Study objective: To determine if aerosolized
medications can be targeted to deposit in the smaller, peripheral
airways or the larger, central airways of adult cystic fibrosis (CF)
patients by varying particle size and inspiratory flow rate.
Design: Randomized clinical trial.
Setting: Outpatient research laboratory.
Patients: Nine adult patients with CF.
Interventions: Patients inhaled an aerosol comprised of
3.68 ± 0.04 μm saline solution droplets (two visits) or
1.01 ± 0.2 μm saline solution droplets (two visits) for 30 s,
starting from functional residual capacity and breathing at a slow or
faster inspiratory flow rate. On all visits, the saline solution was
admixed with the radioisotope 99mTc. Immediately after
inhalation, a gamma camera recorded the deposition pattern of the
radioaerosol in the lungs. Deposition images were analyzed in terms of
the inner:outer zone (I:O) ratio, a measure of deposition in an inner
zone (large, central airways) vs an outer zone (small airways and
Measurements and results: For the 3.68-μm
aerosol, I:O ratios averaged 2.29 ± 1.45 and 2.54 ± 1.48
(p > 0.05), indicating that aerosol distribution within the lungs
was unchanged while breathing at 12 ± 2 L/min vs 31 ± 5 L/min,
respectively. For the 1.01-μm aerosol, I:O ratios averaged
2.09 ± 0.96 and 3.19 ± 1.95 (p < 0.05), indicating that
deposition was predominantly in the smaller airways while breathing at
18 ± 5 L/min and in the larger airways while breathing at 38 ± 8
Conclusions: These results
suggest that the targeted delivery of an aerosol to the smaller,
peripheral airways or the larger, central airways of adult CF patients
may be achieved by generating an aerosol comprised of approximately
1.0-μm particles and inspiring from functional residual capacity at
approximately 18 L/min and ∼ 38 L/min,