Comparison of the clearance of 99mTechnetium-DTPA from the lung and lung function indices derived from the single breath diagram for carbon dioxide in horses with chronic obstructive pulmonary disease.

Abstract

The elimination of carbon dioxide from the lung can be used to monitor ventilation and perfusion, and 99mtechnetium-diethylenetriaminepentaacetate (99mTc-DTPA) clearance is a highly sensitive index of alveolar epithelial integrity, which is a presupposition for effective gas exchange. The aim of this study was to determine whether a correlation exists between indices of lung function derived from the single breath diagram for CO2, and 99mTc-DTPA clearance in horses with chronic obstructive pulmonary disease. The rate of 99mTc-DTPA elimination was negatively and substantially correlated with the dead space according to Bohr's formula, and the physiological and alveolar dead space. Strong and significant correlations existed between the three dead space indices and the alveolar fraction of CO2, and the ratio A1/A2 as an index of alveolar efficiency. The associations found were dependent on the clinical status of health and the mode of calculation of 99mTc-DTPA alveolar clearance.