Ventilation-perfusion relationships in isolated blood-free perfused rabbit lungs.
The multiple inert gas elimination technique (MIGET) was applied to blood-free perfused isolated rabbit lungs. Commonly accepted criteria for reliability of the method were found to be fulfilled in this model. Ventilation-perfusion (VA/Q) distributions in isolated control lungs corresponded to those repeatedly detected under physiological conditions. In particular, a narrow unimodal dispersion of perfusate flow was observed: perfusion of low-VA/Q areas ranged below 1% and shunt flow approximately 2-3%; perfusion of high-VA/Q regions was not detected. Gas flow was characterized by narrow dispersion in the midrange-VA/Q areas. Application of a low level of PEEP (1 cmH2O) reduced shunt flow to less than 1%, and low-VA/Q areas were no longer noted. By using this PEEP-level, stable gas exchange conditions were maintained for greater than 5 h of extracorporeal perfusion. Graded embolization with small air bubbles caused a typical rightward shift (to higher VA/Q ratios) of mean ventilation, associated with the appearance of high-VA/Q regions and an increase in dead space ventilation. Mean perfusion was shifted leftward, and shunt flow was approximately doubled. Whole lung lavage with saline for washout of surfactant evoked a progressive manifold increase in shunt flow, accompanied by a moderate rise of perfusate flow to low-VA/Q areas. We conclude that the MIGET can be applied to isolated blood-free perfused rabbit lungs for assessment of gas exchange and that typical patterns of VA/Q mismatch are reproduced in this model.
Walmrath
D
D
Department of Internal Medicine, Justus-Liebig-University Giessen, Federal Republic of Germany.
König
R
R
Ernst
C
C
Brückner
H
H
Grimminger
F
F
Seeger
W
W
D000818:Animals; D004618:Embolism, Air / Q000503:physiopathology; D005260:Female; D066298:In Vitro Techniques; D008168:Lung / Q000502:physiology; D008297:Male; D008954:Models, Biological; D005741:Noble Gases; D010477:Perfusion; D011175:Positive-Pressure Respiration; D011659:Pulmonary Gas Exchange / Q000502:physiology; D011817:Rabbits; D014692:Ventilation-Perfusion Ratio / Q000502:physiology*
D005741:Noble Gases