Elsevier

Sleep Medicine

Volume 5, Issue 3, May 2004, Pages 247-251
Sleep Medicine

Original article
Preference for fixed or automatic CPAP in patients with obstructive sleep apnea syndrome

https://doi.org/10.1016/j.sleep.2003.09.011Get rights and content

Abstract

Background

The aims of this study were to compare compliance to treatment with fixed CPAP and with autoCPAP, subjective preference for type of CPAP treatment, and factors associated to preference for autoCPAP in patients with OSAS.

Patients and Methods

Twenty-two subjects were studied in a randomized, single blind cross-over fashion. They were treated for one month by fixed CPAP (Élite Sullivan V, ResMed, Sydney, Australia) and one month by autoCPAP (Autoset T, ResMed, Sydney, Australia).

Results

Four subjects who stated a preference for fixed CPAP and four who expressed no preference were pooled together; fourteen preferred autoCPAP. Compliance to treatment using the two machines did not differ in the first group (3.8 (1.9) vs. 3.8 (1.5) h/day, fixed vs autoCPAP), but was higher with autoCPAP in the second group (4.8 (1.8) vs 5.5 (1.5) h/day, P<0.05). Baseline apnea/hypopnea index (AHI) was high in both groups, but was higher in the second group (P<0.02). First treatment was always fixed CPAP in patients who preferred fixed CPAP, while it was either in the other subjects.

Conclusions

Compliance to autoCPAP differs among OSAS patients. As long as factors predicting higher compliance to autoCPAP are not found, a trial with autoCPAP in patients poorly compliant to fixed CPAP may be warranted.

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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