1. Nineteen patients (three normal subjects, and 16 patients with chronic airway disease) were investigated with radionuclide lung-imaging and pulmonary function tests.
2. There was a statistically significant correlation between the ratio of residual volume to total lung capacity and alveolar dead-space ventilation for nitrogen as a percentage of alveolar ventilation (an index of gas mixing inefficiency); rS = 0.54, P < 0.05.
3. There were statistically significant associations between an abnormal ventilation or perfusion radionuclide lung image and (a) the ratio of residual volume to total lung capacity and (b) the alveolar dead-space ventilation for nitrogen as a percentage of alveolar ventilation.
4. The radionuclide counts from the posterior images were normalized for lung size and injected dose; perfusion counts were then subtracted from ventilation counts at locations from the top to the bottom of the lungs.
5. There was a statistically significant association between low ventilation minus perfusion areas and arterial hypoxia.
6. There was a statistically significant association between high ventilation minus perfusion areas and an increased alveolar dead-space ventilation for carbon dioxide as a percentage of alveolar ventilation.
