- Patients who may have had sleep studies earlier may be included, if they have been lost to follow-up by a sleep physician, are not on treatment or are non-compliant to treatment (mean CPAP nightly use <4 hours, or median nightly CPAP use <50% of total sleep time),Severe tracheal or lung disease,Contraindication to CPAP face-mask, Central Sleep Apnea, Significant Cardiac disease(New York Heart Association Functional Class III and IV Severe Valvular Heart Disease, Dilated Cardiomyopathy, Implanted Cardiac Pacemaker, unstable angina)