ABSTRACT
Hemodynamics of the Pulmonary Circulation The pulmonary circulation is a low-pressure circulation. In this respect it differs impor tantly from the high-pressure systemic circulation; this distinction is a key to understand ing many aspects of altered circulatory physiology. Despite its low pressures compared with the systemic circulation (Table 1), the pulmonary vasculature allows passage of the entire cardiac output through the lungs. The mean pulmonary artery pressure is 14-15 mmHg.* The pressure difference across the pulmonary vascular bed is usually less than 5 mmHg when cardiac output is at its basal level, and rises only modestly as cardiac output increases. This small pressure gradient moves 5 -6 L of blood through the circuit every minute.
