Studies of regional ventilation in asthma using 81mKr

Functional images of pulmonary ventilation during tidal breathing can be obtained with a gamma camera by adding a continuous flow of radioactive krypton-81m (half-life = 13 sec) to the inspired air. The procedure is readily repeatable and provides ventilation images.81mKr ventilation scans were obtained in six asthmatic patients in various phases of the disease. During acute exacerbations, while chest x-rays showed only large-volume lungs, ventilation scans were grossly abnormal, showing large, segmental, or even lobar areas of reduced ventilation as well as an increase in size of the lung images. Similar alterations, although less pronounced, were shown in patients with mild-to-moderate shortness of breath and wheezing. Bronchodilators immediately improved the ventilation defects and reduced lung size. There was further improvement and eventual restoration of normal patterns following prolonged hospital treatment