Abstract
Summary
Continuous and simultaneous pressures were recorded from the pulmonary artery, small pulmonary vein (1.5–2.0 mm in diameter), large pulmonary vein and left atrium in 7 intact dogs lightly anesthetized with urethane. Pressures within the pulmonary artery and left atrium remained relatively constant whereas pressure in the small pulmonary vein varied widely. Pressure in the large pulmonary vein fluctuated over a narrower range than did the pressure in the small pulmonary veins. At times the pressure in the large pulmonary vein changed without a corresponding change in left atrial pressure, It is suggested that the pulmonary venous blood reservoir behaves in a manner similar to the systemic venous blood reservoir and that pressure variations reflect spontaneous adjustments in volume of the reservoir. The findings also support the concept of a “throttle valve” action of the pulmonary veins.
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