On Measuring the Changes in Stroke Volume from a Peripheral Artery by Means of Electrical Impedance Plethysmography

In the study, we assessed the change in the left ventricular stroke volume from a radial artery by using an electrical impedance plethysmographic device. This device mainly incorporated tetra-polar electrodes, two of which were excited by an ac constant current source, and the other two are the sensing electrodes. In theory, the voltage difference between the two sensing electrodes was inversely proportional to the radial arterial blood flow of interest. In order to alter the stroke volume, 13 volunteers were recruited to undertake a thirty- second breath-hold maneuver. It was found that the impedance waveform registered in the lower arm had a significantly higher amplitude (2.24 plusmn 0.43 Volts) just after the 30-second breath-hold than in the steady state (1.81 plusmn 0.47 Volts) (p<0.001). In addition, a linear regression coefficient of 0.85 was found between the change in the stroke volume measured by a 2-D ultrasound system, and the change in the impedance amplitude before and after the breath-hold maneuver. In conclusion, we may non- invasively and continuously monitor the subject's stroke volume via a peripheral artery by means of the electrical impedance plethysmography.