Evidence of Efficacy of Auto Titrating Positive Airway Pressure

One important use of APAP devices is selection of a fixed CPAP pressure as an alternative to traditional manual (attended) PAP titration (1,2,10-19). Information stored in the device memory can be analyzed and a pressure can be chosen for fixed CPAP treatment. A common method is to choose the 90th or 95th percentile pressure (pressure exceeded only 10% or 5% of the time, respectively) as the prescription pressure. This assumes periods of high leak have been eliminated from the analysis.

There is considerable evidence that APAP devices can be successfully used to establish a fixed CPAP pressure. However, in reviewing the literature it is important to note whether the studies were attended or unattended and the proportion of patients excluded. There are really two methods with which to judge APAP selection of a fixed CPAP pressure. First, will APAP titration allow selection of a fixed level of CPAP resulting in acceptable treatment [apnea-hypopnea index (AHI) < 10/hour] and/or good clinical outcome? A second approach is to determine if APAP titration can identify an optimal pressure for fixed CPAP treatment that is similar to the pressure chosen by manual titration.

Several studies found that APAP titration could select a fixed CPAP pressure that was effective. For example, Gagnadoux et al. (13) performed an attended APAP titration followed by treatment with fixed CPAP chosen as the P95 (i.e., 95th percentile pressure). After three months of treatment a sleep study on the fixed pressure found the AHI < 10/hour in 21 of 24 patients. Two other attended studies (14,15) reached similar conclusions. Unattended APAP titration also appears to be effective. Berkani et al. (16) found that unattended APAP was successful at identifying an effective CPAP level. Similarly, Series (17) found that treatment with fixed CPAP using a pressure identified by unattended APAP titration reduced the AHI to < 10/hour in 38/40 subjects.

Studies have also compared the CPAP pressure chosen by attended manual titration and APAP titration. Lloberes et al. (18) compared a partially attended APAP titration with a manual CPAP titration on another night. In 15 of 20 patients the difference between the APAP pressure (taken as P95) and the CPAP chosen by manual titration was equal to or less than 1 cm H2O. Stradling et al. (19) used a randomized parallel-group design and found the APAP and manual titration pressures to be very similar in two well-matched groups of OSA patients (APAP: 8.2 ± 2.1, manual CPAP titration: 8.7 ± 2.1 cm H2O). The selection of the effective pressure on the APAP night was performed after visualization of raw data. The pressure effective "most" of the time during APAP titration was chosen.

Fletcher et al. (20) studied the feasibility of using ambulatory monitoring for diagnosis followed by ambulatory APAP titration/treatment as therapy for a large group with OSA. Exclusion criteria included a suspicion of other sleep disorders (narcolepsy, restless legs syndrome), complicating medical illnesses, acute decompensation requiring hospitalization, or a prior diagnosis of OSA. Of the 45 patients that underwent APAP titration, it was deemed adequate in 35 (78%).

Based on a literature search pre-2002 the Standards of Practice Committee of the American Academy of Sleep Medicine did not recommend the routine use of unattended APAP for the choice of a fixed CPAP prescription pressure (1). Since this literature review, further evidence of the ability of APAP devices to function in the unattended auto-titration mode has been published. In a large multicenter study, Masa et al. (21) randomized patients newly diagnosed with OSA to one of the three treatment arms using a parallel-group design. The study groups included: (i) standard attended titration with polysomnography, (ii) auto-titration at home, or (iii) use of a level of CPAP chosen by a prediction formula (22) followed by pressure adjustment based on spouse observations. The randomization was performed after a 20-minute trial of CPAP during the day. Of note, 23% of the original study population was excluded because of severe nasal congestion, prior palate surgery, refusal to participate, psychiatric incapacity, alcohol addiction, inability to place the CPAP mask, and absence of a partner at home. In the auto-titrating arm patients were seen after one night of auto-titration. The CPAP prescription pressure was chosen as the 90th percentile pressure. If the patient slept poorly (patient report) or the machine information revealed high leak, the auto-titration was repeated on a second or third night. About 5% of patients in the auto-adjusting arm were considered titration failures. One night of titration was successful in 98 of 119 patients. In the predicted formula group, CPAP was chosen based on neck size, body mass index, and the AHI (22). Pressure was increased for observed apnea or snoring by fixed protocol. The patients were treated with CPAP in all three groups and adherence and outcomes measures were compared between the groups. There was no difference in the improvement in the Epworth sleepiness scale (subjective sleepiness), adherence (objective hours per night), drop out rates, or quality-of-life measures. The mean CPAP levels in all three groups were similar (around 9 cm H2O). The mean nightly use was approximately five hours. This large study suggests that ambulatory APAP titration is as effective as manual titration (provided similar methods and exclusions are used). However, the large number of excluded patients and the relatively low mean pressure may mean that this finding may not apply to all populations of OSA patients. The 20-minute CPAP trial during the day is a very appealing technique for early identification of patients likely to need attended titration or who will be unable to tolerate positive pressure at all.

In summary, there is convincing evidence that auto-titrating PAP devices can be useful for identifying an appropriate fixed CPAP level in appropriate patients. Recent studies have provided evidence that unattended as well as attended titration can be effective. However, it is likely that unattended APAP titration will not be effective in a significant proportion of OSA patients. In general, patients with a significant proportion of central apneas, those with low baseline SaO2 values or who have difficulty applying the mask and/or operating an APAP device are probably best studied using attended manual titration with polysomnography. A brief practice trial with APAP may be useful to identify mask leak or nasal congestion problems requiring intervention before the patient takes the APAP device home. If APAP titration is performed, close review of the data is needed to ensure that the titration was adequate. Those patients not having an adequate APAP titration should be referred for a traditional CPAP titration.

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