Can bronchoconstriction and bronchodilatation in horses be detected using electrical impedance tomography?
Authors: Secombe Cristy, Adler Andy, Hosgood Giselle, Raisis Anthea, Mosing Martina
Journal: Journal of veterinary internal medicine
Summary
Electrical impedance tomography (EIT) offers a novel non-invasive means of detecting pulmonary airflow changes in horses, but its clinical utility for diagnosing and monitoring bronchoconstriction remained unproven. Researchers induced stepwise histamine bronchoconstriction in 17 sedated horses and measured multiple EIT-derived variables—including peak inspiratory and expiratory flow rates, expiratory flow-volume curve characteristics, and tidal volume surrogates—at baseline, during maximal constriction, and following salbutamol administration. Peak inspiratory and expiratory flow measurements increased significantly at maximum bronchoconstriction and normalised within 10 minutes of bronchodilator therapy, alongside reversal of expiratory flow-volume curve changes, whilst tidal volume remained stable. A combination of peak inspiratory and expiratory flow variables explained approximately 51% of variance in validated bronchoconstriction markers, suggesting EIT shows promise for detecting dynamic airway obstruction. For clinical practitioners, these findings support EIT as a potential tool for objective, real-time assessment of lower airway function in sedated horses—particularly valuable for equine respiratory research and potentially for monitoring response to therapy in horses with clinically suspected obstructive airway disease, though its practical application in field settings and conscious animals requires further investigation.
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Practical Takeaways
- •EIT shows promise as a non-invasive diagnostic tool for detecting airway obstruction and bronchodilator response in horses, potentially enabling objective assessment of respiratory disease severity at clinical examination
- •Multiple EIT-derived flow variables (inspiratory and expiratory flow rates, expiratory flow-volume slope) may be needed together for optimal detection of bronchoconstriction, rather than relying on single measures
- •The technique's ability to detect reversal of airway obstruction within 10 minutes of bronchodilator administration could streamline diagnosis and treatment monitoring in horses with suspected reactive airway disease
Key Findings
- •EIT successfully detected bronchoconstriction at peak histamine challenge (Cmax) with significant increases in PIFEIT, PEFEIT, and FVslope, and decreased FVintercept/VT
- •All EIT variables returned to baseline values 10 minutes after albuterol administration, demonstrating detection of drug-induced bronchodilatation
- •Combined PIFEIT and PEFEIT variables explained 51% of variance in validated bronchoconstriction marker (Δflow)
- •Total impedance change (VTEIT) did not change with histamine challenge, suggesting EIT flow variables are more sensitive than volume-based measurements