- Definition
- Pathophysiology
- Systems Affected
- Incidence/Prevalence
- Geographic Distribution
- Signalment
- Signs
- Causes
BASICS
In animals, dyspnea is used to describe clinical signs associated with difficult, labored breathing or respiratory distress, which can be present throughout the respiratory cycle or be primarily associated with either inhalation (i.e. inspiratory dyspnea) or exhalation (i.e. expiratory dyspnea).
- Generally a sign of impaired gas exchange, with the increased effort to inhale being associated with an increased need to ventilate the lung
- Primary causes—failure of delivery of air into the lung (i.e. alveolar hypoventilation) and of exchange between the lung and blood (i.e. ventilation, diffusion, or perfusion problem). The former can result from airway obstruction, pleural disease, chest wall or diaphragmatic injury, pneumothorax, intrusion of the abdomen on the thorax (e.g. advanced pregnancy, diaphragmatic hernia), or central nervous system disease. Relevant exchange problems primarily are those causing alveolar disease (e.g. pneumonia, pulmonary edema)
- Can also be a sign of decreased oxygen delivery to the tissues (e.g. cardiovascular disease, anemia) and of the need to eliminate more carbon dioxide to correct a metabolic acidosis
- The most severe cases usually result from obstruction of the extrathoracic airways because the negative pressure generated during inhalation tends to collapse these structures
- Respiratory
- Cardiovascular
- Hemic/lymphatic/immune
- Endocrine/metabolic—response to metabolic acidosis
- Nervous
- Inspiratory dyspnea is a sign, but associated signs can indicate the source of the dyspnea
- Inappetence can indicate inflammatory disease, or inability to eat as a consequence of severe dyspnea or pharyngeal dysfunction
- Cough indicates inflammation of the tracheobronchial tree or nasopharynx
- Bilateral nasal discharge usually indicates inflammation of the guttural pouches or lower airways, or bilateral inflammation of the nasal cavities or sinuses
- Unilateral discharge suggests nasal or nasopharyngeal (including the sinuses and guttural pouches) disease
- Noisy breathing (stridor) indicates obstruction of the extrathoracic airways
- Sudden onset of inspiratory dyspnea can indicate acute inflammatory disease of the lung or pleural space; trauma to the chest wall, diaphragm, or extrathoracic airway; or acute blood loss
- Dyspnea of slower onset may result from a space-occupying mass encroaching on the respiratory system
- Flared nostrils, increased excursions of the thorax, and retractions (i.e. “sinking in”) of the intercostal spaces, particularly if laboring against an upper airway obstruction
- Exaggerated excursions of the diaphragm lead to increased movement of the anal sphincter
- Nasal obstruction—noisy breathing, decreased airflow
- Strangles—fever, nasal discharge, swollen or draining lymph nodes
- Guttural pouch tympany—fluctuant swelling of the parotid region (usually bilateral)
- Laryngeal paralysis—if severe or bilateral, severe inspiratory dyspnea and strident inspiratory noise
- Alar fold collapse, laryngeal hemiplegia, and epiglottic retroversion—no signs at rest but can lead to reduced exercise tolerance and inspiratory noise
- Pneumonia—fever, adventitious sounds
- Pulmonary edema—fine, inspiratory crackles
- Pneumothorax—lack of breath sounds and little air movement despite large effort
- Pleural effusion/pleuritis—lack of lung sounds ventrally, friction rubs, fever, depression, abducted elbows indicating pain
- Fractured ribs—signs of trauma, sounds of air entering and leaving wounds
- Diaphragmatic hernia—reduction in lung sounds, signs of colic, or borborygmi audible in chest
- Anemia—pallor
- Cardiac disease—murmurs, thrills, or arrhythmias
- Extrathoracic airway
- Paresis of the external nares, alar fold collapse
- Severe atheroma (rare)
- Congestion of the nasal mucosa—Horner syndrome; inflammatory disease, amyloidosis
- Deviation of the nasal septum
- Space-occupying lesion affecting the nasal cavity—foreign body, intraluminal mass, ethmoid hematoma, or extraluminal mass or swelling
- Congenital pharyngeal cysts
- Pharyngeal or laryngeal paresis, permanent DDSP
- Space-occupying masses protruding inside the pharynx—enlarged lymph nodes; guttural pouch enlargement, abscesses
- Trauma to the hyoid bone or larynx
- Laryngeal or pharyngeal paresis—degenerative nerve disease, lead poisoning, or trauma to recurrent laryngeal nerves (e.g. by jugular perivascular injection)
- Tracheal foreign body or collapse
- Intrathoracic respiratory tract
- Equine asthma (heaves, pasture asthma)—accompanied by expiratory dyspnea, which is predominant
- Pulmonary edema—cardiogenic or noncardiogenic
- Pneumonia—bacterial, viral, or fungal
- Pleuritis/pleuropneumonia
- Accumulation of pleural fluid
- Pneumothorax
- Diaphragmatic hernia
- Fractured ribs/flail chest
- Mediastinal masses
- EMPF
- Equine multisystemic eosinophilic epitheliotropic disease
- Cardiovascular—congenital cardiac defect with right-to-left shunt, cardiac failure, or pulmonary embolus
- Hemic—anemia, methemoglobinemia, carbon monoxide or cyanide poisoning
- Endocrine/metabolic—severe metabolic acidosis; hyperthermia
- Nervous—trauma to recurrent laryngeal nerves or pharyngeal plexus, mediastinal masses, lead poisoning, phrenic nerve injury, or diaphragmatic paralysis
- Reproductive—advanced pregnancy; hydrops
DIAGNOSIS
TREATMENT
MEDICATIONS
FOLLOW-UP
MISCELLANEOUS