title: Functional diameters of alveolar microvessels at high lung volume in zone II.
abstract: To estimate the functional diameter of alveolar microvessels, we perfused isolated rat lungs with fluorescent latex particles (1 diameter/lung) at inflation, pulmonary arterial, and left atrial pressures of 25, 30, and 0 cmH2O, respectively. We used confocal microscopy to count latex particles within septal microvessels and flow cytometry to count particle concentrations in venous outflow. We found 1-, 2-, and 4-micron-diameter particles within septal vessels of 45 +/- 12, 31 +/- 12, and 25 +/- 9%, respectively, of examined alveoli. Particles of 5-micron diameter were absent from septal vessels but were present within a small percentage of corner vessels. Particle concentrations in the venous outflow for 1-, 2-, 4-, and 5-micron-diameter particles were 54 +/- 28, 67 +/- 32, 2.2 +/- 0.3, and 0.4 +/- 0.3%, respectively, of the arterial inflow. Particles with diameters of 6 or 10 micron were absent from venous outflow. Our results suggest that, under these conditions, the functional diameter of the septal microvessels is approximately 4 micron and that the diameter of the adjacent corner vessels is slightly larger but <6 micron.
authors.affiliation: Department of Surgery, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA. rconhaim@facstaff.wisc.edu
authors.forename: R L
authors.initials: RL
authors.lastname: Conhaim
authors.forename: L A
authors.initials: LA
authors.lastname: Rodenkirch
mesh_terms: D000818:Animals; D002196:Capillaries / Q000033:anatomy & histology; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000033:anatomy & histology*; D008297:Male; D018613:Microscopy, Confocal; D008863:Microspheres; D010316:Particle Size; D011650:Pulmonary Alveoli / Q000033:anatomy & histology* / Q000098:blood supply*; D011652:Pulmonary Circulation / Q000502:physiology*; D051381:Rats