Diagnosis of pulmonary complications based on airway pressure-flow waveforms

A method was developed to diagnose the most frequent and lethal intra-operative pulmonary complications - bronchospasm, obstructed endotracheal tube (OETT) and pneumothorax. The method requires airway pressure and flow measured at the mouth. It is based on the slope of expiratory flow and area under the pressure-volume (PV) loop. The method has been successfully tested on a mechanical simulator and animal model. In OETT, the expiratory slope decreases by 77%, whereas in bronchospasm and pneumothorax, the slope increases by 111 and 302%, respectively. In bronchospasm, the area of the expiratory PV loop increases and that of the inspiratory loop decreases. Whereas, in pneumothorax the opposite happens and in OETT both areas increase. The increase in upper airway resistance in OETT, increase in lower airway resistance in bronchospasm and decrease in lung compliance in pneumothorax are believed to cause these differences in pressure and flow behavior. The algorithm is a potential and simplistic approach to partition the upper and lower airway resistance as compared to the already existing complicated lumped and distributed models. Since the analysis is real time and requires minimum noninvasive monitoring, it will aid clinicians to correctly, quickly and easily diagnose the pulmonary abnormalities.