For companion rabbits, respiratory distress is not just a severe symptom—it is a hyper-acute emergency with a very narrow window for intervention. As obligate nasal breathers, rabbits possess a high metabolic rate, a small thoracic volume relative to their abdominal size, and an extreme susceptibility to catecholamine-induced shock. When a rabbit presents with breathing difficulties, the veterinary team's initial approach must differ significantly from that used for dogs or cats. Standard diagnostics like immediate physical restraints, blood draws, or positioning for radiographs can be fatal.

This clinical guide outlines the pathophysiology of rabbit dyspnea, a structured visual triage system, the mandatory "hands-off" stabilization protocol, diagnostic differentiation paths, and emergency airway management procedures.

Pathophysiology of the Dyspneic Rabbit

Rabbits are anatomically and physiologically predisposed to rapid respiratory decompensation:

1. Obligate Nasal Breathers: Their epiglottis is positioned dorsal to the soft palate, effectively locking the larynx in the nasopharynx during normal breathing. Any obstruction of the nasal passages (e.g., from mucopurulent exudate or nasal turbinate distortion) severely compromises airway patency.
2. High Oxygen Demand and Low Reserve: Rabbits have high metabolic rates and small lung volumes relative to their body weight. Their chest wall is highly compliant, and their diaphragmatic movement is easily restricted by abdominal organs or gastric distension.
3. Prey Species Stress Response: In the wild, showing signs of weakness makes a rabbit an easy target. By the time a rabbit shows obvious respiratory effort, it has exhausted its compensatory mechanisms. Furthermore, handling a dyspneic prey animal triggers a massive release of epinephrine and norepinephrine. This catecholamine surge can cause severe cardiac arrhythmias, coronary vasoconstriction, and acute myocardial necrosis, leading to sudden death.

Triage & Visual Assessment: The "Hands-Off" Exam

Upon presentation, the rabbit must be evaluated in its carrier or under a clear oxygen hood without physical contact. The clinician should observe the animal's posture, respiratory pattern, and clinical signs from a distance.

Table 1: Triage Classification for Respiratory Distress

Pathognomonic Warning Signs

• Orthopneic Posture: The rabbit sits with its neck extended dorsally and nose pointed toward the ceiling to straighten the trachea and minimize upper airway resistance. Front limbs are often abducted (spread wide) to expand the chest.
• Open-Mouth Breathing: This is a late-stage, poor-prognostic indicator. Because of their obligate nasal anatomy, rabbits only breathe through their mouth when nasal passages are completely occluded or when they are in terminal respiratory failure.
• Paradoxical Respiration: The chest wall draws inward during inspiration while the abdomen expands. This indicates diaphragmatic fatigue or pleural space disease.

Immediate Stabilization SOP (First 30 Minutes)

The primary goal of the first phase of treatment is to increase inspired oxygen concentration and reduce metabolic demand without causing stress-induced death.

Step 1: Stress Mitigation and Environmental Control

Immediately move the rabbit to a quiet, dimly lit room away from the smells, sights, and sounds of predatory species (dogs, cats, ferrets). Minimize all handling. Do not attempt to take rectal temperature, check heart rate with a stethoscope, or place an intravenous catheter during the first 10–15 minutes of severe dyspnea.

Step 2: Oxygen Therapy

Provide supplemental oxygen immediately. The method chosen must match the patient's stress tolerance:

• Oxygen Cage / Incubator (Preferred): Placing the rabbit in a sealed, temperature-controlled oxygen chamber is the least stressful method. Set the fraction of inspired oxygen ($FiO_2$) to 40%–50%. Monitor the chamber temperature closely; rabbits overheat easily, and hyperthermia increases oxygen demand. Keep the temperature between 65°F and 72°F (18°C–22°C).
• Flow-By Oxygen: If a chamber is unavailable, hold an oxygen line close to the rabbit's nose. Avoid pushing the tube directly into the nose, which can provoke panic.
• Oxygen Hood / Collar: A clear plastic collar or bag placed over the front of the carrier can create a local oxygen-rich zone, but monitor for heat and $CO_2$ buildup.

Step 3: Pharmacological Stabilization (Anxiolysis)

A dyspneic rabbit is in a state of panic, which increases oxygen consumption. Administering a mild sedative helps break the panic cycle:

• Midazolam: 0.25–0.5 mg/kg IM or SC. Midazolam provides excellent muscle relaxation and mild sedation with minimal cardiovascular depression. It can be reversed with flumazenil if necessary.
• Butorphanol: 0.1–0.5 mg/kg IM or SC. Butorphanol provides mild sedation and visceral analgesia. It is particularly useful if pain (e.g., from abdominal disease) is suspected as a secondary trigger for respiratory distress.

These medications should be administered using a small-gauge needle (25G or 27G) while the rabbit is still in its carrier or immediately upon placing it in the oxygen chamber.

Step 4: Hypothermia Correction

Many severely compromised rabbits present with hypothermia (rectal temperature $<99^\circ\text{F}$ or $<37.2^\circ\text{C}$). Hypothermia impairs cardiovascular function and drug metabolism. Once the rabbit is stable under oxygen and sedated, provide gentle warming using a circulating warm-water pad or forced-air warming blanket. Avoid direct heat lamps, which can burn the skin or cause hyperthermia.

Diagnostic Differentiation (Once Stable)

Only when the rabbit's respiratory rate has stabilized, the orthopneic posture has improved, and the patient is resting quietly should diagnostics be initiated.

Step 1: History and Physical Examination

Obtain a detailed history, focusing on:

• Onset: Acute dyspnea (minutes to hours) vs. chronic nasal discharge (weeks).
• Environment: Substrate type (cedar/pine shavings release airway-irritating phenols), ventilation quality, exposure to other rabbits.
• Co-morbidities: History of dental disease, weight loss, or ocular discharge.

Perform a rapid, focused physical exam:

• Auscultation: Listen for upper airway referred noise vs. muffled lung sounds.
• Nasal Check: Check for unilateral or bilateral discharge, crusting, or nasal blockage.
• Palpation: Check for cranial mediastinal compressibility. In normal rabbits, the anterior chest is easily compressed side-to-side. A lack of compressibility suggests a mediastinal mass (thymoma, lymphoma).

Step 2: Targeted Diagnostics

Point-of-Care Ultrasound (POCUS)

Lung ultrasound (Vet BLUE protocol) is highly useful in the emergency setting. It can be performed while the rabbit is sitting upright in the oxygen chamber or with minimal restraint on the exam table.

• B-lines: Multiple B-lines indicate interstitial fluid, pulmonary edema, or pneumonia.
• Pleural Effusion: Anechoic fluid in the pleural space. This can be therapeutically tapped immediately (thoracocentesis) to relieve lung compression.
• Consolidation: Solid lung tissue tissue patterns suggest bacterial pneumonia or abscesses.

Radiographs (Thoracic)

Once the patient can tolerate brief positioning, take lateral and dorsoventral thoracic views. Avoid dorsal recumbency, as this severely compromises respiration.

• Lower Respiratory Tract: Radiographs distinguish pulmonary edema (cardiogenic or non-cardiogenic) from lobar consolidation (pneumonia) and pulmonary abscesses.
• Pleural Space: Pleural effusion presents as a loss of the cardiac silhouette and lung lobe retraction.
• Mediastinum: Look for a cranial mediastinal mass displacing the trachea dorsally and compressing the cranial lung lobes.

Clinical Pathology

• Arterial Blood Gas: If available, this helps monitor oxygenation ($PaO_2$) and ventilation ($PaCO_2$), but the stress of arterial puncture often outweighs the benefit.
• Hematology: A complete blood count may reveal leukocytosis with a heterophil-to-lymphocyte ratio shift, indicating acute bacterial infection (Pasteurella, Bordetella, Staphylococcus).

Table 2: Differential Diagnosis Matrix for Rabbit Dyspnea

Emergency Airway SOP

If a rabbit presents in respiratory arrest or decompensates to agonal gasping, immediate airway security is required.

Endotracheal Intubation

Intubation in rabbits is challenging due to their long, narrow oral cavity, large tongue, and small glottis.

1. Blind Orotracheal Intubation: Place the rabbit in sternal recumbency with the head and neck fully extended. Listen to the distal end of the endotracheal tube (usually a 2.0 mm to 3.0 mm tube) as it is advanced through the oral cavity. Advance the tube during the inspiratory phase when the vocal cords are widest. Condensation in the tube or a cough reflex indicates entry.
2. Visual Intubation (Otoscope / Endoscope): Use a pediatric otoscope or a rigid endoscope to visualize the glottis directly. Guide the stylet through the vocal cords, then slide the endotracheal tube over the stylet.
3. Laryngeal Mask Airway (V-Gel): A rabbit-specific supraglottic airway device (V-gel) is a rapid and effective alternative. It slides over the tongue and seals around the larynx, allowing positive pressure ventilation without entering the trachea.

Emergency Tracheostomy

If the upper airway is fully obstructed by a mass, severe edema, or purulent plug, and intubation is unsuccessful, an emergency tracheostomy must be performed. Under local anesthesia (lidocaine) and light sedation, perform a midline cervical incision, separate the sternohyoideus muscles, make a transverse incision between the third and fourth tracheal rings, and insert a small cuffed tracheostomy tube or modified endotracheal tube.

Sources

• Merck Veterinary Manual. Respiratory Diseases of Rabbits. https://www.merckvetmanual.com/exotic-and-laboratory-animals/rabbits/respiratory-diseases-of-rabbits
• Harcourt-Brown FM. Cardiorespiratory Disease. In: Textbook of Rabbit Medicine (2nd ed.). Open access via NCBI Bookshelf. https://pmc.ncbi.nlm.nih.gov/articles/PMC7150336/
• Harcourt-Brown F. Critical and emergency care of rabbits. Veterinary Nursing Journal 26(12): 443–456 (2011). https://onlinelibrary.wiley.com/doi/full/10.1111/j.2045-0648.2011.00119.x
• Huynh M, Boyeaux A, Pignon C. Assessment and care of the critically ill rabbit. Veterinary Clinics of North America: Exotic Animal Practice 19(2): 379–409 (2016). https://www.rcvsknowledge.org/resource/veterinary-care-of-rabbits
• Merck Veterinary Manual. Management of Rabbits (anaesthesia, intubation, premedication). https://www.merckvetmanual.com/exotic-and-laboratory-animals/rabbits/management-of-rabbits