title: High-sensitivity, high-linearity, low-leak, self-balanced impedance cardiograph.
abstract: An impedance cardiograph (so-called cardioimpedance meter) with the following characteristics is described: preadjustable current generator range of 0-4 mA rms at 100 kHz, crystal-controlled; sensitivity up to 50 V/omega with a resolution of 2 m omega; maximum nonlinearity of 2%; 0.7 microA arms of maximum leak current at 50 Hz; flat frequency response between 0 and 19 Hz. The instrument is self-balanced, using Arenson's bridge [1] with minor modifications, and is also able to operate as a plethysmograph, respirograph, and as an intracardiac Z-meter. Preliminary test as an impedance cardiograph yielded a correlation coefficient better than 0.8 when the stroke volume was evaluated by Kubicek's method and compared with values obtained using thermodilution.
mesh_terms: D000818:Animals; D002307:Cardiography, Impedance / Q000295:instrumentation*; D004285:Dogs; D010992:Plethysmography, Impedance / Q000295:instrumentation*; D013318:Stroke Volume; D013815:Thermodilution