1. Department of Medicine; University of Calgary; Calgary Alberta Canada
2. Department of Medicine; University of Sherbrooke; Sherbrooke Canada
3. Division of Respirology, Critical Care and Sleep Medicine; University of Saskatchewan; Saskatoon Saskatchewan Canada
4. McMaster University; Hamilton Ontario Canada
5. Division of Thoracic Surgery and Interventional Pulmonology, Beth Israel Deaconess Medical Center; Harvard Medical School; Boston Massachusetts USA
6. Respiratory Epidemiology and Clinical Research Unit, Montreal Chest Institute; McGill University Health Centre; Montreal Quebec Canada