Qualitative and quantitative evaluation of equine respiratory mechanics by impulse oscillometry.
Authors: Van Erck E, Votion D, Art T, Lekeux P
Journal: Equine veterinary journal
Summary
# Editorial Summary: Impulse Oscillometry as a Clinical Respiratory Test in Horses Conventional respiratory mechanics testing in horses has proven insensitive to subtle airway dysfunction, prompting investigation into impulse oscillometry (IOS) as a potentially superior clinical tool. Van Erck and colleagues compared IOS with established techniques in two experimental models: healthy horses with induced upper airway obstruction (unilateral nasal blockade or laryngeal hemiplegia) and naturally-affected heaves cases monitored during remission and acute crisis, with sequential bronchodilator dosing. IOS successfully detected partial upper airway obstruction at rest—a limitation of conventional testing—demonstrating frequency-dependent changes in resistance across the 5–35 Hz range without affecting reactance; critically, the frequency-dependent behaviour of resistance and reactance parameters allowed discrimination between upper and lower airway pathology, which conventional methods cannot achieve. In heaves horses, IOS detected dose-dependent responses to ipratropium bromide from the first nebulised dose via reactance changes at 5–10 Hz, and revealed persistent peripheral obstruction even when total pulmonary resistance normalised post-treatment. The system's ability to characterise both disease severity and subtle treatment-induced changes suggests IOS could become a practical, non-invasive addition to routine clinical assessment of obstructive airway disease, offering farriers, veterinarians and rehabilitation specialists quantitative feedback on airway status and therapeutic efficacy that conventional techniques cannot provide.
Read the full abstract on PubMed
Practical Takeaways
- •IOS offers significantly improved sensitivity over conventional testing for diagnosing partial upper airway obstructions in resting horses, enabling earlier intervention
- •The ability to differentiate upper versus lower airway disease patterns with IOS could refine treatment protocols and prognosis discussions with clients
- •IOS provides objective, quantifiable assessment of bronchodilator response and identifies persistent dysfunction post-treatment, supporting treatment efficacy evaluation and clinical decision-making
Key Findings
- •Impulse oscillometry (IOS) detected partial upper airway obstruction in resting horses where conventional reference technique failed, with resistance shift from 5-35 Hz without reactance changes
- •IOS discriminated between upper and lower airway obstructions through frequency-dependent behaviour of resistance and reactance, whereas CRT could not differentiate conditions
- •Bronchodilator treatment (ipratropium bromide) induced dose-dependent changes in reactance at 5-10 Hz from first dose, with total pulmonary resistance affected from second dose
- •IOS remained more sensitive than CRT in detecting persistent peripheral obstruction post-treatment in heaves-affected horses despite comparable total resistance values