Pulmonary distribution of aerosolized technetium Tc 99m pentetate after administration of a single dose of aerosolized albuterol sulfate in horses with recurrent airway obstruction

Objective-To determine whether pulmonary distribution of aerosolized techne tium Te 99m pentetate is improved after inhalation of a single dose of albu terol sulfate in horses susceptible to recurrent airway obstruction (heaves ). Animals-6 horses with heaves and 4 horses with normal respiratory tract fun ction. Procedure-Images were obtained during ventilation of horses at baseline (ma ximal change in pleural pressure during tidal breathing [Delta Ppl(max)] > 15 cm H2O) and after aerosolized albuterol sulfate (360 mu g) administratio n, with a 24-hour washout period between experiments. The Delta Ppl(max) wa s determined prior to the baseline scan, prior to albuterol sulfate adminis tration, and 5 minutes after albuterol sulfate administration, images were assessed by visual inspection (semiquantitative scoring system) and histogr am analysis. Results-Images obtained from horses with heaves had nonuniform pulmonary di stribution of radionuclide characterized by poor penetration in peripheral lung fields and excess deposition in large airways. Histogram analysis of i mages of the caudal portions of the lungs revealed nonuniform radionuclide deposition in horses with heaves and uniform radionuclide deposition in con trol horses. Conclusion-Administration of a single dose of aerosolized albuterol sulfate improved pulmonary distribution of aerosolized radiolabeled pentetate susp ension in horses with heaves but did not alter pulmonary distribution in cl inically normal horses. Clinical Relevance-Precedent bronchodilator administration may improve pulm onary distribution of aerosolized, surface-active anti-inflammatory prepara tions.