Open AccessHigh-resolution spatial measurements of ventilation-perfusion heterogeneity in rats
Author(s) -
H. Thomas Robertson,
Melissa A. Krueger,
Wayne J. E. Lamm,
Robb W. Glenny
Publication year - 2010
Publication title -
journal of applied physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.253
H-Index - 229
eISSN - 8750-7587
pISSN - 1522-1601
DOI - 10.1152/japplphysiol.01161.2009
Subject(s) - perfusion , ventilation (architecture) , cardiology , medicine , anesthesia , physics , thermodynamics
This study was designed to validate a high-resolution method to measure regional ventilation (VA) in small laboratory animals, and to compare regional Va and perfusion (Q) before and after methacholine-induced bronchoconstriction. A mixture of two different colors of 0.04-microm fluorescent microspheres (FMS) was aerosolized and administered to five anesthetized, mechanically ventilated rats. Those rats also received an intravenous injection of a mixture of two different colors of 15-microm FMS to measure regional blood flow (Q). Five additional rats were labeled with aerosol and intravenous FMS, injected with intravenous methacholine, and then relabeled with a second pair of aerosol and intravenous FMS colors. After death, the lungs were reinflated, frozen, and sequentially sliced in 16-microm intervals on an imaging cryomicrotome set to acquire signal for each of the FMS colors. The reconstructed lung images were sampled using randomly placed 3-mm radius spheres. Va within each sphere was estimated from the aerosol fluorescence signal, and Q was estimated from the number of 15-microm FMS within each sphere. Method error ranged from 6 to 8% for Q and 0.5 to 4.0% for Va. The mean coefficient of variation for Q was 17%, and for Va was 34%. The administration of methacholine altered the distribution of both VA and Q within lung regions, with a change in Va distribution nearly twice as large as that seen for Q. The methacholine-induced changes in Va were not associated with compensatory shifts in Q. Cryomicrotome images of FMS markers provide a high-resolution, anatomically specific means of measuring regional VA/Q responses in the rat.