Arterial volume and pressure pulse contours in the young human subject

Abstract

1. 1. Pressure pulses and volume pulses were obtained simultaneously and from the same site of the brachial or femoral artery in 13 young men. Pressure pulses were obtained through a Cournand needle or a short PE-90 catheter connected to a Statham P23AA gauge and DC-amplifier. Volume pulses were obtained by recording impedance changes between the Cournand needle or the tip of the catheter and a cutaneous lead disc placed over the tip of, or a subcutaneous needle (insulated except its tip) inserted as near as possible to the tip of, the Cournand needle or the catheter. The intra-arterial and extra-arterial needles were used for both introducing current and recording resistivity changes. 2. 2. Recorded pressure and volume pulses were compared by adjusting the size of the latter to equal exactly that of the former. Pressure pulses were then fed as positive, and volume pulses as negative, input to a subtracting DC-amplifier. The subtraction curve, as well as the original pulses, were simultaneously recorded. 3. 3. The foot of the volume pulse preceded that of the pressure pulse by a mean of 0.010 second at the elbow. Thereafter, the rise in volume exceeded only briefly the rise in pressure. Thus, the peak was reached first for the pressure and then for the volume pulse. The mean time at which equal heights of upstroke were reached was 0.035 second. The dicrotic notch occurred later in the volume pulse, so that the overall duration of volume systole exceeded by 0.04 to 0.06 second that of the pressure systole. 4. 4. In diastole the height of the volume pulse decreased more slowly than did that of the pressure pulse. The over-all area of the volume pulse exceeded the comparable area of the pressure pulse, despite equal maximal heights; the mean ratio of these areas in the 13 young men was 127:100. No major differences were observed between volume pulses recorded with a skin electrode and those recorded with a subcutaneous electrode, apart from “stabler” pulses obtained with the former electrode. 5. 5. Momentary hypertension was associated with volume pulses diminished in size; their systolic phase lasted still longer, but in diastole the return to the base line was faster. The delay in onset of the pressure pulse got shorter, and, on occasion, the rise in pressure preceded the rise in volume; amyl nitrite reversed these trends. 6. 6. These data indicate that the brachial artery in the young is a partly distensible elastic tube, whose wall becomes, as a whole, more rigid and inert during hypertension, and more distensible during amylnitrite hypotension. Nonlinear relations of pressure and volume in parts of the cycle, particularly in hypertension are suggested. Beat-to-beat arterial capacity seems variable, and this justifies skepticism in regard to determinations of cardiac output with the pressure pulse contour method. 7. 7. Intravascular impedance plethysmography in association with simultaneous manometric data can give significant information on the properties of the vessel under study.