In 1976, when the first comprehensive account of obstructive sleep apnea (OSA) appeared in a mainstream journal (1), no one really appreciated how common this disorder would be, and therefore how expensive it would become to run services for these patients. The initial diagnosis of OSA and related conditions was defined in well equipped and established neurophysiologic sleep laboratories, mostly involved in research. It was not surprising, therefore, that the guidelines on the investigation of OSA should include complex investigative techniques used in research, such as polysomnography (PSG) with detailed analysis of the EEG (2). When the theoretically simple treatment of nasal continuous positive airway pressure (CPAP) arrived (3), these sleep analysis techniques were in turn made part of initiating such therapy (4). The extensive guidelines published on these sleep study techniques always refer to PSG as if it were the gold standard, rather than an investigative technique quite unproven for the purpose for which it was being recommended. Gradually chinks in the armor of the polysomnographer have appeared, mainly from Europe (5, 6), but also from North America (7). Indeed, a telling admission that polysomnography might be most attractive because of its significant reimbursement opportunities came from the Stanford University group itself, although unfortunately buried in a monograph of limited availability (8).
There has now been much written on the necessity or otherwise of complex investigations into potential cases of OSA (9). Initially, simplified techniques had to reasonably mimic PSG results to be accepted (10), but more recently a more pragmatic approach has been taken (11). It has been realized by many that the purpose of the sleep study is really to detect sleep fragmentation due to upper airway obstruction or, even more pragmatically, "CPAP-responsive disease." If such CPAP responsiveness is taken as the outcome of primary interest, then simplified diagnostic tests, even just simple oximetry, have been shown to be at least as good as PSG (11). There is now a real acceptance by most that simplified tests are clearly the way of the future in routine clinical practice, particularly in the face of an increasing disease burden (9).
The article in this issue of the Journal from Masa and coworkers (pp. 1218-1224) takes the simplification of the management of patients with symptomatic OSA one stage further (12). This multicenter study from Spain asked whether simplifying the approach to placing patients on CPAP still led to satisfactory outcomes. The Spanish group randomized 360 patients prescribed CPAP for symptomatic OSA into three groups: (1.) conventional overnight CPAP titration with polysomnographic verification of the efficacy of a final fixed pressure, (2.) one-night home autotitration to establish the subsequent fixed pressure, and (3.) use of an algorithm-derived fixed pressure and subsequent adjustment according to symptoms (such as continuing snoring). A variety of factors were monitored, but the primary outcomes were symptoms and a repeat PSG on CPAP at 12 weeks.
This study found essentially no differences between the three CPAP study groups. The average CPAP pressure in the three groups was 8.8,9.1, and 8.4 cm H2O, in the standard, autotitration and algorithm groups, respectively. The apnea/hypopnea index was lowest in the autotitration group, and highest in the algorithm group, commensurate with the different mean pressures, but not significantly so. The arousal index at 12 weeks was effectively identical in the three groups, as was the cruder sleep stages analysis. The Epworth Sleepiness Scale (ESS) values fell to the same levels, and other symptom measures, such as the Short Form 36, Functional Outcomes of Sleep Questionnaire and Euro-Qol, showed small and inconsistent differences between the groups. CPAP usage was similar, at 5.2, 5.3, and 5.2 hours/night, in the standard, autotitration, and algorithm groups, respectively.
The follow up was only for 3 months, perhaps within a "honeymoon" period: longer-term symptom relief and compliance might differ between the groups, although compliance patterns seem to be established within 3 months (13). The assessment of sleepiness was based on subjective scoring systems, and no objective measure of sleepiness was employed. Another potential endpoint not addressed was blood pressure, and we know that partial OSA relief does not seem to bring the BP falls that complete relief does (14). There is also evidence that there is considerable night-to-night variation in the CPAP pressure needed to abolish obstructive events, making a one-night titration itself relatively unreliable, however well performed (15). This is one argument used to justify the continual use of autotitration machines, and the abandonment of fixed pressure machines, an alternative strategy not addressed by this study. However, autotitrating machines are significantly more expensive than fixed pressure machines, and most health economies will not wish to purchase them for routine use unless they are shown to have significantly better longer-term outcomes. With these four particular limitations in mind, it would nonetheless be reasonable to conclude from the current study that, once again, received wisdom (in this case the necessity for obsessional CPAP titration) is not supported when subjected to the power of controlled trials.
Data from other units have demonstrated similar findings (16, 17), although this current work has somewhat more comprehensive endpoints and larger numbers of subjects. Such randomized and controlled trial work gives us the evidence to justify reducing the complexity, and thus the costs, of treatment. This has to be good for patients, since it provides cheaper and simpler CPAP therapy, available to greater numbers. The authors are to be congratulated for addressing this issue.
Conflict of Interest Statement: J.R.S. does not have a financial relationship with a commercial entity that has an interest in the subject of the manuscript.
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JOHN R. STRADLING, M.D.
Oxford Centre for Respiratory Medicine
Oxford, United Kingdom
Copyright American Thoracic Society Dec 1, 2004
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