Elasticity of Small Pulmonary Arteries in the Cat

Abstract

When synthesizing the available data of vessel elasticity of mammalian lung from the literature, the lack of data in the intermediate range of vessel sizes becomes evident. In an effort to fill this gap, the distensibility of pulmonary arteries of cats, in the range of 100 -1600 \t.m diameter was studied as a function of the perfusion pressure. The resulting percentage changes in vessel diameter (D) were expressed as polynomials of "transmural"pressure, which is taken to be the difference between the perfusion pressure and the pleural pressure, p a -p PL , in the formwhere D 0 is the value of D when p a = p PL , and a. and /3 are constants. Our results show that for vessels whose diameters D 0 are in the range of 100-200 /xm, the mean values of D/D 0 are represented by a = 2.02 percent per cm H 2 0 or 0.202 (KPa) -', |8 = 0.046 percent per (cm H 2 0) 2 or 0.046 (KPa) ~2. For vessels with diameter D 0 greater than 200 pm, the pressure-diameter relationship is linear in the ranges tested, so that (3 = 0. The values of the compliance constant a (slopes of the curves) for vessels in the diameter (D 0

Intrinsic tone and distensibility of in vitro and in situ cat pulmonary arteries

“…It seems unlikely that the mechanical response would be sensitive to how relaxation of the vascular smooth muscle was accomplished, but this is also a possibility. The main point is that neither in the present study nor in previous studies of in situ arteries in the cat lung [11] is there evidence of pressure-induced constriction such as occurred in the in vitro arteries. In other organs such as the brain, vascular tone can be modulated by active responses to increased transmural pressure (antoregulation).…”

“…Figure 4 shows examples of the diameter vs pressure relationships obtained from in vitro arteries studied in Ca2+-free solution (left panel) and in situ arteries of similar diameters studied in papaverine-treated lungs (right panel). The diameter vs pressure relationships for the relaxed arteries were nearly linear over the pressure range used to estimate [3 and D O (10-30 tort) as has been reported previously for cat [11] and dog [2] pulmonary arteries in situ. Thus, for the in vitro arteries in Ca2+-free solution and the in sitn arteries with and without papaverine.…”

Linked mechanical and biological aspects of remodeling in mouse pulmonary arteries with hypoxia-induced hypertension

“…Our static stretch-pressure data demonstrated significant differences between control and hypoxic vessels. Previously, static pressure-diameter and pressurestretch relationships for PAs have been studied in intact lungs using radio-opaque perfusion and X-ray visualization techniques (2,28,42). In the largest PAs of the cat (1,000 -1,600 m), stretch was shown to increase linearly with pressure between 0 and 15 mmHg, with a slope of ϳ3.5%/mmHg (42).…”

“…Previously, static pressure-diameter and pressurestretch relationships for PAs have been studied in intact lungs using radio-opaque perfusion and X-ray visualization techniques (2,28,42). In the largest PAs of the cat (1,000 -1,600 m), stretch was shown to increase linearly with pressure between 0 and 15 mmHg, with a slope of ϳ3.5%/mmHg (42). By way of comparison, the slope of the stretch-pressure curve for control vessels in our study was ϳ3.75%/mmHg (i.e., stretch increased from 100 to 175% as pressure increased from 5 to 25 mmHg), while the 10-and 15-day vessels had slopes of 2.22 and 2.12%/mmHg, respectively.…”

On the Foundations of Biomechanics

“…But such a set of data did not exist for any organ of any animal for a long time. Only recently has a program for collecting such a set of data for the lungs of the cat been completed [57][58][59]. With this data a theoretical analysis of the blood flow through the lungs of the cat was done for the first time [60] with reasonable details and without having to resort to fictitious geometry and elasticity.…”