The purpose of this study is to evaluate the pre and postoperative CPAP compliance rate in OSA surgical patients with or without a CPAP prescription. In this study, all diagnosed OSA patients with or without a CPAP prescription will be approached for informed consent to enroll in the study. Documented OSA is defined as an OSA diagnosis based on a previous laboratory or portable PSG, or on the prescription of CPAP for OSA. The patients with a CPAP prescription will be followed up to determine their compliance with CPAP and data will be collected to determine the O2 saturation. Those patients with diagnosed obstructive sleep apnea without a CPAP prescription will also be followed to objectively determine the severity of OSA which would indicate whether they do not require CPAP owing to their mild OSA or they in fact may require CPAP due to change in weight etc. Preoperative overnight oximetry will be performed on all the OSA patients at home before surgery. In the postoperative period, all patients will be followed up with a nocturnal oximetry in the first two post-operative nights of hospital stay. Postoperative compliance to CPAP will be evaluated and recorded in all the patients. The patients' charts will be reviewed for any postoperative complications. The clinical management of patient will be left to the discretion of the perioperative care team.

Obstructive sleep apnea (OSA) is a common sleep-related breathing disorder. CPAP is established to be the first line treatment for OSA patients with improvement in quality of life and significant reduction in the incidence of cardiovascular events. However, the evidence on the efficacy of CPAP in the perioperative period is largely lacking. A prospective cohort study conducted by Brar et al. found that despite the use of prescibed CPAP therapy, 18% of OSA patients became hypoxic on the night following surgery and they advocated postoperative oximetry monitoring in CPAP treated OSA surgical patients.

The investigators would like to determine the effect of CPAP compliance in reducing postoperative hypoxia and other complications in the surgical patients with OSA. The results from this study would provide valuable data on the rate of non-compliance to CPAP in the surgical patients with a history of diagnosed OSA and a CPAP prescription and the impact of non-compliance to CPAP on postoperative outcomes, especially oxygen saturation.

In this study, all diagnosed OSA surgical patients with or without a CPAP prescription will be approached for informed consent to enroll in the study. All study participants will be monitored for O2 desaturation by using wrist-watch pulse oximeter at home for one night preoperatively and first 3 nights post-operatively at the hospital.

The subjects enrolled will bring their own CPAP units (certified by the hospital engineering department as per hospital policy) and mask to the hospital. The OSA patients without a CPAP prescription will be followed up perioperatively to determine the severity of their OSA and to ascertain the rationale of no CPAP prescription.

Pre and post-operative CPAP usage data will be collected through interviewing the patient, chart review and monitoring recording in the smart CPAP device.

Inclusion Criteria:

1. All adult surgical patients (>18 yr) with a diagnosis of OSA with or without a CPAP prescription.
2. Scheduled for a non-cardiac surgery (general surgery, orthopedics, urology, plastic surgery and spine) that is expected to require a postoperative hospital stay of more than one night.

Exclusion Criteria:

1. They are unwilling or unable to give informed consent to the study.
2. They are on supplemental oxygen preoperatively (daytime or nocturnal).
3. They are pregnant.
4. Surgery included tonsillectomy, septoplasty, uvuloplasty, pharyngoplasty, tracheostomy, or prolonged (> 48 hrs) postoperative mechanical ventilation of the lungs is anticipated. These procedures/interventions are likely to cure or at least modify the severity of OSA.

All adult surgical patients (>18 yr) with a diagnosis of OSA with or without a CPAP prescription.

Scheduled for a non-cardiac surgery (general surgery, orthopedics, urology, plastic surgery and spine) that is expected to require a postoperative hospital stay of more than one night.