Airway Obstruction: What the Research Says
Evidence from 25 peer-reviewed studies
What Professionals Should Know
- •Current evidence for bronchodilator efficacy in equine asthma is limited and underpowered, requiring more robust clinical research
- •Lung function improvements from bronchodilators may not directly correlate with clinical improvement in individual asthmatic horses
- •Veterinarians should base treatment decisions on clinical observation rather than assuming bronchodilator-induced lung function improvements automatically translate to clinical benefit
- •Soaked hay effectively controls airway obstruction in horses with severe asthma, with benefits evident within 2-6 weeks
- •Alfalfa pellets provide a simpler feeding alternative but with less dramatic improvement in lung function
- •The practical inconvenience of the soaking protocol (45-minute immersion, waste disposal) may limit client compliance despite proven efficacy
- •Inhaled budesonide delivered via Respimat device offers effective airway obstruction relief in severe equine asthma with reduced systemic side effects compared to systemic corticosteroids
- •The dose-dependent response indicates clinical flexibility, with higher doses providing effects equivalent to traditional oral/IV dexamethasone therapy
- •Cortisol suppression still occurs with inhaled budesonide, suggesting need for monitoring despite local delivery reducing overall systemic burden
- •Ciclesonide is an effective inhaled corticosteroid for treating equine asthma with similar lung function improvements to systemic dexamethasone but without cortisol suppression and associated systemic side effects
- •The improved safety profile of ciclesonide makes it suitable for longer-term management of asthma in horses where repeated systemic corticosteroid use is contraindicated
- •Experimentally induced asthma may respond differently to treatment than naturally occurring exacerbations, so clinical efficacy in field conditions requires further validation
- •Steaming hay is an evidence-based management strategy for horses with severe asthma and should be considered a primary intervention alongside other dust-avoidance measures
- •The clinical improvement in asthmatic horses suggests steaming is worth the practical effort, particularly for horses that cannot be managed on complete pasture
- •Non-asthmatic horses tolerate both hay types well, so steaming decisions should be tailored to individual respiratory disease status rather than applied universally
- •IV dexamethasone is the most reliable rapid treatment for acute heaves episodes, producing lung function improvement within 3 days during stabling
- •IM dexamethasone-21-isonicotinate offers convenient dosing every 3 days but expect treatment failure in approximately 10-15% of cases
- •Oral prednisone is unreliable for acute relief and requires at least 10 days to show effect in some horses—not recommended for acute crisis management
- •Environmental management (reducing dust and mould exposure through bedding and feed changes) should be the primary treatment strategy for RAO, as significant clinical improvement occurs within 3 days without medication
- •While prednisone reduces inflammation markers more rapidly, it does not speed up functional improvement in airway obstruction—focus resources on stable management rather than solely on corticosteroid therapy
- •Even modifying a single stall's environment in a multi-stall barn can benefit RAO-affected horses, making this approach practical for facilities where full pasture turnout is not feasible
- •Oscillometry may have limitations in detecting early or subclinical airway disease in horses, so practitioners should consider combining it with endoscopy and BALf cytology for comprehensive MEA diagnosis
- •Indirect pleural pressure measurement remains a reliable lung function evaluation method alongside traditional diagnostic approaches for equine asthma
- •Further research is needed to establish oscillometry's clinical utility in routine MEA screening and diagnosis
- •Oiled hay feeding systems may offer a practical dietary management strategy for asthmatic horses that need to maintain forage intake
- •Soybean oil coating on mechanically processed hay mechanically reduces dust inhalation, a primary trigger for severe equine asthma
- •This approach allows horses with SEA to continue hay feeding while potentially reducing clinical exacerbations and airway inflammation
- •Breathing pattern variability loss detected by RIP monitoring may identify early RAO disease onset before standard lung function tests show obstruction—useful for monitoring stabled horses at risk
- •Non-invasive telemetric RIP monitoring can be applied continuously (24 h/d) to detect subtle changes in respiratory dynamics that precede clinical signs of airway obstruction
- •Stabling triggers detectable changes in RAO-affected horses within 8 hours; consider this timeline when assessing respiratory response to housing changes in susceptible horses
- •Do not rely on rapid saline infusion as a treatment for heaves; this study shows it does not improve airway function and may transiently worsen it
- •If saline is administered to heaves-affected horses for other reasons, expect temporary worsening of pulmonary function around 3 hours post-infusion, which resolves within hours
- •Heaves-affected horses may have pre-existing metabolic alkalosis and electrolyte imbalances; saline corrects these but does not address airway obstruction
- •Monitor asthma exacerbations in mares with SEA in relation to their estrus cycle; expect potential worsening during follicular phase and improvement during luteal phase
- •Consider timing of veterinary interventions and management adjustments around the estrus cycle to optimize treatment efficacy in mares with severe respiratory disease
- •Document estrus cycle stage when evaluating lung function changes in mares with asthma to distinguish cycle-related variation from disease progression
- •Sinonasal myxomas are rare in horses but should be considered in cases of unilateral nasal discharge, facial swelling, and decreased airflow; endoscopic and imaging evaluation are essential for diagnosis
- •Surgical excision alone is unlikely to prevent recurrence due to myxoma's infiltrative nature; combining surgery with transendoscopic laser ablation may improve long-term outcomes
- •This combined technique offers an alternative approach for managing benign sinonasal masses that may reduce need for repeated interventions
- •Detailed pathological assessment of diseased arytenoid cartilage can guide surgical choice between partial arytenoidectomy and the more conservative focal medial resection approach
- •The medial wall of affected arytenoids is consistently more severely degenerated than the lateral wall—focal medial resection may preserve more functional cartilage structure
- •Clinical scores and ultrasonographic findings should be correlated with gross lesion measurements to optimize surgical decision-making for individual cases
- •Bone distraction via external fixation is a viable surgical option for correcting wry nose in young foals, offering improvement in both respiratory function and dental occlusion
- •Early surgical intervention in 2-month-old foals can successfully resolve this congenital deformity before it causes secondary respiratory or feeding complications
- •The 90-day treatment timeline should be communicated to owners when planning surgical correction of campylorrhinus lateralis
- •Heaves pathophysiology does not involve eosinophilic airway wall infiltration, suggesting treatment strategies should target other inflammatory mechanisms
- •Eosinophil presence in healthy horses may represent normal baseline airway immunity rather than a pathological feature
- •The dorsal approach provides superior visualization and hemostasis control compared to alternative nasal septum removal techniques—consider this method when septal resection is indicated
- •Horses recover cosmetically well and functionally return to work, making this a viable option for septal pathology causing airway obstruction
- •This technique minimizes complications and bleeding, reducing need for supportive care like transfusion in the recovery period
- •Glucocorticoids are essential for managing equine asthma, but clinicians need better guidance on drug selection and dosing optimization to maximize efficacy while minimizing adverse effects
- •Further research is needed to establish minimal effective doses and comparative effectiveness of different glucocorticoid preparations to improve individual treatment protocols
- •Monitor for glucocorticoid-specific adverse effects in asthmatic horses and consider long-term management strategies given the chronic nature of the disease
- •Intra-articular corticosteroid injections may have unexpected systemic effects on respiratory function in asthmatic horses—consider this when treating severe asthmatic patients requiring joint injections
- •IA methylprednisolone acetate could potentially be beneficial for managing airway obstruction in severe asthmatic horses as an adjunctive therapy
- •If using tongue-ties in your training program, keep application duration as short as possible—complications risk doubles for every 9 minutes of use
- •Avoid assessing tongue-tie tightness by immobilizing the tongue completely; this practice is strongly associated with physical injury and should be replaced with safer adjustment methods
- •Recognize that tongue-ties may help manage airway issues and tongue displacement but are not reliably effective for improving race performance, so weigh their use against documented complication risks (51% of users experience problems)
- •Consider exercising endoscopy under working conditions (harness, overcheck, load) rather than resting exams when evaluating draught horses with respiratory issues, as airway problems are most obvious during actual work
- •Overground endoscopy provides more realistic assessment of URT function in competition draught horses than stationary evaluations
- •Dynamic testing under harness and load may identify airway conditions affecting performance that resting endoscopy could miss
- •Prosthetic laryngoplasty combined with laser ventriculocordectomy is an effective surgical option for treating RLN in racing Thoroughbreds seeking to maintain or improve performance
- •Polyurethane offers a viable prosthetic material choice for laryngoplasty procedures, providing surgeons with an alternative to traditional materials
- •This procedure restores normal airway mechanics, addressing the performance-limiting airway obstruction caused by RLN
- •Even mild respiratory diseases can significantly impair athletic performance in horses; routine respiratory assessment should be part of pre-purchase and performance evaluations
- •Many respiratory problems are subclinical at rest and only manifest during exercise, so diagnostic exercise testing is essential for horses with suspected performance issues
- •Combine multiple diagnostic techniques (exercise testing, airway sampling, blood gas analysis) to identify subclinical lower airway disease and monitor treatment effectiveness in athletic horses
- •Current corticosteroid treatments for equine asthma manage symptoms but don't reverse lung damage—consider emerging cell-based therapies as potential adjunctive approaches
- •Understanding that equine asthma mirrors human disease pathology suggests evidence from equine studies may inform better therapeutic strategies for your affected horses
- •Cell therapy approaches targeting tissue regeneration rather than just inflammation suppression represent a promising future direction for managing chronic respiratory disease
- •Clinical signs of heaves (nasal flaring, abdominal effort) underestimate disease severity in early/mild cases—horses with subtle signs may have significant airway obstruction requiring objective testing for accurate diagnosis
- •A clinical score threshold of 5 appears to represent a clinically meaningful level of obstruction; lower scores warrant further investigation with lung function testing rather than reassurance based on appearance alone
- •Implementation of accessible lung function testing in practice could improve early detection and monitoring of recurrent airway obstruction, preventing progression of subclinical disease
Key Research Findings
Few and underpowered clinical studies have investigated the impact of bronchodilators on clinical signs in asthma-affected horses
Airway obstruction is the main trait of severe equine asthma affecting respiratory function
There is uncertainty about minimal important difference between lung function improvements and clinical sign improvement in equine asthma
Soaked hay reduced lung resistance by 1.31 cmH₂O/L/s over 6 weeks (P<0.001) in horses with severe asthma
Alfalfa pellets reduced lung resistance by 1.06 cmH₂O/L/s over 6 weeks (P=0.03, not significant after correction)
Soaked hay showed greater improvement in airway obstruction compared to alfalfa pellets
Protocol required hay to be soaked for 45 minutes and dried-out hay discarded between meals
Inhaled budesonide at 1800 μg twice daily produced marked and significant improvement in lung function comparable to intravenous dexamethasone
Budesonide showed dose-dependent effects with 450, 900, and 1800 μg doses, with higher dosages comparable to oral dexamethasone efficacy
Neutrophil percentages in bronchoalveolar fluid decreased in all dexamethasone-treated horses and 4 of 6 budesonide-treated horses
Both budesonide and dexamethasone induced significant suppression of serum cortisol concentrations
Ciclesonide 1687.5 μg twice daily significantly improved pulmonary resistance (2.7±1.1 to 1.6±0.8 cm H2O/L/s), pulmonary elastance (5.2±3.1 to 2.2±1.3 cm H2O/L), and clinical scores (13±2.9 to 10.8±4.2) after 7 days of treatment
Dexamethasone produced similar improvements in lung function and clinical signs but caused systematic serum cortisol suppression (<50 nmol/L) from day 3 through day 3 post-treatment
Ciclesonide at all tested doses (450–2700 μg twice daily or 3712.5 μg once daily) did not suppress serum cortisol levels
Placebo had no significant beneficial effect on any measured parameter
Evidence Base
Clinical efficacy of bronchodilators in equine asthma: Looking for minimal important difference.
Calzetta L, Crupi R, Roncada P et al. (2020) — Equine veterinary journal
Effects of soaked hay on lung function and airway inflammation in horses with severe asthma.
Westerfeld Roxane, Payette Flavie, Dubuc Valérie et al. (2024) — Journal of veterinary internal medicine
Efficacy of inhaled budesonide for the treatment of severe equine asthma.
Lavoie J P, Leclere M, Rodrigues N et al. (2019) — Equine veterinary journal
Effect of different doses of inhaled ciclesonide on lung function, clinical signs related to airflow limitation and serum cortisol levels in horses with experimentally induced mild to severe airway obstruction.
Lavoie J-P, Bullone M, Rodrigues N et al. (2019) — Equine veterinary journal
The influence of hay steaming on clinical signs and airway immune response in severe asthmatic horses.
Orard Marie, Hue Erika, Couroucé Anne et al. (2018) — BMC veterinary research
Efficacy of three corticosteroids for the treatment of heaves.
Robinson N E, Jackson C, Jefcoat A et al. (2002) — Equine veterinary journal
Environment and prednisone interactions in the treatment of recurrent airway obstruction (heaves).
Jackson C A, Berney C, Jefcoat A M et al. (2000) — Equine veterinary journal
Differences in pulmonary function measured by oscillometry between horses with mild-moderate equine asthma and healthy controls.
Lo Feudo Chiara Maria, Ferrucci Francesco, Bizzotto Davide et al. (2025) — Equine veterinary journal
Effects of a propriety oiled mixed hay feeding system on lung function, neutrophilic airway inflammation and oxidative stress in severe asthmatic horses.
Jochmans-Lemoine Alexandra, Picotte Khristine, Beauchamp Guy et al. (2020) — Equine veterinary journal
Telemetric analysis of breathing pattern variability in recurrent airway obstruction (heaves)-affeeted horses
Behan Ashley L., Hauptman Joe G., Robinson N. Edward (2013) — American Journal of Veterinary Research
Respiratory and metabolic effects of massive administration of isotonic saline solution in heaves-affected and control horses.
Jean D, Vrins A, Lavoie J P (2004) — Equine veterinary journal
Lung Function Variation during the Estrus Cycle of Mares Affected by Severe Asthma.
Mainguy-Seers Sophie, Diaw Mouhamadou, Lavoie Jean-Pierre (2022) — Animals : an open access journal from MDPI
Surgical Debulking and TransEndoscopic Noncontact Diode Laser Application for Treating a Sinonasal Myxoma in a Horse.
Palozzo Adriana, Celani Gianluca, Varasano Vincenzo et al. (2021) — Journal of equine veterinary science
Clinical and Pathological Features in Horses With Advanced Arytenoid Chondritis.
Bolfa Pompei, Cercone Marta, Dennis Michelle M et al. (2021) — Veterinary pathology
Correcting Campylorrhinus Lateralis in a Foal by Bone Distraction: A Case Report.
Rangel Julia P P, de Oliveira Alvaro P L, Baiotto Gustavo C et al. (2020) — Journal of equine veterinary science
Airway wall eosinophilia is not a feature of equine heaves.
Dubuc J, Lavoie J-P (2014) — Veterinary journal (London, England : 1997)
A dorsal approach for the removal of the nasal septum in the horse.
Shoemaker Ryan W, Wilson David G, Fretz Peter B (2005) — Veterinary surgery : VS
Glucocorticoid treatment in horses with asthma: A narrative review.
Mainguy-Seers Sophie, Lavoie Jean-Pierre (2021) — Journal of veterinary internal medicine
Pulmonary response of severely asthmatic horses after intra-articular administration of methylprednisolone.
Millares-Ramirez Esther M, Picotte Khristine, Lavoie Jean-Pierre (2021) — Equine veterinary journal
The Reported Use of Tongue-Ties and Nosebands in Thoroughbred and Standardbred Horse Racing-A Pilot Study.
Weller Dominic, Franklin Samantha, White Peter et al. (2021) — Animals : an open access journal from MDPI
Show 5 more references
Exercising upper respiratory videoendoscopic findings of 50 competition draught horses with abnormal respiratory noise and/or poor performance.
Hackett E S, Leise B S (2019) — Equine veterinary journal
Racing performance following prosthetic laryngoplasty using a polyurethane prosthesis combined with a laser-assisted ventriculocordectomy for treatment of recurrent laryngeal neuropathy in 78 Thoroughbred racehorses.
Raffetto J A, Wearn J G, Fischer A T (2015) — Equine veterinary journal
Respiratory diseases and their effects on respiratory function and exercise capacity.
Van Erck-Westergren E, Franklin S H, Bayly W M (2013) — Equine veterinary journal
Diseases Causing Airway Obstruction in the Horse
(2004) — Equine Respiratory Diseases
Relationship between clinical signs and lung function in horses with recurrent airway obstruction (heaves) during a bronchodilator trial.
Robinson N E, Olszewski M A, Boehler D et al. (2000) — Equine veterinary journal