Evaluation of histamine-provoked changes in airflow using electrical impedance tomography in horses.
Authors: Secombe Cristy, Waldmann Andreas D, Hosgood Giselle, Mosing Martina
Journal: Equine veterinary journal
Summary
# Editorial Summary: Electrical Impedance Tomography for Detecting Airway Changes in Horses Equine asthma remains challenging to diagnose objectively, and current assessment methods have limitations. Secombe and colleagues investigated whether electrical impedance tomography (EIT)—a non-invasive imaging technique that measures changes in thoracic impedance to map ventilation patterns—could detect airflow obstruction induced by histamine challenge in the same way that conventional flowmetric plethysmography does. Six sedated horses underwent simultaneous EIT belt monitoring and flowmetric plethysmography whilst receiving incremental histamine nebulisation until respiratory changes were clinically apparent and airflow resistance increased by ≥50%. Analysis of global and regional inspiratory and expiratory flow signals derived from EIT data revealed significant increases in global flow indices alongside the measured plethysmographic changes, with ventral lung regions showing the most consistent regional flow alterations; a regression model combining global expiratory flow and bilateral ventral expiratory flow variables explained 82% of the variance in measured airflow obstruction. Whilst the study cohort was small and comprised only healthy horses, these findings suggest EIT could potentially become a standardised tool for objective airway assessment in equine practice, offering advantages over plethysmography such as continuous regional ventilation mapping and reduced movement artefact. Further validation in horses with clinical respiratory disease would be necessary before clinical application, but the technique warrants consideration for research into asthma phenotyping and therapeutic response monitoring.
Read the full abstract on PubMed
Practical Takeaways
- •EIT may offer a non-invasive alternative to flowmetric plethysmography for detecting airway reactivity and changes consistent with equine asthma
- •Regional analysis of lung ventilation using EIT provides detailed airflow distribution data that could help localize respiratory dysfunction in clinical cases
- •Further validation in larger populations of affected horses is needed before implementing EIT as a diagnostic tool in clinical practice
Key Findings
- •EIT-derived global flow indices increased significantly in response to histamine challenge, consistent with flowmetric plethysmography measurements
- •Regional inspiratory flow increased significantly in right and left ventral lungs and dorsal right lung following histamine provocation
- •Multiple regression analysis identified ExFglobal and right/left ventral expiratory flow as best predictors of delta flow variance (r² = 0.82)
- •EIT can detect standardized airflow changes during histamine challenge in horses, suggesting potential diagnostic application for equine asthma