Respiratory airflow estimation by acoustical means

The purpose of this study was to estimate respiratory airflow by acoustical means. Based on some preliminary results, a piecewise linear model was used to estimate respiratory airflow from lung sound average power. The model was tested using data from ten healthy subjects. Model coefficients were derived from a few breath sound segments with known airflow at medium flow rate and then applied to the rest of the lung sound segments to estimate airflow. The estimated airflow was compared with the actual recorded flow to calculate the error. The results showed an overall estimation error of 10.2 ± 3.3%. The results also showed that the error at high (low) flow rate was mainly due to a consistent underestimation (overestimation) because the model coefficients were derived from medium flow rate. Therefore, it is suggested to reduce the error by applying a scaling factor to the proposed model.