CPAP with autotitration has moved from the sleep lab to the home and has been shown to improve patient compliance

Continuous positive airway pressure (CPAP) is the preferred treatment for obstructive sleep apnea (OSA), a condition characterized by repeated episodes of apnea and hypopnea during sleep. CPAP increases air pressure in the throat so that the airway will not collapse during inspiration. CPAP allows progressive restoration of airflow, as the pressure applied exceeds the airway opening pressure. Appropriate CPAP can resolve OSA in many patients, so long as the patient continues to comply with treatment. In addition to improving sleep quality in patients with OSA,1,2 CPAP has been shown to decrease daytime sleepiness and lower blood pressure.3,4

Continuous-flow CPAP titration has traditionally been performed at a sleep center, with the pressure adjustment performed either on the night following polysomnography to diagnose OSA or, using a split-night protocol, during the second half of the diagnostic night. Treatment then proceeds at home using the pressure titrated at the sleep center. CPAP with autotitration performed at home, however, has become more prevalent as the number of available devices has increased and the clinical evidence demonstrating their efficacy has grown.

Prevalence and Treatment Rationale
 Screening studies5-7 in the United States, Europe, and Australia have shown that a substantial proportion of the adult population has mild-to-moderate OSA. According to the American Lung Association,8 as many as 18 million US residents have OSA. Men are more susceptible than women, and sleep apnea clusters have been observed within families.8 Obesity appears to be a predisposing factor.9

Apnea and hypopnea cause temporary elevations in blood pressure in association with oxygen desaturation, arousal, and sympathetic activation and may cause elevated blood pressure during the day (and, ultimately, sustained hypertension). Individuals with sleep apnea are, therefore, at risk for hypertension and, possibly, heart disease.10

OSA is associated with neurohormonal and electrophysiological abnormalities that may increase the risk of sudden death from cardiac causes, especially during sleeping hours. This was demonstrated in a postmortem review11 of the polysomnograms and death certificates of 112 patients who had undergone polysomnography and had died suddenly from cardiac causes. For four equal portions of the day, the investigators compared the rates of sudden death from cardiac causes for patients with OSA with rates for people without OSA, rates for the general population, and expected rates according to chance alone. From midnight to 6 am, sudden death from cardiac causes had occurred in 46% of the patients with OSA, compared with 21% of people without OSA (P=.01), 16% of the general population (P<.001), and the 25% expected by chance alone (P<.001). As the investigators noted, the finding that people with OSA have an increased risk of sudden cardiac death during sleeping hours contrasts strikingly with the low incidence of sudden cardiac death during sleeping hours in people without OSA and in the general population.

Individuals who have severe OSA may lose so much sleep that their level of alertness during wakefulness is seriously impaired. Such a lack of alertness may pose a serious hazard if they operate heavy machinery or drive a car. In fact, numerous investigators12-15 have found a strong correlation between sleep apnea and the risk of traffic accidents.

Continuous and Autotitrated CPAP
Autotitrated CPAP is a relatively recent technology by which a CPAP device automatically adjusts the level of delivered pressure to the patient’s requirements. Autotitration makes sense because patients’ pressure requirements can vary over both the shorter and longer terms.16 Autotitrated CPAP should achieve the same treatment efficacy as continuous-flow CPAP with greater comfort, improving compliance and reducing adverse effects.16 The evidence base supporting the use of autotitrated CPAP is growing.

Meurice et al17 performed a randomized study to compare the efficacy of an autotitrated CPAP device with that of continuous-flow CPAP in 16 patients with OSA. Sleep improvements were similar in both groups, and the apnea/hypopnea index (AHI) was within the normal range at the study’s end in both groups.

Hukins18 performed a randomized, single-blind, crossover trial to compare compliance and treatment response for continuous-flow CPAP and autotitrating CPAP. Patients with OSA who required CPAP treatment underwent 2 months each of continuous-flow CPAP and autotitrating CPAP in random order. Outcomes measures included the Epworth Sleepiness Scale (ESS) score, the Short Form 36 (SF-36) health survey, a visual analog scale used to measure ease of and attitude to treatment, side effects, treatment pressures, and system leaks. There were no differences between treatment modalities in overall compliance, ESS scores, or SF-36 scores. There were fewer reported side effects in autotitrating CPAP mode, and compliance was greater with autotitrating CPAP in patients reporting any side effects. Autotitrating CPAP delivered significantly lower airway pressures and resulted in fewer system leaks. In this study, compliance, subjective sleepiness, and quality of life were similar between patients who used standard CPAP and those who used autotitrating CPAP.

Senn et al19 evaluated the efficacy of two different auto-titrating CPAP devices in comparison with fixed-pressure CPAP in 29 patients with OSA. Patients were treated over three consecutive 1-month periods with three regimens in random order: an autotitrating CPAP device responding to apnea-hypopnea and snoring, another autotitrating CPAP device responding to snoring and changes in flow contour, and fixed CPAP at the 90th percentile of the pressure titrated by an autotitrating CPAP device over 2 weeks. At the end of each treatment period, symptoms, quality of life, and nocturnal breathing disturbances were evaluated. All three treatment modalities improved symptoms, quality of life, and AHI significantly, and to a similar degree. The investigators concluded that both of the autotitrating CPAP devices were as effective as fixed-pressure CPAP in improving outcomes in patients with OSA.

More recently, Nussbaumer et al20 performed a randomized, controlled, double-blind, crossover trial comparing the efficacy of a novel autotitrating CPAP machine operated in autotitrated or constant mode in 30 patients with OSA. Patients were randomly assigned to 1 month of home therapy with autotitrating CPAP followed by 1 month with CPAP, or vice versa. After 1 month with either treatment, mean ESS score and mean AHI were significantly improved; 26 patients preferred autotitrating CPAP and four preferred CPAP.

Autotitrating CPAP is not without potential disadvantages. Ineffective adjustment of pressure can result from mouth or mask leaks, rapid alteration between sleeping and waking periods, or occurrence of central hypopneas.21 In addition, prolonged periods of high pressure may aggravate both leaks and sleep instability.

Conclusion
 Autotitrating CPAP does not require initial titration in a sleep center and is a simple and promising modality for the treatment of OSA. A growing body of evidence suggests that autotitrating CPAP is as effective as conventional CPAP, and may enhance compliance because of its ease of use. Larger studies are needed to establish more definitively the relative efficacy of autotitrating CPAP and conventional CPAP.

John D. Zoidis, MD, is a contributing writer for RT.

References
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