📋 At a Glance
⚠️ Respiratory Signs Requiring Veterinary Contact
- Labored breathing at rest — visible abdominal effort on expiration; flared nostrils without exertion
- Any open-mouth breathing — horses cannot mouth-breathe normally; this indicates severe upper airway obstruction
- Abnormal respiratory noise at exercise that has newly developed or significantly worsened
- Bilateral nasal discharge with fever — potential infectious respiratory disease
- Epistaxis (nosebleed) — bilateral or at rest is particularly concerning
- Progressive exercise intolerance over weeks — chronic airway disease or cardiac cause
- Respiratory rate consistently above 20 breaths/min at rest in a settled horse
Upper vs. Lower Airway — Why the Distinction Matters
Equine respiratory conditions divide meaningfully by anatomical location. Upper airway conditions affect the nasal passages, pharynx, larynx, and guttural pouches — producing respiratory noise, nasal discharge, and exercise limitation from flow resistance. Lower airway conditions affect the trachea, bronchi, bronchioles, and alveoli — producing cough, secretion accumulation, and inflammatory changes that impair gas exchange.
The distinction matters for diagnostics and treatment. Upper airway conditions often require endoscopy for diagnosis. Lower airway conditions require different evaluation (rebreating bag, tracheal wash, BAL cytology) and respond to environmental management and inhaled or systemic medications rather than surgical correction.
| Condition | Location | Primary Signs | Diagnosis | Treatment |
|---|---|---|---|---|
| Laryngeal hemiplegia ('roaring') | Left recurrent laryngeal nerve; laryngeal cartilage | Inspiratory noise at exercise; exercise intolerance | Endoscopy at rest and/or during exercise (overground endoscopy) | Prosthetic laryngoplasty ('tie-back'); ventriculocordectomy |
| Mild-moderate equine asthma (formerly IAD) | Lower airway — bronchioles | Chronic intermittent cough; mild exercise intolerance; mucus | BAL cytology — determines inflammatory cell pattern | Environmental modification; bronchodilators; inhaled corticosteroids |
| Severe equine asthma (formerly heaves/RAO) | Lower airway — widespread bronchospasm | Chronic cough; exercise intolerance; labored breathing at rest; heave line | Clinical exam + BAL + response to management changes | Environmental modification (most important) + bronchodilators + systemic/inhaled corticosteroids |
| Guttural pouch empyema | Guttural pouch (air-filled pouches connecting to Eustachian tubes) | Unilateral nasal discharge; lymph node swelling; head shaking | Endoscopy; radiographs | Lavage; drainage; systemic antibiotics for chondroid formation |
| Pharyngeal lymphoid hyperplasia | Pharyngeal mucosa | Young horse respiratory signs; post-infectious | Endoscopy | Often self-limiting; management of underlying respiratory infection |
| DDSP (dorsal displacement soft palate) | Soft palate displaced over epiglottis | Intermittent gurgling noise at exercise; 'making a noise' | Overground endoscopy during exercise | Palate cauterization; staphylectomy; training modification |
Equine Asthma — The Most Common Chronic Respiratory Condition
The term 'equine asthma' now encompasses what was previously called RAO (recurrent airway obstruction), heaves, and IAD (inflammatory airway disease) — recognizing that these represent a spectrum of the same underlying condition: lower airway inflammation driven by inhaled organic particles (mold spores, hay dust, bacterial endotoxins, stable air pollutants).
The fundamental pathophysiology is airway hyperreactivity — the airways of susceptible horses mount an exaggerated inflammatory response to particle exposure that leads to bronchoconstriction, mucus accumulation, and airway wall thickening. In mild cases, this produces subtle cough and mild exercise intolerance (mild-moderate equine asthma). In severe cases, the inflammation is profound enough to cause labored breathing at rest and the visible 'heave line' from chronically hypertrophied abdominal expiratory muscles.
| Category | BAL Cytology Pattern | Clinical Signs | Environmental Response |
|---|---|---|---|
| Mild-moderate equine asthma (formerly IAD) | Increased neutrophils, eosinophils, or mast cells — variable patterns | Chronic intermittent cough; subtle exercise limitation; may appear normal at rest | Good response to hay steaming/soaking and increased turnout |
| Severe equine asthma (formerly heaves/RAO) | Markedly elevated neutrophils (often >25%) | Chronic cough; significant exercise intolerance; labored expiration at rest; 'heave line' | Significant improvement with maximum outdoor turnout; some horses require medication alongside management |
Environmental Modification — The Most Effective Intervention
- Maximum outdoor turnout is the single most impactful change — outdoor air has dramatically lower respirable particle concentrations than any stable environment
- Hay soaking (30+ minutes submerged in water) reduces respirable particles by >90% — logistically demanding but highly effective
- Hay steaming (commercial hay steamer) kills mold spores without leaching nutrients — nutritionally superior to soaking; higher setup cost
- Hay alternatives (cubes soaked, haylage, complete hay replacers) for most severe cases
- Dust-free bedding — paper, rubber matting, or pelleted bedding instead of straw
- Stable ventilation — airflow dilutes particle concentration; open doors and windows benefit all horses even when some cannot be turned out
- Feed from ground level — hay positioned at head height dramatically increases particle inhalation per breath
EIPH — Exercise-Induced Pulmonary Hemorrhage
EIPH — bleeding from pulmonary capillaries during high-intensity exercise — is extremely common in racehorses (estimated >80% affected) and occurs at meaningful rates in other performance horses working at high intensities. Most EIPH is subclinical: blood is visible in the trachea by endoscopy after exercise but does not reach the nostrils. Epistaxis (visible nosebleed) represents a small fraction of EIPH cases.
The mechanism involves capillary stress failure under the extreme pulmonary pressures generated during maximal effort. Management in racing horses includes furosemide (Lasix/Salix), which reduces pulmonary arterial pressure. For non-racing performance horses, management is primarily training modification and addressing concurrent airway inflammation that may elevate baseline pulmonary pressures.
✅ Supporting Respiratory Health
- Maximize hay quality and dust reduction — soak or steam hay for any horse with a respiratory history
- Maximize turnout — outdoor air consistently has lower particle loads than stables
- Optimize barn ventilation — open doors and windows year-round where climate allows
- Use dust-free bedding for horses with airway sensitivity
- Monitor resting respiratory rate — establish your horse's normal; increases signal worsening airway disease
- Schedule evaluation if chronic cough, increased RR at rest, or exercise intolerance develops
📋 Respiratory Health Discussion Points for Your Vet
- BAL cytology — identifies inflammatory cell pattern and guides medication selection
- Endoscopy for upper airway — appropriate if exercise noise or epistaxis is present
- Inhaled medication delivery — equine inhaler masks (AeroHippus, EquineHaler) for horses needing inhaled bronchodilators or corticosteroids
- Hay quality testing and treatment options — soaking vs. steaming vs. haylage
- Seasonal variation management — many horses worsen in late summer/fall (peak mold) and winter (increased stabling)
Questions to Ask Your Veterinarian
- Would BAL cytology be informative for this horse, and what would it change about treatment?
- What environmental changes will have the most impact given my specific management situation?
- Do you recommend inhaled or systemic corticosteroids, and what are the tradeoffs for this horse?
- What resting respiratory rate should I target as a goal of treatment?
- When should I expect to see improvement after implementing environmental changes?
