Nasal FOI can be done both awake and under general anesthesia.
Awake Nasal FOI
As with oral FOI, the key to success in an awake nasal fiberoptic intubation is adequate topical anesthesia. (And, as with anything in anesthesia, there is more than one way to do this procedure.)
The nasal mucosa can be anesthetized and vasoconstricted simultaneously with a mixture of lidocaine and phenylephrine (1 mL phenylephrine 1% in 3 cc lidocaine 4%). This provides anesthesia and vasoconstriction with minimal hemodynamic effects. Oxymetazoline 0.05% (Afrin) can also be used for vasoconstriction. Some sources cited using topical cocaine; however, this is a controlled substance and needs to be adequately documented and obtained from pharmacy.
The topical anesthetic/vasoconstrictor solution is applied with cotton-tipped applicators. The applicators are gently inserted into each nostril and gently advanced until they reach the posterior wall of the nasopharynx. Alternatively, the solution can be dripped in using a 20 gauge intravenous catheter or sprayed using an atomizer. It is advisable to prepare both nares.
After topical anesthesia and vasoconstriction have been achieved, the nares can be progressively dilated with nasal airways that have been well lubricated with lidocaine jelly.
For nasal intubation, a small endotracheal tube (7 mm for a normal adult) should be used. Prior to insertion, the tube can be softened by soaking in warm saline, and well-lubricated with lidocaine jelly. The bronchoscope is inserted into the nare, care being taken to stay between the nasal turbinates and septum. Trauma to these structures can cause significant bleeding which can obstruct view of the vocal cords. The scope is passed carefully through the nasal passages and key anatomic structures should be visualized. The nasal cavity eventually leads to the posterior pharynx and the tracheal inlet is visualized. This view is what is seen during oral FOI and once the scope is passed through the vocal cords to the carina the ETT can be passed over the scope and its position confirmed. The endotracheal tube often gets stuck on the arytenoid cartilages. If the endotracheal tube meets resistance, pull the endotracheal tube back slightly, rotate the tube 90-180 degrees, and advance it again. Confirm tube placement with an adequate end-tidal carbon dioxide monitor reading, auscultation of breath sounds, and misting of the tube with ventilation.
Once the position is confirmed, administer propofol to the patient intravenously and secure the tube in position with tape.
Nasal FOI under general anesthesia
The technique of intubating nasally with the patient under general anesthesia differs only slightly from that of an awake intubation.
Apply topical vasoconstrictor before the patient is sedated. After general anesthesia is induced, mask ventilate the patient in the supine position. An oral airway often makes this easier and also lifts the tongue off the posterior pharyngeal wall, facilitating exposure of the larynx. As in an oral intubation, the tongue can be grasped by an assistant with gauze or Magill forceps. Dilate and numb the nasal cavity as described in the anesthesia section above. Load an appropriately sized endotracheal tube over the shaft of the fiberoptic scope. The scope is then passed through the nasal cavity taking care to avoid causing trauma to the turbinates and septum. Observe the laryngeal anatomy of the epiglottis, vocal folds, and arytenoid cartilages. While the patient inhales, advance the tip of the scope through the true vocal folds. The tracheal rings and carina should be observed. Advance the endotracheal tube over the shaft of the scope into the airway. Connect the endotracheal tube to the ventilator.