[1] Hosp Sultanah Aminah, Resp Med, Johor Baharu, Malaysia
[2] Chulalongkorn Univ, Div Pulm & Crit Care Med, Dept Med, Fac Med, Bangkok, Thailand
[3] King Chulalongkorn Mem Hosp, Excellence Ctr Sleep Disorders, Thai Red Cross Soc, Bangkok, Thailand
[4] Hosp Taiping, Chest Dept, Taiping, Malaysia
[5] Rajamangala Univ Technol Suvarnabhumi, Sect Math, Fac Sci & Technol, Phranakhon Si Ayutthaya, Thailand