1. McGill University, 845 Sherbrooke Street West, Montreal, QC, Canada H3A 2T5
2. Department of Pulmonary & Critical Care Medicine, King Fahad Medical City, P. O. Box 59046, Riyadh 11525, Saudi Arabia
3. Department of Critical Care and Department of Medicine, Respiratory Division, Respiratory Epidemiology Clinical Research Unit, McGill University Health Centre, 687 Pine Avenue West, Montreal, QC, Canada H3A 1A1