Detection of upper airway obstructions by spectral analysis of breathing signals

The capability of time-frequency distributions (TFDs) to differentiate between open and obstructed airways was examined. Accordingly, a controlled in vitro study with an airway model and a preliminary in vivo study with healthy subjects and patients with airway diseases were conducted. The TFDs demonstrated the ability to discriminate between open and obstructed airways. A clear relation was found in the in vitro study between the high frequency content and: degree of obstruction; distance from measurement point; and intensity of breathing maneuver. The in vivo study revealed that a simple non-invasive measurement of breathing signals with a moderate respiratory effort contains important spectral information.