 RESEARCH METHOD We will conduct a series of four studies to demonstrate the effectiveness of the Near Infrared Spectroscopy Indocyanine Green Dye NIRS-ICG technique for the non-invasive measurement of Respiratory Muscle Blood Flow RMBF. The first two studies will occur in healthy volunteers and the second two studies will occur in clinical populations mechanically ventilated patients recovering from exacerbations of COPD or recovering from ARDS. The first two studies will occur in our respiratory physiology laboratory the Health and Integrative Physiology Laboratory at the University of British Columbia and the second two will occur in the Intensive Care Unit ICU at VGH. 