic review of published studies. MVCs, equipment and physician costs were obtained from the British Columbia Medical Association, published cost-of-illness studies and the price lists of established vendors of CPAP equipment in British Columbia. Findings were examined from the perspectives of a third-party payer and society. RESULTS: From the third-party payer perspective, CPAP therapy was more effective but more costly than no CPAP (incremental cost-effectiveness ratio [ICER] of $3,626 per quality-adjusted life year). From the societal perspective, the ICER was similar ($2,979 per quality-adjusted life year). The ICER was most dependent on preference elicitation method used to obtain utility values, varying almost sixfold under alternative assumptions from the base-case analysis. CONCLUSION: After considering costs and impact on quality of life, as well as the risk of MVCs in individuals with OSAH, CPAP therapy for OSAH patients is a highly efficient use of health care resources. Provincial governments who do not provide funding for CPAP therapy should reconsider.

Risk and severity of motor vehicle crashes in patients with obstructive sleep apnoea/hypopnoea.

BACKGROUND: Obstructive sleep apnoea/hypopnoea (OSAH) appears to be associated with an increased risk of motor vehicle crashes (MVCs). However, its impact on crash patterns, particularly the severity of crashes, has not been well described. A study was undertaken to determine whether OSAH severity influenced crash severity in patients referred for investigation of suspected sleep-disordered breathing. METHODS: Objective crash data (including the nature of crashes) for 783 patients with suspected OSAH for the 3 years prior to polysomnography were obtained from provincial insurance records and compared with data for 783 age- and sex-matched controls. The patient group was 71% male with a mean age of 50 years, a mean apnoea-hypopnoea index (AHI) of 22 events/h and a mean Epworth Sleepiness Scale score of 10. RESULTS: There were 375 crashes in the 3-year period, 252 in patients and 123 in controls. Compared with controls, patients with mild, moderate and severe OSAH had an increased rate of MVCs with relative risks of 2.6 (95% CI 1.7 to 3.9), 1.9 (95% CI 1.2 to 2.8) and 2.0 (95% CI 1.4 to 3.0), respectively. Patients with suspected OSAH and normal polysomnography (AHI 0-5) did not have an increased rate of MVC (relative risk 1.5 (95% CI 0.9 to 2.5), p = 0.21). When the impact of OSAH on MVC associated with personal injury was examined, patients with mild, moderate and severe OSAH had a substantially higher rate of MVCs than controls with relative risks of 4.8 (95% CI 1.8 to 12.4), 3.0 (95% CI 1.3 to 7.0) and 4.3 (95% CI 1.8 to 8.9), respectively, whereas patients without OSAH had similar crash rates to controls with a relative risk of 0.6 (95% CI 0.2 to 2.5). Very severe MVCs (head-on collisions or those involving pedestrians or cyclists) were rare, but 80% of these occurred in patients with OSAH (p = 0.06). CONCLUSION: Patients with OSAH have increased rates of MVCs, and disproportionately increased rates of MVCs are associated with personal injury.

The impact of obstructive sleep apnea and daytime sleepiness on work limitation.

BACKGROUND: Many patients with obstructive sleep apnea (OSA) participate in the work force. However, the impact of OSA and sleepiness on work performance is unclear. METHODS: To address this issue, we administered the Epworth Sleepiness Scale (ESS), the Work Limitations Questionnaire (WLQ), and an occupational survey to patients undergoing full-night polysomnography for the investigation of sleep-disordered breathing. Of 498 patients enrolled in the study, 428 (86.0%) completed the questionnaires. Their mean age+/-standard deviation (SD) was 49+/-12 years, mean body mass index (BMI) was 31+/-7 kg/m(2) mean apnea hypopnea index (AHI) was 21+/-22 events/h, and mean ESS score was 10+/-5. Subjects worked a mean of 39+/-18 h per week. The first 100 patients to complete the survey were followed up at two years. RESULTS: In the group as a whole, there was no significant relationship between severity of OSA and the four dimensions of work limitation. However, in blue-collar workers, significant differences were detected between patients with mild OSA (AHI 5-15/h) and those with severe OSA (AHI>30/h) with respect to time management (limited 23.1% of the time vs. 43.8%, p=0.05) and mental/personnel interactions (17.9% vs. 33.0%, p=0.05). In contrast, there were strong associations between subjective sleepiness (as assessed by the ESS) and three of the four scales of work limitation. That is, patients with an ESS of 5 had much less work limitation compared to those with an ESS 18 in terms of time management (19.7% vs. 38.6 %, p<0.001), mental-interpersonal relationships (15.5% vs. 36.0%, p<0.001) and work output (16.8% vs. 36.0%; p<0.001). Of the group followed up, 49 returned surveys and 33 who were using continuous positive airway pressure (CPAP) showed significant improvements between the initial and second follow-up in time management (26% vs. 9%, p=0.0005), mental-interpersonal relationships (16% vs. 11.0%, p=0.014) and work output (18% vs. 10%; p<0.009). CONCLUSION: We have demonstrated a clear relationship between excessive sleepiness and decreased work productivity in a population referred for suspected sleep-disordered breathing. Screening for sleepiness and sleep-disordered breathing in the workplace has the potential to identify a reversible cause of low work productivity.

Effects of mandibular advancement on airway curvature and obstructive sleep apnoea severity.

In a curved tube, the amount of airflow appears to be influenced by the amount of curvature. The purpose of this study was to investigate changes in obstructive sleep apnoea (OSA) severity and awake velopharyngeal curvature in response to an anteriorly titrated mandibular position in 20 male OSA patients. Baseline supine cephalometry was obtained before the initial insertion of a titratable oral appliance and follow-up supine cephalometry was undertaken after titration of the mandibular position with the appliance in place. The mean apnoea/hypopnea index (AHI) before treatment (31.6 +/- 13.0 events x h(-1)) was significantly reduced (9.8 +/- 7.4 events x h(-1)) after titration of the mandibular position in all 20 patients. There was a significant increase in the anteroposterior calibre and the radius of the curvature of the anterior wall of the velopharynx in 14 good responders who exhibited an AHI reduction to < or = 15. Similar observations were not found in six poor responders. To conclude, an anteriorly titrated mandibular position reduced obstructive sleep apnoea severity, enlarged the velopharynx and diminished the curvature of the anterior velopharyngeal wall in good responders. It is proposed that this change in the upper airway curvature associated with mandibular advancement may effect obstructive sleep apnoea severity through its effect on airflow dynamics.

Overnight home oximetry: can it identify patients with obstructive sleep apnea-hypopnea who have minimal daytime sleepiness?

BACKGROUND: Overnight home oximetry is being widely used as a case selection technique for patients with suspected obstructive sleep apnea-hypopnea (OSAH). In the absence of excessive daytime sleepiness (EDS), patients with snoring and/or witnessed apnea are considered to have low probability of OSAH. METHODS: Patients suspected to have OSAH, who denied EDS, and had a normal overnight home oximetry were studied by polysomnography for presence of significant OSAH (apnea/hypopnea index (AHI) > 15/h). RESULTS: Twelve (40%) of the 30 patients studied had significant OSAH. All had a 2% oxygen desaturation index of less than 10/h. The sensitivity of oximetry increased at lower desaturation indices butthis was associated with decreased specificity. Review of oximetry waveform pattern, by experienced physicians, did not improve the diagnostic accuracy. Combining oximetry with a clinical prediction rule would have reduced the need for polysomnography by 30%. CONCLUSION: Many patients, who present with snoring and/or witnessed apnea and are referred to a sleep disorder clinic for suspected OSAH, may have significant OSAH even if they deny EDS. Overnight home oximetry did not help discriminate between those patients with or without OSAH.

Cephalometric and physiologic predictors of the efficacy of an adjustable oral appliance for treating obstructive sleep apnea.

The purpose of this study was to investigate whether any physiologic or cephalometric parameters could be used to predict the efficacy of an adjustable mandibular advancement appliance for treating obstructive sleep apnea (OSA). Forty-two male and 5 female patients with OSA were recruited on the basis of baseline polysomnography with a documented Apnea and Hypopnea Index (AHI) greater than 15 per hour. Repeat polysomnography was performed with the appliance in place. Baseline cephalometry was performed for each patient, and follow-up cephalometry was completed for 19 of the subjects. The subjects were divided into 3 groups on the basis of the degree of change in the AHI with oral appliance therapy: good response (> 75% decrease in AHI), moderate response (25% to 75% decrease in AHI), and poor response (< 25% decrease in AHI). Patients with a good response were younger and had smaller upper airways. In a linear regression analysis, the change in AHI (%) was associated with physiologic (age and body mass index), cephalometric (overjet, height of the maxillary molars, vertical height of the hyoid bone), and airway variables. However, changes in either overbite or overjet were not related to changes in any of the polysomnographic variables for the 19 subjects. A stepwise regression analysis revealed a better treatment response with the adjustable mandibular advancement appliance in patients who were younger and had a lower body mass index, a longer maxilla, a smaller oropharynx, a smaller overjet, less erupted maxillary molars, and a larger ratio of vertical airway length to the cross-sectional area of the soft palate.

Sleep bruxism in patients with sleep-disordered breathing.

The aim was to test the hypothesis of a direct association between sleep-disordered breathing and sleep bruxism. The frequency of masseter contraction (MC) episodes and rhythmic jaw movements (RJM) was measured in patients with mild and moderate obstructive sleep apnoea (OSA). The diagnosis of sleep bruxism was made from a combination of questionnaire, clinical observation and all-night polysomnographic recording which included masseter electromyography. A total of 21 patients (19 males/two females, mean age 40.0 years+/-9.2 SD) were randomly selected from a provisional diagnosis of snoring and OSA by a sleep physician. In the patients with mild OSA [n=11, mean apnoea hypopnoea index (AHI)=8.0+/-4.1 SD, body mass index (BMI)=29.1+/-5.0], the diagnosis of sleep bruxism was made in six out of 11 patients (54%); similarly, four out of 10 patients (40%) with moderate OSA (n=10, mean AHI=34.7+/-19.1, BMI=30.6+/-5.0) were identified as bruxists. Although the combination of clinical, subjective estimation and nocturnal electromyographic recording of masseter muscle might provide a more solid base for the diagnosis of sleep bruxism, the result is biased by the variation in the bruxing activity. MC episodes were associated with the termination of apnoea or hypopnoea episodes in only 3.5% of the mild group and 14.4% of the moderate group (p<0.05). It appears that sleep bruxism is rarely directly associated with apnoeic events, but is rather related to the disturbed sleep of OSA patients.

Treatment, airway and compliance effects of a titratable oral appliance.

STUDY OBJECTIVES: To measure the effects of a titratable anterior mandibular repositioner on airway size and Obstructive Sleep Apnea (OSA) and to evaluate its compliance. DESIGN: Before and after insertion sleep studies were obtained in a total of 38 OSA patients of varying severity from three different sites. Covert compliance was measured by means of a newly-developed, miniaturized, temperature-sensitive, imbedded monitor. Validity testing was completed in six adult volunteers who wore monitors imbedded into small acrylic appliances. MEASUREMENTS AND RESULTS: The mean RDI before treatment was 32.6 (SEM 2.1) and after the insertion of the appliance, the RDI was reduced to 12.1 (SEM 1.7, p<0.001). RDI was reduced to less than 15/hour in 80% of a group of moderate OSA patients (RDI 15 to 30) and in 61% of a group of severe OSA patients (RDI > 30) with respect to baseline RDI. Fiber optic video endoscopy was performed on 9 OSA patients with and without the appliance. No significant differences in hypopharynx or oropharynx cross sectional areas were found, but at the level of the velopharynx, the airway size was significantly increased (p<0.05). The index of agreement was 0.99 between the monitor clock time and the subject's log sheets. Compliance data from eight OSA subjects instructed to wear the appliance during sleep indicated that it was worn for a mean of 6.8 hours with a range of 5.6 to 7.5 hours per night. CONCLUSION: The titratable adjustable mandibular advancement appliance, made from thermoelastic acrylic, significantly reduces RDI in moderate to severe OSA patients, has a direct effect on airway size and is well worn throughout the night.

Cephalometric comparisons between Chinese and Caucasian patients with obstructive sleep apnea.

The purpose of this study was to compare two groups of adult men from different ethnic backgrounds and with obstructive sleep apnea; they were selected by matching age, gender, skeletal pattern, body mass index, and respiratory disturbance index. Pretreatment cephalometric radiographs and overnight polysomnograms of 30 Chinese and 43 Caucasian patients with Class II, Division 1 malocclusions were analyzed to investigate if there were craniofacial and upper airway structural differences between the two ethnic groups. The Chinese group, when compared with the group of Caucasian patients, revealed more severe underlying craniofacial skeletal discrepancies with significantly smaller maxilla and mandibles, more severe mandibular retrognathism, proclined lower incisors, increased total and upper facial heights, and steeper and shorter anterior cranial bases. However, no significant differences were found between the two groups in posterior facial height, ratio of upper to lower anterior facial height, and the position of hyoid bone, maxilla, and upper incisors. With regard to soft tissue and upper airway measurements, there were no significant ethnic differences in tongue and soft palate size, vertical length of oropharynx, and anteroposterior dimensions of the upper airway at most of the levels except for a larger super-posterior airway space, a larger nasopharynx and oropharynx cross-sectional area, and a smaller tongue height in the Chinese group. We conclude that there are a number of craniofacial and upper airway structures that differ between the two ethnic groups that may be relevant to the treatment of obstructive sleep apnea in various ethnic groups.

Shape of the face and tongue in obstructive sleep apnea patients--statistical analysis of coordinate data.

OBJECTIVES: To determine the shape difference of the face and tongue of obstructive sleep apnea (OSA) patients, in comparison to those of non-apneic patients. DESIGN: Retrospective analysis of observational data on a cohort of patients. SETTING: A university teaching hospital and sleep referral center. SAMPLE POPULATION AND METHOD: Eighty patients referred for overnight polysomnography and lateral cephalometry and who met the selection criteria were included. Upright and supine cephalograms were obtained and subgrouped based on the severity of clinical symptoms. Shape differences between the groups were assessed by a multiple analysis of variance and a Hotelling's T2. MEASUREMENTS AND RESULTS: A set of anatomical landmarks were selected for outlines of the face and the tongue on cephalograms. X and Y coordinates of each landmark were utilized as variables. As symptoms become severe, the hyoid bone and the submental area positioned inferiorly and the fourth vertebra relocated posteriorly with respect to the lower mandibular border. When subjects changed their body position from the upright to the supine, the posterior part of the tongue appeared to sink down. The hyoid bone position to epiglottis-retrognathion line in the supine position distinguishes OSA patients from non-apneic subjects. CONCLUSION: Despite many limitations, we demonstrate that the supine cepahlometrics during wakefulness can be a useful adjunctive diagnostic tool for OSA, when cephalograms are analyzed in a coordinate data form.

Mandibular advancement oral appliance therapy for obstructive sleep apnoea: effect on awake calibre of the velopharynx.

BACKGROUND: The mechanisms of action of oral appliance therapy in obstructive sleep apnoea are poorly understood. Videoendoscopy of the upper airway was used during wakefulness to examine whether the changes in pharyngeal dimensions produced by a mandibular advancement oral appliance are related to the improvement in the severity of obstructive sleep apnoea. METHODS: Fifteen patients with mild to moderate obstructive sleep apnoea (median (range) apnoea index (AI) 4(0-38)/h, apnoea-hypopnoea index (AHI) 28(9-45)/h) underwent overnight polysomnography and imaging of the upper airway before and after insertion of the oral appliance. Images were obtained in the hypopharynx, oropharynx, and velopharynx at end tidal expiration during quiet nasal breathing in the supine position. The cross sectional area and diameters of the upper airway were measured using image processing software with an intraluminal catheter as a linear calibration. RESULTS: AI decreased to a median (range) value of 0 (0-6)/h (p<0.01) and AHI to 8 (1-28)/h (p<0.001) following insertion of the oral appliance. The median (95% confidence interval) cross sectional area of the upper airway increased by 18% (3 to 35) (p<0.02) in the hypopharynx and by 25% (11 to 69) (p<0.005) in the velopharynx, but not significantly in the oropharynx. Although in general the shape of the pharynx did not change following insertion of the oral appliance, the lateral diameter of the velopharynx increased to a greater extent than the anteroposterior diameter. Following insertion of the oral appliance the reduction in AHI was related to the increase in cross sectional area of the velopharynx (p = 0.01). CONCLUSIONS: A mandibular advancement oral appliance increases the cross sectional area of the upper airway during wakefulness, particularly in the velopharynx. Assuming this effect on upper airway calibre is not eliminated by sleep, mandibular advancement oral appliances may reduce the severity of obstructive sleep apnoea by maintaining patency of the velopharynx, particularly in its lateral dimension.

Mandibular posture during sleep in patients with obstructive sleep apnoea.

Vertical mandibular posture is thought to be related to narrowing of the upper airway, because mouth opening is associated with an inferior-posterior movement of the mandible and the tongue which influences pharyngeal airway patency. To test whether the mandibular posture is related to the occurrence and/or termination of obstructive sleep apnoea (OSA), the vertical mandibular position was recorded intraorally using a magnet sensor during a standard sleep study in seven patients with OSA. Measurements were recorded during sleep both in the supine and lateral recumbent positions. The percentage of total sleep time spent with mandibular opening greater than 5 mm was significantly larger (p<0.001) in patients with OSA (69.3+/-23.3%) compared with our previous results obtained from healthy adults without OSA (11.1+/-11.6%). The stage of sleep affected the vertical mandibular posture during sleep in the supine position, but not in the lateral recumbent position in patients with OSA. In non-rapid eye-movement sleep, mandibular opening increased progressively during apnoeic episodes and decreased at the termination of apnoeic episodes. In contrast, no significant change in mandibular posture occurred in apnoeic episodes during rapid eye-movement sleep. It was concluded that the vertical mandibular posture is more open during sleep in patients with OSA than in healthy adults and that mandibular opening increases progressively during apnoeic episodes and decreases at the termination of those episodes.

Mandibular posture during sleep in healthy adults.

To test whether the mandible opens more during deep sleep and whether the mandibular position is affected by body position during sleep, the vertical mandibular position was recorded intraorally using a magnet sensor at the same time as a standard sleep study in seven normal healthy male adults. Measurements were recorded during the period before sleep onset (WAKE) and during sleep. Two-way ANOVA showed that vertical mandibular position was significantly affected by sleep stage but not by body position (supine vs lateral recumbent). The proportion of time during which the mandible was in a near-closed position (0-2.5 mm) significantly and progressively decreased, and significantly more time was spent at wider gaps (2.5-5 mm) as non-rapid-eye-movement (NREM) sleep deepened. In REM sleep, the proportion of time during which the mandible was at wider gaps was significantly greater than in WAKE and stage 1 (but not later stages) of NREM sleep. It was concluded that mandibular posture during sleep in healthy adults is significantly influenced by sleep stage but not by body position. Mandibular opening progressively increases with the depth of NREM sleep stage, and the mandible is more open in REM sleep than in light NREM sleep.

Prevalence of sleep disordered breathing in a population of Canadian grainworkers.

OBJECTIVES: To determine the prevalence of sleep disordered breathing (SDB) in a Canadian population of industrial workers (grainworkers). To determine the clinical features that are predictive of SDB and the validity of self-reported snoring. DESIGN: Cross-sectional, interviewer-administered questionnaire with selective recruitment of subjects for home sleep monitoring. SETTING: Community setting, Vancouver, British Columbia. PARTICIPANTS: All male grainworkers at grain elevators in Vancouver were approached for completion of a questionnaire. Eighty-three per cent of 524 subjects completed the questionnaire and were divided by presumed risk for SDB into four groups. All subjects in the highest risk group (group 1- frequent snoring and witnessed apneas) and a random sample of 40 subjects in the other three groups (group 2 - frequent snoring without witnessed apneas; group 3 - infrequent snoring rare; group 4 - nonsnoring) were approached for home sleep monitoring and 42% consented. INTERVENTIONS: Interviewer-administered questionnaire and home sleep monitoring. RESULTS: The overall prevalence of SDB in this relatively overweight group was estimated to be 25%, with a stepwise increase from group 4 to group 1 (7%, 29%, 40%, 60%). Presence of snoring and witnessed apneas, a greater body-mass index and a larger neck circumference were associated with SDB. Self-reported snoring was not found to be predictive. CONCLUSIONS: This first study of the prevalence of SDB in Canada suggests that SDB is at least as prevalent in Canada as in other industrialized nations and may actually be more common than previously thought. Further studies are required to determine the morbidity, mortality and economic loss associated with SDB in industrial workers.

Natural head posture, upper airway morphology and obstructive sleep apnoea severity in adults.

Enlarged tonsils, adenoids, and chronic respiratory problems have been associated with the compensatory adaptations of natural head posture (NHP) in children. Recently, it has been shown that adult patients with Obstructive Sleep Apnoea (OSA) also tend to exhibit a craniocervical extension (CCE) with a forward head posture (FHP). This study was designed to search for some characteristics of OSA patients that may be related to these adaptive changes in NHP. Overnight polysomnographic, demographic, and cephalometric records of 252 adult male subjects with various types of skeletal patterns and dental conditions were examined. Apnoea Index (AI) and Apnoea + Hypopnoea Index (AHI) variables were assessed to separate the non-apnoeic snorers (n = 35), and mild (n = 101), moderate (n = 63), and severe (n = 53) OSA groups. Results of the Tukey tests revealed that severe OSA patients had a greater tendency to exhibit a CCE with a FHP (P < or = 0.05 to P < or = 0.001). Differences in head extension (NSL.VER) between groups could not be identified. Pearson's 'r' correlation coefficients revealed that the CCE and FHP in OSA patients were associated with a higher disease severity, a longer and larger tongue, a lower hyoid bone position in relation to the mandibular plane, a smaller nasopharyngeal and a larger hypopharyngeal cross-sectional area, and a higher body mass index (P < or = 0.05 to P < or = 0.001). It is concluded that a CCE with a FHP is more likely to be seen in severe and obese OSA patients with certain morphological characteristics of the upper airway and related structures.

A short-term controlled trial of an adjustable oral appliance for the treatment of mild to moderate obstructive sleep apnoea.

BACKGROUND: Although oral appliances are effective in some patients with obstructive sleep apnoea (OSA), they are not universally effective. A novel anterior mandibular positioner (AMP) has been developed with an adjustable hinge that allows progressive advancement of the mandible. The objective of this prospective crossover study was to compare efficacy, side effects, patient compliance, and preference between AMP and nasal continuous positive airway pressure (nCPAP) in patients with symptomatic mild to moderate OSA. METHODS: Twenty four patients of mean (SD) age 44.0 (10.6) years were recruited with a mean (SD) body mass index of 32.0 (8.2) kg/m2, Epworth sleepiness score 10.7 (3.4), and apnoea/hypopnoea index 26.8 (11.9)/hour. There was a two week wash-in and a two week wash-out period and two treatment periods (AMP and nCPAP) each of four months. Efficacy, side effects, compliance, and preference were evaluated by a questionnaire and home sleep monitoring. RESULTS: One patient dropped out early in the study and three refused to cross over so treatment results are presented on the remaining 20 patients. The apnoea/hypopnoea index (AHI) was lower with nasal CPAP 4.2 (2.2)/hour than with the AMP 13.6 (14.5)/hour (p < 0.01). Eleven of the 20 patients (55%) who used the AMP were treatment successes (reduction of AHI to < 10/hour and relief of symptoms), one (5%) was a compliance failure (unable or unwilling to use the treatment), and eight (40%) were treatment failures (failure to reduce AHI to < 10/hour and/or failure to relieve symptoms). Fourteen of the 20 patients (70%) who used nCPAP were treatment successes, six (30%) were compliance failures, and there were no treatment failures. There was greater patient satisfaction with the AMP (p < 0.01) than with nCPAP but no difference in reported side effects or compliance. CONCLUSIONS: AMP is an effective treatment in some patients with mild to moderate OSA and is associated with greater patient satisfaction than nCPAP.