Continuous positive airway pressure (CPAP), usually nasally applied, is the established treatment for moderate-to-severe obstructive sleep apnea (OSA) (1). Nasal CPAP therapy for sleep apnea was first described in 1981 (2). Although there was initial skepticism of its efficacy and concern regarding its potential adverse effects on breathing (3,4), there was also early recognition of the importance of having a treatment that could essentially prevent disordered breathing during sleep in OSA patients. This is in contrast to the efficacy of other alternatives available, including partial or variable response to surgery (5). By 1985, more than 100 patients were using this therapy on a regular basis (6). Over the past 20 years, the evidence base supporting the use of CPAP has improved both in quantity and quality, driven at least in part by the demands of government funding authorities and health maintenance organizations and the availability of industry sponsorship with the increasing commercial success of companies selling CPAP equipment (7).
There are methodological problems designing studies to assess and validate a mechanical device such as CPAP, compared with those required for medications. Performing true double-blind randomized controlled trials (RCTs) of CPAP treatment or variants are technically and logistically difficult. "Sham CPAP" by its nature will have less efficacy on unavoidably observable variables such as snoring or apnea with consequent difficulties to truly "blind" study participants. Due to the requisite modification to the equipment, it is also quite difficult to effectively blind a CPAP therapist or doctor involved in such studies compared with pharmaceutical trials involving placebo medications. Also the advent of automatically titrating CPAP devices (see Chapter 8) has major implications for the delivery of healthcare to patients with sleep apnea and for the traditional sleep laboratory-patient relationship.
CPAP is currently the "gold standard" treatment for moderate-to-severe OSA because of its demonstrated efficacy. Even so, many patients do not use it, or use it irregularly, reducing the delivered effectiveness of the therapy. Comparative, double-blind intention-to-treat trials in all degrees of OSA severity are needed to delineate treatment pathways in this condition. Currently, studies focusing on comparative treatments and ways in which there are better effectiveness of CPAP, including timely and economical initiation of therapy, are forming the next phase in the historical development of this treatment modality. Although there are tremendous interest and active research in potential pharmacotherapy for OSA, the absence of any currently available viable pharmacological therapy for sleep apnea (8-10) suggests that CPAP will remain the appropriate therapy standard in the foreseeable future for OSA of more than mild degree.
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