The effect of breathing frequency on deposition of drug aerosol using an inhalation‐synchronized dosimeter in healthy adults

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Abstract
The deposition of inhaled drug aerosol between the tongue, the upper and lower respiratory tract, the lungs and the gastrointestinal tract (GI tract) in 11 healthy adults was studied by using a nebulizer with an inhalation-synchronized dosimeter. The effect of breathing frequency on deposition was studied using radioaerosol (mixture of salbutamol and technetium bound to diethylenetriamine pentacetate, [99mTc]DTPA) and a gamma-camera. In healthy subjects who were breathing at their own frequency (16 ± 5 breaths min–1, mean ± SD), the proportion of inhaled aerosol deposited in the lungs was 48 ± 14 (mean percentage ± SD). The proportion deposited in the upper airway tract and the GI tract was 19 ± 13 and 25 ± 9 respectively, and the remainder was deposited on the tongue (6 ± 4) and in the lower airway tract (3 ± 2). Guided, slower breathing frequency (11 ± 5 breaths min–1) changed the deposition remarkably. The proportion of the pulmonary deposition of the inhaled dose increased significantly (PP<0·005) by half of the initial deposition. We conclude that a slow controlled breathing frequency is an important factor if we want to increase the drug deposition in the lungs. It is also essential in decreasing the variation in the deposition of the lungs.