Forces on Teeth During Videolaryngoscopy

Forces Exerted on Upper and Lower Teeth During Intubation: a Randomized, Cross-over Trial Comparing Indirect Videolaryngoscopy to Direct Videolaryngoscopy.

In this randomized crossover trial the investigators test whether three different brands of videolaryngoscopes (VLS) exhibit reduced forces on both upper and lower teeth, and compare them with a classic Macintosh laryngoscope blade.

During endotracheal intubation the anesthesiologist uses a laryngoscope blade to distract the tongue to achieve the best view of the glottis opening, thereby avoiding using the maxillary incisors as a fulcrum to lever the soft tissues upwards. Using the maxillary incisors as a fulcrum may otherwise result in dental trauma. It is obvious that contact with teeth and - even worse - the incidence of accidental dental trauma, is directly related to the difficulty of the intubation. Indirect videolaryngoscopy has proven advantageous over direct laryngoscopy using a classic Macintosh blade, for improved viewing of the glottis, with subsequent more successful intubations, and a shorter effective airway time both in patients with normal and difficult airways. Previously, it has been demonstrated that the forces exerted by the anesthesiologist on the patient's maxillary incisors are reduced when using a VLS, compared with a classic Macintosh laryngoscope. However, only one type of VLS (V-MAC®, Karl Storz, Tuttlingen, Germany) was used or only forces applied to upper teeth were being registered.

Macintosh laryngoscope (Karl Storz, Tuttlingen, Germany), McGrath® (Aircraft Medical Ltd, Edinburgh, UK), C-MAC® (Karl Storz, Tuttlingen, Germany), GlideScope® Cobalt (Verathon Medical, Bothell, WA, USA)., Flexiforce® sensors (A201-25, Tekscan, MA, USA)

Anesthesia will be induced in the conventional matter. The classic Macintosh laryngoscope will be placed in the patient's mouth and a tube will be brought into position in front of the glottis. Hereafter, one of the three videolaryngoscopes will be placed in the patient's mouth and the endotracheal tube will be actually passed through the vocal cords. The measurement of forces applied to the teeth will be performed using Flexiforce® sensors.

One of the three videolaryngoscopes will be placed in the patient's mouth. The measurement of forces applied to the teeth will be performed using Flexiforce® sensors.

Measuring the magnitude of the forces being applied and registering the differences between (video)laryngoscopes.

Inclusion Criteria: Informed patient consent ASA I -III Age > 18 years Elective surgery, other than head and/or throat surgery Pre-operative Mallampati I -III Fasted (≥6 hours) Exclusion Criteria: No informed patient consent ASA ≥ IV Age < 18 year Emergency surgery, surgery of head and/of throat Locoregional anaesthesia Pre-operative Mallampati IV Fasted < 6 hours Pre-operative expected difficult airway No teeth, bad dentition Dental crowns and/or fixed partial denture

Lee RA, van Zundert AA, Maassen RL, Willems RJ, Beeke LP, Schaaper JN, van Dobbelsteen J, Wieringa PA. Forces applied to the maxillary incisors during video-assisted intubation. Anesth Analg. 2009 Jan;108(1):187-91. doi: 10.1213/ane.0b013e31818d1904.

Lee RA, van Zundert AA, Maassen RL, Wieringa PA. Forces applied to the maxillary incisors by video laryngoscopes and the Macintosh laryngoscope. Acta Anaesthesiol Scand. 2012 Feb;56(2):224-9. doi: 10.1111/j.1399-6576.2011.02541.x. Epub 2011 Oct 14.