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Efficacy of Automatic Continuous Positive Airway Pressure Therapy That Uses an Estimated Required Pressure in the Treatment of the Obstructive Sleep Apnea Syndrome

Frederic Series, MD; and Isabelle Marc, MD
[+] Article and Author Information

From Hopital Laval, Sainte-Foy, Quebec, Canada Acknowledgment: The authors thank Nathalie Dupuis, Andree Veilleux, Sandra Jolin, Michel Leblond, Isabelle Boucher, and Germain Ethier for technical assistance and Serge Simard for statistical analysis. Grant Support: In part by Pierre Medical France. Requests for Reprints: Frederic Series, MD, Centre de pneumologie, Hopital Laval, 2725 chemin Sainte-Foy, Sainte-Foy, Quebec G1V 4G5, Canada. Current Author Addresses: Drs. Series and Marc: Centre de pneumologie, Hopital Laval, 2725 chemin Sainte-Foy, Sainte-Foy, Quebec G1V 4G5, Canada.


Copyright ©2004 by the American College of Physicians


Ann Intern Med. 1997;127(8_Part_1):588-595. doi:10.7326/0003-4819-127-8_Part_1-199710150-00002
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Background: Continuous positive airway pressure (CPAP) is effective therapy for the obstructive sleep apnea syndrome (OSAS). Automatic CPAP devices continuously adjust the positive pressure to the required levels.

Objective: To determine the efficacy of an automatic CPAP machine used with an estimated reference pressure value.

Design: A before-and-after, single-blind trial in which patients were randomly allocated to one of three modes of CPAP administration.

Setting: Referral-based sleep center in a public health care institution.

Patients: 36 outpatients with OSAS.

Intervention: Continuous positive airway pressure was given at a conventional fixed pressure (group 1), automatic CPAP was given at a measured reference pressure (group 2), and automatic CPAP was given at an estimated reference pressure (group 3). In group 1, the effective pressure was determined during a titration sleep study. In groups 2 and 3, the pressure interval was allowed to vary from 4 cm H2O below reference pressure to 3 cm H2O above reference pressure. In group 3, the estimated value of the reference pressure was determined according to individual anthropometric characteristics.

Measurements: Sleep studies were performed and measurements of diurnal sleepiness were obtained at each visit.

Results: Sleep and breathing disorders and hypersomnolence were alleviated similarly in the three groups. The apnea + hypopnea index remained abnormal in one patient in group 3 for whom the reference pressure had been underestimated. A strong negative correlation was found between the percentage of time spent below reference pressure during CPAP and the difference between the effective and estimated pressures.

Conclusion: Automatic CPAP can be used with an estimated reference pressure without doing a titration sleep study. The positive pressure trend can be used to determine whether treatment failure is caused by an inadequate pressure setting and to determine the amount of pressure to apply.

Figures

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Figure 1.
Apnea + hypopnea index values for individual patients observed at baseline and after 3 weeks of continuous positive airway pressure (CPAP) therapy in the three treatment groups.

Each solid line represents one patient. Similar improvements occurred in each group. The black circle indicates one patient in group 3 who had persistent obstructive breathing abnormalities; the black square indicates one patient in group 3 who had residual sleep fragmentation caused by periodic leg movements. Dashed line represents the normal value.

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Figure 2.
Arousal index values for individual patients obtained at each visit.

Sleep fragmentation was similarly alleviated in the three treatment groups. Each line represents one patient. The black circle indicates one patient in group 3 who had persistent obstructive breathing abnormalities; the black square indicates one patient in group 3 who had residual sleep fragmentation caused by periodic leg movements. Dashed line represents the normal value. CPAP = continuous positive airway pressure.

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Figure 3.
Results of the maintenance-of-wakefulness test for individual patients obtained at each visit.

Sleep latency increased greatly by the end of continuous positive airway pressure (CPAP) therapy in the three treatment groups. Each line represents one patient. The black circle indicates one patient in group 3 who had persistent obstructive breathing abnormalities; the black square indicates one patient in group 3 who had residual sleep fragmentation caused by periodic leg movements. Dashed line represents the normal value.

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Figure 4.
Relation between the values for the percentage of the time during which continuous positive airway pressure (CPAP) was applied that was spent below the reference pressure and the difference between the effective and estimated pressure in patients in group 3.

A highly significant negative relation was found between these variables. Each symbol represents one patient. The black circle indicates one patient who had persistent obstructive breathing abnormalities; the black square indicates one patient who had residual sleep fragmentation caused by periodic leg movements.

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