Posts Tagged ‘lumber’
Sawn Figured
Sunday, November 28th, 2010
What is the relation between right atrial pressure and cardiac output ?
What is the relation between right atrial pressure and cardiac output ? does the cardiac output increase ? decrease ? or what ? I saw many figures in Guyton’s showing that it is a direct relation (increase) but I am not convinced because I know that when right atrial pressure increases , the venous return decreases and thus the cardiac output will decrease ? Any explanation ?
According to the concept of Guyton, cardiac output is largely controlled by venous return, which is determined by the difference between mean systemic venous pressure and right atrial pressure. In the analysis of the venous return curve, other authors have suggested that right atrial pressure is the dependent variable and venous return is the independent variable (right atrial pressure decreased because cardiac output increased). The present report analyzes this historical debate, which has already lasted > 50 years.
One of the definitions of physiology is that it is “the science of how the body works.” The key to obtaining a full understanding of the human circulatory function is the determination of its autoregulation. In the steady state, the traditional teaching is that pulsatile BP is the result of cardiac function (output), and vascular structure and function (large vessel compliance and peripheral arterial resistance). As cardiac output must equal venous return, a decrease in cardiac output means a decrease in venous return.1 Since this has been taught to three generations of intensivists, venous return is defined as the result of a constant mean circulatory pressure (ie, pressure under the condition of no flow) and an independently variable “back pressure” right atrial pressure.2 The venous return-right atrial pressure illustration was used to argue that venous return increases because right atrial pressure decreases, given a constant mean circulatory pressure.3 Stated in this way, right atrial pressure-mean circulatory pressure is the gradient for venous return (driving force)
Evgeni Plushenko…Awesome!!!!!
