Simplified assessment of fine aerosol distribution in human airways

We characterized homogeneity of bronchopulmonary distribution of a 0.9% saline aerosol with a mass median aerodynamic diameter (MMAD) of 1.12 μm (σg = 2.04) labeled with [^99mTc]sulfur colloid in nine normal subjects and nine patients with asthma. Aerosol distribution was quantified from frequency distribution histograms generated from Anger camera scans. Skew (a measure of histogram asymmetry) and kurtosis (a measure of histogram range) were significantly elevated (p < 0.05) in the asthma patients with 0.68 ± 0.30 and 2.62 ± 0.81, respectively, compared with 0.39 ± 0.12 and 1.89 ± 0.18, respectively, in the normal subjects. Skew and kurtosis were significantly correlated with baseline forced expiratory volume in 1 sec (FEV₁, an index of airway obstruction) with r(s) = -0.4799 (p < 0.05) and -0.5929 (p < 0.01), respectively. Skew and kurtosis were also significantly correlated with mucociliary clearance after ~90 min (an index of large, central airway deposition) with r(s) = 0.6801 and 0.6373, respectively (p < 0.01). This simplified method of analysis does not require additional study days or procedures and facilitates the detection of airflow obstruction in asthma.