Comparative efficacy of three common treatments for equine recurrent airway obstruction

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Virginia Tech


Objective - evaluate horses with acute airway obstruction using three treatment regimens: tapering doses of dexamethasone (DEX), environmental modification (ENV), and a combination of both treatments (DEX + ENV) by analyzing clinical parameters, pulmonary function testing, bronchoalveolar lavage fluid (BALF) cytology and BALF cell expression of the cytokines IFN-? and IL-4

Animals - 6 horses with recurrent airway obstruction (RAO)

Procedures - Clinical examination, pulmonary function test, and collection of BALF prior to treatment and during 22 day treatment period

Hypothesis - Alterations in clinical parameters, pulmonary function and airway inflammation in acute equine RAO will return to remission values by treating with DEX, ENV or DEX + ENV

Results - All horses demonstrated clinical disease, reduced pulmonary dynamic compliance (Cdyn) and an increased maximum change in pleural pressures (?Pplmax) when in a challenge environment. All treatments improved clinical parameters, ?Pplmax and Cdyn. BALF cytology during an RAO crisis demonstrated neutrophilic inflammation. ENV or DEX + ENV resulted in a significant decrease in airway neutrophilia that was maintained throughout the treatment period. In contrast, treatment with DEX caused a reduction in airway neutrophilia initially followed by a rebound neutrophilia as the period between administrations of dexamethasone (0.05mg/kg) was increased to 72 hours. The rebound neutrophilia was not accompanied by equivalent deterioration in clinical parameters or pulmonary function.

Conclusions - Environmental modification is important in the management of RAO horses. Treatment of clinical RAO with a decreasing dosage protocol of corticosteroids in the absence of environmental modification results in the persistence of airway inflammation without recrudescence of clinical disease.



Pulmonary Function Testing, Airway Inflammation, Asthma, Equine Recurrent Airway Obstruction (RAO), Equine Heaves, Allergy, Dexamethasone, Environmental Modification, Airway Neutrophilia, Bronchoalveolar Lavage Fluid