A method for the elimination of artefacts in electric field plethysmography of the lung.

The reliability of electric plethysmography for respiration monitoring is reduced by artefacts caused by the cardiac activity, by motions, electromagnetic cross-talk and others. For artefact suppression, a constant-current field-plethysmography technique is discussed which uses the voltage of an auxiliary electrode in addition to the conventional four-electrode arrangement. By means of a differential amplifier, a respiration signal is produced which is almost entirely free from heart artefacts, while the intensity of additional artefacts is suppressed.