Pulmonary and Bronchial Circulation
Pulmonary blood flow is the denominator of the ventilation-perfusion ratio, V A/Q, and is of equal importance with breathing in determining the overall efficiency of pulmonary gas exchange (Table 104.1). A major hemodynamic difference between the systemic and pulmonary circulations [4,6] is that the entire cardiac output passes through the lungs — which has only about 1% of the body mass — and it does so with a mean pulmonary arterial-to-left atrial driving pressure that is less than one-tenth that of the systemic circulation. The difference is that in the pulmonary circulation the small muscular arteries and arterioles, both by their enormous number and their low basal smooth muscle tone, contribute much less to total flow resistance than their systemic counterparts.
KeywordsPulmonary Vascular Resistance Pulmonary Circulation Pulmonary Blood Flow Bronchial Artery Transmural Pressure
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