Determination of Systemic Vascular Resistance by a Noninvasive Technic

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Abstract
Measurement of systemic vascular resistance in man currently requires arterial and venous cannulation, so that cardiac output and mean arterial blood pressure may be simultaneously determined. This report describes a noninvasive technic for determining systemic vascular resistance (SVRn), utilizing an ultrasonic method for cardiac output measurement, and a combination of sphygmomanometry and external carotid pulse tracing analysis for determination of mean arterial blood pressure. SVRn was measured by this technic in 18 patients and compared with systemic vascular resistance determined by conventional methods at cardiac catheterization (SVRc). There was excellent correlation, with SVRc = 0.865 SVRn+216 and r = 0.85. The sensitivity of the method was verified in studies on 12 normal subjects in whom SVRn while supine (1235 ± 61 dyne-sec-cm–5, mean ± se) was less than SVRn while standing (1416 ± 81, P < 0.01) and greater than SVRn supine after amyl nitrite inhalation (652 ± 41,P < 0.0001). It is concluded that this noninvasive, simple, and safe technic should prove to be a useful bedside method for routine clinical measurement of systemic vascular resistance.