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.
