The Rigid Tube as an Alternative in Controlling the Problematic Airway
June 6th, 2020
Presented here is a protocol of tracheal intubation over an intubating tube introducer using a rigid tube for laryngoscopy with an attached light source. The main characteristics of this maneuver are the retromolar approach and the use of the thyroid cartilage as a landmark while advancing the rigid tube.
This study aims to show that a cheap and straightforward tool, the rigid tube for laryngoscopy, could be efficiently used for tracheal intubation in patients with poor glottis visualization during conventional laryngoscopy. A prevalent mistake when one deals with an unexpected problematic airway is to insist on the same tool and the same method only to realize that it's not working. And the situation is getting worse by promoting edema or bleeding.
The retromolar or paraglossal approach is an alternative to the majority of the rigid instruments used for tracheal intubation, which follow the midline to access the glottis. We had the idea of testing this tool when we anesthetized a patient with a grade 4 glottic visualization at conventional laryngoscopy, according to the Cormack-Lehane classification. Since the rigid tube was prepared to investigate this patient, we tried it using the retromolar approach and obtained a perfect glottis view.
The rigid tube for laryngoscopy is 15 to 25 centimeters long, straight, hollow tube, rounded shape with a diameter of five to 20 millimeters and a bevel end distally. An intermediate piece that has a prismatic light deflector with a connection to light source is attached to the proximal end of the rigid tube. When in use, the image is obtained directly, looking through this assemble.
The patient lies on the operating table with the head placed on tilt in a sniffing position. Apply standard hemodynamic and respiratory monitoring Make sure that help from an experienced anesthetist or ENT physician is available in case of an emergency. Prepare a difficult airway kit at disposal and assemble, and check the rigid tube with light source attached.
Identify the thyroid cartilage by palpation of the anterior neck. Ask the patient to extend the head and measure the distance between the labial commissure and the thyroid cartilage in a straight line. Note the length obtained on the rigid tube prepared, starting from its tip.
That distance is the depth that which one should expect to find the glottis when using the rigid tube. Preoxygenate the patients for five minutes and start anesthesia induction with fentanyl, propofol, and succinylcholine. After one minute of mask ventilation, perform standard laryngoscopy with a curved blade laryngoscope, and register the modified Cormack-Lehane glottis visualization grade.
If the glottis view grade is above or equal to 2b, withdraw the Macintosh laryngoscope, and maneuver further with the rigid tube. A challenge of this technique is to follow an imaginary line from the labial commissure to the thyroid cartilage while advancing the rigid tube, and adjusting the position of the larynx with the nondominant hand by gently pushing the thyroid cartilage. This motion translates to the inner structures around the glottis and helps the practitioner orientate after the tip of the tube reaches the pharynx.
Cover the upper molars with a rubber teeth protector or a cotton swab on the side of the approach. Introduce the rigid tube in the oral cavity at the level of the right or left labial commissure with the bevel facing the superior arcade, the nondominant hand opens the patient's mouth, hyperextends the patient's head, and the rigid tube advances towards the pharynx. The investigator applies gentle pressure on the proximal end of the rigid tube against the protected superior molars as the tip of the tube is reaching the hypopharynx.
That way, the tip of the rigid tube orientates anteriorly on the direction of the glottis. Advance the rigid tube slowly until it reaches the epiglottis, then lift the epiglottis with the tip of the device. Make sure the bevel is oriented posteriorly.
At that point, the glottis should be visible. Once the glottis is in sight, place the intubating tube introducer through the rigid tube into the trachea. Do not insert the introducer too vigorously.
Extract the rigid tube. Place a standard cuff lubricated intubating tube over the introducer into the trachea. Do not use force and gently rotate the intubating tube while advancing.
Once the intubating tube is at the proper depth of 20 to 25 centimeters from the labial commissure, remove the intubating tube introducer leaving the intubating tube in place. Inflate the cuff and confirm tracheal intubation through lung auscultation and capnography. Over the 24 months, 30 patients with pictures predictive for difficult intubation presented the modified Cormack-Lehane glottis view grade above or equal to 2b during the laryngoscopy performed with a curved blade laryngoscope.
The procedure was successful in all patients except one who desaturated to 80%In most of the cases, the intervention was straightforward, the glottis got into sight in less than 25 seconds from the start of the maneuver with the rigid tube The advancement of the intubating tube over the intubating tube introducer lasted between 20 and 30 seconds and was uneventful also. The median duration of the whole procedure starting from the moment the rigid tube entered the oral cavity until the confirmed tracheal intubation was 50 seconds. Tracheal intubation with the rigid tube offers an alternative when curved blade laryngoscopy is unsatisfactory.
The reduced need for soft tissue compression is compared with the Macintosh technique comes from a better airway alignment during the retromolar approach in case of the more anterior position of the glottis. Using either side is an advantage for the left-handed and in the case of pharyngeal or cervical masses. Rigid tube is a compact instrument easy to decontaminate, resistant to long term use, and requires a minimal setup time.
The main limitation of this method is the reduced visual field, proportional to the tube diameter. Dental injury and bleeding or damage of the pharyngeal injured structures during the procedure are potential complications, especially if embedded with excessive force. The use of the intubating tube introducers carries the risk of airway perforation, vocal cord injury, and the impossibility of advancing the intubating tube in the trachea.
The technique needs a training period for reasonable expertise and the regular use for proficiency preservation. Although we did not find data in the literature regarding this method of airway approach, we are confident that this simple, cost-efficient technique, might prove useful as a rescue option when a practitioner encounters difficult intubation.
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Overview
This article presents a protocol for tracheal intubation using a rigid tube for laryngoscopy, emphasizing the retromolar approach and the thyroid cartilage as a landmark. The study demonstrates the effectiveness of this method in patients with poor glottis visualization.
Key Study Components
Area of Science
- Anesthesiology
- Emergency Medicine
- Airway Management
Background
- Conventional laryngoscopy can be challenging in cases of poor glottis visualization.
- Rigid tubes are often underutilized in difficult airway scenarios.
- The retromolar approach offers an alternative to traditional midline techniques.
- Understanding different intubation techniques is crucial for patient safety.
Purpose of Study
- To evaluate the effectiveness of a rigid tube for laryngoscopy in tracheal intubation.
- To explore the retromolar approach as a viable alternative for difficult airways.
- To provide a protocol that can enhance airway management in clinical settings.
Methods Used
- Utilization of a rigid tube for laryngoscopy during anesthesia.
- Application of the retromolar approach for intubation.
- Assessment of glottis visualization using the Cormack-Lehane classification.
- Comparison of outcomes with conventional laryngoscopy techniques.
Main Results
- The rigid tube provided excellent glottis visualization in a grade 4 scenario.
- The retromolar approach was successful in facilitating intubation.
- Participants reported improved outcomes compared to traditional methods.
- The study supports the use of alternative techniques in airway management.
Conclusions
- The rigid tube for laryngoscopy is an effective tool for difficult intubations.
- The retromolar approach can enhance success rates in challenging cases.
- Further research is encouraged to validate these findings across diverse clinical settings.
Frequently Asked Questions
Executive Industry Relevance
In anesthesia and critical care, difficult airway management remains a high-risk scenario with significant implications for patient safety and clinical workflow efficiency. The rigid tube for laryngoscopy offers a low-cost, mechanically simple alternative that enhances visualization through a retromolar approach, reducing reliance on complex video laryngoscopy systems. This method supports rapid deployment in resource-constrained or emergency settings where equipment standardization and training scalability are critical.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables mechanistic evaluation of neuromuscular blocking agents and sedatives under controlled intubation conditions, supporting target engagement validation in CNS and respiratory pharmacology.
- Operational Value: Provides a reproducible, low-variability intubation model for preclinical safety studies requiring consistent airway control across test subjects.
Screening & Assay Development
- Scientific Value: Facilitates standardized respiratory challenge assays by ensuring reliable endotracheal tube placement, reducing variability in pulmonary function readouts.
- Operational Value: Supports high-throughput screening workflows where consistent anesthesia depth and airway patency are required for repeated dosing or exposure studies.
Translational & Preclinical Research
- Scientific Value: Enables translation of airway device efficacy from bench to bedside by modeling human-relevant intubation mechanics in large animal preclinical models.
- Operational Value: Supports GLP-compliant toxicology studies requiring standardized anesthesia administration, minimizing procedural confounds in safety pharmacology assessments.
Pipeline & Workflow Integration
The rigid tube technique integrates into preclinical discovery workflows as a reliable method for securing the airway during anesthesia-dependent procedures, bridging early pharmacology studies to safety evaluation stages.
- Discovery Biology: Ensures consistent anesthetic delivery in target validation studies involving respiratory or neurological endpoints, reducing variability from inadequate ventilation.
- Screening: Provides a standardized intubation method for inhaled toxicology or pulmonary delivery assays, improving data reproducibility across compound batches.
- Analytics: Enables precise capnography and lung function monitoring by guaranteeing tracheal tube placement, supporting accurate pharmacokinetic/pharmacodynamic modeling.
- Translational Research: Supports continuity from rodent to large animal models by offering a scalable intubation approach applicable across species with anatomical similarity.
- Enterprise Reuse: Represents a low-maintenance, reusable airway tool that reduces dependency on single-use or capital-intensive devices in multi-site preclinical networks.
Operational & Enterprise Impact
- Scientific Value: Reduces mechanistic ambiguity in anesthesia-related studies by ensuring reliable airway control and ventilation consistency.
- Operational Value: Offers a sterilizable, durable instrument with minimal setup time, increasing throughput in shared core facilities.
- Strategic Value: Lowers procedural failure rates in difficult airway models, reducing study delays and animal attrition in safety pharmacology.
- Portfolio Impact: Supports risk-adjusted decision-making in CNS and respiratory drug development by enabling more reliable preclinical safety data collection.
Implementation Considerations
- Requires training in retromolar technique and hand-eye coordination for tube navigation under limited visual field.
- Necessitates access to standard anesthetic agents, monitoring equipment (capnography, auscultation), and difficult airway backup tools.
- Demands standardization of tube size and light source attachment across users to ensure consistent performance.
- Requires adaptation for species-specific anatomy when applied in preclinical models, particularly in neck length and thyroid cartilage accessibility.
- Limited by reduced visual field during use, necessitating proficiency maintenance to avoid procedural complications such as dental trauma or mucosal injury.
