Video laryngoscopy — channelled vs non-channelled devices, GlideScope, McGrath, C-MAC, and the evidence versus direct laryngoscopy

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Red flags

• The defining pitfall of the non-channelled device is 'can see but cannot tube' — a full, centred glottic view on the screen does not guarantee that the tube can be delivered to it. The tube must be steered around the hyperangulated corner with a pre-shaped hockey-stick stylet, introduced from the right corner of the mouth; a tip that catches anteriorly or in the vallecula is fixed by withdrawing, reshaping the stylet and re-advancing, not by repeating a failing delivery.
• Fogging, blood or secretions can blind the tip camera entirely. The camera sits at the mucosa, so where a direct laryngoscope looking from a distance may still see, the video laryngoscope can be rendered useless. Carry an anti-fog wipe or saline flush, and always have a direct laryngoscope immediately available for the bleeding or vomiting airway.
• The hyperangulated video laryngoscope is screen-dependent and cannot be used without power. A flat battery, a disconnected cable or a failed monitor converts it into a poor direct laryngoscope — the acute blade angle is not designed for a direct view, except in the dual-role devices (the C-MAC and the McGrath MAC). Check the battery and the image before induction, every time.
• The technique is a midline approach watching the screen, not the right-sided tongue sweep of direct laryngoscopy. A right-sided sweep distorts the hyperangulated blade's view, and the operator who delivers the tube while looking into the mouth has abandoned the one advantage the device provides.
• A substantial proportion of difficult intubations remain unanticipated — the preoperative airway assessment predicts difficulty imperfectly, and the airway that looked easy on the ward can still fail in theatre. The video laryngoscope must be immediately available for every induction, and the operator must be competent in its use before the crisis in which it is needed.