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Equine veterinary journal2026; doi: 10.1002/evj.70212

Oscillometric assessment of bronchodilator response in horses with severe asthma during remission.

Abstract: During clinical remission of severe equine asthma (SEA), affected animals can be challenging to distinguish from healthy horses. In humans, the degree of bronchodilation achieved with a β-adrenergic bronchodilator is helpful in differentiating asthmatics from healthy subjects. Objective: To determine whether the response to an inhaled bronchodilator improves the sensitivity of oscillometry in detecting subclinical airway obstruction in horses with asthma. Methods: In vivo experiments. Methods: Nine control university-owned horses and 10 SEA horses in remission from a research herd were studied in the main sub-study. Oscillometry was performed at baseline, 8, and 30 min after the inhalation of a β-adrenergic bronchodilator. Whole-breath and within-breath resistance (R) and reactance from 3 to 7 Hz were compared. Data were analysed with two-way ANOVAs. Results: At baseline, the inspiratory reactance at 3 Hz was significantly higher in the healthy control group (0.014 ± 0.007 kPa/L/s) compared to the asthma remission group (0.003 ± 0.01 kPa/L/s, p = 0.01). The R3/R7 ratio, a variable representing the frequency-dependence of airway obstruction, was improved at 30 min in both groups (from 0.77 ± 0.08 to 0.68 ± 0.06 kPa/L/s in the control group [p = 0.003] and from 0.76 ± 0.09 to 0.69 ± 0.10 kPa/L/s in the SEA group [p = 0.01]). Similarly, the bronchodilator produced comparable improvements in pulmonary reactance in both groups. Conclusions: The small number of horses. Conclusions: Only within-breath analysis with oscillometry distinguished horses with SEA in remission from control horses. Salbutamol administration did not improve this discrimination, as the magnitude of bronchodilation was similar in both groups.
© 2026 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2026-06-12 PubMed ID: 42285769DOI: 10.1002/evj.70212Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study investigated whether measuring lung function changes after giving a bronchodilator could help detect subtle airway problems in horses with severe equine asthma during their symptom-free periods.
  • The researchers used oscillometry, a technique to assess airway resistance and reactance, and compared responses between healthy horses and those with asthma in remission before and after bronchodilator inhalation.

Background

  • Severe equine asthma (SEA) is a chronic respiratory condition in horses causing airway obstruction and breathing difficulties.
  • During remission phases, horses with SEA may not show obvious clinical signs, making it difficult to differentiate them from healthy horses with standard tests.
  • In human asthma patients, measuring bronchodilator response (how much airways open after a medication) helps identify subtle airway dysfunction.
  • This study explored whether a similar approach could improve detection of airway obstruction in horses during remission using oscillometry.

Methods

  • Subjects:
    • 9 healthy control horses.
    • 10 horses diagnosed with SEA but currently in remission.
  • Oscillometry measurements were taken at:
    • Baseline (before bronchodilator).
    • 8 minutes after inhaling a β-adrenergic bronchodilator (salbutamol).
    • 30 minutes after inhalation.
  • Parameters measured:
    • Whole-breath and within-breath respiratory resistance (R) and reactance at frequencies 3 to 7 Hz.
    • Special focus on inspiratory reactance at 3 Hz and the R3/R7 ratio (a measure of frequency-dependent airway obstruction).
  • Statistical analysis used two-way ANOVA to compare groups and time points.

Results

  • At baseline, inspiratory reactance at 3 Hz was significantly higher in healthy horses (0.014 ± 0.007 kPa/L/s) than in those with SEA in remission (0.003 ± 0.01 kPa/L/s, p = 0.01), indicating subtle airway differences even during remission.
  • The R3/R7 ratio improved at 30 minutes post-bronchodilator in both groups:
    • Control group: 0.77 ± 0.08 to 0.68 ± 0.06 (p = 0.003).
    • SEA group: 0.76 ± 0.09 to 0.69 ± 0.10 (p = 0.01).
  • Both groups experienced similar improvements in pulmonary reactance after bronchodilator administration, showing comparable airway relaxation.
  • Only within-breath analysis (finer detail on breathing phases) distinguished horses with SEA from controls during remission.
  • Bronchodilator inhalation did not enhance differentiation because the degree of airway opening was similar in both groups.

Conclusions

  • Oscillometry can detect subtle airway obstruction in horses with SEA even during remission, specifically by assessing within-breath reactance changes.
  • The inhaled bronchodilator (salbutamol) caused similar airway improvement in healthy and SEA horses, therefore it did not increase the test’s ability to differentiate horses with subclinical asthma.
  • The findings suggest that bronchodilator response testing may not add diagnostic value for SEA during remission.
  • Limitations included a relatively small sample size, which may affect generalizability.

Implications for Practice and Future Research

  • Veterinarians assessing horses suspected of SEA should consider oscillometric within-breath analysis to detect subclinical airway changes.
  • Bronchodilator challenge tests might not be necessary when horses are in clinical remission.
  • Further studies with larger numbers of horses could verify these findings and explore other markers or techniques to improve asthma detection during remission.

Cite This Article

APA
de Wasseige S, Mainguy-Seers S, Lavoie JP. (2026). Oscillometric assessment of bronchodilator response in horses with severe asthma during remission. Equine Vet J. https://doi.org/10.1002/evj.70212

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

de Wasseige, Séléna
  • Department of Clinical Sciences, Université de Montréal, Faculty of Veterinary Medicine, Saint-Hyacinthe, Quebec, Canada.
Mainguy-Seers, Sophie
  • Department of Clinical Sciences, Université de Montréal, Faculty of Veterinary Medicine, Saint-Hyacinthe, Quebec, Canada.
Lavoie, Jean-Pierre
  • Department of Clinical Sciences, Université de Montréal, Faculty of Veterinary Medicine, Saint-Hyacinthe, Quebec, Canada.

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