Pflügers Archiv : European journal of physiology
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Guyton's theory on venous return, implying a linear relationship between blood flow and central venous pressure, was tested in an intact circulation after thoracotomy and airtight chest closure. In eleven Yorkshire pigs (approx. 10 kg) we measured flow in the pulmonary artery and aorta and pressure in the central veins and aorta during pentobarbital anesthesia and mechanical ventilation. To change central venous pressure different lung volumes were randomly applied at intervals of 5 min in a series of inspiratory hold procedures of 7.2 s. ⋯ After a delay of 2-4 heart beats also a decrease in left ventricular output and aortic pressure occurred. Subsequently, the lower venous return during inspiratory hold was mainly sustained by the lower aortic pressure, but nevertheless fulfilled the linear relationship mentioned above. For analysis of flow and pressure changes in the systemic circulation during changes of central venous pressure a tube of constant flow resistance was used as a conceptual mode.(ABSTRACT TRUNCATED AT 250 WORDS)