In order to evaluate the performance of the device under the range of conditions encountered in the clinical environment, the respiratory volume monitor (RVM) was tested throughout a range of respiratory rates and also during erratic breathing patterns. At 4 and 36 breaths per minute (the extremes of the rates anticipated to be encountered in the clinical setting), and during erratic breathing, RVM and spirometry measurements were found to be highly-correlated (r=0.98 ±0.01 (mean ±95%CI) at 4 breaths/min, 0.97 ±0.01 at 36, and 0.93 ±0.04 during erratic breathing). These studies also included calibration of the ExSpiron to the spirometer.