dures are shown to be safe and effective and become widely available .... way becomes unstable and vibrates. To detect ... Although the indices of sleep-disordered breath- ing suggest a ... CPAP system that utilizes an algorithm to detect air-.
Sleep, 19(6):497-501 © 1996 American Sleep Disorders Association and Sleep Research Society
Treatment of Obstructive Sleep Apnea With a Self-Titrating Continuous Positive Airway Pressure (CPAP) System S. Sharma, S. Wali, Z. Pouliot, M. Peters, H. Neufeld and M. Kryger Section of Respiratory Medicine, University of Manitoba, Winnipeg, Manitoba, Canada
Summary: Conventional manually adjusted continuous positive airway pressure (CPAP) is an effective therapy for sleep-disordered breathing. We prospectively investigated the efficacy of a self-titrating nasal CPAP system in the acute treatment of obstructive sleep apnea (OSA) syndrome. Twenty patients with moderately severe OSA [apnea hypopnea index (AHI) > 15/hour] were enrolled in a randomized, controlled, prospective clinical trial. An initial diagnostic sleep study was performed, followed by randomization to a manually adjusted CPAP titration on one night and self titrating CPAP on the other night. On the conventional CPAP night, the CPAP was manually adjusted until abolition of all apneas and electroencephalographic (EEG) arousals, whereas the self-titrating CPAP was set in automatic mode at lights out. The self-titrating CPAP system utilized an algorithm based on airway vibration patterns to detect airway stability. The AHI decreased from 50.8 :±: 28.8/hour [mean:±: standard deviation (SD)] at baseline to 3.8 :±: 3.I/hour (p < 0.005) during manually adjusted and 6.1 :±: 5.3/hour (p < 0.005) during self-titrating CPAP. The arousal index (Ar-I) decreased from 34.1 :±: 23.1/hour (baseline) to 11.2 :±: 5.0/hour on manual adjustment (p < 0.005) and 11.3 :±: 0.3/hour on self titration (p < 0.005), whereas total sleep time was unchanged. No significant differences in any measure of oxygenation or sleep architecture were observed between the manually adjusted and self-titrating CPAP nights except that the lowest arterial oxygen saturation (Sa02) was higher with manual titration (84.4 :±: 4.2% vs. 79.9 :±: 9.7%, P < 0.05). The maximum pressure required for abolition of apneas and arousals was significantly lower (p < 0.05) during the selftitrating study (10.1 :±: 3.8 cmH20) as compared to manually adjusted CPAP (12.3 :±: 3.9 cmH20). Failure to increase pressure and failure to maintain minimum pressure occurred in 7 of the 20 subjects during the self-titrating study. This required manual resetting of the system in five subjects, but the system self-corrected in two subjects. An unsupervised study would have resulted in undertreatment of OSA. Based on a single-night laboratory study, self-titrating CPAP was well tolerated and improved OSA and sleep architecture comparable to manually adjusted CPAP. The future modifications of this prototype will require further research to assess its efficacy and safety in the laboratory and home environments before its recommendation for general long-term use. Key Words: Obstructive sleep apnea syndrome (OSAS)--Continuous positive airway pressure (CPAP)--CPAP titration-Self-titrating CPAP.
Nasally applied continuous positive airway pressure (CPAP) is a highly effective form of treatment for obstructive sleep apnea (OSA). Since it was first described in 1981, it has become the major long-term form of treatment for OSA (l,2). Following a diagnostic polysomnographic (PSG) night study, the nasal CPAP required for treating a patient with OSA is usually determined by a highly trained technician during 1 or 2 nights of continuously supervised PSG studies (3). Presently, CPAP titration is done in the sleep laboratory and takes up a significant amount of the technician's time. It is therefore Accepted for publication April 1996. Address correspondence and reprint requests to M. Kryger, M.D., Sleep Disorders Centre, 351 Tache Avenue, Winnipeg, Manitoba R2H 2A6, Canada.
likely that if automatic nasal CPAP calibration procedures are shown to be safe and effective and become widely available, patients with OSA can be effectively and safely calibrated in the laboratory or home environment at reduced cost and labor compared to the standard procedure. The concept of a single ideal CPAP level for any individual patient is overly simplistic (4). Changes in upper airway resistance are produced by variable degrees of nasal congestion, changing sleep states, body position, blood alcohol level, and sleep deprivation. The CPAP required to treat OSA effectively by maintaining upper airway patency will vary depending on these factors. A low pressure prescribed based on single-night study may not adequately treat a patient (5). On the other hand, too high a pressure may be uncom-
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fortable during awake hours and may lead to decreased compliance. It may also cause poor sleep quality due to microarousals (6). We evaluated the efficacy and safety of a self-titrating nasal CPAP system in the acute treatment of OSA. This system is a prototype developed by Respironics Inc. (Murrysville, PA).
METHODS A randomized, controlled, prospective clinical trial was designed to evaluate the treatment of OSA with self-titrating CPAP compared to conventional manually adjusted CPAP. Outpatients referred to the Sleep Disorders Centre with symptoms of OSA (snoring, excessive daytime sleepiness, and witnessed apneas) were prospectively evaluated. Once diagnosed with OSA, patients with moderately severe OSA [apnea hypopnea index (AHI) > I5/hour] were included in the prospective trial. Patients were excluded if they had been hospitalized with pulmonary, cardiac, neuromuscular, or musculoskeletal disease in the last 6 months. Patients with artificial airways, upper airway tumors, and surgery with in the past 6 months were also excluded. Twenty patients with moderately severe OSA (AHI > 15/hour) were evaluated with three consecutive overnight PSG studies. A diagnostic study was performed on the first night, followed by randomization to manually adjusted CPAP on one night and the self-titrating CPAP on the other. On the conventional CPAP night, the CPAP titration was started at 3 cmH 20 and increased by 2 cmH 20 every 5 minutes until abolition of all apneas and arousals, whereas the self-titrating CPAP was set in automatic mode at lights out. The baseline pressure in the self-titrating system is adjustable; it was set at 5 cmH 20 in the present study. A trained sleep laboratory technologist constantly supervised all three studies. During the self-titration study night, manual resetting of the system was permitted upon recurrence of snoring and apneas or hypopneas if the system did not respond. The CPAP was manually increased by the technologist under these circumstances to abolish the obstructive events. The maximum pressures attained for manual and self-titration are shown in Fig. 1. We recorded the electroencephalogram (EEG; C4/Al, OllA2), electrooculogram (EOG), and mental electromyogram (EMG) using surface electrodes. Arterial oxygen saturation (Sa0 2 ) was recorded continuously, using a pulse oximeter (BIOX 3700, Ohmeda, Boulder, CO) with an ear probe. Respiratory excursions of the chest wall and abdomen were monitored using respiratory inductive plethysmography (SARA unit, Vitalog Inc., Redwood, CA). The electrocardioSleep, Vol. 19, No.6, 1996
gram (ECG) was recorded, and heart rate was determined beat by beat using a tachometer. Airflow was detected by monitoring expired CO 2 at the nose and mouth through a nasal cannula attached to a CO2 analyzer (Normocap 200, Datex Medical Instruments, Tewksbury, MA). The EMG of the anterior tibialis was recorded using surface electrodes on both legs. All variables were recorded at a speed of 10 mm/second onto paper using a polygraph (Grass model 78E, Grass Instruments, Quincy, MA). All respiratory excursions, Sa0 2 , airflow, and heart rate were sampled using a microcomputer system (IBM compatible).
Statistical analysis Sleep stages were scored manually according to standard criteria (7). The PSGs were scored by two experienced technologists and a clinical polysomnographer who were blinded to the CPAP algorithm. Apneas were defined as a cessation of airflow for at least 10 seconds, and hypopneas were defined as a reduction of effort or volume by 50%. Both the apneas and hypopneas were required to have a 4% decrease in Sa02 as compared to baseline values. Arousals were defined as alpha activity or increased EEG frequency lasting for 3-15 seconds. The AHI, total sleep time (TST), percentage of each sleep stage, arousal index (Ar-I; number of arousals per hour of sleep), percentage of TST spent below 90% Sa02 , percentage of TST spent below 85% Sa02 , and percentage of TST spent below 80% Sa0 2 were determined for baseline, manually adjusted CPAp, and self-titrating CPAP. The profile of airway pressure during the CPAP treatment nights was also determined. Data from the 3 nights were compared by two-way analysis of variance (ANOVA). Data obtained on two treatment nights were also compared using a paired t test.
Algorithm for self-titrating CPAP OSA is characterized as complete (apnea) or partial (hypopnea) airway collapse. Prior to collapse the airway becomes unstable and vibrates. To detect airway instability, the self-titrating CPAP system utilizes an algorithm that uses a pressure transducer and microprocessor to monitor the airway for vibration patterns. When three airway instability events are detected within I minute, the pressure increases by 2 cmH 20 over a I-minute period to prevent airway collapse. When no events indicating instability are detected, the pressure decreases by I cmH 20 over a 5-minute period. The baseline pressure in this study was kept at 5 cmH 20 (8).
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OSA TREATMENT WITH SELF-TITRATING CPAP TABLE 1.
Sleep architecture in 20 patients
,
Manually adjusted CPAP (2)
Baseline (I)
TST (minutes) Stage 1 sleep (%) Stage 2 sleep (%) Stage 3/4 sleep (%) REM Sleep (%) Ar-I
363.2 ::':: 9.7 ::':: 63.6::':: 9.1 ::':: 17.8::':: 34.1 ::'::
361.7 ::':: 6.2::':: 55 ::':: 16.7 ::':: 22.7::':: 1l.2 ::'::
6l.6 8.1 10.8 8.5 8.1 23.1
70.1 5.8 13.1 9.8 7.9 5
Self-titrating CPAP (3) 360.9::':: 6.1 ::':: 50.9 ::':: l7.1 ::':: 25.3 ::':: 11.3 ::'::
(I vs. 2 and 3)
p value (2 vs. 3)
NS
