The Flexible Rhino-Laryngoscope for Awake Nasotracheal Intubation

Presented here is a protocol for awake nasotracheal intubation using a flexible rhino-laryngoscope with a 300 mm working length. As this tool is minimally invasive and easy to manipulate, awake intubation performed with a flexible rhino-laryngoscope is well-tolerated, fast, and safe for patients with difficult airways.

Difficulties or failures in securing the airway still occur and can lead to permanent disabilities and mortality. Patients with head and neck pathologies obstructing airway access are at risk of airway management failure once they lose spontaneous respiration. Awake flexible scope intubation is considered the gold standard for controlling the airway in such patients. Following a feasibility trial involving 25 patients with challenging airways, this article presents a step-by-step protocol for awake nasotracheal intubation using a flexible video rhino-laryngoscope, which is significantly shorter than conventional intubating flexible scopes. The flexible video laryngoscope only exceeds the intubating tube length by a few centimeters, allowing the tube to closely follow the flexible scope during the procedure. Once the scope reaches the pharynx, it can be easily manipulated with one hand, enabling the operator to focus on the safe advancement of the scope-intubating tube assembly through the glottis. Based on previous results and experience gained, this article highlights the potential benefits of the technique: the opportunity for a minimally invasive "quick look" preoperatively to establish a final management plan, a more convenient and safer tool for navigating distorted anatomy with a lower chance of intubating tube impingement and airway injury, and a fast and smooth procedure resulting in improved patient satisfaction.

Airway management has developed substantially over the last 20 years, but difficulties or failures in securing the airway still occur and can lead to permanent disabilities and mortality¹. Patients with known or unknown pathologies of the base of the tongue, hypopharynx, glottic aperture, or trismus pose a risk of difficult or impossible facemask ventilation, supraglottic device placement, and tracheal intubation after the induction of general anesthesia^1,2,3.

Standard preoperative airway examinations often fail to reveal these lesions due to discrete accompanying clinical signs and symptoms^2,3. Awake flexible scope intubation is considered the gold standard in securing the airway in such cases because it allows for spontaneous respiration, preserves airway reflexes, and mitigates the risks of losing the airway or bronchopulmonary aspiration⁴. Despite its benefits, awake intubation remains an underused technique, even when indicated (around 1% of all intubations), due to reservations regarding its use related to lack of practice or the pressure of a busy operating theatre^2,4. With the development of airway control devices, awake intubation now includes procedures employing flexible scopes, rigid or semirigid optical stylets, and video laryngoscopes⁵.

Nasopharyngeal flexible endoscopy, sometimes referred to as flexible nasopharyngoscopy, flexible nasolaryngoscopy, transnasal flexible laryngoscopy, or flexible fiberoptic nasopharyngolaryngoscopy, is a medical technique that aids the practitioner in examining the nasal passages, nasopharynx, oropharynx, hypopharynx, and larynx⁶. It is a routine instrument in ENT (ear, nose, and throat) practice and has the advantage of being minimally invasive and easy to handle⁷. Its use has expanded across different medical specialties, including maxillofacial surgery, anesthesiology, speech and language therapy, and neurology. In an office or hospital setting, flexible rhinolaryngoscopy provides a valuable assessment of the airway and alerts healthcare providers to the presence of pathological pharyngolaryngeal structures that may impact airway management.

The flexible fiberoptic endoscope used for the adult population has a rigid part designed to be used with one hand and a flexible fiber optic cable. The effective length of the scope is between 300 and 350 mm with a flexibility of 130˚ to 160˚. The flexible tip has a length of 20 mm with a visualization angle of 80˚ to 90˚ in newer models. The depth of field can be easily adjusted with the handpiece roller, ranging from 3 to 60 mm. The diameter of the insertion tube may range from 3 mm to 4.5 mm, and certain models are equipped with a working or suction channel (Figure 1). Technology has advanced further, and the device has evolved from fiberoptic to new chip-on-the-tip flexible digital scopes, ensuring high-resolution imaging^6,7.

Traditionally, practitioners perform awake flexible scope intubation using a fiberoptic bronchoscope with a 600 mm working length⁵. This protocol, based on a previous prospective study⁸, aims to describe in detail a technique for awake nasotracheal intubation using a 300 mm flexible rhino-laryngoscope.

The study, approved by the "Iuliu Hațieganu" University of Medicine and Pharmacy Ethics Committee (no. 100/12.02.2018) and registered under ClinicalTrials.gov identifier NCT03546088, enrolled adult patients with ASA physical status I-IV⁸. These individuals had distorted airway anatomy due to laryngopharyngeal pathology and were scheduled for surgery under general anesthesia. Informed consent was obtained from all participants. The inclusion criteria were a Simplified Airway Risk Index (SARI) score of 4 or higher and distorted airways from laryngopharyngeal masses, prior radiotherapy, or inflammation, with awake intubation deemed the safest method following ENT and pre-anesthetic evaluations⁸. Exclusion criteria included obstructed nasal passages, bleeding disorders, allergy to local anesthetics, lack of understanding or cooperation, or refusal of the procedure, in which case an alternative airway management approach was suggested⁸. The details of the reagents and equipment used in the study are listed in the Table of Materials.

1. Preoperative assessment

1. Consider awake flexible scope intubation in every patient with potentially complex airway management and in patients who may benefit from maintaining spontaneous ventilation and intrinsic airway tone until the placement of an endotracheal tube⁴.
2. Perform a careful pre-anesthetic airway assessment, including an ENT exam, imagistic examinations, and bedside inspection. Obtain a complete patient history (including previous surgical interventions, airway history, radiotherapy in the cervical area, snoring, or obstructive sleep apnea) and execute a careful clinical exam.
3. Calculate the SARI score (comprising of mouth opening, thyromental distance, Mallampati score, neck mobility, ability to prognath, weight, and history of difficult intubation) and consider the patient at risk of difficult intubation if the score ≥4 (maximum 12 points)⁹.
4. Conclude the preoperative airway evaluation with trans-nasal flexible nasopharyngolaryngoscopic examination whenever there is a suspicion of airway pathology¹⁰. Position the patient sitting upright. Apply xylometazoline 0.1% and lidocaine spray 10% in both nostrils.
5. Advance the flexible rhino-laryngoscope through one of the nares beneath the inferior turbinate until it reaches the nasopharynx. Pause when the tongue base or the epiglottis are visible, and inspect the hypopharynx and the glottis. Urge the patient to sniff, protrude the tongue, vocalize, or breathe deeply to improve visualization^6,10 (Supplementary Video 1).
   NOTE: When performing the procedure in an emergency, such as extensive edema or large friable tumoral masses, use added care, as even a minor injury could lead to complete airway obstruction.
6. Utilise point of care ultrasonography (POCUS) to evaluate airway difficulty and review relevant imaging (such as computer tomography or magnetic resonance imaging scans) to anticipate the optimal path for the endotracheal tube (ETT) and determine the appropriate tube size. Identify and mark the cricothyroid membrane and the trachea in case emergency front-of-the-neck access is needed¹¹.
7. Considering the examinations provided, assess whether awake fiberoptic intubation is the best option for airway management, considering that the loss of spontaneous breathing or other airway techniques may pose a significant risk. Begin the preparations for awake intubation.
8. Explain the procedure to the patient and obtain informed consent. Emphasize the risks of intubation after anesthesia induction in problematic airway patients and the safety benefits of an awake technique. Inform the patient to expect a mild level of discomfort but reassure them that topical anesthesia and light sedation will be provided.

2. Equipment preparation and checklist

1. Keep in mind that successful awake intubation requires careful planning. Before starting the procedure, ensure all necessary personnel and infrastructure are available.
2. Follow the checklist for awake intubation recommended by The Difficult Airway Society (DAS) to improve performance and ensure that essential steps are not missed⁵.
3. Safeguard that at least one anesthetist, separate from the airway operator, and an anesthesia nurse are present to assist during the procedure. Additionally, have an ENT team on standby for an emergency tracheostomy in the event of obstructive airway pathology.
4. Ensure the patient's physiologic monitors are immediately visible when manipulating the airway. Check that the supplemental oxygen delivery device and suction are working.
5. Ensure the anesthesia machine or ventilator is readily accessible and operational. Prepare the difficult airway kit, a video laryngoscope, and several alternative airway devices, including different-sized laryngeal mask airways and ventilation masks, a front-of-the-neck access kit, and different sizes and types of ETT (endotracheal tubes).
6. Check all the airway management tools that are part of the management plan and ensure they are at hand. Prepare, dilute, and label all the medication as needed.

3. Patient preparation

1. Premedicate the patient with 0.5-1 mg of midazolam intravenously (IV) and glycopyrrolate 0.2 mg IV or 0.4 mg atropine IV if glycopyrrolate is not available. Use a face mask with a nebulizer to nebulize 10 mL of lidocaine 2%-4% for 10 min at a flow rate of 3-8 L/min⁸. In a patient with a high risk of gastric content aspiration, administer prophylaxis to increase gastric pH and reduce gastric volume.
   CAUTION: Do not use atropine in patients prone to tachyarrhythmia or with a high ventricular pace. In elderly, frail patients and patients with severe airway compromise due to obstructive pathology, omit sedation.
2. Administer 100-200 mg of hydrocortisone intravenously if tissue edema leading to airway compromise is of concern⁸. Add 500 µg of epinephrine to the nebulized lidocaine solution in patients with severe obstruction to reduce edema.
3. Transfer the patient to the operating theater and place them on the operating table in a sitting or semi-recumbent position. Provide standard ASA monitoring: pulse oximetry, respiratory rate, non-invasive blood pressure (NIBP), ECG, end-tidal CO₂, and inspired oxygen concentration.
4. Administer lidocaine 10% and xylometazoline 0.1% nasal spray and place a nasal cannula for supplementary oxygen delivery.
5. Evaluate the airway using the same tool prepared for awake intubation, a 300-350 mm working length flexible video rhino-laryngoscope with a diameter of 3-4 mm, identifying the most suitable nostril for passing the ETT⁸.
   1. Check for septal deviation, bony spurs, and turbinate hypertrophy. Inspect the pharynx and the peri-glottic space (base of the tongue, vallecula, epiglottis, pyriform fossa), vocal cords, and sub-glottic region to the mid-trachea.
   2. Determine the optimal path for the ETT based on the distortion of airway anatomy by tumors or inflammation, airway compression, or deviation from the midline.
6. Estimate the appropriate ETT size (usually between 5.5-6.5 mm) based on the minimal cross-section area throughout the nasal passage, supraglottic area, and glottis until mid-tracheal level. Use ETT with softer tips to reduce the chances of impingement and injury while advancing along the airway (such as soft reinforced tubes or Parker flex-tip). Have smaller diameter ETT available in case there is a nasal or glottic blockage.
7. Decide a final airway management plan based on the fiberoptic evaluation. Consider alternative airway strategies in patients with significant airway narrowing or massive edema, including surgical front-of-neck access under regional anesthesia.
8. For patients undergoing awake intubation, administer midazolam 0.5-1 mg IV and fentanyl 50-100 µg IV, titrating doses over 5 min intervals. Aim for an Observer's Assessment of Alertness/Sedation Scale (OAA/S) of 4-5 (oriented but cooperative and calm). Omit sedation or use carefully adjusted doses for frail patients or where airway collapse, obstruction, or inadequate ventilation is of concern⁸.
   NOTE: Sedative medication should be administered with high precaution by the assisting anesthetist, who watches the patient carefully. Sedation should not substitute airway topicalization.
9. Begin by administering 2% lidocaine for gargling. Then, using the working channel of the scope or a curved oropharyngeal catheter under fiberoptic guidance, in case the scope does not have a working channel, administer additional lidocaine topically, dripping over the glottis and the vocal cords. Ask the patient to inspire and vocalize during this step⁸.
10. Consider the anesthesia level to be adequate when administering more lidocaine in the glottis does not elicit a cough response anymore. Insert cotton gauze soaked with a 4% lidocaine solution with ephedrine 5% along the chosen nostril and leave it in place for 2 min⁸.
    CAUTION: Do not exceed a total of 9 mg/kg of lidocaine (both nebulized and topical).

4. Intervention

1. After 5-7 min from sedation and topical anesthesia, start the maneuver with the flexible rhino-laryngoscope armed with an intubating tube. Use a reinforced, cuffed ETT with an internal diameter of 5.5-6.5 mm and lubricate it with 2% lidocaine gel.
2. Place the fiberscope inside the ETT, ensuring that the proximal end of the tube covers the transitional part of the fiberscope handle. This will help stabilize the setup and allow for smooth advancement of both the fiberscope and ETT simultaneously⁸ (Figure 1).
3. Ensure that the ETT does not obstruct the flexible distal tip of the fiberscope. If using a 6.5 mm ETT (320 mm long) with a 300 mm working length flexible scope, remove the connecting piece to ensure the tip of the fiberscope has unrestricted movement.
   NOTE: There is no need to remove the connecting piece when using a flexible rhino-laryngoscope whose articulate head exceeds the tip of the ETT.
4. Introduce the fiberscope-ETT ensemble in the selected nostril. Orient the bevel of the ETT laterally during the nasal passage, then slowly advance the fiberscope and ETT following the nasal floor and the septum as close as possible.
5. Rotate the tube with small movements if an obstacle is encountered during the nasal passage. Aspirate secretions as needed when the scope reaches the pharynx, stop the advancement, and search for the structures of interest: epiglottis, arytenoids, or vocal cords. Maintain verbal contact with the patient during the procedure.
6. If the glottis cannot be visualized entirely or partially due to tumors, inflammation, or extrinsic compression, reposition the patient's head by left-to-right or flexion-extension movements or urge the patient to protrude the tongue for better glottic exposure. Manipulate the fiberscope with the dominant hand while adjusting the patient's head position with the non-dominant hand⁸.
   NOTE: In case of large tumors of the anterior airway, it may be useful to have an assistant holding the tongue protruded during the intervention for better glottic exposure.
7. If the ETT and the glottis form too sharp of an angle while advancing or if an obstacle is impeding the passage of the tube, withdraw the ETT a few centimeters and rotate it 90° counterclockwise. Alternatively, reposition the patient's head in the same manner as for poor glottic visualization⁸.
8. To minimize discomfort, do not withdraw the ETT above the nasopharynx when attempting to reposition unless major complications occur or the patient requests so. If there is an obstruction at the level of the glottis, instruct the patient to breathe deeply while the fiberscope- ETT assembly passes the glottic aperture.
9. Advance the tube to the mid-tracheal level. Ask the patient to take deep breaths while the fiberscope-ETT assembly advances through the tracheal lumen.
10. Confirm proper tube placement with the tip 2-4 cm above the carina by fiberoptic visualization and remove the fiberscope.
11. Connect the patient to the ventilator to ensure the capnography waveform is adequate and spontaneous movement of the ventilation bag is present. If using a 6.5 mm tube, reattach the connecting piece before connecting to the ventilator. Secure the ETT in position with tape and use a flexible extension corrugated tube (catheter mount) to connect the ETT to the breathing circuit.

5. General anesthesia and extubation

1. Induce anesthesia after securing the airway. Use fentanyl 2-3 µg/kg, propofol 2-3 mg/kg, and atracurium 0.5 mg/kg, adapting induction medication and doses to individual patients based on hemodynamic response and comorbidities.
2. Monitor anesthesia depth, ventilation, capnography, and hemodynamic parameters. Use either a volatile-based technique or total intravenous anesthesia (TIVA) for maintenance⁸.
3. Evaluate the risk for post-extubation airway compromise at the end of the procedure. Perform a cuff leak test⁸. Deflate the cuff of the ETT and ventilate the patients. Significant airway edema is likely if no audible air leak is present during expiration.
4. If the risk for post-extubation airway compromise is low, ensure the patient is fully awake and responsive and extubate the trachea in the operating theatre, then monitor them closely for signs of respiratory distress or airway obstruction. Have equipment and staff for emergency reintubation immediately available.
5. Ask the ENT surgeon to perform an airway evaluation before deciding the best course for extubation and consider ultrasonography for airway assessment. If significant edema or bleeding has occurred and the patient is at risk following extubation, transfer the patient to the intensive care unit (ICU). Keep the patient intubated and sedated for 24-48 h.
6. Consider cortisone IV to reduce edema and reassess the patient by repeating the cuff leak test, ultrasound, and ENT exam. When extubation seems possible, have all the equipment and drugs necessary for emergency reintubation or front-of-the-neck access available. Ideally, perform the procedure in the operating room as the ergonomics are better.
7. Aspirate the secretions and have a skilled anesthetist and ENT surgeon on standby. Consider placing an airway exchange catheter before removal of the ETT.

This article aims to describe in detail a technique for awake nasotracheal intubation using a 300 mm flexible rhino-laryngoscope. In the first study, 25 out of 32 consecutive patients, aged between 34 years and 82 years, were considered suitable for awake tracheal intubation and included in the trial (Table 1)⁸. Each patient's trachea was successfully intubated using a flexible rhino-laryngoscope. The average ± standard deviation duration from the insertion of the intubating tube through one nostril to the confirmation of endotracheal intubation, indicated by free bag movement and capnography, was 76 ± 36 s (Figure 2)⁸. The pathology of the study patients was of a tumoral nature (Figure 3)⁸.

The patients tolerated the procedure without significant incidents and declared mild to no discomfort while filling in the 24 h post-procedural questionnaire⁸. We did not encounter any significant complications. The patients showed no significant variations in heart rate, arterial pressure, or oxygen saturation⁸.

Figure 1: The flexible rhino-laryngoscope armed with a 5.5 mm diameter reinforced intubating tube (A), the flexible rhino-laryngoscope control body (B), and a comprehensive image (C). Please click here to view a larger version of this figure.

Figure 2: Intubation time with flexible rhino-laryngoscope. The extreme values are shown at the bottom and top of the chart, while the median value and interquartile range are highlighted in blue¹². Please click here to view a larger version of this figure.

Figure 3: Representative challenging cases. (A) Glottis tumor. * - large tumor obstructing the glottic aperture, x - indicates arytenoid cartilages. (B) Laryngeal tumor associated with ankylosing spondylitis. # - epiglottis, * - laryngeal tumor. (C) Epiglottic cyst. # - supraglottic cystic tumor, x - glottic aperture, * - arytenoid cartilage. (D) Base of tongue tumor. * - base of tongue tumor with extension in the vallecula, x - epiglottis, # - arytenoids. This figure is adapted from Marchis et al.⁸. Please click here to view a larger version of this figure.

Table 1: Patients' characteristics. Abbreviations: ASA - American Society of Anesthesiologists; SD - standard deviation; SARI - Simplified Airway Risk Index. This table is adapted from Marchis et al.⁸.

Supplementary Video 1: Transnasal fiberoptic pharyngolaryngoscopy of a patient with a tumor at the base of the tongue. Please click here to download this File.

There are several reasons why awake fiberoptic intubation is a relatively uncommon practice: it seems challenging to learn, the skill requires regular training to maintain proficiency, or a previous bad experience with this technique combined with the reluctance of an awake patient about the procedure^13,14.

When using a 600 mm fiberscope, the practitioners concentrate on how to hold the fiberscope in position, which may dilute their focus on advancing and orientating the scope to the desired target⁸. Other troubleshooting experiences when using a flexible bronchoscope for awake nasotracheal intubation include the difficulty of navigating the nasal passage once the fiberscope is already in the trachea and the risk of impingement, airway trauma or esophageal sliding during the "railroading" of the tube over the scope - a blind maneuver when using a 600 mm long flexible scope intubation¹⁵.

Since the flexible rhino-laryngoscope only extends a few centimeters beyond the ETT, there is no need to railroad the fiberscope. Once the fiberscope-tube assembly reaches the trachea, the practitioner extracts the scope after confirming the ETT position⁸. The sitting or semi-recumbent positions are recommended for awake fiberoptic intubation, offering both the practitioner and the patient more safety and comfort. In cases of epiglottic tumors or large neck masses, these positions also protect an already compromised respiratory space and guard against gastric content regurgitation¹⁶.

Contemporary recommendations stress the significance of preoperative endoscopic assessment of the airway to ensure a safe airway management strategy⁴. Transnasal flexible endoscopy serves as a valuable diagnostic tool for patients experiencing hoarseness, stridor, or suspected pharyngo-laryngeal cancer⁶. The thin and easily manageable nature of the flexible rhino-laryngoscope, owing to its length, results in patients reporting only minor discomfort, with a minimal risk of bleeding or injury⁶.

Many of these patients will eventually need general anesthesia; therefore, the attending anesthetist will benefit from the images stored during the endoscopic exam^7,17. A flexible rhino-laryngoscope can provide information about the patency of the nasal cavity and the risks associated with airway management related to the revealed pathology, guiding the steps for a successful procedure¹⁸. In this study, pre-intubation nasendoscopy was provided on all patients using the same 300 mm fiberscope to create a tailored airway management plan based on the patient's specific anatomical challenges⁸. This approach is time-effective and is performed on the operating table, under topical anesthesia, immediately before airway management. Pre-intubation nasendoscopy can help reduce unnecessary discomfort in patients where intubation following induction of general anesthesia is deemed safe and can also inform the decision to perform a surgical tracheostomy under regional anesthesia when there is a significant airway narrowing¹⁸.

The device proved to be efficient in cases of large supraglottic tumors where it is crucial to advance very gently and fit into a narrow space without causing bleeding or swelling of the tumoral tissue⁸. Therefore, the maneuver was straightforward in most cases, except for a patient with a large hypopharyngeal Ewing Sarcoma, where the successful maneuver lasted more than 3 minutes⁸. The literature on the matter is sparse, but there are signs of increased interest. In an article published in 2021, Tsunoda et al. described the same method for intubating four patients with epiglottitis due to pharyngeal and deep neck abscesses¹⁹.

Once the flexible rhino-laryngoscope reaches the pharynx, it is easy to manipulate with one hand. This leaves the non-dominant hand available for positioning the patient's head for better alignment between the scope and the glottis, focusing on proper anatomical landmark identification^6,8. The tube closely follows the tip of the fiberscope along the nasal cavity to the pharynx and glottis, providing the operator with the capacity to anticipate the moment when the ETT could impinge on arytenoids or peri glottic masses and apply the necessary measures: ETT rotation, deep breaths, tongue protrusion, or head movements⁸. These actions may partially overcome a larger gap between the diameters of the rhino-laryngoscope and the tube, reducing the chances that arytenoids or pathological structures block the ETT.

Minimizing the gap between the fiberscope and the internal diameter of the ETT can lead to a higher rate of success and a lower risk of ETT impingement¹⁵. A 300 mm fiberscope with a 3-3.5 mm diameter is appropriate when opting for a smaller diameter ETT (5-6 mm) in patients with limited airspace due to tumor invasion. However, a flexible bronchoscope or video rhino-laryngoscope with a more significant working length and diameter might still be the preferred choice when using a larger ETT.

Adequate topicalization is essential for patient's comfort and cooperation. Providing local anesthesia in multiple steps and using different administration methods provides the best results⁵. Sedation should be carefully titrated in high-risk patients, as relatively small doses of medication can lead to upper airway obstruction¹⁶. This protocol results from a single-center study with a limited number of participants, and the results rely on the personal experience and perception of a limited number of investigators. Amnesia associated with sedation or general anesthesia could have influenced patients' satisfaction levels.

While awake video laryngoscopy has gained popularity over awake fiberoptic techniques in recent years, awake flexible scope intubation undoubtedly still holds an essential role in anesthesia practice and may be the only option in patients with limited mouth opening and anterior airway pathology²⁰. This method may provide a safe, simple, cost-effective alternative to the conventional fiberoptic bronchoscope. It may also result in a shorter procedure duration, increased patient comfort, and a shallower learning curve. The flexible rhino-laryngoscope could be a valuable addition to the airway toolkit of anesthesia providers, proving useful for airway assessment and control when an airway pathology is involved.

The authors have nothing to disclose.

The Brazilian Journal of Anesthesiology granted permission to reuse Table 1 and Figure 3.