Funds were redirected to other projects with higher priority

The PRA Effect on APAP Therapy Pressure Study is a randomized, controlled, crossover study in PAP-adherent participants with OSA. Pre-screening is conducted to establish potential eligibility based on regular usage of > 4 hours/night on patients who use an APAP device with a PRA mode. Participants would then be recruited as described below. For those who sign an informed consent, they will be instructed to use the device for the next 8 days with the PRA turned on for four consecutive nights and off for four consecutive nights, but in random orientation. To make sure that the device is not limited to APAP range when adjusting to respond to PRA, the upper limit will be changed to 20 cmH2O during the study. Additionally, only patients who have a current P95 of 8 cmH2O or greater will be eligible so that the maximum PRA setting of 3 cmH2O can be used.

The first phase of recruiting for the PRA Effect on APAP Therapy Pressure Study will be done during a single phone contact following an email recruitment. During this call, participants will be explained the study along with risks and benefits and evaluated for inclusion and exclusion criteria. If the participant is eligible to enter the study, they will be sent an electronic Informed Consent Form to sign. Once the form is signed and verified, the study can then start that evening, after the participant's device has been set for the study.

During both arms of the study, every aspect of operation of the APAP devices will be the same as those the patient normally uses, except for the following three things:

• APAP upper range limit will be set to 20 cmH2O
• PRA or 3 cmH2O will be either on or off
• Participants cannot use a V̇-Com™ device. Participants will randomly be assigned to start with or without PRA. Once the settings are remotely assigned to the device, the patient will sleep on these settings for four nights, ideally consecutively.

After four nights, the PRA setting will be remotely switched to the 2nd arm setting (on or off), and median and P95 pressure, Usage, AHI, and Leak averaged over those four nights will be downloaded. The participant will then use the device with the new settings for an additional four nights, hopefully also sequentially.

Following the 2nd group of four nights, median and P95 pressure, Usage, AHI, and Leak averaged over those four nights will be downloaded, the participant will be informed that their involvement in the study is complete, and the device will be remotely set back to the settings it had prior to the study. Participants will then receive the compensation credit.

Inclusion Criteria:

1. Adherent use of ≥ four hours/night over previous 2 months.
2. P95 ≥ 8 cmH2O.

Exclusion Criteria:

1. Excessive alcohol consumption (>14 drinks/week).
2. The use of any illegal drug(s).
3. Any condition that in the investigator's opinion would present an unreasonable risk to the participant, or which would interfere with their participation in the study or confound study interpretation.

Only plan to publish results.

Participants will not be told which are they are in during any point of the study, although since they are adherent (use their device regularly), they likely will be able to tell.