Antonio M Esquinas1, Joerg S Steier2,3, Habib M R Karim4. 1. Intensive Care Unit, Hospital Morales Meseguer, Murcia, Spain. 2. Respiratory and Sleep Medicine, Life Sciences and Medicine, King's College London, London, UK. 3. Lane Fox Unit/Sleep Disorders Centre, Guy's and St Thomas' NHS Foundation Trust, London, UK. 4. Dept of Anaesthesiology and Critical Care, All India Institute of Medical Sciences, Raipur, India.