Mouth and Throat Deposition of 3.6 μm Radiolabelled Particles in Asthmatics

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Abstract
Deposition in mouth and throat of 3.6 μm (aerodynamic diameter) monodispersed Teflon particles labelled with 111In was studied in agroup (n=29) of mild to moderately severe asthmatics. The particles were inhaled at 0.5 1/sec. with maximally deep inhalations. Immediately after the inhalation radioactivity was measured in mouth and throat, lungs, stomach, rinsing water and exhalation filter. Radioactivity in mouth and throat, rinsing water and stomach were considered to represent the amount deposited in mouth and throat. From measurements on a phantom factors of selfabsorption in mouth and throat, lungs and stomach was 2, 2.5 and 4, respectively. Calculations using rather large changes in the interrelationship between these selfabsorption factors effected only to a minor extent the calculated depositions in mouth and throat. There was a large variation in deposition in mouth and throat among the subjects, range 7-66% with about 3/4 in the range 0-30% and 1/4 in the range 30-70%. The women had higher deposition than the men. In 20 of the asthmatics who inhaled the test particles twice, the deposition correlated well between the two inhalations, r=0.84. This fairly high reproducibility suggests that it might be valuable to measure deposition in mouth and throat of a test aerosol in patients with asthma in order to estimate individual risks or benefits of aerosols of similar particle sizes.