title: Pulmonary gas-exchange analysis by using simultaneous deposition of aerosolized and injected microspheres.
abstract: Numerical methods for determining end-capillary gas contents for ventilation-to-perfusion ratios were first developed in the late 1960s. In the 1970s these methods were applied to validate distributions of ventilation-to-perfusion ratios measured by the multiple inert-gas-elimination technique. We combined numerical gas analysis and fluorescent-microsphere measurements of ventilation and perfusion to predict gas exchange at a resolution of approximately 2.0-cm3 lung volume in pigs. Oxygen, carbon dioxide, and inert gas exchange were calculated in 551-845 compartments/animal before and after pulmonary embolization with 780-micrometers beads. Whole lung gas exchange was estimated from the perfusion- and ventilation-weighted end-capillary gas contents. Before lung injury, no significant difference existed between microsphere-estimated arterial PO2 and PCO2 and measured values. After lung injury, the microsphere method predicted a decrease in arterial PO2 but consistently underestimated its magnitude. Correlation between predicted and measured inert gas retentions was 0.99. Overestimation of low-solubility inert gas retentions suggests underestimation of areas with low ventilation-to-perfusion ratios by microspheres after lung injury. Regional deposition of aerosolized and injected microspheres is a valid method for investigating regional gas exchange with high spatial resolution.
authors.affiliation: Department of Medicine, University of Washington, Seattle, Washington 98195-6522, USA.
authors.forename: W A
authors.initials: WA
authors.lastname: Altemeier
authors.forename: H T
authors.initials: HT
authors.lastname: Robertson
authors.forename: R W
authors.initials: RW
authors.lastname: Glenny
mesh_terms: D000336:Aerosols; D000818:Animals; D005069:Evaluation Studies as Topic; D005456:Fluorescent Dyes; D007267:Injections; D008168:Lung / Q000503:physiopathology; D055370:Lung Injury; D008863:Microspheres; D005741:Noble Gases; D010100:Oxygen / Q000502:physiology; D011655:Pulmonary Embolism / Q000503:physiopathology; D011659:Pulmonary Gas Exchange; D012129:Respiratory Function Tests / Q000379:methods* / Q000706:statistics & numerical data; D013552:Swine; D014692:Ventilation-Perfusion Ratio
chemical_list: D000336:Aerosols; D005456:Fluorescent Dyes; D005741:Noble Gases; D010100:Oxygen