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 (Delta 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 research tool, consisting of a respiration belt, digital stethoscope, data collection system and MATLAB algorithm, to measure this delay. We conducted a feasibility study with three healthy individuals that involved safely manipulating lung volume, through subject position and activity, and plotting Delta t against volume measurements obtained via spirometry. The results indicated that Delta t was measurable and changed with lung volume and, therefore, has the potential to serve as a lung condition monitoring tool.