1. From the Robarts Research Institute (R.L.E., G.P.), Department of Medical Biophysics (R.L.E., G.P.), and Division of Respirology, Department of Medicine (C.L., D.G.M., G.P.), Western University, 1151 Richmond St N, London, ON, Canada N6A 5B7; and Department of Medicine, McMaster University, Hamilton, Canada (S.S.)