Airway responses to aerosolized methacholine and citric acid in ponies with recurrent airway obstruction (heaves).
Abstract: We measured lung function and airway reactivity in response to methacholine and citric acid administered by aerosol in 2 groups of ponies (principal and control). Principal ponies had a history of heaves, a disease characterized by recurrent airway obstruction. Control ponies had no history of respiratory disease. Both principal and control ponies were paired (principal and control), and measurements were made when principal ponies were in clinical remission (Period A), following barn exposure when principal ponies had acute airway obstruction (Period B), and 1 and 2 wk after they were returned to pasture (Periods C and D). Differences between groups were primarily found at Period B. Barn housing (Period B) decreased dynamic compliance (Cdyn) and increased pulmonary resistance (RL) of principal but not of control ponies. When compared with control ponies at Period B, principal ponies demonstrated airway hyperreactivity. The dose of methacholine required to reduce Cdyn to 65% of baseline (ED65Cdyn) was lower, the change in RL induced by an aerosol of 0.1 mg/ml methacholine (delta RL 0.1) was higher, and the percent change in Cdyn in response to an aerosol of 0.1 mg/ml methacholine (delta %Cdyn 0.1) was larger in principal than in control ponies. A 10-min inhalation of 10% citric acid aerosol did not cause changes in Cdyn in either group of ponies. Control ponies did not increase RL in response to citric acid, whereas at Period B, RL of principal ponies increased following citric acid. We conclude that ponies in clinical remission from heaves are not hyperreactive to aerosols of methacholine or citric acid. Hyperreactivity only exists during acute exacerbations of airway obstruction.
Publication Date: 1986-03-01 PubMed ID: 3513681DOI: 10.1164/arrd.1986.133.3.357Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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The research article discusses a study on the lung function and airway reactivity of ponies with recurrent airway obstruction (also known as heaves) and healthy ponies in response to methacholine and citric acid. The key finding is that heaves-prone ponies display airway hyperreactivity only during acute exacerbations of airway obstruction.
Research Methodology
- The researchers formed two groups of ponies: one group with a history of recurrent airway obstruction (the principal group) and a control group with no history of respiratory disease.
- Responses were gauged at four different periods: when the principal ponies were in clinical remission (Period A); after barn exposure when the principal ponies had acute airway obstruction (Period B); and one week (Period C) and two weeks (Period D) after returning to pasture.
Main Findings
- The main differences between the two groups were discovered at Period B, after barn exposure and during an acute airway obstruction episode in the principal group.
- During this period, barn housing resulted in a decrease in dynamic compliance (the lung’s ability to expand) and an increase in pulmonary resistance (resistance to air flow) in principal ponies, but not in the control group.
- Also at this stage, the principal ponies showed signs of airway hyperreactivity, as seen by lower doses of methacholine required to reduce dynamic compliance, a larger change in pulmonary resistance induced by methacholine, and a larger percentage change in dynamic compliance in response to the same dose of methacholine.
Response to Citric Acid
- Ten-minute exposure to a 10% citric acid aerosol didn’t cause any changes in dynamic compliance in either group.
- The control ponies did not show an increase in pulmonary resistance in response to citric acid, but the pulmonary resistance of the principal ponies increased at Period B following citric acid exposure.
Conclusion and Implications
- The research concludes that ponies in remission from heaves do not exhibit hyperreactivity to aerosols of methacholine or citric acid.
- Hyperreactivity is only present during acute exacerbations of airway obstruction. Therefore, treatment or prevention strategies need to focus on these exacerbation periods.
Cite This Article
APA
Armstrong PJ, Derksen FJ, Slocombe RF, Robinson NE.
(1986).
Airway responses to aerosolized methacholine and citric acid in ponies with recurrent airway obstruction (heaves).
Am Rev Respir Dis, 133(3), 357-361.
https://doi.org/10.1164/arrd.1986.133.3.357 Publication
Researcher Affiliations
MeSH Terms
- Aerosols
- Airway Obstruction / etiology
- Airway Obstruction / physiopathology
- Airway Obstruction / veterinary
- Airway Resistance / drug effects
- Animals
- Citrates / pharmacology
- Citric Acid
- Female
- Histamine / pharmacology
- Horse Diseases / etiology
- Horse Diseases / physiopathology
- Horses
- Housing, Animal
- Hypersensitivity / complications
- Lung Compliance / drug effects
- Male
- Methacholine Chloride
- Methacholine Compounds / pharmacology
Grant Funding
- HL-27619 / NHLBI NIH HHS
- HL-30669 / NHLBI NIH HHS
Citations
This article has been cited 3 times.- Frippiat T, Art T, Tosi I. Airway Hyperresponsiveness, but Not Bronchoalveolar Inflammatory Cytokines Profiles, Is Modified at the Subclinical Onset of Severe Equine Asthma. Animals (Basel) 2023 Aug 1;13(15).
- Doucet MY, Vrins AA, Ford-Hutchinson AW. Histamine inhalation challenge in normal horses and in horses with small airway disease. Can J Vet Res 1991 Jul;55(3):285-93.
- Nyerges-Bohák Z, Kovács L, Povázsai Á, Hamar E, Póti P, Ladányi M. Heart rate variability in horses with and without severe equine asthma. Equine Vet J 2025 May;57(3):611-618.
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