Obstructive Sleep Apnea Treatment With CPAP With and Without the Use of Expiratory Pressure Relief Technology

Expiratory pressure relief (EPR) is a technology designed to improve patient comfort during continous positive airway pressure (CPAP) treatment for obstructive sleep apnea (OSA). The investigators hypothesized that the use of CPAP with EPR is less effective in controlling OSA when compared to CPAP without EPR, applied at the same treatment pressure. The investigators also hypothesized that the CPAP pressure necessary to abolish respiratory events during both manual and automatic CPAP titration with EPR will be greater than the pressure titrated with CPAP without EPR. OSA participants will undergo full polysomnography during CPAP and EPR will be turned on and off in order to test the impact of EPR on airflow and residual AHI.

Participants will be recruited at the sleep clinic. The study will be carried out in 4 steps, the first 2 during one night of full polysomnography (PSG) and the last 2 during CPAP treatment for 4 weeks at home:

1) PSG part 1: Intermittent application of expiratory pressure relief (EPR) during inspiratory flow limitation. Peak inspiratory flow will be measured with and without turning EPR technology on. 2) PSG part 2: After the intermittent application of EPR, polysomnography with manual CPAP titration will be performed with EPR technology on (CPAP-EPRon) and without EPR (CPAP-EPRoff), under random order and one blinded observer.

3) CPAP: Use of outpatient CPAP, in random order, for a total of 3 weeks: i. adjusted to CPAP-EPRoff, without turning EPR on (1 week) and turning EPR on(1 week).

ii. adjusted to CPAP-EPRon, turning EPR on, for 1 week. 4) Use of outpatient CPAP, in random order, for a total of 2 weeks: i. adjusted in automatic mode without turning EPR on (1 week) and turning EPR on (1 week).

Before the start of step 1, participants will be assessed using questionnaires to assess excessive daytime sleepiness (Epworth Sleepiness Scale) and sleep quality (Pittsburgh Sleep Quality Index).

The investigators will perform physical examination with measurement of cervical and abdominal circumference, measurement of height, weight and blood pressure. The investigators will inspect the oropharynx and classify according to the modified Mallampati scale.

In steps 1 and 2 of the study, a CPAP device (model AirSense 10 AutoSet, ResMed Ltd.) will be used coupled to an adapted nasal mask (model ConfortGel Blue Nasal, Philips Respironics), with a sealed hole, which allows the passage of one pharyngeal intraluminal pressure catheter (Millar, Houston, TX, USA). In addition, a heated pneumotachograph (model 3700A, Hans Rudolf, Kansas City, MO) will be attached to the mask.

In steps 3 and 4 of the study, a CPAP device (model AirSense 10 AutoSet, ResMed Ltd.) will be used coupled to a nasal mask (model ConfortGel Blue Nasal, Philips Respironics). This equipment has a technology that allows to change the device settings remotely.

In all steps of the study, the expiratory pressure relief - EPR will be adjusted to level 3, corresponding to 3 cmH2O.

Eligibility Criteria:
Inclusion Criteria:

* both sexes
* aged eighteen or over
* already have baseline polysomnography showing a severe Apnea-Hypopnea Index (AIH), defined according to the current criteria of the American Academy of Sleep Medicine (AASM) as 30 events / hour of sleep or more
* already be using a continuous positive pressure device (CPAP) at a pressure equal to or greater than 9 cmH2O with good adherence, defined as an average use equal to or greater than 4 hours per day.

Exclusion Criteria:

Patients with:

* severe or decompensated respiratory or cardiac diseases
* previous pharyngeal surgery or other sleep disorders, such as parasomnias, narcolepsy or primary insomnia
* users of sedative medications such as opioids, benzodiazepines and muscle relaxants
* uncontrolled diabetes or hyperthyroidism