1. Speech Pathology Department, Royal North Shore Hospital, Sydney, Australia;Department of Speech, Voice and Swallowing, Wythenshawe Hospital, Manchester, UK
2. North West Ventilation Service, Wythenshawe Hospital, Manchester, UK
3. Department of Speech, Voice and Swallowing, Wythenshawe Hospital, Manchester, UK; Division of Infection Immunity and Respiratory Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, UK