[1] Univ Sydney, Royal Prince Alfred Hosp, Camperdown & Fac Med, Dept Resp Med, Sydney, NSW, Australia
[2] Univ Ulster, Sch Hlth Sci, Shore Rd, Newtownabbey BT37 0QB, North Ireland
[3] Univ Sydney, Royal Prince Alfred Hosp, Ctr Resp Faiture & Sleep Disorders, Dept Resp Med & Clin Senior Lecturer,Sleep Unit, Camperdown, NSW 2050, Australia