Quantitation of Changes of Vasomotor Tone. ∗ Change of Vasomotor Tone as Cause of Traube Hering Waves

This paper presents a technic for expressing quantitatively changes in vasomotor tone which has been applied successfully in a number of experiments. The description will, however, be limited to a single typical experiment in which the vasomotor tone was oscillating spontaneously (Traube Hering waves). Method. The hind limb of an anesthetized dog was isolated at mid-thigh by two tight wire ligatures which compressed all structures except the femoral artery and vein and the sciatic and saphenous nerves. The dog was heparinized† and blood flow from a constant pressure reservoir into the femoral artery measured with a photographically recording orifice meter 1 at each of a series of perfusion pressures from 10 to 105 mm Hg. The femoral arterial (perfusion), femoral venous and aortic pressures were recorded simultaneously.

Results. The aortic pressure oscillated rhythmically between 100/80 and 120/100 at the rate of one cycle per 17 seconds; the venous pressure was 10 mm Hg. At perfusion pressures of 10 and 30 mm Hg, no flow occurred; at a pressure of 48 mm Hg the flow oscillated rhythmically from 0 to 0.7 cc/min., each increase and decrease of flow preceding slightly the associated decline and rise of aortic pressure. At higher perfusion pressures the flow was continuous but oscillated between maximum and minimum rates. The simultaneous measurements of flow (abscissal scale—blood flow cc/min.) and the difference of pressure between the femoral artery (perfusion pressure) and vein (ordinate scale AP-VP mm Hg) at moments of maximum (a, b, c, etc.) and of minimum (a 1 , b 1 , c 1 , etc.) flow at each perfusion pressure are plotted in Fig. 1.

Discussion. Since the curves P,F_{unconstricted} and P,F_constricted drawn through the points of maximum and minimum flow respectively yield smooth divergent lines it is felt that the vessels assumed the same degree of constriction and dilation at the minimum and maximum points throughout the series of flow measurements.