Intubating a dog involves placing an endotracheal tube through the mouth, past the vocal folds, and into the trachea to secure the airway during anesthesia or emergency resuscitation. The procedure is straightforward in most dogs when you can clearly identify the key landmarks: the epiglottis, soft palate, arytenoid cartilages, and the opening of the larynx. Getting it right depends on choosing the correct tube size, positioning the dog properly, and confirming placement before moving forward.
Equipment and Tube Sizing
Endotracheal tubes are sized by their internal diameter in millimeters. Selecting the right size matters because a tube that’s too large risks traumatizing the trachea, while one that’s too small increases airway resistance and makes it harder to maintain a proper seal. Always have one tube size above and one below your target ready in case the initial choice doesn’t fit.
The standard canine sizing chart based on body weight:
- 1 to 2 kg: 5 mm tube
- 3 to 5 kg: 6 mm tube
- 6 to 7 kg: 7 mm tube
- 8 to 11 kg: 8 mm tube
- 12 to 14 kg: 9 mm tube
- 15 to 20 kg: 10 mm tube
- 21 to 30 kg: 12 mm tube
- 31 kg and above: 14 mm tube
Beyond the tube itself, you’ll need a laryngoscope with an appropriately sized blade, a syringe for cuff inflation, water-soluble lubricant, a tie or gauze strip to secure the tube, and ideally a capnograph to confirm placement. Pre-measure the tube against the dog by holding it alongside the neck: the tip should reach roughly from the thoracic inlet (the point where the neck meets the chest) to the mouth, ensuring it sits in the mid-trachea rather than advancing into a bronchus.
Pre-oxygenation Before Induction
Delivering pure oxygen before inducing anesthesia buys critical time in case intubation takes longer than expected. Three minutes of oxygen via a fitted face mask at a flow rate of 100 mL per kilogram per minute is effective in healthy dogs. This fills the lungs with an oxygen reserve that delays the drop in blood oxygen levels during the period when the dog is apneic (not breathing on its own) and you’re placing the tube.
A snug-fitting face mask with a diaphragm works significantly better than simply holding a tube near the nostrils. Flow-by oxygen, where you position the breathing circuit a few centimeters from the nose, fails to deliver a high enough oxygen concentration to achieve adequate pre-oxygenation. If the dog tolerates a mask, use one.
Positioning and Visualization
Once the dog is induced and the jaw relaxes, place it in sternal recumbency (lying on its chest) or, more commonly, lateral recumbency. Many practitioners prefer sternal positioning because it gives a straight line of sight down the oropharynx. Have an assistant hold the upper jaw open and tilt the head slightly upward to extend the neck.
Use the laryngoscope blade to gently press the tongue downward and forward. This brings the epiglottis into view, the leaf-shaped cartilage flap sitting over the airway entrance. In dogs, the epiglottis often rests behind the soft palate. Use the tip of the laryngoscope blade or the tube itself to gently flip the epiglottis forward, exposing the arytenoid cartilages and the vocal folds beneath. You’re looking for the triangular opening between the arytenoid cartilages, the laryngeal aperture, which is the entry point into the trachea.
Placing the Tube
With the laryngeal opening clearly in view, advance the lubricated tube between the vocal folds during an inhalation, when the arytenoids are most open. Use a smooth, controlled motion. If you meet resistance, do not force the tube. Back off and try a smaller size, or adjust the angle. In some dogs, placing a rigid stylet inside the tube helps guide the tip between the arytenoids by giving it more structure and allowing you to direct it like a wedge.
Advance the tube until the cuff sits just past the vocal folds. If the tube is pre-measured, align your reference mark at the level of the incisors. Over-advancing pushes the tube into one of the main bronchi (usually the right), meaning only one lung gets ventilated. Under-advancing leaves the cuff at the level of the larynx, which risks trauma and a poor seal.
Once positioned, secure the tube by tying it to the muzzle or behind the ears with gauze. This prevents the tube from migrating during the procedure.
Inflating the Cuff
The cuff creates a seal between the tube and the tracheal wall, preventing gas leaks and protecting against aspiration. The target cuff pressure is 20 to 30 cmH2O. Pressures above 30 cmH2O compress the blood vessels supplying the tracheal lining, which can lead to mucosal damage, tracheal necrosis, or even perforation.
The most commonly used technique in dogs is minimal occlusive volume: slowly inject air into the cuff via the pilot balloon while someone delivers a breath through the tube. Listen for a hissing sound around the tube at the mouth or along the trachea. Stop inflating at the point where the leak just disappears. This approach gives you the lowest effective seal pressure. If you have a cuff pressure manometer, verify the reading falls within that 20 to 30 cmH2O window. If you don’t have a manometer, gently palpate the pilot balloon. It should feel slightly yielding, not rock-hard.
Recheck the seal periodically during long procedures, especially after repositioning the patient, since changes in head and neck position can alter cuff pressure.
Confirming Correct Placement
Never assume the tube is in the right place. Several methods confirm tracheal (not esophageal) placement:
- Capnography: A normal waveform on the capnograph, showing a rhythmic rise and fall of exhaled carbon dioxide, is the gold standard. If the tube is in the esophagus, you get no CO2 reading.
- Chest wall movement: When you deliver a breath through the tube, you should see the chest expand symmetrically.
- Condensation: Moisture fogging inside the tube during exhalation suggests placement in the airway.
- Auscultation: Listen over both sides of the chest with a stethoscope. Breath sounds should be equal on both sides. If sounds are louder on one side, the tube may have advanced into a bronchus.
- Reservoir bag movement: The ventilator bellows or reservoir bag should fill and empty with each breath cycle.
Brachycephalic Breeds Need Special Attention
Flat-faced breeds like Pugs, French Bulldogs, Pekingese, and English Bulldogs present consistently more difficult airways. These dogs have elongated soft palates, narrowed nostrils, and, critically, hypoplastic (underdeveloped) tracheas. This means they typically require a much smaller endotracheal tube than you’d expect based on body weight alone. A French Bulldog weighing 12 kg might need a 3.5 mm tube rather than the 9 mm tube the weight chart suggests.
Prepare a wider range of tube sizes when working with brachycephalic breeds, including sizes several steps smaller than the chart recommends. Warming the tube in a warming cabinet softens the material, making it easier to navigate a tight or irregularly shaped airway. Lubricate generously with lidocaine-containing jelly, which reduces laryngeal irritation and can help blunt the reflex response. In cases where even small tubes won’t pass, a supraglottic airway device designed for cats can sometimes secure the airway in these smaller brachycephalic dogs. Emergency backup plans for these breeds include jet ventilation and tracheostomy.
Risks and Complications
The most immediate risk during intubation is stimulating a vagal response. Mechanical contact with the larynx activates the vagus nerve, which can cause a sudden drop in heart rate and blood pressure. This is why gentle technique matters, and why monitoring heart rate continuously during the attempt is essential. If the heart rate drops sharply, stop the attempt and allow the dog to recover before trying again.
Traumatic intubation, whether from forcing an oversized tube, repeated attempts, or rough technique, can cause swelling, bleeding, or damage to the vocal folds and arytenoid cartilages. Post-procedure, a dog with a traumatized larynx may show stridor (noisy breathing), coughing, or difficulty swallowing. Excessive cuff pressure over the course of a long procedure remains one of the most preventable causes of tracheal injury, reinforcing the importance of monitoring cuff pressure rather than relying on feel alone.
Esophageal intubation, where the tube enters the food pipe instead of the trachea, delivers no oxygen to the lungs. This is why confirmation of placement immediately after insertion is non-negotiable. If there’s any doubt, remove the tube and start again.