Dynamic Adaptations in the Human Low-Pressure Compartment Facilitating Cardiovascular Responses at Rest and Exercise

Abstract

The experimental description of the low-pressure cardiovascular compartment was developed from studies involving anesthetized whole animals. There are few studies in alert, conscious humans delineating the acute adaptations of the low-pressure compartment to maintain cardiovascular function and homeostasis in the variable demands of changing body positions and from rest to exercise. Available empirical data shows that the low-pressure compartment is effective at sequestering blood volume in response to medications and volume loading. Additionally, this unstressed blood volume can be mobilized acutely in situations of increased cardiac output such as exercise or mental stress. This mobilization during exercise is also associated with acute improvement of the low-pressure compartment conduit function (pulmonary and IVC conduit vessels). The unstressed volume mobilized from peripheral beds is also used to load the pulmonary vascular reservoir in addition to dilating low-pressure compartment conduit vessels. The low-pressure compartment is gravity and extramural pressure sensitive which leads to differences in cardiac filling capabilities in different body positions and body habitus. In this chapter we will review available data primarily in alert, conscious humans which provides insights to low-pressure compartment functioning at rest and at mental and physical stress.