Abstract
The fractal dimnension (Df), defined as the ratio of the variability of a measured quantity to the scale over which the quantity is measured, describes its self-similarity and spatial heterogeneity I computed Df of the airspaces in the lungs of rabbits (27d gest.) treated with air, Exosurf (EXO), or rabbit (RAB) surfactant (n=4 each). The left lung was video imaged at 40X in situ through a window cut in the chest wall. Images were captured at end-insp. during ventilation (PIP/PEEP=25/0 cmH2O). Contrast was enhanced so that air was white on a black field. The coeff. of variability (COV) of white pixels was computed for successively smaller parts of the image from 16 to 0.005mm2. Log COV was plotted vs. the scale to obtain Df values (slope of plot). Df was dependent on the scale of measurement: without surfactant only larger airways were seen on a scale of 1.5nm2. Df significantly decreased above an anatomic scale of 0.05mm2approximately the size of the unit saccules. Df quantifies the heterogeneity of surfactant-lung interaction.
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Heldt, G. FRACTAL DIMENSION OF AIRSPACES OF PRETERM RABBIT LUNGS. Pediatr Res 32, 634 (1992). https://doi.org/10.1203/00006450-199211000-00177
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DOI: https://doi.org/10.1203/00006450-199211000-00177