Fractional deposition from a jet nebulizer: how it differs from a metered dose inhaler

The fractional deposition from an Inspiron 'Mini-Neb' jet nebulizer was assessed in six normal and two asthmatic subjects using technetium-99m-labelled millimicrospheres of human serum albumin suspended in saline. Sixty-six per cent of activity was retained in the apparatus tubing, 20% exhaled, 2% deposited in the mouth and 12% was retained in the lungs. The nebulizer fractional deposition therefore differs from the findings reported for a metered dose inhaler (Newman et al. 1981; Spiro et al. 1984), where 80-85% of particles leaving the cannister deposits in the mouth, and only 5-10% in the apparatus. The lung fraction from a nebulizer is, however, similar to the 9-11% from an MDI.