Endotracheal intubation may be performed via the orotra-cheal or nasotracheal route; however, orotracheal intubation is by far the most common mechanism. Orotracheal intubation involves using a laryngoscope or fiberoptic broncho-scope to visualize the vocal cords and direct the endotracheal into the trachea. In the intensive care or emergency setting, orotracheal intubation is usually done via a technique known as rapid sequence intubation/induction (RSI). RSI allows for rapid, safe intubation in patients who have a potentially full stomach and are at risk for aspiration.
RSI involves using a short-acting sedative (etomidate, midazolam, fentanyl, ketamine) to relax the patient followed by a short-acting neuromuscular blocker (succinylcholine, vecuronium) to disable the patients reflex to fight intubation. Before administering medications, patients are pre-oxygenated with 100% oxygen to a goal saturation of 100%. The medications are then given. Once neuromuscular blockade is in place, intubation is attempted. Applying cricoid pressure (Sellick maneuver) to compress the esophagus and prevent aspiration is essential throughout the entire procedure until tracheal intubation is confirmed. Children undergoing RSI can develop profound reflex bradycardia (to vagal stimulation, hypoxia, medications), thus pre-medication with atropine is essential. Fiberoptic assistance may be needed in difficult airways.
Nasotracheal intubation involves directing an ETT through the nasal passage and into the trachea. It can be done blindly or with a fiberoptic bronchoscope. It is done without the assistance of a laryngoscope and has been advocated by some to be the method of choice in cervical spinal cord injury where manipulation of the neck is to be avoided. Its primary indication is for rapid awake intubations (e.g. decompensat-ing COAD) where sedation would be undesirable. Other indications for nasotracheal intubation include elective oral surgery or limited mouth opening (e.g. temporo-mandibular joint (TMJ) dysfunction). It is contra-indicated in severe facial trauma to avoid placement of the tube through the cribiform plate, which has happened! Advantages of nasotra-cheal intubation are ease of communication for the patient (and potentially less need of sedation), easier mouth care, avoidance of occlusion of the tube by biting down (good in pediatrics or head injury). Disadvantages are that a smaller tube is needed, making procedures such as bronchoscopy difficult. It also is associated with a higher incidence of sinusitis, nasal trauma, and epistaxis.
ETTs are usually made of an inert material and have a low-pressure cuff which is blown up in the trachea creating a seal. This allows for positive pressure ventilation without an air leak. Uncuffed tubes are usually used in infants and small children to reduce the risk of damage to the tracheal mucosa. The size of the internal diameter of the tube is written on the outside. For most women a 7.5-8.0 mm ETT is appropriate; for men an 8.0-9.0 mm ETT is used. The diameter of the little finger can be used to size pediatric ETTs; an alternative is the calculation, child's age divided by four plus four. The ETT is guided into place under direct vision and then immediately checked for placement in the lungs. Visualization of placement, ETCO2 detectors, and auscultating for bilateral breath sounds are all indicated to ensure the trachea is intubated (and not the esophagus). The tube is then secured and a chest radiograph done to confirm proper placement of the end of ETT approximately two finger breadths above the tracheal bifurcation. In addition to the standard single lumen tubes, double lumen ETT are available to allow each lung to be ventilated separately. These are used during thoracotomy or for independent lung ventilation.
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