Key result
Norepinephrine infusion cuts intrapulmonary vein distensibility and diameter by ~33%.
Why the study?
The distensibility of intrapulmonary veins in the dog lung over a range of vascular pressures and the effect of norepinephrine on this distensibility were not well characterized.
In dog lungs, intrapulmonary vein distensibility averages 1.2%/Torr and is significantly reduced by norepinephrine infusion.
Norepinephrine may alter pulmonary venous properties in vitro; leaves open translation to in vivo hemodynamics or therapy.
To determine the distensibility of the intrapulmonary veins (250-2,900 microns diam) of the dog lung, we obtained X-ray angiograms from isolated lung lobes over a vascular pressure range of approximately 0-30 Torr. Over this pressure range the diameter vs. pressure curves tended to flatten out at the high pressures. In the pressure range of 0-19 Torr, we characterized the vessel distensibility by alpha (the ratio of the slope, beta, of the graph of diameter vs. intravascular pressure to the intercept, Do). The average value of alpha was approximately 1.2%/Torr. There was a weak negative correlation (r = -0.32) between alpha and Do. Infusion of enough norepinephrine to produce approximately 50% increase in total lobar vascular resistance produced a decrease in Do and alpha of approximately 33 and 32%, respectively.
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Altinawi et al. (1992) studied this question. Norepinephrine infusion vs. baseline was evaluated on Distensibility of intrapulmonary veins (alpha) and intercept (Do). Infusion of norepinephrine to increase lobar vascular resistance by 50% decreased the intercept (Do) and distensibility (alpha) of intrapulmonary veins by approximately 33% and 32%, respectively.
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