Removal of cardiac beat artifact in esophageal pressure measurement via a modified adaptive noise cancellation scheme

Information on volume-pressure relationships of human lungs is usually based on indirect determination of intrapleural pressure (P-ip) obtained from the esophagus. Unfortunately, cardiac beat artifact frequently corrupts measurement of esophageal pressure (P-es). In this study, we presented a modified adaptive noise cancellation (MANC) scheme for removing the cardiac beat artifact in the P-es signal. The proposed methodology used an airflow signal as the reference signal with least-mean-square method as the adaptive algorithm. The results of six experiments on two Brown-Norway rats showed a significant reduction of the apparent cardiac pulsation with minimal:distortion of the P-es signal. The MANC filter also showed evidence of peak suppression at integer multiples of heart rate in the fast Fourier transform of the P-es signal while leaving the remaining spectrum largely unperturbed. A t-test method and the ratio of standard deviation to mean (std/mean) statistics of airway resistance (R-aw) values were used to evaluate the performance of the MANC filter. In all six experiments, a reduction of std/mean of R-aw by 12.5%-68% was obtained, indicating the effectiveness of the proposed scheme. (C) 2001 Biomedical Engineering Society.