Respiratory oscillometry testing in relation to exercise in healthy and asthmatic Thoroughbreds.
Authors: Lo Feudo Chiara Maria, Stucchi Luca, Bizzotto Davide, Dellacà Raffaele, Lavoie Jean-Pierre, Ferrucci Francesco
Journal: Equine veterinary journal
Summary
# Respiratory Oscillometry in Racehorses: Identifying Fitness-Limiting Airway Dysfunction Healthy racehorses typically experience exercise-induced bronchodilation—a beneficial opening of the airways during exertion—whereas those with mild equine asthma (MEA) may show impaired or absent responses that could compromise performance. Lo Feudo and colleagues employed oscillometry, a non-invasive technique measuring airway resistance (Rrs) and reactance (Xrs), to track lung function changes in 14 Thoroughbreds (5 healthy, 9 with MEA) across rest, exercise, and recovery phases, correlating findings with bronchoalveolar lavage cytology and fitness metrics including heart rate dynamics and speed thresholds. Healthy horses demonstrated significant Rrs reduction 15 minutes post-exercise (from 0.5 to 0.3 cmH₂O/L/s), confirming normal bronchodilation, whilst MEA horses maintained elevated resistance (0.6 cmH₂O/L/s), failing to show this adaptive response. Multiple significant correlations emerged between oscillometry parameters and performance indicators: resting Rrs inversely predicted speed at 200 bpm heart rate, post-exercise Rrs correlated with both mean and maximum speed achieved, and post-exercise Xrs associated with heart rate variability and haemosiderin presence (an indicator of previous airway inflammation). Oscillometry appears valuable for detecting subclinical airway obstruction that may limit racing fitness, potentially identifying horses with undiagnosed MEA before performance deteriorates, though practitioners should note the small sample size and acknowledge that upper airway dysfunction could confound interpretation in individual cases.
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Practical Takeaways
- •Oscillometry testing at 15 minutes post-exercise can differentiate healthy racehorses from those with mild asthma, providing an objective measure for fitness assessment and subclinical airway obstruction detection
- •Healthy racehorses show normal exercise-induced bronchodilation while asthmatic horses fail to show this response, making post-exercise oscillometry a useful clinical screening tool for pre-race fitness evaluation
- •Oscillometry parameters correlate with racing performance metrics (speed, heart rate variability), suggesting potential utility in identifying horses not reaching athletic potential due to undiagnosed airway disease
Key Findings
- •MEA horses showed significantly higher respiratory resistance at 15 min post-exercise (0.6 cmH2O/L/s) compared to healthy horses (0.3 cmH2O/L/s, p<0.01)
- •Healthy horses exhibited exercise-induced bronchodilation with decreased Rrs at 15 min post-exercise versus rest, while MEA horses showed no oscillometry parameter variation with time
- •Post-exercise reactance inversely correlated with haemosiderin score (r²=0.51, p<0.01), and resting resistance inversely correlated with speed at 200 bpm (r²=-0.61, p=0.03)
- •Post-exercise resistance inversely correlated with mean speed (r²=-0.60, p=0.04) and HR variability (r²=-0.74, p<0.01), suggesting oscillometry potential for predicting racing fitness