5-ELECTRODE FIELD PLETHYSMOGRAPHY TECHNIQUE FOR SEPARATION OF RESPIRATION AND CARDIAC SIGNALS

Respiration monitoring by means of electric field plethysmography is i nfluenced by cardiac activity, which represents an artefact although o f physiological relevance itself. For a separation of respiration and cardiac signals, a portable plethysmograph was developed, which uses a fifth electrode in addition to the conventional tetrapolar electrode arrangement. The separation is attained by weighted software subtracti on of two detected signals. In a comparative way, three mathematical m ethods are discussed for the effective determination of individual wei ghting factors. Results of the practical applications indicate the bes t results for a method based on Fast Fourier Transformation.