High-resolution maps of regional ventilation utilizing inhaled fluorescent microspheres

H. Thomas Robertson, Robb W. Glenny, Derek Stanford, Lynn M. McInnes, Daniel L. Luchtel, and David Covert Division of Pulmonary and Critical Care Medicine, Department of Medicine, and Departments of Atmospheric Sciences, Environmental Health, and Statistics, University of Washington, Seattle, Washington 98195-6522 Received 30 April 1996; accepted in final form 28 October 1996. Robertson, H. Thomas, Robb W. Glenny, Derek Stanford, Lynn M. McInnes, Daniel L. Luchtel, and David Covert. High-resolution maps of regional ventilation utilizing inhaled fluorescent microspheres. J. Appl. Physiol. 82(3): 943-953, 1997. The regional deposition of an inhaled aerosol of 1.0-µm diameter fluorescent microspheres (FMS) was used to produce high-resolution maps of regional ventilation. Five anesthetized, prone, mechanically ventilated pigs received two 10-min inhalations of pairs of different FMS labels, accompanied by intravenous injection of 15.0-µm radioactive microspheres. The lungs were air dried and cut into 1.9-cm 3 pieces, with notation of the spatial coordinates for each piece. After measurement of radioactive energy peaks, the tissue samples were soaked in 2-ethoxyethyl acetate, and fluorescent emission peaks were recorded for the wavelengths specific to each fluorescence label. The correlation of fluorescence activity between simultaneously administered inhaled FMS ranged from 0.98 to 0.99. The mean coefficient of variation for ventilation for all 10 trials (47.9 ± 8.1%) was similar to that for perfusion (46.2 ± 6.3%). No physiologically significant gravitational gradient of ventilation or perfusion was present in the prone animals. The strongest predictor of the magnitude of regional ventilation among all animals was regional perfusion ( r = 0.77 ± 0.13). pulmonary aerosol deposition; ventilation heterogeneity; ventilation-perfusion heterogeneity; gravitational gradient; radial gradient; pigs 0161-7567/97 $5.00 Copyright © 1997 the American Physiological Society