Noninvasive Method and Metric for Monitoring Lung Condition.

For hospitalized patients with pulmonary conditions, the onset of respiratory decline can occur unnoticed, due to the absence of a way to continuously and noninvasively monitor lung condition. Based on the relationship between lung volume and pleural pressure, we hypothesized that the time delay (∆t) between the start of a respiratory cycle and the occurrence of lung sounds associated with inspiration would correlate with lung volume. Additionally, we developed a re-search tool, consisting of a respiration belt, digital stethoscope, data collection system and MATLAB algorithm, to measure this delay.