1 Hacettepe University Medical School, Department of Physical Medicine and Rehabilitation, Ankara, Turkey; Mubarak Al-Kabeer Hospital, Department of Physical Medicine and Rehabilitation, Jabriya, Kuwait. Electronic address: dr.ahmad.j.abdulsalam@gmail.com.
2 Sleep and Ventilation Unit, Royal Brompton Hospital, Guy's and St Thomas' NHS Foundation Trust, London, UK.
3 Hacettepe University Medical School, Department of Physical Medicine and Rehabilitation, Ankara, Turkey.