Thursday, July 14, 2011

Air Leak and Adherence to Auto-titrating CPAP

In the June edition of the Sleep Journal is an article about the association of air leak and adherence to auto-titrating continuous positive airway pressure (APAP). Before we get to the study, let me explain about APAPs.

Normally, a patient that is suspected to have obstructive sleep apnea (OSA) has an overnight sleep study in the sleep lab. After that, the patient will have to spend another night in the sleep lab to calibrate the CPAP to determine the appropriate settings.

Some sleep centers and other physicians have attempted to shorten the above process. Some use home sleep studies (a separate topic altogether) to make the diagnosis. Instead of a CPAP titration study, they will send the patient home with an APAP that is able to automatically calibrate itself while the patient sleeps at home. Usually this is done for a week or two, then the APAP and patient come back to the clinic where the APAP data is downloaded. The physician can then set the APAP to a fixed, unchangeable pressure that hopefully corresponds to what the pressure would be had the patient been calibrated in the sleep lab initially.

In the current study, researchers set up 96 patients with such a model. Home study / questionnaire diagnosis of OSA followed by a week of APAP and then 5 more weeks of straight CPAP. These patients were not diagnosed or calibrated in a sleep lab. The researchers were interested in the association of air leaks in the APAP systems and APAP compliance. The results showed that larger air leaks during APAP therapy was associated with poor adherence compared to smaller air leaks. The researchers speculated why air leaking might reduce adherence. If the air leak was because of mouth opening, this could cause mouth / throat dryness, which then could decrease compliance. Also, the APAP might not perform as well with a leak in the system, as normally APAP is a closed system under pressure. If the APAP can not respond to the OSA as easily because of the leak, then the APAP might not have been as effective and this could reduce adherence.

One thing the researchers did not mention is the noise level that occurs when the APAP leaks. Normally, an APAP that is not leaking is whisper quiet. But the air leaks can be quite loud, disturbing the patient and a bedpartner. This could lead to reduced compliance.

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