| BackgroundObstructive sleep apnea hypopnea syndrome (OSAHS) is a common sleep breathing disorder, with a worldwide prevalence of4%of men and2%of women among the adult population, and it has become an important research domain. Obstructive sleep apnea may result in nocturnal desaturation, sympathetic nervous excitement, systemic inflammatory, oxidant stress and metabolic disorders due to upper airway total or partial blocking during sleep. The main symptoms of the obstructive sleep apnea hypopnea syndrome include:snoring, sleep apnea, shallow breathing and sleep behavior disorder; excessive daytime sleepiness, concentration difficulties, headache and neuropsychological disorders. What’s more, OSAHS increases risk for motor vehicle accidents and the burdens on family and society. Obstructive sleep apnea not only causes nocturnal desaturation and carbon dioxide retention, but also results in or worsen the pulmonary hypertension, pulmonary heart disease, respiratory failure, hypertension, coronary heart disease, diabetes mellitus, arrhythmia and cerebral apoplexy. There are more and more people begin to concern this disease, and many therapeutic methods have been proposed. Continuous positive airway pressure (CPAP) is an effective and common treatment for patients with obstructive sleep apnea. CPAP is effective in preventing upper airway collapsibility during sleep and normalizing sleep architecture, resolving nocturnal desaturation, and improving daytime sleepiness and reducing risks of motor vehicle crashes and the development of cardiovascular morbidity. The standard process is that all subjects have a titration study conducted during a full PSG study to determine the effective pressure, which is used to eliminate apneas, hypopneas, snoring, and flow limitation in all positions and sleep stages. Given that the pressure may change according to sleep stage, body position, and other factors, such as gain weight, taking the tranquilizer or ingestion of alcohol, the set pressure may be higher than minimum level necessary to maintain airway patency. It may cause some side effects, such as mask leak or difficulty in exhaling, which may critically impair compliance. Statistics found that60%-75%patients were satisfied with the effect of fixed continuous positive airway pressure devices, but there were only46%patients regular use it for a long run. However, the effectiveness of the symptomatic therapy mainly depends on regular use.Automatic continuous positive airway pressure (auto-CPAP) theoretically can perceive the apnea/hypopnea, the resistance of the upper airway, sleep stages and sleep positions, and then modify therapy pressure in response to patients’needs. It has been hypothesized that this reduction in mean therapy pressure may improve patient tolerance, therapy resulting in an improved compliance.There have been several randomized controlled trials assessing the effect of auto-CPAP compared to fixed CPAP in patients with obstructive sleep apnea hypopnea since1996. A meta-analysis conducted by Ayas et al., which contained nine studies from1996-2003, concluded that auto-CPAP and fixed CPAP were similar in adherence. With the development of the automatic continuous positive airway pressure, there are several new published additional randomized controlled trials examining the effectiveness of auto-CPAP versus fixed CPAP in patients with obstructive sleep apnea. However, whether auto-CPAP or fixed CPAP is more effective is still being debated. Therefore, an updated meta-analysis focused on the effect of auto-CPAP versus fixed CPAP is now necessary so that clinicals are able to make up-to-date, evidence-based treatment decisions.ObjectiveTo evaluate the effect of automatic continuous positive airway pressure versus fixed continuous positive airway pressure for the treatment of obstructive sleep apnea, which can provide the best evidence for clinical decision.Methods1. After put forward a question, an detailed inclusion and exclusion criteria were established according to PICO steps, and then comprehensive search strategy of literature were made to search the relevant randomized controlled trials.2. We searched the electronic databases MEDLINE, EMBASE, the Cochrane Library, and Google Scholar.3. The methodology quality of each inclusion study was critically assessed according to the quality criteria of RCT which include four items:randomization, allocation concealment, blindness and follow-up. The validity of each trial was referred to as A, B, or C scale according to Cochrane handbook for systematic reviews.4. After critical appraisal, data of each RCT on relevant outcome parameter were extracted. Software Revman5.0the Cochrane Collaboration provided were used for meta-analysis. For each study, continuous variables were presented as mean differences (MD) and dichotomous data as odds ratio (OR), both with95%confidence intervals (CI). Before outcome measures of each trial were pooled, clinical heterogeneity should be considered. If interventions of each trial were different, subgroup analysis should be applied. Heterogeneity between comparable studies was tested, with the use of a standard Chi square test. We used a fixed effects model in the meta-analysis unless there was significant heterogeneity (P<0.1) between studies, when we used a random effects model of DerSimonian and Laird.Results1. Search resultsA total of58randomized controlled trials were identified from the literature search. After reviewing the abstract and entire article, the19trial studies including845patients met all the inclusion criteria and proved eligible for this review during1996-2011.2. Meta-analysis2.1Auto-CPAP versus fixed CPAP:mean therapy pressure and compliance2.1.1Mean therapy pressureSeventeen studies involving652patients reported mean therapy pressure. Significant heterogeneity was present among the studies (I2=98%, P<0.00001). Therefore, a random effects model was used. As shown in the study, the use of auto-CPAP was associated with reduction in mean therapy pressure compared to fixed CPAP (MD:-1.64cm H2O;95%CI:-2.46to-0.82; P<0.0001). According to the design type of the randomized controlled trials, we did a subgroup of the mean therapy pressure. Both crossover studies and parallel studies showed that the mean therapy pressure was lower by using auto-CPAP,(MD=-2.1cmH2O;95%CI:-3.32to-0.88; P=0.0008);(MD=-1.01cmH20;95%CI:-1.44to-0.57; P<0.00001, respectively).2.1.2Patient complianceFor the difference in patient compliance with treatment in terms of hours of use per night between auto-CPAP and fixed CPAP in14studies including693patients, significant heterogeneity was present among the studies (I2=65%, P=0.0004). Therefore, a random effects model was selected for this analysis. According to the design type of the randomized controlled trials, we did a subgroup of the therapy compliance. The crossover studies showed improvement in average machine use of auto-CPAP was superior in studies with a crossover design (MD:0.28hours per night;95%CI:0.05to0.51; P=0.02), the improvement did not reach statistical significance in studies with a parallel design(MD:0.18hours per night;95%CI:-0.09to0.46; P=0.19). The study showed that compliance with auto-CPAP was significantly better than with fixed-CPAP (MD:0.23hours per night;95%CI:0.06to0.39; P=0.006).2.2Auto-CPAP versus fixed CPAP:clinical outcomes2.2.1Apnea hypopnea index (AHI)Thirteen studies including538patients reported the post-treatment AHI after using auto-CPAP or fixed CPAP. The study showed that there was a considerable heterogeneity (I2=89%, P<0.00001) across the analysis. So we used a random effects model to pool estimate. There was no significant difference in post-treatment AHI in two group (MD:-0.43events per hour;95%CI:-1.10to0.23; P=0.20).2.2.2Epworth Sleepiness Scale (ESS)ESS can easily and effectively assess the degree of daytime sleepiness, the higher score indicates the higher degree of daytime sleepiness. Data were available for the ESS from12studies including515patients that compared auto-CPAP to fixed CPAP. As showed in the study, the change of ESS score across the studies was heterogeneous (I2=74%, P<0.0001). Therefore, a random effects model was used. There was no difference in post-treatment ESS after using auto-CPAP or fixed CPAP (MD:-0.24;95%CI:-0.74to0.25; P=0.33).2.3Auto-CPAP versus fixed CPAP:sleep architecture The American Academy of Sleep Medicine (AASM) sleep scoring criteria divide sleep into rapid eye movement (REM) sleep and three stages of non rapid eye movement (NREM) sleep:N1, N2and N3. The stages of N1and N2are the light sleep, and the N3is also termed slow wave sleep or deep sleep. There was an increase in light sleep and a decrease in deep sleep in obstructive sleep apnea patients. Three studies including53patients showed the difference in the sleep architecture between auto-CPAP and fixed CPAP. There was no significant heterogeneity (I2=10%, P=0.34) across the analysis, and thus a fixed effects model was used. The study showed that the percentage of total sleep time (TST) in slow wave sleep (SWS) with auto-CPAP was significantly more than with fixed-CPAP (MD:5.11;95%CI:1.34to8.88; P=0.008), and the percentage of TST in stage2sleep was less with auto-CPAP (MD:-4.75;95%CI:-9.38to-0.11; P=0.04).2.4Auto-CPAP versus fixed CPAP:patient preferenceAfter the treatment, patients were asked to choose a device that is comfortable and useful. Four studies including263patients compared the number of patients who accept auto-CPAP and fixed-CPAP. We decided to use a random effects model because there was a significant heterogeneity (I2=72%, P=0.01). As shown in the study, more patients preferred auto-CPAP to fixed-CPAP therapy (OR:3.65;95%CI:1.27to10.53; P=0.02).Conclusion1. The use of auto-CPAP was associated with a reduction in mean therapy pressure and an improvement in patient compliance.2. Compared to fixed CPAP, auto-CPAP improved the sleep architecture.3. There were no significant differences between the treatments in terms of post-treatment AHI and ESS score.4. More patients preferred auto-CPAP therapy. |
PDF Full Text Request