Videolaryngoscopy constitutes one of the significant advances in airway management over the last 20 years. Placing a chip at the end of the laryngoscope obviates the need to establish a line of sight path from the mouth to larynx, facilitates vocal cord visualization, shortens learning curves and makes endotracheal intubation easier at minimal levels of experience. The modality may make it rational to use ancillary providers such as respiratory therapists, medics or non-anesthetist physicians for airway management in remote locations or after hours, situations where more highly trained individuals are often unavailable. Indeed, the national VA Anesthesiology Service has prepared a directive with the goal of training such personnel to provide out-of-operating room airway management. Videolaryngoscopy is part of that plan. Videolaryngoscopy does not guarantee successful intubation, however. Due to the anatomic characteristics of some patients, even experienced anesthetists have difficulty passing the endotracheal tube through vocal cords that are in plain view with a videolaryngoscope. The cause is misalignment with the vocal cords: videolaryngoscopy does not create a straight line path and the tube must conform to a sharp angle that takes it to the larynx but aimed in the wrong direction. Maneuvers exist to overcome the difficulty, but an inexperienced operator would be unlikely to find the appropriate techniques in an emergency setting. Our goal is to develop simulation-based training methods to improve the safety of out-of-OR airway management in the VA system.
The project objectives were to: (1) produce partial task trainers for teaching difficult videolaryngoscopy skills; (2) develop a training program around these task trainers; and (3) test whether the program enables successful intubation by novice providers in situations where an untrained operator would fail.
Objective 1 required design work. Partial task trainers were designed that mimic difficult videolaryngoscopy in patients. The prototype trainer was an adjustable airway manikin, developed by the investigator and collaborators, that allows variation in several features affecting laryngoscopy difficulty. Configurations that appear to cause videolaryngoscopy difficulty were tested by experienced anesthesiologists. Videolaryngoscopy difficulty will be assessed based on the time required to accomplish intubation and with a survey of the anesthesiologist panel about the source of difficulty.
Objective 2 was accomplished with a prospective education study in which subjects acted as their own control before and after training on manikins developed in Objective 1. Pre- and post-training tests were used to provide evidence for effectiveness. A retention test 1-month after training was performed to determine whether skill persisted for at least that period of time.
Five manikin configurations were identified that caused difficulty with videolaryngoscopy. Three configurations were selected by a panel of consulting anesthesiologists as reliable models of difficulty. The anesthesiologists took over 60 seconds to intubate the three difficult configurations, compared to 20-25 seconds for non-difficult configurations. The difficult configurations were reported to cause problems with positioning the endotracheal tube at the glottis inlet and with passing the tube into the trachea.
Through a process of discovery learning, the anesthesiologist investigators were able to reduce the time taken for intubations to less than 30 seconds. A qualitative analysis of how their technique changed with time as they practiced revealed five factors that appeared important for intubation under difficult circumstances: (1) The Glidescope blade was inserted on the left side of the mouth, rather than the midline, creating more space to maneuver the endotracheal tube. (2) The blade was positioned just proximal to the vallecula and lifting was minimized. Pressure on the larynx during intubation could accentuate the angle between the trachea and the line of approach of tube to vocal cords. (3) The endotracheal tube was inserted with tip pointing right to left toward the vocal cords, minimizing the amount of rotation needed to line the tube on the path to the cords. (4) The endotracheal tube was held toward its proximal end. This allowed big movements of the distal end near the larynx, necessary to rock the tip of the tube into position to pass through the cords. (5) The stylet was withdrawn once the tube was at the glottic inlet to provide the tube with more flexibility and allow it to pass into the trachea without hanging up on the tracheal rings.
For objective 2, 22 anesthesiology residents without specific training in difficult videolaryngoscopy intubations learned how to use these five techniques on a manikin that was easy for Glidescope intubations and on one of the adjustable manikin configurations that were difficult. Skill was assessed on a difficult manikin that was different from the one used for training. The skill measure was laryngoscopy duration and it was assessed before training, immediately after training and 1 month later. The training session lasted about 40 minutes.
The instructional program resulted in significant improvement in the speed of intubation both on the easy manikin and on the difficult manikin. On the easy manikin, duration decreased from 38.8 +/- 4.9 second pre-training to 15. 4 +/- 1.4 seconds after training.(P < 0.0003). On the difficult manikin, the improvement went from 66.2 +/13.1 to 23.4 +/- 1.9 seconds (P < 0.0128). At the 1 month retention tests, speed had diminished but was still significantly better than pre-training, 20.4 +/- 2.2 seconds for the easy manikin and 32.8 +/- 5.9 seconds for the difficult manikin. Durations on the easy manikin were significantly less than for the difficult manikin at all time points.
This project has resulted in training tools for difficult videolaryngoscopy that have not been available until now.
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Grant Number: I21HX001317-01
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