Observation of electrocardiograms through tap water

Preventive diagnosis is important. Daily medical check-ups in the home which require little effort or practice on the patient's part could be one way to achieve this goal. We investigated the acquisition of electrocardiograms from a human subject in a regular bathtub. In order to prevent power line interference and base line drift due to body movements, an active notch filter and specially designed Ag/AgCl electrodes were utilised. The amplitude of the QRS complex obtained from the water (40 degrees C) was approximately 1/10 that of the direct body surface measurement. Increasing the electrical conductivity of the tap water by adding NaCl (0.2% in weight) resulted in a decrease in amplitude to 1/100 of the direct measurement. Otherwise, the waveform distortion was minimal. It was confirmed that acquisition of electrocardiograms of monitoring quality was feasible in a regular bathtub filled with ordinary tap water.