DIGITAL pulse volume studies have proved of great value in the study of the peripheral circulation. The methods most commonly used have the disadvantage that they necessitate placing the digit in an airtight or watertight cylindrical compartment. In most of them the tracings are recorded on photographic paper, and analysis of data must wait until the film is developed. The present study is concerned with a method of recording pulse volume changes by alterations in electrical impedance of the digit under study. This method requires only the attachment of electrodes to the digit and utilizes a direct-writing recorder.
The biophysical background of tissue impedance and impedance plethysmography has been summarized extensively by Nyboer and his associates.1 Impedance plethysmograms are recordings of variations in the electrical resistance and reactance of segments of the body to intermediate and high frequency alternating currents. The impedance pulse tracings reflect the mechanical pulse volume