title: Exercise alters fractal dimension and spatial correlation of pulmonary blood flow in the horse.
abstract: We determined the changes in fractal dimensions and spatial correlations of regional pulmonary blood flow with increasing exercise in race horses (n = 4) by using 15-microm fluorescent microspheres. Fluorescence was measured to quantitate regional blood to 1.3-cm(3) samples (n = 1,621-2,503). Perfusion distributions were characterized with fractal dimensions (a measure of spatial variability) and spatial correlations. On average, the fractal dimension decreased with exercise (trot 1.216 to gallop 1.173; P < 0. 05) despite a variable fractal dimension at rest. Spatial correlation of flow to neighboring pieces increased with exercise (trot 0.57 +/- 0.074 to gallop 0.73 +/- 0.051) and was inversely correlated with fractal dimension, indicating better spatial correlation as blood flow distribution becomes more uniform. This is the first study to document a change in fractal dimension as a result of increasing pulmonary blood flow. Spatial differences in response to vasoregulatory mediators may play a role in this phenomenon.
authors.affiliation: Department of Medicine, University of Washington, Seattle 98195-6522, USA. scottes@u.washington.edu
authors.forename: S E
authors.initials: SE
authors.lastname: Sinclair
authors.forename: S
authors.initials: S
authors.lastname: McKinney
authors.forename: R W
authors.initials: RW
authors.lastname: Glenny
authors.forename: S L
authors.initials: SL
authors.lastname: Bernard
authors.forename: M P
authors.initials: MP
authors.lastname: Hlastala
mesh_terms: D000465:Algorithms; D000818:Animals; D005453:Fluorescence; D017709:Fractals; D006736:Horses / Q000502:physiology*; D008297:Male; D008863:Microspheres; D008955:Models, Cardiovascular; D009043:Motor Activity / Q000502:physiology*; D011652:Pulmonary Circulation / Q000502:physiology*