Human Lung Deposition of Particles Suspended in Air or in Helium/Oxygen Mixture

Abstract

Deposition in mouth and throat and the fraction of alveolarly deposited particles in the lung of 3.6- to 3.8-μ Teflon particles labeled with ^99mTc were estimated in nine healthy subjects. The particles were inhaled in air or helium/oxygen mixture with a flow of 0.5 l/s by subjects with or without induced bronchoconstriction. The bronchoconstric-don (two- to threefold increase in airway resistance) was induced by an aerosol of metha-choline bromide. As the Reynolds number is three times lower for the helium/oxygen mixture than for air, and the sedimentation rate of the particles is about the same in both, a different regional deposition between particles suspended in air and helium/oxygen mixture should be due to turbulence. Deposition in mouth and throat did not differ significantly between air and the helium/oxygen mixture. The alveolarly deposited fraction tended to be larger for unconstricted airways and was significantly larger for constricted airways for inhalations in the helium/oxygen mixture compared to air. In real life, air pollutants and therapeutic aerosols may be inhaled with larger flow rates and bronchoconstriction may be more pronounced in patients, so that deposition of particles due to turbulence can he important.