A simple technique for reducing cardiogenic artefact on oesophageal pressure signals: {Found in} Abstracts for the Annual Scientific Meeting of the Thoracic Society of Australia and New Zealand, 26 February – 3 March 1999, Canberra, Australia

Balloon catheter measurements of esophageal pressure (Poes) provide the basis for determining important aspects of respiratory mechanics. Poes signals are frequently distorted by significant cardiogenic artefact that grossly affect measurements such as dynamic intrinsic positive endexpiratory pressure (iPEEP). We developed a simple technique for reducing the cardiogenic component of Poes. Methods: Data were collected from 1 subject with normal lung function and 4 COPD patients. Poes and ECG were sampled at 200Hz and the mean cardiogenic component of Poes determined as the average pressure versus time waveform between the P and T waves of approximately 50 consecutive heart cycles, assuming a zero cardiogenic component to Poes at each R- wave. For each cardiac cycle this waveform was subtracted from the recorded Poes signal. Results: The cardiogenic component of Poes appeared to be highly reproducible, well characterised by averaging many beats and only mildly lung volume dependent in 1 subject who performed open glottis breath-hold manoeuvres at various lung volumes. Subtraction of the mean cardiogenic waveform from Poes substantially improved the Poes signal and enabled identification of the onset of inspiratory effort that was otherwise obscured by artefact. In COPD patients this significantly improved the reliability of iPEEP measurements. Conclusions: Subtracting an averaged cardiogenic waveform from Poes appears to substantially remove the artefact component and facilitate measurements of iPEEP.