[1] Univ Crete, Sleep Disorders Ctr, Dept Resp Med, Sch Med, Iraklion, Heraklion, Greece
[2] Univ Zurich, Univ Zurich Fac Med, Fac Med, Zurich, Switzerland
[3] Univ Zurich, Fac Med, Zurich, Switzerland
[4] Univ Palermo, PROMISE Dept, Div Resp Med, Fac Med & Surg, Palermo, Italy
[5] Univ Coll Dublin, St Vincents Hosp Grp, Dept Resp & Sleep Med, Dublin, Ireland
[6] Aristoteleio Panepistemio Thessalonikes, Med Sch, Resp Failure Unit, Schole Epistemon Ygeias,G Papanikolaou Hosp, Thessaloniki, Greece