1. Department of Pulmonology, King Fahad Medical City, Riyadh 12231, Saudi Arabia; College of Medicine, Alfaisal University, Riyadh 11533, Saudi Arabia
2. Department of Medicine, Pulmonary Division, College of Medicine, King Saud for Health Sciences, Riyadh 11481, Saudi Arabia; Pulmonary division, McGill University, Montreal, QC H4A 3J1, Canada