Original articlePreference for fixed or automatic CPAP in patients with obstructive sleep apnea syndrome
Introduction
Treatment of obstructive sleep apnea syndrome (OSAS) by continuous positive airway pressure (CPAP) is well established. Candidates for CPAP treatment include subjects with moderate to severe respiratory disorders and excessive daytime sleepiness (EDS); indications for CPAP treatment in patients with mild OSAS are controversial [1], [2]. Overall, less than satisfactory compliance to treatment is usually the most important limitation of CPAP effectiveness.
Automatic CPAP (autoCPAP) ventilators, compared to fixed level CPAP machines, administer a lower mean level of positive pressure during the night. This may lead to improved compliance, as the lower pressure could be easier to apply and to tolerate; high CPAP pressure levels may also be more commonly associated with side effects [3], [4].
The enhancement of compliance with autoCPAP is uncertain. In previous studies compliance to treatment was not related to CPAP level [5], [6], [7], while it was related to CPAP side effects in some [5], [8] but not in other investigations [7], [9], [10]. Among studies directly evaluating the effects of autoCPAP on compliance to treatment, a few showed a positive effect [11], [12], [13], [14], while others did not [15], [16], [17].
Data comparing fixed and automatic CPAP treatment have mainly focused on mean ventilator use in groups of patients; inter-individual use of ventilators, and characteristics of patients who accept or preferentially use each type, have received little attention. Even if autoCPAP machines do not determine increased compliance in unselected OSAS patients, it is possible that there is a subpopulation of OSAS patients who preferentially use them [4], [18], [19]. In this regard, one non-cross-over study found that subjects with both stage-dependent and posture-dependent sleep apnea have a lower use of fixed and a similar use of automatic CPAP, as compared to other patients [20]. A recent cross-over study showed a significant but slightly higher compliance to autoCPAP in selected subjects with fixed CPAP needs pressure of ≥10 cm H2O, but made no comparison to subjects needing lower CPAP levels [14].
The aims of this study were to compare: compliance to fixed and autoCPAP treatment; subjective preference for type of CPAP treatment; and associated preference factors for autoCPAP among patients with OSAS diagnosed in two Italian centres.
Section snippets
Patients and methods
Subjects referred for suspected OSAS to the Palermo National Research Council and the Bari University Sleep Respiratory Disorders Centre underwent a nocturnal polysomnography for diagnosis. Polysomnographic studies included recordings of EEG (2 unipolar leads), left and right EOG, submental EMG, oro-nasal airflow by nasal cannulas, thoracic and abdominal movements, oxyhemoglobin saturation (SaO2), and snoring by a microphone on the sternal notch. Sleep stages were scored according to standard
Results
Sleep structure substantially improved with CPAP application compared to the baseline night (Table 1). AutoCPAP was effective in reducing sleep-respiratory disorders in all subjects. AHI, calculated on PSG during its application, was 6.9 (4.5) compared to 68.4 (12.1) during the baseline night (P<0.001). In the baseline study, four patients (2 in each centre) showed posture-dependent sleep apnea, defined as AHI in lateral posture <50% than AHI in supine posture; none had respiratory disorders
Discussion
Use of two machines delivering fixed and variable CPAP resulted on average in a similar compliance to treatment, but subjective preference for, and use of, the ventilators differed among subjects. More subjects preferred autoCPAP, and more prolonged use of this machine in some cases determined a substantially higher compliance to treatment; among the other patients a similar compliance to both types of treatment was found.
Not unexpectedly, age, BMI, and degree of subjective somnolence were
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2011, Handbook of Clinical NeurologyCitation Excerpt :In patients with high within-night variability in pressure requirements, the use of auto-CPAP compared with fixed-pressure CPAP did not confer compliance advantage and both methods were equivalent in terms of AHI reduction; however, mean Epworth Sleepiness Scale score was slightly and significantly lower on auto-CPAP (Noseda et al., 2004). A small study of CPAP preference, i.e., fixed versus auto, suggested better compliance to auto-CPAP in the auto-preferring group but the study was not able to identify factors that predicted in advance those who would prefer auto-CPAP (Marrone et al., 2004). Another small study found no difference between fixed and auto-CPAP in outcomes of symptom and AHI reduction, and was associated with similar frequency of side-effects and compliance, though at the end of the study more preferred fixed than auto-CPAP (Hussain et al., 2004).