Continuous positive airway pressure (CPAP) is the preferred treatment for obstructive sleep apnea syndrome (OSAS). It allows progressive restoration of airflow, as the pressure applied exceeds the airway opening pressure. Appropriate CPAP can resolve OSAS in many patients.1,2 In addition to improving sleep quality in patients with OSAS,3,4 CPAP has been shown to decrease daytime sleepiness and lower blood pressure.5,6 Standard CPAP administered at a sleep center requires pressure titration. Home CPAP utilizing auto-adjusted titration has become more prevalent as the number of available devices has increased and the clinical evidence demonstrating their efficacy has grown, although the degree of growth has been constrained by reimbursement issues.

Despite the positive aspects of CPAP, compliance can be difficult to achieve. CPAP can cause nasal congestion, claustrophobic sensations, and other side effects. Adequate compliance is being recognized increasingly as a major determinant of treatment success, and various strategies have been employed to enhance compliance with CPAP.

Prevalence of OSAS

Studies in the United States, Europe, and Australia have shown that a substantial proportion of the adult population has mild-to-moderate OSAS.7,8,9 According to the American Lung Association, as many as 18 million Americans suffer from OSAS.10 Men are more susceptible than women, and sleep apnea clusters have been observed within families.10 Obesity appears to be a predisposing factor.11

Why Treat OSAS?

Apnea and hypopnea cause temporary elevations in blood pressure in association with blood-oxygen desaturation, arousal, and sympathetic activation, and can cause elevated blood pressure during the daytime and, ultimately, sustained hypertension, putting individuals with sleep apnea at risk for hypertension and, possibly, heart disease.12

OSAS is associated with neurohormonal and electrophysiological abnormalities that may increase the risk of sudden death from cardiac causes, especially during sleeping hours. This was demonstrated in a postmortem review of polysomnograms and death certificates of 112 patients who had undergone polysomnography and had died suddenly from cardiac causes.13 At four intervals of the day, the investigators of this study compared the rates of sudden death from cardiac causes among patients with OSAS and rates among people without OSAS; rates in the general population; and expected rates according to chance alone. From midnight to 6:00 am, sudden death from cardiac causes occurred in 46% of people with OSAS, compared with 21% of people without OSAS (P = 0.01); 16% of the general population (P < 0.001); and 25% expected by chance alone (P < 0.001). As the investigators noted, the findings from this study demonstrate that people with OSAS have an increased risk of sudden cardiac death during sleeping hours. This contrasts strikingly with the low incidence of sudden cardiac death during sleeping hours in people without OSAS and in the general population.

Individuals who experience severe OSAS can lose so much sleep that their level of alertness during wakefulness is seriously impaired. Such a lack of alertness can pose a serious hazard if they are operating heavy machinery or driving a car. In fact, numerous investigators have found a strong correlation between sleep apnea and the risk of traffic accidents.14,15,16,17

Laboratory-Based CPAP Versus Home CPAP

Home CPAP is a relatively recent technology by which a CPAP device automatically adjusts the level of mask pressure to the patient’s requirements. The rationale for home CPAP is to improve treatment efficacy, enhance compliance with treatment, and perform automatic titration. Auto-titration makes sense because patients’ pressure requirements vary over both the short and long term.18 The rationale behind improved compliance with treatment is that home auto-adjusted CPAP should achieve the same treatment efficacy with lower nasal pressures, thereby reducing adverse effects and improving compliance.18 The evidence base supporting the use of home CPAP is growing.

Meurice and colleagues19 performed a randomized study to compare the efficacy of an auto-titration CPAP (aCPAP) device (Morphee Plus®, Mallinckrodt, St Louis) with that of conventional CPAP in 16 patients with OSAS. Sleep improvements were similar in both groups, and the apnea/hypopnea index (AHI) was within the normal range at study end in both groups.

Huskins20 performed a randomized, single-blind, crossover trial to compare compliance and treatment response between standard CPAP and aCPAP. Patients with OSAS who required CPAP treatment underwent 2 months each of CPAP and aCPAP in random order at a sleep center. Outcome assessments included Epworth Sleepiness Scale (ESS) Score, Short Form–36 (SF-36) Health Survey, visual analog scale to measure ease of and attitude to treatment, side effects, and treatment pressures or system leaks obtained from an Autoset T® device (ResMed, Poway, Calif). There were no differences between treatment modalities in overall compliance, ESS scores, or SF-36 scores. There were fewer reported side effects in aCPAP mode, and compliance was greater with aCPAP in patients reporting any side effects. Auto-titrated CPAP delivered significantly lower airway pressures and resulted in fewer system leaks. In this study, compliance, subjective sleepiness, and quality of life were similar between patients who used standard CPAP and those who used aCPAP.

Senn and colleagues21 evaluated the efficacy of two different CPAP devices with automatic mask pressure adjustment in comparison with fixed CPAP in 29 patients with OSAS. Patients were treated over three consecutive 1-month periods with three regimens in random order: an aCPAP device responding to apnea-hypopnea and snoring, another aCPAP device responding to snoring and changes in flow contour, and fixed CPAP at the 90th pressure percentile titrated by aCPAP over 2 weeks. At the end of each treatment period, symptoms, quality of life, and nocturnal breathing disturbances were evaluated. All three treatment modalities improved symptoms, quality-of-life domains, and AHI significantly and to a similar degree. The investigators concluded that both aCPAP devices were as effective as fixed-pressure CPAP in improving outcomes in patients with OSAS.

More recently, Nussbaumer and colleagues22 performed a randomized, controlled, double-blind, crossover trial comparing the efficacy of a novel aCPAP machine (REMStarAuto®, Respironics, Murrysville, Pa) operated in auto-adjusted or constant mode in 30 patients with OSAS. Patients were randomly assigned to 1 month of home therapy with aCPAP followed by 1 month with CPAP, or vice versa. After 1 month with either treatment, mean ESS score, sleep resistance time, and mean AHI were significantly improved; 26 patients preferred aCPAP, and four patients preferred CPAP. Although these results are encouraging, the overall efficacy of auto-titrated CPAP in increasing the hours of use remains unclear.

Home CPAP is not without potential disadvantages. Ineffective adjustment of pressure can result from mouth or mask leaks, rapid alteration between sleep and wake periods, or occurrence of central hypopneas.23 In addition, prolonged periods of high pressure may aggravate both leaks and sleep instability.

Strategies to Increase Compliance with CPAP

Most CPAP devices now contain circuitry that records hours of usage and the pressure at any given time. There are also software tools that can be used to help the respiratory therapist monitor how patients are using CPAP. However, the most important strategy for ensuring compliance with CPAP appears to be proper education of clinicians and adequate follow-up of patients. When these strategies are followed, CPAP compliance rates of >70% can be achieved, even in the primary care setting. This was demonstrated in a retrospective trial performed by Ball and colleagues.24 In this study, sleep-disorder specialists provided a community with education, diagnostic equipment, and ongoing support as sleep disorders expertise was established locally. Outcomes for a 2-year period were assessed by chart review, patient questionnaire, tabulation of polysomnographic data, and comparison with published reports from specialized centers. Data were collected from all community physicians on 360 new patients who underwent polysomnogram testing. The investigators found that with the provision of proper education, referral for sleep testing increased by almost eightfold. This resulted in the diagnosis of sleep-related breathing disorders in 81% of patients and periodic movement disorder in 18%. Nasal CPAP treatment was given to 228 patients, which represented a greater volume of patients than at many traditional sleep centers, yet compliance with CPAP was comparable. This study suggests that OSAS is significantly underrecognized by primary care physicians. The researchers noted that as a result of the intervention, local sleep expertise was established and large numbers of OSAS patients were discovered and treated in the community.

Patient education is also important to enhancing compliance with CPAP. In a randomized trial of 12 subjects, the effect of education on the consequences of OSAS and the efficacy of CPAP was evaluated.25 One group received two 45-minute sessions designed to provide education on the consequences of OSAS and the efficacy of CPAP. The control group received the same extent of therapist contact but did not receive information on OSAS or CPAP. Compliance data were collected using CPAP devices with internal microprocessors that were read at 1, 4, and 12 weeks after treatment initiation. The provision of education enhanced compliance by the 12-week assessment period. Patients who received the education were using CPAP more regularly at 12 weeks and showed greater improvement on vigilance at follow-up.

Sin and colleagues studied patients with sleep apnea to determine short-term and long-term compliance with this treatment, baseline predictors for long-term CPAP compliance, and whether CPAP use provides sustained improvement in daytime sleepiness.26 The design was a prospective, longitudinal study of patients referred to a university sleep disorders center; 296 patients with moderate-to-severe obstructive sleep apnea, as defined by an AHI of 20 or more events per hour on polysomnography, were enrolled. Participants were provided with a CPAP device that contained a computer chip for monitoring compliance. They were informed that noncompliance would result in the loss of the machine. Within the first week of the study, patients began making daily telephone contact with a CPAP clinic nurse and were followed up in the office at 2 weeks, 4 weeks, 3 months, and 6 months. During each follow-up visit, patients were asked to complete a questionnaire regarding their degree of daytime sleepiness. Compliance rates (defined as use of the CPAP machine for 3.5 hours or longer per day) were at or above the 80% mark at each of the follow-up visits. The daytime sleepiness score improved over the entire follow-up period, with the lowest score occurring at 6 months. Three variables were found to correlate with increased use of CPAP—female gender, increased age, and reduction of daytime sleepiness scores. The investigators concluded that a population-based CPAP program consisting of consistent follow-up, “trouble-shooting,” and regular feedback to both patients and physicians can achieve CPAP compliance rates of >85% over a 6-month period.

It is important for patients to establish an effective CPAP usage pattern. Several studies have shown that CPAP usage patterns are developed early in the course of treatment.27,28 Weaver and colleagues reported that differences in duration and pattern of CPAP use between compliers and noncompliers could be distinguished by the fourth night of treatment.28 Other investigators demonstrated that average nightly use during the first 3 months was highly predictive of long-term CPAP use.29

According to the results of a systematic review,30 the evidence supporting increased compliance through self-titration and humidification is lacking, but there is some evidence that psychological and educational interventions might improve CPAP usage. States Lawrence Epstein, MD, an instructor in medicine at Harvard Medical School and regional medical director of Sleep HealthCenters®,31 the four cornerstones of ensuring compliance with CPAP are (1) the maximization of comfort with the patient-device interface; (2) optimization of the patient’s experience with CPAP during the early treatment period; (3) appropriate treatment of side effects; and (4) the provision of long-term support.


Although CPAP is an effective treatment for OSAS, success may be limited by poor compliance. Optimal compliance is predicated on the provision of adequate education for both providers and patients; utilization of a CPAP program consisting of consistent follow-up, “trouble-shooting,” and regular feedback to both patients and physicians; maximization of comfort with the CPAP device; and treatment of side effects. Additional factors include the provision of long-term support and the optimization of the patient’s experience early in the course of CPAP therapy.

John D. Zoidis, MD, is a contributing writer for  RT. For further information, contact [email protected].


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