The characterization of radioaerosol deposition in the healthy lung by histogram distribution analysis.

Thirteen healthy nonsmoking volunteers inhaled an 8.1 micrometers (MMAD) radioaerosol on two occasions. Aerosol deposition pattern within the right lung, as recorded by a gamma camera, was expressed as the 3rd and 4th moments of the distribution histogram (skew and kurtosis) of radioactivity during the first ten minutes after aerosol inhalation. Deposition pattern was also expressed as the percentage of deposited activity retained within the lung at 24 hr (24 hr % retention) and found to be significantly correlated with measures of skew (P less than 0.001). Tests of pulmonary function (FEV1, FVC, and MMFR) were significantly correlated with skew. Correlations were also demonstrated for these pulmonary function tests with 24 hr % retention but at lower levels of significance. Results indicate that changes in measures of forced expiratory airflow in healthy human volunteers influence deposition pattern and that the skew of the distribution of inhaled radioactivity may provide an acceptable index of deposition pattern.