Pulmonary vascular resistance during unilateral pulmonary arterial occlusion in ducks
Powell, F.L.; Hastings, R.H.; Mazzone, R.W.
American Journal of Physiology 249(1 Pt 2): R39-R43
1985
ISSN/ISBN: 0002-9513 PMID: 4014495 Document Number: 258059
Mean pulmonary arterial pressure (.hivin.Ppa) was measured during temporary unilateral pulmonary arterial occlusion (TUPAO) in 10 ducks. .hivin.Ppa increased from 11.4 .+-. 0.8 mm Hg during control conditions to 18.8 .+-. 1.8 during TUPAO. In 5 of the 10 ducks also measured mean left atrial pressure (.hivin.Pla) and cardiac output (.ovrhdot.Q). In these ducks .hivin.Ppa significantly increased with TUPAO form 13.9 .+-. 0.4 to 22.0 .+-. 1.2 mm Hg, whereas .hivin.Pla and .ovrhdot.Q did not change significantly. Pulmonary vascular resistance (PVR) increased from 10.6 .+-. 1.3 to 24.1 .+-. 5.3 mm Hg .cntdot. min .cntdot. l-1 on TUPAO. By assuming equal vascular resistance in either lung it can be calculated that the vascular resistance in only one lung was 22.5 .+-. 3.5 mm Hg .cntdot. min .cntdot. l-1 during control conditions. Doubling flow resulted in no significant change in one lung's vascular resistance. A morphometric study of both lungs of a domestic goose that were rapidly frozen during TUPAO indicated very little compliance in pulmonary blood capillaries. The relative volume of exchange tissue occupied by blood capillaries was 0.28 in the occluded lung and 0.36 in the perfused lung. Surface-to-volume ratios of blood capillaries were 12,524 cm-1 in the occluded lung and 11,056 cm-1 in the perfused lung. PVR in birds is relatively insensitive to changes in .ovrhdot.Q, in contrast to mammals.