Residency · Residency · Anesthesiology

Video Laryngoscopy: Techniques, Devices, and Evidence

Principles of Video Laryngoscopy

How VL Differs from Direct Laryngoscopy

Direct laryngoscopy (DL) requires alignment of the oral, pharyngeal, and laryngeal axes to create a line of sight to the glottis. Video laryngoscopy (VL) uses a camera at or near the blade tip, eliminating the need for line-of-sight alignment. VL can "see around the corner," providing a view of the glottis even with an anterior larynx, limited mouth opening, or restricted neck extension. It also reduces force on tissues, which decreases the hemodynamic response and lowers the risk of dental trauma.

Blade Geometry Classification

Blades fall into three categories. Macintosh-geometry (standard curve) blades have a shape similar to a Macintosh and can be used for both DL and VL (examples: C-MAC standard blade, McGrath MAC). Hyperangulated (acute curve) blades have approximately 60-degree curvature near the tip and are designed exclusively for indirect (video) viewing (examples: GlideScope, C-MAC D-blade, McGrath X-blade). Channeled blades contain a tube-guiding channel that directs the ETT toward the glottis (examples: King Vision channeled, Airtraq, Pentax AWS).

Major Video Laryngoscope Devices

GlideScope

The GlideScope features a hyperangulated blade with a 60-degree curve and a camera at mid-blade. It is available in reusable (Titanium) and single-use (Spectrum) versions in neonatal, pediatric, and adult sizes (3 and 4). It requires a pre-shaped stylet (GlideRite or hockey-stick bend) for tube delivery. It is the most extensively studied VL device. A key pitfall is that a good glottic view does not guarantee easy tube delivery — the hyperangulated blade creates a sharp angle for tube passage.

C-MAC (Karl Storz)

The C-MAC is available in standard Macintosh geometry (Mac 2, 3, 4) and the hyperangulated D-blade. The standard blade allows both DL and VL technique (the operator can look directly and at the screen), while the D-blade provides a hyperangulated view similar to the GlideScope. It offers high-resolution video with recording capability and a Miller blade for pediatric use. Its key advantage is standard blade versatility — it functions as a conventional laryngoscope with video backup.

McGrath MAC (Medtronic)

The McGrath MAC is portable and battery-powered with a single-use blade and reusable handle with an integrated LCD screen (no separate tower needed). It comes in Macintosh-geometry (standard) and X-blade (hyperangulated) configurations. It is lightweight and compact, making it widely used in prehospital and military settings.

King Vision (Ambu)

Available in channeled and non-channeled versions, the King Vision's channeled blade guides the ETT toward the glottis without requiring a stylet. It uses disposable blades and is useful for clinicians with less advanced laryngoscopy skills.

Airtraq

The Airtraq is a single-use optical laryngoscope with a built-in channel. It does not require an external monitor (it has a built-in viewfinder with a video adapter available), needs minimal mouth opening (approximately 18 mm), comes in multiple sizes including neonatal, and is a cost-effective single-use option.

Techniques for Successful VL Intubation

Hyperangulated Blade Technique

The blade is inserted in the midline (not with a lateral sweep as in Macintosh DL) and advanced slowly until the epiglottis and glottis are visible. A common error is over-insertion, placing the camera too close to the larynx. The ETT should be pre-shaped with a rigid stylet to approximately a 60-degree hockey-stick curve. The tube is advanced alongside the blade, watching the tip approach from the right side of the screen. Once past the vocal cords, the stylet is retracted and the tube advanced. The key tip: lift the blade less than you would with DL — the goal is glottic visualization, not line-of-sight alignment.

Standard Macintosh-Geometry VL Technique

The traditional lateral sweep technique or a midline approach can be used. The blade tip is placed in the vallecula and lifted to expose the glottis, just as in DL. The video screen is used for confirmation and optimization. A less aggressively curved stylet (standard shape) is usually sufficient. This approach allows seamless transition between direct and indirect views.

Tube Delivery Challenges

The "Grade 1 view, Grade 3 intubation" phenomenon — an excellent glottic view on screen but inability to pass the tube — occurs from excessive blade angulation bringing the camera too close, an inadequate stylet curve, or failure to use external laryngeal manipulation. Solutions include slightly withdrawing the blade to create more working space, using a more aggressively curved stylet, or bougie-assisted intubation through the VL.

Bougie Use with VL

A bougie is especially useful when tube delivery is difficult despite a good view. The bougie is inserted under video guidance and the ETT is railroaded over it. Studies show that a bougie-first approach may improve first-pass success in some settings.

Evidence Base

First-Pass Success

Meta-analyses consistently show VL improves first-pass success compared to DL, particularly in predicted and unpredicted difficult airways. Lewis et al. (2016 Cochrane) found that VL reduces failed intubation and improves glottic view. Aziz et al. (2012) demonstrated VL was associated with fewer failed intubations and Cormack-Lehane grade improvement.

Routine Use vs. Selective Use

Whether VL should be used for all intubations (routine first-line) or reserved for anticipated difficult airways is debated. Arguments for routine use include improved teaching through a shared view, higher first-pass success, documentation capability, and reduced dental injuries. Arguments against include cost, the risk of over-reliance without developing DL skills, and equipment availability in all settings. The trend is toward many institutions adopting VL as the first-line device for all intubations.

Emergency and ICU Settings

The MACMAN trial (2017) found no difference in first-pass success between VL and DL in the ICU, though operator experience was variable. The DEVICE trial (2022) showed bougie plus DL was non-inferior to VL for emergency intubation. Prehospital data favors VL, especially for providers with variable experience. Overall, VL is likely beneficial in emergency settings but does not eliminate the need for DL proficiency.

When DL Still Matters

Blood or vomit can obscure the camera lens, rendering VL useless while DL may succeed. Equipment failure (battery, screen, cable issues) can occur. Resource-limited settings may lack VL. Some neonatal or pediatric scenarios may have an oral cavity too small for the VL blade. Maintaining DL skills remains essential for backup competency.

Complications and Pitfalls

Palatopharyngeal Arch Injury

A rigid stylet tip can perforate the posterior pharynx, palatopharyngeal arch, or tonsillar pillars. This occurs when the tube is advanced blindly alongside the blade without continuous video visualization. Prevention requires always keeping the tube tip in view on the screen, advancing slowly, and never forcing the tube.

Over-Reliance on VL

Exclusive VL practice leads to loss of DL skills. Training programs should ensure competency in both techniques. In CICO situations, reverting to DL may be necessary.

Fogging and Soiling

Camera fogging can be managed with anti-fog solutions, warming the blade, or defogging wipes. Blood and secretions require suctioning before and during laryngoscopy. Some devices have anti-fog and anti-soiling coatings.

<image>A side-by-side comparison of blade geometries showing: (1) standard Macintosh blade profile with gentle curve, (2) hyperangulated blade profile with 60-degree distal curve, and (3) channeled blade with integrated ETT guide. For each, the corresponding glottic view perspective is shown (line-of-sight for Macintosh, around-the-corner for hyperangulated), along with the recommended stylet shape and tube delivery trajectory. Representative device examples labeled for each category.</image>

<image>A step-by-step illustrated guide to hyperangulated VL intubation technique: (1) patient positioned with head on pillow, no extreme extension needed, (2) blade inserted in midline with camera positioned above epiglottis showing Grade 1 view on screen, (3) pre-shaped ETT with hockey-stick stylet advanced from the right side of the mouth alongside the blade, (4) tube tip approaching glottis on screen with trajectory arrow, (5) tube passed through cords with stylet being withdrawn, (6) final tube position confirmed with capnography. Common errors shown in red insets: blade too deep, stylet curve too shallow, and palatopharyngeal perforation from blind advancement.</image>

<image>A forest plot summary of meta-analyses comparing video laryngoscopy versus direct laryngoscopy for key outcomes: first-pass success rate, failed intubation rate, glottic view improvement (Cormack-Lehane grade), time to intubation, and complication rates (dental trauma, airway trauma). Overall effect sizes with confidence intervals shown for each outcome. Studies labeled by patient population (elective, emergency, ICU, predicted difficult airway). Key message box summarizing when VL provides the greatest benefit.</image>

Clinical Pearls

A great view does not guarantee a great intubation — tube delivery technique is as important as glottic visualization with hyperangulated blades. The midline insertion technique differs from the traditional DL left-sided sweep; inserting a hyperangulated blade with a lateral sweep often provides a suboptimal view. The tube tip must always be kept visible on the screen during advancement to avoid posterior pharyngeal perforation — this is the most important safety principle. The C-MAC standard blade offers the best of both worlds: use it as a direct laryngoscope with video backup, maintaining DL skills while having VL available. In a blood- or vomit-soaked airway, video cameras may be obscured, making DL skills and a suction strategy essential. Bougie use through a VL significantly improves success when tube delivery is challenging despite a good view. For teaching, VL provides a shared view that dramatically improves trainee learning because the instructor sees exactly what the learner sees.

References

• Lewis SR, et al. Videolaryngoscopy versus direct laryngoscopy for adult patients requiring tracheal intubation. Cochrane Database Syst Rev. 2016;11:CD011136.
• Aziz MF, et al. Comparative effectiveness of the C-MAC video laryngoscope versus direct laryngoscopy. Anesthesiology. 2012;116(3):629-636.
• Lascarrou JB, et al. Video laryngoscopy vs direct laryngoscopy on successful first-pass orotracheal intubation among ICU patients (MACMAN). JAMA. 2017;317(5):483-493.
• Apfelbaum JL, et al. 2022 ASA practice guidelines for management of the difficult airway. Anesthesiology. 2022;136(1):31-81.
• Pieters BMA, et al. Videolaryngoscopy vs. direct laryngoscopy: a systematic review and meta-analysis. Anaesthesia. 2017;72(12):1532-1541.

Read this lecture as Markdown