Nebulizer choice for inhaled colistin treatment in cystic fibrosis

To develop practical ways of nebulizing colistin by determining the rate of drug output, total drug output, and particle-size distribution of two commercially available jet nebulizers, the disposable Hudson 1730 Updraft II (Hudson Respiratory Care; Temecula, CA) and the reusable Pari LC Star breath-enhanced nebulizer (Pari Respiratory Equipment; Midlothian, VA).

The nebulizers contained colistin, 75 mg, in 4 mL of isotonic solution. Particle-size distribution was measured by helium-neon laser diffraction, allowing calculation of the respirable fraction (RF), the mass of aerosol comprised of droplets < 5 microm.

The mean (95% confidence interval [CI]) total rate of output of the Updraft II was 2.6 mg/min (2.0, 3.1; n = 4) with 1.3 mg/min (1.0, 1.5) mg/min within the RF. The rate of output of the LC Star increased in a quadratic relationship to the inspiratory flow, delivering 1.8 mg/min (0.7, 2.0; n = 4) with 1.4 mg/min (1.3, 1.6) within the RF, and 6.2 mg/min (5.6, 6.8) with 5.3 mg/min (4.8, 5.7) within the RF, at 0 L/min and 20 L/min inspiratory flows, respectively. Efficiency, as the rate of expected pulmonary deposition divided by rate of total output, was then calculated. The LC Star estimated 56% (51, 61) efficiency, with pulmonary delivery of 29% (26, 32) of the charge of the nebulizer, compared to the Updraft II at 22% (22, 23) efficiency and expected pulmonary deposition of 10% (10, 10) of the dose.

Colistin can be successfully nebulized with both nebulizers tested. This study provides an estimate of in vivo efficiency and expected pulmonary deposition that may be used in future trials.