Endotracheal Intubation: Technique, Airway Management, and Troubleshooting

Endotracheal Intubation: Technique, Airway Management, and Troubleshooting

Quick Answer: Endotracheal intubation establishes a secure, patent airway for anesthetized patients. Select the correct tube size for the species (cat 3.5–4.5 mm ID, small dog 5–7 mm ID, large dog 8–14 mm ID), apply topical lidocaine to the feline larynx to prevent laryngospasm, confirm placement with capnography immediately, and inflate the cuff only to a just-seal pressure of 20–30 cmH2O. Never force a tube through a tight larynx and never overinflate the cuff — tracheal necrosis follows.

Endotracheal Tube Selection

The endotracheal tube (ETT) must match the patient's airway diameter and length. A tube too large traumatizes the larynx; too small leaks around the cuff and compromises ventilation.

Tube materials:

• Silicone — flexible, resists kinking, reusable, widely preferred for routine cases.
• Red rubber — stiffer, reusable, useful when more rigidity helps passage, but harder to sterilize and less common today.
• PVC (single-use) — inexpensive, rigid at room temperature, softens at body temperature.

Cuffed vs uncuffed: Most dogs are intubated with a cuffed tube to create an airway seal and prevent aspiration. Cats are frequently intubated with uncuffed tubes because the feline larynx is narrow and a cuff can cause trauma and post-extubation edema. When a cuffed tube is used in a cat, inflate with extreme care.

Length check: Measure the tube against the patient externally from the rami of the mandible to the thoracic inlet. A tube too long advances into a mainstem bronchus (endobronchial intubation); too short risks accidental extubation or laryngeal trauma. Cut or mark the tube at the correct depth before induction.

Trap: Have at least one size larger and one size smaller ready before induction. The patient will desaturate while you rummage for the right tube.

Intubation Technique

Preparation (before induction)

1. Select and measure the tube; check the cuff by inflating with a syringe to confirm it holds air without leaking.
2. Lubricate the distal end with water-soluble jelly.
3. Have a laryngoscope with the correct blade (Miller for cats and small dogs, long Miller or McIntosh for large dogs), lidocaine for cats, and suction ready.
4. Pre-oxygenate the patient with a mask for 3–5 minutes before induction.

Feline intubation

Cats are prone to laryngospasm — forceful closure of the arytenoid cartilages that blocks intubation and causes trauma. The cardinal rule is no force.

1. After induction, place the cat in sternal recumbency with the head and neck extended.
2. Visualize the larynx with the laryngoscope.
3. Apply 0.1–0.2 mL of 2% lidocaine (without epinephrine) to each arytenoid cartilage using a cotton-tipped applicator or drop. Wait 30–60 seconds.
4. Gently advance the tube during inspiration, when the glottis opens widest. Rotate the tube slightly if resistance is met.
5. If the tube does not pass, do not push harder — withdraw, reapply lidocaine, and try a smaller tube.

Trap: Forcing a tube through a spasming feline larynx causes mucosal trauma, edema, and post-extubation airway obstruction that can be fatal. Lidocaine drop, wait, and gentle rotation is the standard.

Canine intubation

1. Position in sternal or dorsal recumbency with the head and neck extended.
2. Visualize the larynx with the laryngoscope, pressing the epiglottis forward.
3. Advance the tube through the glottis during inspiration.
4. In brachycephalic breeds (Bulldogs, Pugs), excess pharyngeal tissue and a long soft palate obscure the view; have suction and a stylet available and consider a smaller tube.

Cuff inflation and confirmation

1. Once the tube is placed to the marked depth, connect the breathing circuit.
2. Inflate the cuff slowly with a syringe while listening at the mouth for a leak, or use a cuff pressure manometer to reach 20–30 cmH2O.
3. The goal is a just-seal — the lowest pressure that prevents leak at peak inspiratory pressure.
4. Immediately confirm placement with capnography: a steady EtCO2 trace (35–50 mmHg) confirms endotracheal position. Chest rise alone is unreliable — esophageal intubation can move the chest.
5. Secure the tube to the maxilla or mandible with gauze or a tube tie.

Trap: Never overinflate the cuff to 'make sure it seals.' Pressures above 30 cmH2O exceed tracheal mucosal capillary pressure, causing ischemia, necrosis, stricture, or tracheal rupture. Check cuff pressure with a manometer, not by feel.

Troubleshooting Common Airway Problems

During the procedure

• Monitor EtCO2 continuously. A sudden drop or loss of trace suggests tube displacement, leak, kink, or cardiac arrest.
• Monitor peak airway pressure. A rising peak pressure with falling EtCO2 suggests kinking or obstruction.
• Reposition the head periodically during long procedures to prevent tube kinking at the atlanto-occipital junction.
• Check cuff pressure periodically — nitrous oxide diffuses into the cuff and increases pressure over time.

Extubation

• Extubate with the cuff partially deflated only after the patient can swallow and lift its head.
• In cats, extubate during a breath-in to reduce the chance of laryngospasm.
• Keep the patient sternal with the head lowered to allow drainage of secretions and watch closely for the first 15 minutes — post-extubation laryngeal edema can develop rapidly.

A secure airway is the difference between controlled anesthesia and an emergency. Confirm placement with capnography, respect cuff pressure limits, and handle the feline larynx with lidocaine and patience.