Rib cage and abdominal piezoelectric film belts to measure ventilatory airflow

Piezoelectric film-based respiratory belts are described and tested. To the extent that a two-degree of freedom model consisting of rib cage and abdominal motion is able to assist in quantifying ventilation, the piezoelectric belts can monitor flow in a manner analogous to the monitoring of volume with two magnetometer pairs or two respiratory inductive plethysmograph belts. The piezoelectric belts are shown to measure flow linearly when compared with a screen pneumotachometer to a flow of at least 2.6 L/s. There is no phase shift between the peak flow of belts and the pneumotachometer up to a frequency of at least 9.2 Hz. During normal ventilation, 68 and 95% of the peak flows measured with the belts fall within +/- 10 and 20%, respectively, of the flows measured with a screen pneumotachometer.