© 2003 American Thoracic Society
Can Continuous Positive Airway Pressure Be Self-Titrated?Pulmonary, Allergy, Critical Care Division Center for Sleep and Respiratory Neurobiology University of Pennsylvania and Philadelphia VAMC Philadelphia, Pennsylvania Continuous positive airway pressure (CPAP) is the most frequently used medical treatment for patients with obstructive sleep apnea (1). One of the difficulties in initiating this treatment is the need to determine each patient's specific pressure requirement. It is currently recommended that this be accomplished by a manual titration performed during an attended full night or split-night in-laboratory polysomnogram (2, 3). Automatically adjusting CPAP machines are also used for in-laboratory and out-of-laboratory CPAP titrations (4). In this issue of AJRCCM (pp. 716–722), Fitzpatrick and coworkers (5) report an alternative approach to initiating CPAP therapy—allowing the patient to self-adjust the pressure setting at home using symptomatic cues. In this randomized crossover study, Fitzpatrick and coworkers (5) compared self-titration with titration during an in-laboratory polysomnogram. Their study was preceded by the retrospective, entirely out-of-laboratory study of Coppola and Lawee (6). The latter investigators reported the feasibility of initiating CPAP at home in 11 patients with obstructive sleep apnea who were instructed to adjust their CPAP settings during a phone interview based on the presence or absence of snoring. Before one can determine where to titrate CPAP, the criteria that determine the "optimal" CPAP setting should be established. Polysomnographic endpoints for "optimal" CPAP can include the elimination of snoring, apneas/hypopneas, and inspiratory flow limitation. There are no widely accepted clinical practice guidelines that standardize in-laboratory manual CPAP titration. Evidence exists, however, that correcting inspiratory flow limitation is associated with better adherence and functional outcomes compared with pressures set to eliminate only snoring and apneas/hypopneas (7). A pressure setting that eliminates snoring and apneas/hypopneas will be lower than a setting that prevents flow limitation on the nasal pressure cannula signal (8). In the present study, 5 of the 16 participants self-adjusted their CPAP to a lower pressure than that on their in-laboratory titration (5). Condos and coworkers (9) reported dramatic changes in the flow profile with changes in CPAP level, which were of the same magnitude as the 1–2 cm H2O differences between in-laboratory and self-adjusted CPAP reported by Fitzpatrick and coworkers (5). Therefore, self-titration determined only by the presence or absence of snoring may undershoot the pressure needed to prevent flow limitation. The amount of time available for the in-laboratory titration is also a factor in determining "optimal" CPAP. As in the study by Fitzpatrick and coworkers (5), research studies usually compare out-of-laboratory CPAP titration to a full-night, in-laboratory manual CPAP titration. The in-laboratory titration is a good technique for documenting pressure levels that are not effective; all too often, however, by the time the "optimal" pressure is reached during the polysomnographic recording, insufficient time is left to document that it is indeed "optimal." This gold standard for CPAP titration in research studies is further tarnished in clinical sleep laboratories by the common use of split-night polysomnograms. Studies that compare CPAP titration during split-night and full-night polysomnograms report general agreement between the two methods, but also caution about significant discrepancies (10, 11). We can learn a lot about self-titration from our experiences with out-of-laboratory autoCPAP titration (4). Self-adjustments in CPAP level at home are likely to be in response to snoring, gasping, and snorting reported by the bed partner. AutoCPAP machines that use the presence or absence of snoring as a primary determinant of pressure adjustment are not as effective as models that incorporate inspiratory flow limitation in their algorithms (12, 13). Like autoCPAP titration, self-titration may be successful in establishing the "optimal" setting, but does not assure that oxygenation has been restored to acceptable levels. In general, attempts to titrate CPAP out-of-laboratory, either by the patient's self-adjustments or by autoCPAP machines, are made easier by the wide therapeutic window of CPAP treatment. Over the normally applied pressure range of 4–20 cm H2O, CPAP is usually safe and efficacious as long as it exceeds the patient's "optimal" pressure. The level of CPAP has not been reported to affect patient adherence to treatment (14). AutoCPAP titration, however, is currently not recommended for patients with underlying cardiopulmonary or neuromuscular diseases who may suffer from central sleep apnea. One wonders whether or not patients with these disorders should also be excluded from self-titration (4). Most autoCPAP algorithms take into account that central apneas may persist or appear as pressure is increased, and the machines are programmed not to increase pressure above a predetermined level, despite the persistence of apneas. The untrained bed partner assisting in a self-titration would not be able to distinguish central apneas and might mistakenly advocate unwarranted increases in pressure. In addition to determining "optimal" CPAP in terms of a physiologic response on an in-laboratory polysomnogram, the study by Fitzpatrick and coworkers (5) is strengthened by their comparison of self-titration with in-laboratory titration in terms of daytime outcome measures and CPAP adherence. It is possible that slightly different levels of CPAP may be equally efficacious in terms of clinical outcomes. Fitzpatrick and coworkers (5) found no differences in quality of life or objective and subjective measures of daytime sleepiness between the in-laboratory and self-titration treatment arms. The authors also report that self-titration did not affect adherence to treatment. This is of particular importance because long-term patient adherence to CPAP therapy is determined in the first several days of use (15). During initiation of CPAP by self-titration—a critical phase—it is possible that patients will be on an ineffective pressure. Studies on self-titration need to document that this period of possible inadequate treatment does not compromise patient adherence to therapy. Despite the encouraging results of Fitzpatrick and coworkers (5), further studies are needed before self-titration is ready for clinical use. We should establish uniform procedures for determining "optimal" CPAP on in-laboratory manual CPAP titration polysomnograms. Self-titration and titration with the new generation of autoCPAP machines should be compared with in-laboratory titration, not only in terms of "optimal" pressures, but also in terms of safety, functional outcomes, and objective measures of treatment adherence. We need to determine which patients are suitable candidates for self-titration, and whether patients, once empowered, will continue to self-adjust their CPAP after the initial titration. Studies on self-titration should state the signals recorded during testing, identify the criteria used to determine pressure settings during the use of different titration methods, specify the input provided by bed partners, and avoid exposing the patients to an "optimal" pressure experience before randomization. Much of the current clinical research in obstructive sleep apnea is focused on determining the effect of treatment on the daytime and cardiovascular consequences of this disorder. As we pursue the answer to that important question, we need to validate clinical pathways that initiate our patients on a pressure that is truly "optimal." REFERENCES
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