HUMAN TRACHEOBRONCHIAL DEPOSITION AND EFFECT OF 2 CHOLINERGIC AEROSOLS

The effects of two methacholine aerosols with mass median diameters co ngruent-to 7 and 3 mum were measured in 10 healthy subjects. The conce ntrations of the two aerosols were increased until forced expiratory v olume in 1 s (FEV1) decreased with about 20%. Pulmonary fraction (FEV1 , FVC, FE V25-75%, FEF75-85%, R(aw), and phase III of single breath O2 test) and deposition of 3.6-mum radiolabeled Teflon particles were st udied before and after bronchial challenge with the two aerosols. Outp ut from the nebulizers and size distribution were measured and from th ese data and from data on deposition of Teflon particles from this and seven earlier studies the doses of the two methacholine aerosols to t he tracheobronchial region were calculated. The changes in all pulmona ry function parameters and deposition of 3.6-mum particles were simila r for the two aerosols. The calculated dose for the aerosol with the l arge particles was 3-4 times higher than that with the smaller particl es. The results indicate greater effect of a certain dose to the trach eobronchial part of the lung if the mass is spread on many small parti cles than on fewer large ones.