During oral and maxillofacial surgery and dental treatment, the airway is commonly maintained via nasotracheal intubation. One nostril must be selected for nasotracheal intubation, and generally, if there is no obstruction in breathing with one nostril blocked, neither nostril is contraindicated. However, in many cases, patients who are in need of oral and maxillofacial surgery have anatomical anomalies within the nasal cavity that result in deformities of several structures within the cavity, which render airway management difficult [12]. Such structural anomalies may hinder the passage of the tube through the nasal cavity, requiring the intubation to be re-attempted on the other nostril, and may also induce various complications, including epistaxis.

Hence, predicting and selecting the nostril that would be easier for nasotracheal intubation and less associated with complications, such as epistaxis, would be conducive to a safer airway management. Furthermore, in some cases, a particular nostril must be selected due to the location of the lesion in surgery; thus, it would be beneficial for the patient if the risks and incidences of complications associated with the selection of nostril were examined.

Although nostril selection has been largely neglected by the literature, some reports have suggested a higher incidence of complications when intubation is performed through the left nostril [23]. Smith et al. [4] reported that using a nasal endoscope could be useful for nostril selection. Panoramic radiographs or skull radiographs, which show the anatomical structures within the nasal cavity, are usually taken for patients undergoing nasotracheal intubation. This study was performed because there has been no previous report of prediction of the most appropriate nostril using radiographs.

In this study, we first examined whether there were nostril-specific differences in the incidence of complications for nasotracheal intubation. Then, we conducted a post hoc analysis of the patients' panoramic or posteroanterior skull radiographs, which are generally taken for patients who undergo oral and maxillofacial surgery, to determine the severity of nasal septal deviation. We then compared the results with the incidence of complications after the nasotracheal intubation to examine whether the presence of septal deviation influences the development of complications. We expect the findings of this study to provide important information that can assist in nostril selection for nasotracheal intubation and contribute to safer patient management.

Generally, orotracheal intubation is performed to control the airway during general anesthesia, but nasotracheal intubation is crucial for oral and maxillofacial surgery as well as dental procedures because the oral area is the operation site. However, passing the tube through the nasal cavity, a structurally complex and relatively narrow space, before reaching the trachea during nasotracheal intubation, induces complications such as epistaxis, turbinate fracture, nasal septal fracture, and sinusitis, as well as nasal obstruction or stenosis, rendering intubation difficult [56]. The most common complication is epistaxis. It makes airway management difficult during intubation as it clouds the visual field and may cause airway obstruction when the blood flows into the airway [7].

Many studies have been conducted to identify methods to reduce complications associated with nasotracheal intubation. Using a PVC tube as opposed to the usual rubber tube [8], softening the tube by soaking it in hot water [9], applying surgical jelly [5], spraying vasoconstrictors such as epinephrine in the nasal cavity [10], or using tubes with smaller radii [5] were reported to be useful for reducing epistaxis. Furthermore, the red-rubber catheter technique [11], using an esophageal stethoscope [12], or using a nasogastric tube [13] have been reported to reduce epistaxis, but there are no certain methods that prevent epistaxis heretofore; thus, various conditions must be considered to choose the most effective method for reducing complications.

In addition, it is also important to select the nostril that is predicted to be less associated with complications. According to existing literature, intubation through the left nostril may increase the incidence of complications [14], and nasotracheal intubation through the right nostril may be more beneficial due to the Murphy eye and sharp linings on the right side of the tube [11]. However, many reports have noted that there are generally no differences in using either nostril [515]. One report has suggested that selecting the nostril with the high flow rate during expiration with one nostril blocked may be clinically useful [16]. Nostril selection is complex due to the site of operation and the position of the surgeon during surgery, but many reports have reported that intubation through the left nostril is more useful for orthognathic surgery [17].

A physical examination must precede nostril selection. Currently, the most widely used examination method to prevent complications is to block one nostril and breathe through the other nostril to identify nasal obstruction. In addition, a thorough history taking to identify and avoid the nostril with polyps or sinusitis may also be useful in preventing complications. There may be several causes of epistaxis, and intubation should proceed with caution when the patient has a systemic hemorrhagic disease [18]. These physical examinations and history taking are helpful for reducing complications, but many anesthesiologists tend to neglect physical exams prior to nasotracheal intubation due to a lack of supporting literature. In particular, the findings, as in the present study, that suggest that incidence of complications is largely similar for both nostrils may further promote such tendencies, but these findings may also be useful for selecting nostrils requested by the surgeon for patients with no particular intranasal disease. Furthermore, the fact that this study showed radiographs to be a useful tool to prevent complications is expected to contribute to nostril selection and encourage dental anesthesiologists to refer to panoramic or posteroanterior skull radiographs to verify the presence of intranasal diseases.

In conclusion, this study found no significant difference in the incidence of complications depending on the selection of the nostril for nasotracheal intubation (20.4% and 18.1% for left and right nostril, respectively). However, the incidence of complications significantly increased when the tube was inserted into the nostril found to have septal deviation through posteroanterior skull radiograph and/or panoramic radiograph analyses. Hence, this study concludes that analyzing panoramic or posteroanterior skull radiographs to determine the severity of nasal septal deviation prior to nasotracheal intubation to select the nostril with less septal deviation would be helpful for reducing the incidence of complications, such as epistaxis or intubation difficulty.