Respiratory Effort Belts in Postoperative Respiratory Monitoring: Pilot Study with Different Patients

Respiratory complications are common in patients after the general anaesthesia. Respiratory depression often occurs in association with postoperative opioid analgesia. Currently, there is a need for a continuous non-invasive respiratory monitoring of spontaneously breathing postoperative patients. We used calibrated respiratory effort belts for the respiratory monitoring pre- and postoperatively. Used calibration method enables accurate estimates of the respiratory airflow waveforms. Five different patients were measured with the spirometer and respiratory effort belts at the same time. Preoperative measurements were done in the operating room just before the operation, whereas postoperative measurements were done in the recovery room after the operation. We compared three calibration models pre- and postoperatively. Postoperative calibration produced more accurate respiratory airflows. Results show that not only the tidal volume, minute volume and respiratory rate can be computed precisely from the estimated respiratory airflow, but also the respiratory airflow waveforms are very accurate. The method produced accurate estimates even from the following challenging respiratory signals: low airflows, COPD, hypopneic events and thoracoabdominal asynchrony. The presented method is able to produce estimates of postoperative respiratory airflow waveforms to enable accurate, continuous, non-invasive respiratory monitoring postoperatively.