MIST THERAPY RECONSIDERED; AN EVALUATION OF THE RESPIRATORY DEPOSITION OF LABELLED WATER AEROSOLS PRODUCED BY JET AND ULTRASONIC NEBULIZERS

Abstract

Aerosol deposition in the upper and lower respiratory tract using technetium-labelled water aerosol, produced by jet and ultrasonic nebulizers, with and without 10% propylene glycol, was examined under conditions of nasal, normal mouth, and tube breathing in 15 normal adults. With nasal breathing, 91.5% (± 5.5) and 83.2% (± 6.3) of the mass of the aerosol produced by the jet and ultrasonic nebulizers, respectively, was deposited in the upper respiratory tract. Similar fractional depositions were observed with the addition of 10% propylene glycol. When breathing was carried out via a mouth tube, 43% to 59% of the mass of the aerosol produced by the nebulizers was deposited in the upper respiratory tract. The mass median diameters of the available aerosols produced by the jet and ultrasonic nebulizers were 6.0 µ (geometric standard deviation = 2.5) and 2.8 µ (geometric standard deviation = 2.1), respectively; the densities of the aerosols produced were 8 and 34 µl/liter air. With nasal or normal mouth breathing, the volume of water, in aerosol form, that could be deposited per 24 hours in the lower respiratory tract of an adult was calculated to be about 6 ml and 49 ml for the jet and ultrasonic nebulizer, respectively.