Several investigators have attempted to take various approaches to remedying the problem of CPAP adherence. Common approaches can fall into one of two categories: technological interventions or behavioral interventions. The success of these will be briefly summarized here. A more thorough review of these methods and their relative success or failure can be obtained through one of two comprehensive reviews (144,145).
Recent technological advances in the delivery of airflow have occurred, aiming to improve patient comfort, adherence, and effectiveness for reducing apneas and inspiratory flow limitation. Many of these advances, such as auto-titrating PAP (APAP), have been designed to adjust PAP throughout the night, keeping the pressure elevated when upper airway collapsing forces are high and lowering pressure when the likelihood of airway collapse is low (146). Other devices, including bilevel devices, deliver different set pressures during exhalation (lower pressure) and inhalation (higher pressure) in an attempt to improve comfort (103). Despite these advances, previous studies suggest that these different flow delivery devices do not substantially improve treatment adherence over traditional CPAP (103,147). In a Cochrane Review conducted in 2004 (145), investigators also found little evidence of a strong advantage of auto devices over fixed devices, though they are careful to mention that these devices may have utility for a subset of patient who are as yet unidentified. They also state that the limited advantage provided bilevel ventilation may be outweighed by the cost of the device. The most recent technological advancement has come in the form of flexible pressure delivery. This type of device alternates airway pressure between exhalation and inhalation on a breath-by-breath basis. Airway pressure is reduced during early exhalation in proportion to the patient's expiratory flow rate. Pressure is then increased again toward the end of exhalation when airway collapse is most likely (102). Adherence to flexible pressure technology was compared to fixed CPAP in one controlled, nonrandomized study (148). Flexible pressure was demonstrated to show an advantage of 1.7 hours a night by three months, but differences were not demonstrated on clinical outcome variables. Finally, heated humidification has also resulted in mixed findings, with a one hour a night advantage demonstrated in one study (138), while another demonstrated no advantage (149). Despite the mixed and sometimes unimpressive findings associated with technological advancements, investigators and clinicians agree that improvements in the comfort of the method of flow delivery might serve as one important target in attempting to improve patient adherence.
Several studies have applied educational and behaviorally-based interventions to the problem of CPAP adherence [for review see Engleman and Wild (144) and Haniffa et al. (145)]. Three studies have evaluated the efficacy of simple education on adherence, reasoning that increased knowledge about OSA risks and the consequences of nonadherence would result in greater use (150-152). Some improvement in adherence over short follow-up periods resulted. Two additional studies examined the efficacy of more intensive interventions for adherence compared to standard care (153,154). Findings from these studies were equivocal. Finally, one previous study reported enhanced PAP use in a small sample of participants who received systematic desensitization and sensory awareness training for CPAP-related claustrophobia (155). Collectively, these findings suggest that interventions that focus on enhancing knowledge, increasing patient-therapist interaction, or removing only one potential barrier to PAP use produce nightly improvements ranging from 0 to 2.5 hours. Some of these studies have been limited by small sample sizes, the absence of control groups, and the inclusion of programs that would present practical and fiscal barriers for most sleep clinics to implement. Nonetheless, a Cochrane report concluded that: "There is some evidence that psychological/educational interventions improve CPAP usage." (145). Aloia et al. (155) proposed applying a therapy to PAP adherence that stems from psychological theories of behavior change, which have been found to predict CPAP adherence robustly in previous studies (143,144,156). This motivational enhancement therapy (MET) employs motivational interviewing techniques to the problem of poor adherence to treatment. Early results from this therapy suggest that brief therapies in general can reduce CPAP discontinuation rates compared to standard care. The MET therapy performed best under the condition of flexible delivery of PAP, though differences were not statistically significant (157).
In summary, several studies have demonstrated small to modest effects of both technological and behavioral interventions on adherence to CPAP. The single best approach, however, has not yet been identified. This may be because there is no single best approach. It may be that patients who are strong users of treatment early on need very little if any intervention to ensure their continued use; while those struggling early on may need both technological advantages coupled with therapeutic interventions targeting behavior change. This stepped-care approach to adherence has not yet been tested but may indeed be the most efficacious manner by which to approach the problem of nonadherence.
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