1 Department of Respiratory Medicine, Critical Care and Sleep Disorders, Jaipur Golden Hospital, Rohini, New Delhi, India. E-mail: chawla.rakesh@rediffmail.com.
2 Department of Pulmonary Medicine, Sharda Medical College and Hospital, Sharda University, Noida, Uttar Pradesh, India.
3 Department of Pulmonary Medicine, Shri Ram Murti Smarak Institute of Medical Sciences, Bareilly, Uttar Pradesh, India.