The Tracheal Access Times

A deep dive into tracheal access issues of intubation.

The age of VL will be organized around understanding and improving tracheal access.

Time to get started.

September 2024

Sean Runnels, MD; Dip. ABA

Associate Professor of Anesthesiology

Department of Anesthesiology, University of Utah SOM

Co-Director of American Society of Anesthesiology Swimming with the Sharks

CEO TTCmed.com

[email protected]

Video Laryngoscope Based Intubation. Evidence of VL Superiority Brings Evidence of a New Failure Mode:

Failure of Tracheal Access!

Intubating the trachea safely, with one attempt, in any setting is the goal. While this goal may be forever elusive; striving towards it drives innovation and improvement. How are we doing? When Video Laryngoscopy (VL) is compared to Direct Laryngoscopy (DL) for visualization of the glottis, VL is ‘best in class’, consistently providing easier and better glottic visualization. When VL is compared to DL in terms of intubation success, VL is ‘best in class’, consistently providing higher first pass rates. Best in class visualization does not mean we have met our goal.

Two well conducted multicentered randomized controlled trials were recently published demonstrating superior first pass rates for VL when compared to DL. Prekker et.al. reported first pass rates of 85.1% for VL and 70.8% for DL in critically ill patients in EDs and ICUs. 1? Kriege et.al. demonstrated first pass rates of 94% for VL and 82% for DL in OR settings. 2 These studies complement and reinforce the clinical superiority of VL over DL found by Hansel et.al. in a comprehensive metanalysis of VL and DL. 3 Togather these studies offer solid evidence of the superior clinical utility of VL based intubation in comparison to DL.

The question of the clinical utility of intubation with VL vs intubation with DL is settled. That milepost has passed. Intubation with VL is ‘best in class” in terms of success when compared to intuabtion with DL.?

Still, first pass failures and multiple attempt failures with VL happen at rates short of our goal of 100% first pass success. First pass failure rates using VL of 15% and 6% reported by Prekker and Kriege respectively, as well as overall failure to intubate with VL of 2.5% and 1% reported by Kreig and Phelan et.al. signal that the journey to 100% first pass success is not yet over. 4

Why do intubation attempts fail with VL? What problem of intubation should we study and solve next??

The secondary data reported by Prekker, Krieg and Phelan points to an new intubation failure mode anecdotally recognized by many but not yet systematically characterized, studied, named, and solved. Failure of tracheal access!?

A deeper look into the publications of Prekker, Krieg, and Phelan provides three important insights.

First, all three studies demonstrate that the cause of intubation attempt failure with VL is predominantly a failure of tracheal access not a failure of visualization!?

Phelan noted in a series of 997 intubations with VL published in 2022 that 73% of intubation failures were failures of tracheal access. “There were 24/997 (2.5%) failed intubations, with consultants or senior anaesthetists conducting laryngoscopy in the majority of these; in 16/22 failed intubations, a grade I or II glottic view was obtained on the video laryngoscope screen.”?

In the VL subgroup of Prekker’s study, VL intubation failure due to failure of tracheal access; 49/105 (46.7%), was two times as common as failure due to inadequate visualization of the glottis; 26/105 (24.8%).?

In Kriege’s study the cause of intuabtion failure in the VL subgroup was due to tracheal access failure in 48/56 (86%) of attempt failures while inadaquate visualization of the glottis was reported as (8/56 (14%) of attempt failures.

Second, Prekker’s secondary data demonstrates a subtle but no less important point. Failure to intubate in the DL subgroup was predominantly due to inadequate visualization of the glottis; 123/208 (59%) approximately twice as frequent as failure to access the trachea (51/208 (24%).

Third, these studies provide quantitative evidence of what many have anecdotally suspected, the transition from DL to VL has, in fact, traded one failure mode for another. The predominant failure mode of DL is visualization and the predominant failure mode of VL is tracheal access!

The age of DL, with its failure mode of inadaquate visualization, is coming to an end and the age of VL is now ascendent and inevitable. New ages bring new problems. The current failure mode of the age of VL is tracheal access. Just as the visualization failure mode of the age of DL drove the development of VL. The failure mode of tracheal access of VL based intubation will drive new tracheal access solutions.?

What do we systematically know about tracheal access? Other than it is the number one cause of intubation failure when using VL, not much!?

There is no agreement on a tracheal access classification system analogous to Cormack Lehane or POGO for visualization. This indicates that it has not been systematically studied.?

We have no standardized language around the problem. Is it ‘Tube delivery’, ‘Tube advancement’, ‘Intubation difficulty’, or ‘Tracheal access? This indicates that it has not been systematically recognized. I believe Tracheal access is the best term as it encompasses all other colloquial terms.

What about the geometry of tracheal access with VL? Are we still aligning three linear axes proposed by Bannister in 1944 or are we now navigating a serpentine pathway of two opposing curves with an inflection point between the two proposed by Greenland in 2010?5

What is the magnitude of the force applied to tissue using different types of tracheal access equipment??

Is a bent metal rod really the best equipment to move through a serpentine pathway!?

Prekker, McNarry and Kriege make clear that the age of VL has arrived and the challenge of tracheal access is the primary failure mode of VL. It is time to standardize the terminology of tracheal access and develop the tools, knowledge, techniques, and skills to systematically understand and solve tracheal access failure.?

The age of DL was organized around systematically understanding and improving visualization; the age of VL will be organized around understanding and improving tracheal access. Time to get started.

1. Prekker, M. E. et al. Video versus Direct Laryngoscopy for Tracheal Intubation of Critically Ill Adults. New England Journal of Medicine 389, 418–429 (2023).

2. Kriege, M. et al. A multicentre randomised controlled trial of the McGrathTM Mac videolaryngoscope versus conventional laryngoscopy. Anaesthesia 78, 722–729 (2023).

3. Cook, T. M. & Aziz, M. F. Has the time really come for universal videolaryngoscopy? British Journal of Anaesthesia vol. 129 474–477 Preprint at https://doi.org/10.1016/j.bja.2022.07.038 (2022).

4. Phelan, H. M., Stobbs, S. L., Sorbello, M., Ward, P. A. & McNarry, A. F. A prospective cohort evaluation of the McGrathTM MAC videolaryngoscope in a series of 979 cases. Trends in Anaesthesia and Critical Care 48, (2023).

5. Greenland, K. B. et al. Changes in airway configuration with different head and neck positions using magnetic resonance imaging of normal airways: A new concept with possible clinical applications. Br J Anaesth 105, 683–690 (2010).