Abstract
BACKGROUND: Bronchoalveolar lavage (BAL) is a common procedure for evaluation of the equine lower airways. Time to resolution of post-BAL inflammation has not been clearly defined. HYPOTHESIS: Residual inflammation, evident by changes in immune cell populations and inflammatory cytokines, will resolve by 72 hours after BAL. ANIMALS: Six adult, healthy, institution-owned horses. METHODS: Randomized, complete cross-over design. Each horse underwent 3 paired BALs, including a baseline and then 48, 72, and 96 hours later, with a 7-day washout between paired BALs. Each sample underwent cytological evaluation and cytokine concentrations were determined by a commercially available multiplex bead immunoassay. Statistical analysis was performed by multilevel mixed-effects Poisson regression analysis. Data are reported as marginal means and 95% confidence interval (CI). RESULTS: Neutrophil, eosinophil and mast cell percentages were not significantly different at any time points. Macrophage percentages were higher at 72 hours (45.0 [95% CI, 41.6-48.4]%) and 96 hours (45.3 [95% CI, 42.9-47.7]%) vs baseline (37.4 [95% CI, 33.5-41.4]%; P < .001 and P = .01, respectively), and at 72 hours and 96 hours vs 48 hours (31.9 [95% CI, 28.1-35.6]%; P < .001). Neutrophil percentage was not significantly increased at 48 hours (P = .11). Interleukin (IL)-6 concentration was increased at 72 hours (5.22 [95% CI, 3.44-6.99] pg/mL) vs 48 hours (4.38 [95% CI, 2.99-5.78] pg/mL; P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE: Significant lung inflammation was not detected at 72 and 96 hours, suggesting that repeating BAL at 72 hours or more can be done without concern of residual inflammation.