Previous studies have shown that the ExSpiron™ can provide non-invasive, real-time, accurate measurements of minute ventilation (MV), tidal volume (TV) and respiratory rate (RR) after calibration with a spirometer. The purpose of this study is to compare the MV, TV and RR values measured by the ExSpiron™ without prior spirometer calibration to values obtained with a spirometer calibration. In this study, the MV and TV values will be compared between the ExSpiron™ with and without prior patient-specific calibration of the ExSpiron™ to a spirometer