title: Intrapulmonary shunt in excised dog lobes: comparison of oxygen and inert gas methods.
abstract: We evaluated the contribution of measurement errors in PO2 to the discrepancy between the intrapulmonary shunt values simultaneously obtained by the conventional O2 method (O2-shunt) and the multiple inert gas elimination technique (IG-shunt). Excised left lower lobes of dogs were perfused at a constant flow and ventilated at constant volume. Variable degrees of intrapulmonary shunt were created by O2 absorption while the lobes were collapsed. IG-shunt ranged from 0 to 66%. Although the O2-shunt and IG-shunt values correlated well (r = 0.97), the slope was only 0.74 and the regression line crossed the line of identity at 12% IG-shunt. The gas-to-blood ratio of the oxygen electrode was constant over the range 80-687 Torr and therefore did not seem to be an important factor in the shunt discrepancy. Errors due to nonlinearity of the O2 electrode also had only a minor effect. However, PO2 history of the electrode just before injection of blood samples into the cuvette had a profound and complex effect on the measured PO2. We conclude that PO2 electrode hysteresis can be a major factor in the wide variability of PO2 measurements and could account for most of the differences between our O2-shunt and IG-shunt data.
authors.affiliation: First Department of Internal Medicine, Yamagata University School of Medicine, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Sato
authors.forename: M P
authors.initials: MP
authors.lastname: Hlastala
authors.forename: J
authors.initials: J
authors.lastname: Hildebrandt
mesh_terms: D000818:Animals; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000378:metabolism; D004285:Dogs; D004566:Electrodes; D005740:Gases / Q000378:metabolism; D066298:In Vitro Techniques; D008168:Lung / Q000502:physiology*; D010100:Oxygen / Q000097:blood*; D010477:Perfusion; D011652:Pulmonary Circulation / Q000502:physiology; D012129:Respiratory Function Tests
chemical_list: D005740:Gases; D002245:Carbon Dioxide; D010100:Oxygen