Large Animal Internal Medicine Resident Texas A&M University College Station, Texas, United States
Background: Nebulizers are widely used in equine medicine to deliver therapeutics directly to the lungs for conditions such as equine asthma and pneumonia. Although clinicians often dilute drug solutions to speed delivery, dilution can alter aerosol output and particle size distribution (PSD)—key determinants of pulmonary deposition. This effect has been shown with two drugs in a now-discontinued ultrasonic nebulizer but has not been systematically evaluated in current commercial equine devices. Hypothesis/
Objectives: To determine how serial dilution of four drug solutions (albuterol, budesonide, ceftiofur sodium, gentamicin) alters aerosol flow rate and particle size profiles generated by two vibrating-mesh and two jet nebulizers used in horses. Animals: No animals used.
Methods: Albuterol, budesonide, ceftiofur sodium, and gentamicin were nebulized undiluted or diluted with saline at 2:1 (67 %), 1:1 (50 %), or 1:2 (33 %) ratios. Aerosols were generated into a closed inhalation chamber, where PSD and bulk flow were measured via laser diffraction. Each drug × dilution × device combination was run in triplicate. PSD metrics and flow rates were averaged per test and compared using linear mixed-effects models (p < 0.05).
Results: Significant variation in PSD metrics reflecting predicted pulmonary deposition occurred for all drugs between dilutions within a nebulizer (p < 0.01) and at the same dilution across devices (p < 0.01). Conclusions and Clinical Importance: Dilution impacts aerosol performance differently across drugs and nebulizer types; a single dilution rate will not work for all devices. Clinicians should account for these differences to achieve the best therapeutic outcomes.
