1. National Institute of Health Research Biomedical Research Unit in Respiratory Disease, University Hospital Southampton NHS Foundation Trust, Southampton, UK.
2. Department of Medical Physics and Bioengineering, University Hospital Southampton NHS Foundation Trust, Southampton, UK.
3. Faculty of Health Sciences, University of Southampton, Southampton, UK.
4. Medical Gases Group, Air Liquide Santé International, Centre de Recherche Claude-Delorme, Les Loges-en-Josas, France.
5. Department of Mechanical Engineering, Lafayette College, Easton, PA.