Mechanical strain to maxillary incisors during direct laryngoscopy

Quantifying Intubation Forces on Incisors and Tongue Base Across Exposure Difficulty and Experience in a Simulator

OBJECTIVE

Laryngoscopy simulators quantifying forces on critical structures in progressively challenging airways and operator expertise are lacking. We aimed to quantify laryngoscopy forces across expertise and exposure difficulty.

STUDY DESIGN

Prospective observational study Setting: Tertiary care medical center Methods: Force gauges were affixed to a difficult airway mannequin to quantify teeth and tongue forces across increasingly challenging airway exposure. Medical students (n=10), residents (n=11), and otolaryngology staff (n=10) performed direct laryngoscopy using a Miller size 3 laryngoscope with 1) normal neck/jaw mobility, 2) restricted neck extension, 3) restricted jaw opening, and 4) restricted neck/jaw mobility. Incisor and tongue pounds of force (lbf) were continuously measured.

RESULTS

As the difficulty setting increased, forces exerted by the students, residents, and staff on the incisors and tongue base increased (p=0.01). Between normal and maximally restricted settings, force delivered to the incisors increased by 6.95 lbf (standard error (SE) 1.29), 5.93 lbf (SE 0.98), and 5.94 lbf (SE 0.70) for the students, residents, and staff, respectively. At the tongue base, force increased by 0.37 lbf (SE 0.18), 0.46 lbf (SE 0.14), and 0.73 lbf (SE 0.15) for the students, residents, and staff, respectively. Esophageal intubations occurred in 50% of the students, 23% of the residents, and 45% of the otolaryngology staff at maximal difficulty, with none at the easiest setting (p=0.33). Compared to the residents, the staff applied significantly increased pressure on the tongue base during laryngoscopy (p=0.02).

CONCLUSION

Forces exerted on the incisors and tongue base varied across exposure difficulty and expertise levels, suggesting that they may be useful markers for training and competence assessment.

Effect of table inclination angle on videolaryngoscopy and direct laryngoscopy: Operator's muscle activation and laryngeal exposure analysis

BACKGROUND

Optimal vocal cord visualization depends on the patient's anatomical factors, characteristics of the laryngoscope, and the operator's muscle action. This study evaluated the effect of table inclination and three different laryngoscopic methods on procedural variables. The primary aim of this study is to compare differences in laryngoscopic view among clinicians based on the instrument used and table orientation. The secondary aim is to determine differences in upper extremity muscle activity based on laryngoscope use and table inclination.

METHODS

Fifty-five anesthesia providers with different experience levels performed intubations on a manikin using three angles of table inclination and three laryngoscopy methods. Time to intubation, use of optimization maneuvers, glottic view, operator's comfort level, and upper extremity muscle activation measured by surface electromyography were evaluated.

RESULTS

Table inclination of 15° and 30° significantly reduced intubation time and the need for optimization maneuvers. Fifteen degrees inclination gave the highest comfort level. Anterior deltoid muscle intensity was decreased when table inclination at 15° and 30° was compared to a flat position.

CONCLUSION

Table inclination of 15° reduces intubation time and the need to use optimization maneuvers and is associated with higher operator's comfort levels than 0° and 30° inclination in a simulated scenario using a manikin. Different upper extremity muscle groups are activated during laryngoscopy, with the anterior deltoid muscle exhibiting significantly higher activation levels with direct laryngoscopy at zero-degree table inclination.

Comparison of Dental Injury Rates in Perioperative Intubation and Suspension Laryngoscopy for Otolaryngology Procedures

Objective

Direct laryngoscopy is an essential skill during perioperative intubation and otolaryngology procedures. Dental injury is a common complication of direct laryngoscopy. However, the technique and tools used by anesthesiologists, nurse anesthetists, and others during perioperative intubation and by ear, nose, and throat surgeons for their procedures are different. The purpose of this review is to explore the literature for all studies detailing rates of dental injury in each of these settings and to compare them to see if the approaches have a significant difference in rate of dental injury.

Data Sources

PubMed.

Review Methods

A comprehensive search of PubMed was performed through February 2021 with search terms “dental” and “intubation” or “laryngoscopy.” PRISMA guidelines were followed. Studies documenting rates of dental injuries during intubation or during laryngologic procedures were included, and the 2 groups were compared.

Results

Twenty-three studies met inclusion criteria: 17 in the perioperative intubation group and 6 in the suspension laryngoscopy group. There was an increased incidence of dental injury in the perioperative intubation group (4.86%) as compared with the suspension laryngoscopy group (1.70%).

Conclusions

The difference in dental injury rate between the groups could be due to the differences in direct laryngoscopy technique or tools used, the presence vs absence of a dental guard, or a combination of these factors. More studies need to be performed to develop definitive and specific conclusions to recommend changes that prevent dental injury.

Comparison of the new flexible tip bougie catheter and standard bougie stylet for tracheal intubation by anesthesiologists in different difficult airway scenarios: a randomized crossover trial

Background

Incidence of difficult endotracheal intubation ranges between 3 and 10%. Bougies have been recommended as an airway adjunct for difficult intubation, but reported success rates are variable. A new generation flexible tip bougie appears promising but was not investigated so far. We therefore compared the new flexible tip with a standard bougie in simulated normal and difficult airway scenarios, and used by experienced anesthesiologists.

Methods

We conducted a observational, randomized, cross-over simulation study. Following standardized training, experienced anesthesiologists performed endotracheal intubation using a Macintosh blade and one of the bougies in six different airway scenarios in a randomized sequence: normal airway, tongue edema, pharyngeal obstruction, manual cervical inline stabilization, cervical collar stabilization, cervical collar stabilization and pharyngeal obstruction. Overall success rate with a maximum of 3 intubation attempts was the primary endpoint. Secondary endpoints included number of intubation attempts, time to intubation and dental compression.

Results

Thirty-two anesthesiologist participated in this study between January 2019 and May 2019. Overall success rate was similar for the flexible tip bougie and the standard bougie. The flexible tip bougie tended to need less intubation attempts in more difficult airway scenarios. Time to intubation was less if using the flexible tip bougie compared to the standard bougie. Reduced severity of dental compression was noted for the flexible tip bougie in difficult airway scenarios except cervical collar stabilization.

Conclusion

In this simulation study of normal and difficult airways scenarios, overall success rate was similar for the flexible tip and standard bougie. Especially in more difficult airway scenarios, less intubation attempts, and less optimization maneuvers were needed if using the flexible tip bougie.

Trial registration

clinicaltrials.gov Identifier: NCT03733158. 7th November 2018.