Vascular distensibility and vascular surgery.

The elastic property of an arterial wall decreases considerably with aging and/or with a variety of pathological conditions. The resulting decrease in vascular compliance has a profound physiological effect on arterial perfusion. The objectives of this study were to assess a quantitative measure of peripheral vascular distensibility (D), to apply it in some clinical conditions, and to establish a potential means of predicting success in vascular surgery for limb salvage. A technique described earlier by us for the determination of D based on an accurate measurement of volume change (delta V) with pressure change (delta P) was further analyzed and then tested in four groups: the first two were non-surgical, 18 normal subjects, and 23 hypertensive men paired with 22 normotensive men; the last two were surgical, patients undergoing aortofemoral bypass (AFB) operations for limb salvage (salvaged vs unsalvaged); and patients who underwent below-knee amputations (BKA) for severe arterial insufficiency (healed vs unhealed). The results indicate that D can be used as a reliable assessment of the pathophysiological status of the arterial system in the lower extremity; furthermore, D can be used as a predictor of success in at least two types of vascular procedures: AFB with profundoplasty for limb salvage and BKA for severe arterial insufficiency.

Calibrated impedance plethysmograph.

The accuracy of quantitative pulse-volume measurement with a calibrated electrical impedance plethysmograph was determined on a laboratory limb-segment model. Changes in electrical impedance detected via a tetraprolar electode configuration were related to pulse-volume changes by the parallel-impedance model described by Nyboer et al. (The Impedance Plethysmograph: An Electrical Volume Recorder. Natl. Res. Council, Comm. Aviation Med. 149, 1943). The instrument employed in this study calculated pulse volume assuming two standard conditions: distance between voltage electrodes, l, is 15 cm, and resistivitiy of blood, rho b, is 150 omega x cm. The effects of varying tissue and blood resistivity, pulse frequency, and electrode distance were investigated. Measurements under three ionically distinct conditions gave an overall accuracy of 96.6% with correlation coefficients of 0.99 for each condition. Measurement accuracy was maintained with a pulse-frequency variation in the range of 15-150 pulses/min and with application of correction factors for electrode distance and blood resistivity other than the standard values.

The calibrated impendance plethysmograph: laboratory and clinical studies.

By careful experimental studies a calibrated impedance plethysmograph has been shown to be highly accurate (standard error = 3.8%). Its ability to measure the rate of pulsatile volume change has been extremely useful in the diagnosis of arterial insufficiency of the lower extremities. By helping in the objective definition and documentation of arterial perfusion, this instrument can greatly improve our selectivity of patients for angiography and subsequent revascularization.

Noninvasive assessment of the peripheral vascular system.

Forty-five limbs varying clinically from normal through moderate to severely ischemic were studied by noninvasive measurements of both arterial blood pressure and perfusion. From the values plotted on a two-coordinate system, they arranged themselves well into three clinical categories: (1) normal, (2) intermittent claudication, and (3) ischemia or ulceration and rest pain. Good clinical responses to arterial reconstruction were corroborated by postoperative measurements. Reinforcing the results of one measurement with those of the other has provided an objective, numerical, and graphic basis for decisions regarding the advisability of angiography or arterial reconstructive procedures or both. To date, almost 400 patients have been evaluated by these techniques.

Noninvasive measurement of pulsatile blood volume changes. Its usefulness in peripheral vascular disease.

A clinical trial was made of a new noninvasive technic for the measurement of arterial blood volume changes in a limb segment. The instrument employed is small, portable, provides a digital display in cc/min, is readily calibrated, gives reproducible values of the segmental phen be used to screen patients with peripheral vascular disease and to assess postoperative results.