Relationship of Total Peripheral Resistance to the Pressure Gradient From the Arteries to the Veins

¹ From the Department of Physiology and Biophysics, University of Mississippi School of Medicine, Jackson, Mississippi

The relationship of total peripheral resistance to the pressure gradient between the arteries and the veins has been studied in 59 dogs by three different methods. Some measurements were made in live dogs with normal vasomotor tone, and others were made in dead dogs with all vasomotor tone eliminated. The total peripheral resistance of the systemic circulation increases progressively as the pressure gradient decreases, which is the same effect that has been noted many times previously in isolated vascular beds. The resistance to blood flow at each respective pressure was one-fifth to one-seventh as great in the dog with normal vasomotor tone as in the dead dog without any vasomotor tone. The results obtained in this study were consonant with the concept of ‘critical closing pressure’ but also could be explained by simple elastic stretch of the vascular walls without assuming absolute ‘critical closure’ of the vessels.