[Clinical evaluation of Kr-81m inhalation study through a dead space]

A new inhalation technique of 81mKr gas was applied to evaluate the pathophysiological abnormality of ventilation. 81mKr gas (370 MBq) was continuously supplied into a mouth piece directly (without dead space), VE, or through a dead space of 500 ml, VL, in 110 subjects with various lung diseases. Subjects were divided in four groups by a combination of distribution patterns of 81mKr gas obtained by these two inhalation techniques. Group 1: No ventilatory defect in both techniques. Group 2: Defects larger in VE than VL. Group 3: Defects larger in VL than VE. Group 4: No remarkable difference in defects in both techniques. Cases of group 1 were normal in pulmonary function test and chest X-ray. Finding of group 2 reflects early airway closure. This group consisted of cases in remission of bronchial asthma, small air way disease and pulmonary congestion. In group 3, restrictive disease and obstructive disease, especially emphysema, were included. Patients with severe obstructive disease and organized change of pulmonary parenchyma were belonged in group 4. In ventilation study with 81mKr gas, a combined study of inhalation technique through a dead space and by direct infusion may be useful to evaluate a pathophysiological change of various pulmonary diseases.