The forced expiratory volume–time curve estimation using the electrocardiogram

The feasibility of estimating the forced expiratory volume–time curve from the amplitude modulation of the electrocardiogram was studied using a numerical torso model and ECG signal processing. A two dimensional numerical model of the torso was solved for the maximum expiration and inspiration to study the changes in the surface potential as a result of changes in the lung volume. The numerical model showed that significant changes in the surface potential amplitude occur between maximum inspiration and maximum expiration and that this amplitude change in the left–right axis of the torso might be three times as large as in the front–back axis. In the experimental setup, ECG waveforms from the surface of the chest and the mouth air flow were simultaneously recorded from four male subjects during several forced vital capacity (FVC) maneuvers. The amplitude of the QRS complex was measured for different expired lung volumes and an estimation of the forced expiratory volume–time curve was obtained. The FVC and the FEV 1 (forced expiratory volume after 1 s) spirometry indices were calculated for the two volume–time curves obtained from the electrocardiogram and from the spirometry measurements. The results differ between 0.1 and 0.8 l. These preliminary results are encouraging and might indicate that a relationship between the volume–time curve during FVC test and the electrocardiogram signals does exist. Further validation in a larger number of subjects and patients is needed before the technique can be applicable for clinical use.