Respiratory oscillometry testing in relation to exercise in healthy and asthmatic Thoroughbreds.

Abstract

BACKGROUND: Racehorses may experience exercise-induced bronchodilation or bronchoconstriction, with potential differences between healthy and asthmatic individuals. OBJECTIVES: To identify exercise-related lung function variations by oscillometry in racehorses, compare lung function between healthy and mild equine asthma (MEA) horses, assess oscillometry's potential as a predictor of racing fitness. STUDY DESIGN: Prospective case-control clinical study. METHODS: Fourteen Thoroughbred racehorses (5 healthy, 9 MEA) underwent a protocol including respiratory oscillometry at rest, exercise with fitness monitoring, oscillometry at 15 and 45&#x2009;min post-exercise, and bronchoalveolar lavage fluid (BALf) cytology. Oscillometry parameters (resistance [Rrs] and reactance [Xrs]) were compared within and between healthy and MEA groups at different timepoints. Associations between Rrs and Xrs at rest and 15&#x2009;min post-exercise and BALf cytology and fitness indices were evaluated. RESULTS: MEA horses showed higher Rrs at 15&#x2009;min post-exercise (0.6&#x2009;&#xb1;&#x2009;0.2&#x2009;cmHO/L/s) than healthy horses (0.3&#x2009;&#xb1;&#x2009;0.1&#x2009;cmHO/L/s) (p&#x2009;<&#x2009;0.01). In healthy horses, Rrs decreased at 15&#x2009;min post-exercise compared with resting values (0.5&#x2009;&#xb1;&#x2009;0.1&#x2009;cmHO/L/s) (p&#x2009;=&#x2009;0.04). In MEA horses, oscillometry parameters did not vary with time. Post-exercise Xrs inversely correlated with total haemosiderin score (p&#x2009;<&#x2009;0.01, r&#x2009;=&#x2009;0.51). Resting Rrs inversely correlated with speed at 200&#x2009;bpm (p&#x2009;=&#x2009;0.03, r&#x2009;=&#x2009;-0.61), and Xrs with maximum heart rate (HR) during exercise (p&#x2009;=&#x2009;0.02, r&#x2009;=&#x2009;-0.62). Post-exercise Rrs inversely correlated with mean (p&#x2009;=&#x2009;0.04, r&#x2009;=&#x2009;-0.60) and maximum speed (p&#x2009;=&#x2009;0.04, r&#x2009;=&#x2009;-0.60), and HR variability (p&#x2009;<&#x2009;0.01, r&#x2009;=&#x2009;-0.74). MAIN LIMITATIONS: Small sample size, oscillometry repeatability not assessed, potential interference of upper airway obstructions, external variables influencing fitness indices. CONCLUSIONS: Oscillometry identified lung function differences between healthy and MEA horses at 15&#x2009;min post-exercise. Only healthy horses exhibited exercise-induced bronchodilation. Oscillometry showed potential in predicting subclinical airway obstruction.