Videolaryngoscopes

In this article Dr Simon Clarke, Consultant Anaesthetist at University College London Hospital, discusses the use of videolaryngoscopes and how they have changed airway management.

The evolution of videolaryngoscopy in a relatively short space of time has transformed airway management. Laryngoscopy was once considered an art which could only be mastered with years of experience. As the view was only available to the laryngoscopist, subtleties of technique were not easily shared and expertise required a great deal of practice. With the advent of videolaryngoscopes it has become a more accessible and attainable skill.

Brief History

A true videolaryngoscope has a digital video camera on a laryngoscope blade with no fibreoptic components; this makes it easy to handle the camera images and also easy to produce.

Prior to the development of the first true videolaryngoscope, there were several devices on the market that provided indirect fibreoptic views of the larynx, such as the Bullard scope. The first commercially available videolaryngoscope was the Glidescope® in 2001. It was designed and developed by vascular surgeon Dr John Pacey, who had witnessed two anaesthetists struggle with a difficult intubation for nearly half an hour. He had been involved in the development of a video retractor for surgery and realised that the same technology could be applied to laryngoscopy. Many more videolaryngoscopes have subsequently been developed.

Principles of laryngoscopy

Standard direct laryngoscopy requires alignment of three axes with the eye to achieve a direct view of the larynx: the oral axis, the pharyngeal axis, and the laryngeal axis. Traditionally the ‘sniffing the morning air’ position is used (flexion of the neck and extension of the head) to create a ‘line of sight’.

Angles of alignment- Oral axis (OA), Pharyngeal axis (PA) and Laryngeal axis (LA)

The camera lens on a videolaryngoscope is sited towards the tip or distal end of the laryngoscope blade. This allows the operator to have a closer and wider-angle view of the laryngeal structures than a direct laryngoscope but it is also in effect an ‘around the corner’ view which is further extended when the blade has a hyper-angulated shape. The hyper-angulated or ‘difficult’ blades have greater radius of curvature than the standard Macintosh laryngoscope blades and were designed to be used in patients in whom it is difficult or impossible to obtain a direct line of sight view.

Increased angle of view (60°) with a videolaryngoscope Macintosh type blade and a hyper-angulated blade, compared with a 15° view using direct laryngoscopy

Classifications

Videolaryngoscopes can generally be divided into two groups: those with Macintosh type blades and those with hyperangulated blades. Devices with hyperangulated blades are further subdivided into non-channelled and channelled.

Devices with a Macintosh type blade can be used either for a direct, line of sight view or for an indirect, enhanced view via the camera and screen. A wider angled view of the larynx is provided. Tube insertion technique is similar to direct laryngoscopy, a stylet, introducer or bougie may be helpful but are not essential. Examples include Storz C-MAC, Glidescope Titanium MAC and AP Advance Normal Macintosh blade.

The hyperangulated blades provide indirect glottic visualisation via the camera and screen, they do not provide a direct view of the larynx. The channelled devices have a back wall or ‘open tunnel’ shape incorporated into the blade design and this helps direct the tracheal tube towards the glottis. Examples include Pentax AWS, AP Advance Difficult airway blade & King Vision. A preformed malleable stylet or introducer is not needed with channelled devices.

When using non-chanelled hyperangulated devices a stylet with a similar curvature to the blade, introducer or bougie is recommended to help guide the tip of the tracheal tube through the cords. Examples include Storz D-Blade, Glidescope LoPro and McGrath X-blade.

Glidescope Macintosh blade and hyper-angulated blade

The technique for laryngoscopy depends on the blade you are using and varies from one device to another. There are other differences between devices which are sometimes quite subtle; these include screen position, portability, single-use (disposable) blades or reusable blades. Familiarity and expertise with one device may not be completely transferable to another.

Tracheal tube mounted on a stylet

Intubating stylet removal after tracheal tube intubation using hyperangulated blade

Advantages

Videolaryngoscopy (VL) offers the following advantages:

  • The view of the larynx is better than with direct laryngoscopy
  • Successful intubation is more likely in those patients who have difficult airways
  • Less soft tissue force is needed to obtain a view of the larynx which results in less sympathetic stimulation
  • Sore throat and dental trauma are less common
  • The indirect view is not obscured by the advancing tracheal tube, so there is more precise visual control when inserting the tracheal tube
  • VL improves teamwork and human factors. All team members share the view and can offer advice, see the effect of cricoid/anterior pressure and anticipate next steps such as the need for suction or alternative intubating aid
  • The shared view aids the teaching and training of novice ‘intubators’. Airway anatomy can be demonstrated during intubation and the attempts at intubation by a novice can be more closely and clearly observed. Instruction and advice can be given in real time and the need to intervene can be judged more easily
  • The position of the tube in relation to the cords can be checked
  • Nasogastic and orogastric tube insertion is easier
  • VL can be used to assist fiberoptic intubation and tube exchange
  • VL can be used for awake intubation in selected patients

Disadvantages

  • Although it is usually easy to view the larynx with a videolaryngoscope, it may not be easy to pass the tube into the trachea. This is a particular feature of hyper-angulated blade devices, the working space is different, perception of depth is altered, and it can be challenging to direct the tube through the vocal cords. Impingement of the tube can occur as it approaches the glottis at a slightly more acute angle than with direct laryngoscopy. This problem can be overcome with good technique and experience

  • Videolaryngoscopes are relatively expensive to buy and to maintain

  • Technical problems such as fogging, poor connections, availability of components can be problematic

Summary

The introduction of videolaryngoscopy has been a significant step forward in airway management. Some anaesthetists argue that videolaryngoscopy should be the first-line technique for intubation. Although this is not yet the universal standard of care, it is recommended that videolaryngoscopes should be immediately available wherever intubation is performed and all anaesthetists be trained and expert in their use.

Do you think videolaryngoscopy should be the first choice for all intubations? Why?

What difficulties might you encounter when trying to introduce videolaryngoscopy into your work-place?

With so many makes and models widely available, how do you decide which videolaryngoscope to purchase for your department?

Is it better to choose one device or to have a selection and master them all?

In the “Downloads” section you will find an infographic summary on video laryngoscopes

References

Seeing is believing: getting the best out of Videolaryngoscopy F. E. Kelly, T. M. Cook British Journal of Anaesthesia 117 (S1): i9–i13 (2016)

Videolaryngoscopy versus direct laryngoscopy for adult patients requiring tracheal intubation: a Cochrane Systematic Review† S. R. Lewis, A. R. Butler, J. Parker, T. M. Cook, O. J. Schofield-Robinson and A. F. Smith British Journal of Anaesthesia, 119 (3): 369–83 (2017)

Videolaryngoscopy vs. direct laryngoscopy use by experienced anaesthetists in patients with known difficult airways: a systematic review and meta-analysis B. M. A. Pieters, E. H. A. Maas, J. T. A. Knape and A. A. J. van Zundert. Anaesthesia 2017, 72, 1532–1541

Strategies for the prevention of airway complications – a narrative review. Cook TM Anaesthesia 2018 73: 93-111

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Airway Matters

UCL (University College London)