Quantitative evaluation of aerosol deposition pattern in the lung in patients with chronic bronchitis

A number of numeric measurements have been suggested to describe the pattern of deposition of inhaled aerosols, but there is little information about the relationship between the different measurements. We compared four different methods for analysis of aerosol deposition pattern with respect to their ability to separate patients with chronic bronchitis (CB) from healthy subjects, and with respect to their relationship to a simple index of airflow obstruction. Twelve healthy subjects and 22 patients with CB were studied. All the subjects inhaled a radiolabelled aerosol produced with an air-jet nebulizer. The aerosol contained albumin millimicrospheres labelled with 99Tcm. The ratio of peripheral to central deposition--the penetration index, the coefficient of variation, the coefficient of skewness and the quotient between maximum and mean value deposition were calculated using a gamma camera. The differences between the patients and the healthy subjects were statistically significant for all variables (p < 0.001). The sensitivity of measurements of aerosol deposition for detection of CB was similar to that of forced expiratory volume in one second (FEV1). We found strong correlations between the indices of aerosol deposition and FEV1 between all indices. In clinical routine practice, studies of aerosol deposition offer little advantage in the evaluation of patients with CB. Any of the indices may be suitable for evaluation of aerosol deposition in e.g. studies of inhaled pharmaceuticals.