Abstract
High concentrations of oxygen were administered to patients with chronic lung disease and the changes in the regional distribution of ventilation-perfusion in the lung and right ventricular ejection fraction were measured using radioisotope methods.
Ventilation-perfusion imaging of the lung and right ventriculography were performed while breathing room air and 90% oxygen inhalation in 8 patients with chronic obstructive lung disease and 3 patients with both restrictive and obstructive disorders due to old lung tuberculosis. The ventilation scan was performed by inhalation of 10mCi of Xe-133 gas. Single breath, rebreathing and washout images were obtained in the anterior projection. The perfusion images were made in the same projection during 10 to 20 seconds breath-holding with continuous infusion of Kr-81m glucose solution. Tc-99m-MAA perfusion images were also obtained for comparison with the Kr-81m perfusion images. During continuous infusion of Kr-81m glucose solution, the ECG-gated right ventriculography in the right anterior oblique view was performed and the radionuclide right ventricular ejection fraction was determined by the first pass technique. A region of normal ventilation and perfusion and regions of abnormal ventilation and/or perfusion were selected to compare regional ventilation and perfusion and their changes with oxygen inhalation.
There was excellent agreement in the estimation of regional distribution of lung perfusion by Kr-81m and Tc-99-MAA perfusion lung scan.
The results suggested that the regional distribution of perfusion increased in abnormal areas and decreased in normal areas during 90% oxygen inhalation. No significant change in the distribution of ventilation in both regions suggests the alteration of ventilation versus perfusion relationships due to oxygen inhalation. These findings suggest that high concentrations of oxygen cause vasodilatation in abnormal areas which then draws blood away from normal areas. Then the ventilation-perfusion ratio may decrease in abnormal areas and increase in normal areas.
Decrease of heart rate without significant change of right ventricular ejection fraction was observed, resulting in decrease of right ventricular cardiac output. The decrease of right ventricular cardiac output induced decrease of the blood flow and increase of ventilation-perfusion ratio in normal areas. These findings indicated that an increase of dead space took place in normal areas.
