A 68-year-old man (American Society of Anesthesiologists Class II, weight 70 kg, height 171 cm), who had been diagnosed with stage 4 squamous cell carcinoma of the maxillary sinus (#21–23 area) and had undergone three cycles of adjuvant chemotherapy, was admitted for near total maxillectomy and reconstruction with rectus abdominis muscle free flap operation. In addition to the cancer, he experienced hypertension, for which he was treated with an antihypertensive drug. Laboratory tests, electrocardiography, and chest x-ray results were all within the normal ranges. Mouth opening was 3 finger breadths (FB), and there was no limitation of neck extension. However, radiographic findings indicated a thyromental distance of 2 FB and retroposition of the mandible [6] (Fig. 1).

Induction of anesthesia was performed by preoxygenation, followed by intravenous injection of 4 mg/kg of thiopental sodium and 0.2 mg/kg of cisatracurium. There were no problem with mask ventilation after loss of consciousness. When a laryngoscope was used to check the airway for oral intubation, structures associated with the oral airway were not identified due to the limited glottic view (Cormack Lehane Grade IV) [7]. After the initial attempt at oral intubation under direct laryngoscopy had failed, a second attempt was made with a flexible fiberoptic scope, which also failed. Based on the determination that intubation through the nasal cavity may be more favorable than oral intubation due to the poor view, nasal intubation with a fiberoptic scope was attempted. Intubation was successfully performed by passing the fiberoptic scope through the nasal cavity, locating and entering the vocal cord, and finally inserting the nasal endotracheal tube while checking the tracheal ring. Exchange to oral intubation was required for total maxillectomy; thus, a 14 Fr. airway exchange catheter (AEC) (Cook airway exchange catheter, Cook Critical Care, Bloomington, IN, USA) was inserted; the exchange to an oral endotracheal tube was safely performed after removing the nasal endotracheal tube (Fig. 2). During the intubation procedure, SpO2 did not drop below 95%, while a single dose of 5 mg ephedrine was administered for a single episode of blood pressure fluctuation.

The operation was completed in 12 h without any major events. For safety reasons, extubation was performed on the day after the operation. Meanwhile, there were no complications associated with the general anesthesia.

Consent: Informed consent was obtained from the patient for the case report.

Nasotracheal intubation was first introduced by Kuhn and popularized by Magill [8]. Currently, it is used primarily for securing the airway for intraoral operation, due to concerns about morbidities, such as epistaxis and sinusitis. However, Tintinalli et al. reported that when nasotracheal intubation was performed on 71 patients, only one patient required nasal packing due to severe hemorrhage [9]. Compared with oral intubation in patients with facial trauma, nasotracheal intubation is easier to perform; because of this advantage, operators prefer this method [10]. Especially in situations involving difficult or failed oral intubation, fiberoptic nasotracheal intubation has been reported to be an excellent alternative [3]. This is because manipulation of the fiberoptic scope is easier through the relatively straight nasal route, rather than the oral route that requires insertion through an acute angle.

When an experienced operator fails in two attempts at direct laryngoscope-assisted intubation, the case can be viewed as a difficult intubation case [11]. If mask ventilation is possible, other airway management devices may be considered [12]. Recently, clinical application of video laryngoscopy has been very helpful in resolving difficult intubation cases [1]. Moreover, the method of intubation after the insertion of a supraglottic device, such as a laryngeal mask airway, is also applied [4]. Meanwhile, the flexible fiberoptic scope has been in use for some time to resolve difficult intubation situations, and is especially useful for awake intubation [313]. In situations where oral intubation is impossible, and if fiberoscopy can be used, then nasotracheal intubation may be attempted for airway management. Indeed, fiberoptic nasotracheal intubation is known to easily enable airway management, even when the laryngeal view is poor [5].

There are cases in which switching to nasal intubation becomes necessary for intraoral approach during an operation with oral intubation [1], or in which nasal to oral endotracheal tube exchange is necessary for nasal or facial surgery [14]. The method of switching from a nasotracheal tube to an orotracheal tube without extubation has been introduced [15], and there are reported cases of its use as well [14]. However, this method involves the nasal RAE tube itself being removed from the nose to the mouth; considering the rigidity of the tube, there are concerns of possible tissue injury during the process of removing the endotracheal tube from the oropharynx after passing through the nasopharynx, as well as possible extubation due to the movement of the tube. In difficult airway patients with limited mouth opening, there may not be sufficient room to allow manipulation to remove the tube through the mouth.

By switching from a nasal to an oral approach with a tube exchanger, it becomes possible to perform the procedure, even with limited space inside the mouth [16]. Moreover, existing methods require two operators, whereas the method introduced in the present case offers the advantage of only requiring a single operator to perform the procedure. Compared with existing methods, the method of exchange using a tube exchanger is limited by the difficulty associated with preventing aspiration from nasal bleeding, which occurs after removing the nasoendotracheal tube. However, if the exchange can be made quickly with oral suction, blood aspiration may be avoided to a certain degree.

In conclusion, if oral intubation is absolutely necessary in a patient who presents difficult oral intubation, performing the fiberscopic nasal intubation and switching to oral intubation with a tube exchanger may be a viable alternative.