Tips for naso-tracheal intubation: a clinical practice review

Introduction

Endotracheal intubation is essential for oral and maxillofacial surgeries, as the nasal and oral airways often serve as the surgical field. Nasotracheal intubation is typically the preferred method for these procedures. However, despite its fundamental differences from oral intubation, the principles of nasotracheal intubation are seldom thoroughly explained, and associated complications are infrequently discussed. This concise review aims to clarify the specific principles of nasotracheal intubation, highlighting its unique aspects and potential challenges. We hope this clinical practice review serves as a valuable reference for anesthetists specializing in this field, enhancing their understanding and application of this critical technique.

Historical background and theoretical techniques for easier and safer nasotracheal intubation

Exploring safer methods to maintain an airway

At the dawn of general anesthesia, anesthetists recognized the critical importance of securing a patient’s airway. A significant number of anesthetized patients appeared to succumb to respiratory insufficiency. Before the invention of the laryngoscope, visualizing the larynx remained an elusive goal. Anesthetists sought practical methods to access the larynx, often relying on respiratory sounds as a guide for tubing placement. By inserting tubing through the nasal meatus, these sounds could direct the tube toward the larynx, using the audible airflow as a navigational aid. Securing an airway became a vital medical intervention, particularly for injured soldiers on the battlefield. Damage to the maxillofacial region often prevented anesthesia induction until the airway was secured, making blind nasal intubation a feasible solution in such cases (1,2).

An easier approach: nasotracheal intubation vs. oral intubation

Oral intubation has become the standard method for tracheal intubation during development of surgical anesthesia. Consequently, laryngoscopy techniques for oral intubation are widely regarded as the benchmark for airway management. However, the approach to nasotracheal intubation differs fundamentally from oral intubation—a distinction that often goes unnoticed among anesthetists (Figure 1). For oral intubation, the oral and tracheal axes must align with the visual axis, as the tube enters parallel to the line of sight (Figure 1B). Aligning these three axes requires positioning the neck unnaturally, a maneuver facilitated by laryngoscopy. In contrast, nasotracheal intubation does not require this awkward positioning; in fact, such a posture can complicate the procedure. Instead, the neck should remain in a more physiological position—neither flexed, extended, nor rotated—to avoid interfering with natural breathing. The tubing should follow the spontaneous airflow, tracing the theoretical pathway for nasotracheal intubation.

Figure 1 Difference of the laryngoscopy for oral and naso-tracheal intubation. (A) Nasotracheal intubation. The tubing enters the trachea in an upward direction, so the larynx does not need to be lifted to align the tubing axis with the tracheal axis. (B) Oral intubation. The tubing enters the trachea in a downward direction along the visual axis, requiring the larynx to be lifted to align the visual axis with the tracheal axis.

To ensure the tube follows the natural nasal airway, three key principles must be observed. First, the trachea should not be lifted as it is during oral intubation to fully visualize the vocal cords. When the vocal cords are entirely exposed, the laryngeal axis elevates and intersects with the axis of the tube entering from the posterior nares (Figure 1A). Second, the head should not be tilted into the “sniffing position”. This adjustment ensures a smooth transition from the nasal airway to the pharyngeal airway, allowing the tube to enter the trachea seamlessly. Third, the operating table should be elevated higher than it would be for oral intubation. By avoiding laryngeal elevation, a higher head position naturally discourages lifting the larynx (Figure 1A).

For nasotracheal intubation, video laryngoscopy is recommended. Unlike traditional laryngoscopy, video-assisted techniques do not require lifting the larynx to visualize the vocal cords, making them well-suited for this approach.

Specifications of commercially available preformed nasotracheal tubing

Straight endotracheal tubing, typically used for orotracheal intubation, can also be employed for nasotracheal intubation. In the context of respiratory management in the intensive care unit (ICU), straight tubing is often more practical than preformed tubing because it facilitates easier tracheal suctioning. However, during oral and maxillofacial surgery, a straight tubing protruding from the nostril can obstruct the surgeon’s access to the surgical field. To address this, preformed nasotracheal tubing—designed with a bend at the nostril outlet—is commercially available. The length of this bent segment is fixed, which may result in it being either too long or too short, depending on each product.

For safe nasotracheal intubation, the tubing tip must be positioned at an appropriate distance from the carina to prevent bronchial intubation, while the cuff should be placed at a sufficient distance from the vocal cords to avoid damage on the vocal cords. Preformed tubing is engineered to meet these requirements. Previous studies have demonstrated that the nasolaryngeal distance (NLD) (from the nares to the larynx) is primarily influenced by patient height. Several formulas have been proposed to predict the appropriate length for endotracheal tube (ETT) fixation based on height, with variations noted across Asian and Caucasian populations (3-5). These formulas estimate the ideal ETT length as follows:

• A proposed formula for the appropriate length of fixation [from Thailand (3)]: ETT length at the right external naris (cm) = 9 + (body height/10);
• A proposed formula for the appropriate length of fixation [from USA (4)]: ETT position at nares (cm) = 0.12 × height + 5;
• A proposed formula for the nasolaryngeal distance [from Germany (5)]: NLD (mm) = 13.2 + 1.1 × (body height in cm).

(The definitions of length follow the original expressions in these articles.)

These formulas demonstrate that the nasotracheal distance increases by approximately 10–12 mm for every 10 cm increase in height.

The proposed ideal fixation lengths for nasotracheal intubation based on patient height are presented in Table 1.

Correct positioning of the ETT within the trachea, between the carina and vocal cords, is critical. A study of over 300 patients (7) found that tracheal length correlates more strongly with sex than with nostril size, reporting average tracheal lengths of 11.9±1.4 cm for males and 10.9±1.2 cm for females. This approximately 1.0 cm difference likely reflects the average height difference of about 10 cm between sexes.

Commercially available preformed nasotracheal tubing varies in specifications. The average fixation length from the bent segment can be calculated using the aforementioned estimation formulas and data from prior research. The proper length of each preformed nasotracheal tube, along with recommended fixation lengths derived from averaged values, is provided in Tables 2-5 (6).

For pediatric patients, tracheal length increases with age and height. A previous study (4) measured the average nasotracheal distance for children of varying heights. Using these results and the estimated ideal fixation length formula, the optimal position of the tubing tip can be calculated. Although these values are averages and may vary between individuals, they serve as a useful reference to prevent bronchial intubation (Table 6).

Careful tips for nasotracheal intubation

Ulcer at the nasal ala

Several complications associated with nasotracheal intubation warrant attention. An ulcer at the nasal ala can persist and potentially leave a scar if not addressed prophylactically. During anesthesia, the tubing may be pulled upward, continuously pressing against the upper nasal ala. To prevent this, the tubing should be fixed downward at the nostril. Proper taping techniques can help mitigate upward pressure (see Figure 2).

Figure 2 Tips of fixation of the tubing to avoid ulcer at the nasal ala. (A) Wrap the tape around the tube in a direction away from the upper part of the nasal wing. (B) When wrapped from above the tube: it is less likely to put pressure on the upper part of the nasal wing. (C) When wrapped from below the tube: as long as it is away from the upper part of the nasal wing, pressure is less likely to be applied.

Damage to the pharyngeal wall

Nasotracheal tubing enters the pharynx via the nasal meatus. While it typically slides along the pharyngeal wall without issue, a sharp angle of entry can cause damage. Pharyngeal injury from nasotracheal tubing has been documented (8) and may lead to subcutaneous emphysema or mediastinal emphysema. Careful handling during tube insertion is essential to minimize this risk.

Nasal bleeding

Nasal bleeding after extubation can be a time-consuming complication requiring hemostasis following anesthesia. The Kiesselbach area—an anastomotic arterial plexus located in the anterior inferior quadrant of the nasal septum—is particularly susceptible to injury during tube insertion. Preventive measures include pharmacological vasoconstriction with agents such as naphazoline or epinephrine prior to intubation. Additionally, the tubing should be well-lubricated before insertion, and stiff materials can be softened by warming in advance. Gentle and precise handling during insertion into the nostril is also critical.

Conclusions

Nasotracheal intubation differs procedurally from oral intubation. A key tip for smooth intubation is maintaining the physiological position of the nasal airway, avoiding tracheal elevation to facilitate the process. Preformed nasotracheal tubing is particularly well-suited for oral and maxillofacial surgery. This review has outlined the specifications of commercially available tubing and emphasized the need for careful consideration to prevent associated complications.

Acknowledgments

None.

Footnote

Peer Review File: Available at https://joma.amegroups.com/article/view/10.21037/joma-2025-18/prf

Funding: None.

Conflicts of Interest: The author has completed the ICMJE uniform disclosure form (available at https://joma.amegroups.com/article/view/10.21037/joma-2025-18/coif). T.I. serves as an unpaid editorial board member of Journal of Oral and Maxillofacial Anesthesia from February 2024 to January 2026. The author has no other conflicts of interest to declare.

Ethical Statement: The author is accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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