 The subjects selected were randomized to receive CPAP or sham CPAP Figure 1. They were evaluated at baseline before any intervention and after three months of follow-up. The assessment was performed on the basis of a LVEF. In addition, hypertension, subjective daytime sleepinesssleepiness scale ESS 17, quality of life questionnaire according to the Spanish version of the SF-36 were also studied 18 The answers of the SF-36 were codified and divided into two groups, physical PCS and mental MCS with eight subclasses physical function, physical role, bodily pain, general health, vitality, social function, emotional role, mental health. Other measurements were: dyspnea using the Borg scale 19, the New York Heart Association scale NYHA scale, and the 6-minute walking test 20-21. The obstructive group accounting for 83 of all the patients were also studied. CPAP and sham CPAP compliance were recorded by a built-in device in the machine and registered at 4 weeks and at the end of the treatment period. After one month of treatment, another PSG was performed to re-assess the AHI. All visits were registered in a database on an encrypted website of the homepage of the Basque Health Service 