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Despite the expanding array of video and other imaging laryngoscopes there are some fundamental principles that apply to all new airway devices that emergency physicians should know. Below we review four critical concepts: epiglottoscopy and suctioning, lifting to expand the viewing area, tilting the optics toward the ET tube, and two-stage tube delivery.

1. Suctioning and epiglottoscopy
Emergency patients with poor muscular tone, head injury, increased intracranial pressure, trauma or overdose have numerous causes of regurgitation and vomiting. Vomitus, blood, and secretions commonly show themselves in the emergent airway. I sometimes consider myself a “vomitologist” because of the frequency of this clinical situation. Fluids in the oral cavity in the supine patient will pool in the hypopharynx. Head elevated laryngoscopy positioning – ideally ear-to-sternal notch when viewed from a lateral perspective – permits jaw distraction and maximizes the displacement space (i.e. the thyromental distance, where the tongue gets displaced). Head elevation reduces regurgitation risk and also improves pulmonary physiology (better pre-oxygenation and passive apneic oxygenation).

Check out the article on NO DESAT – Nasal Oxygen During Efforts Securing A Tube 

Upon starting airway management with any device that has a retraction blade, I gently bring the tongue and mandible forward holding the instrument in my left hand, using the mouth opening to introduce the Yankauer with my right. I dab the posterior pharyngeal wall, identify the uvula, and progress down the tongue, until I identify the epiglottis. With a standard laryngoscope (or direct-video devices, C-Mac, McGrath Mac, etc.) the epiglottis comes into direct view.

With hyperangulated imaging devices (Glidescope, AirTraq, King Vision) there is no direct view—epiglottoscopy is done on the monitor or in the viewer. A common error of novice airway managers is over-running the epiglottis and inserting the imaging element into a fluid pool. Epiglottis camouflage is common (the epiglottis mucosal appearance can match the posterior pharyngeal mucosa) so use the Yankauer to drain the fluids and the retractor to lift the epiglottis off the posterior pharyngeal wall. With correct head positioning (ear-to-sternal notch, and face plane parallel to ceiling, not over-extended), gentle jaw distraction, and methodical advancement down the tongue until the epiglottis is seen, airway management becomes a predictable sequence of events: epiglottoscopy, laryngoscopy, and tube delivery. I think epiglottoscopy is the secret to routine success. With the imaging devices, as with direct laryngoscopy, epiglottoscopy remains fundamental; I never expose the larynx without first identifying the epiglottis. Depending on the epiglottis morphology and the imaging device, the epiglottis is elevated (indirectly or directly) to expose the larynx and permit tube delivery.

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Ideal positioning of the larynx using the Glidescope.  The larynx is midline, and kept in the upper part of the monitor, which leave the lower half of the monitor for visualizing tube delivery.  This positioning of the target also lessens the angulation between the video laryngoscope blade and the tracheal axis, which is beneficial for tube insertion into the trachea.

2. Lift the mandible to expand the viewing space.
The above first stage of the procedure is done with slight force. The operator is lifting only 2-3 pounds of jaw and tongue, opening the mouth, to enable epiglottosopy and permit suctioning. If the tongue is engaged with too much force at the outset it becomes impossible to adjust tongue position relative to the retractor. With hyperangulated blades, the tongue is kept midline (Glidescope, AirTraq, King Vision, etc.). With the C-Mac, McGrath Mac (DL/VL combination devices), sweep the tongue to the left (as is done with direct laryngoscopy). The second phase of the procedure, additional jaw distraction and epiglottis control is done with significantly greater force. This opens the hypopharynx, maximizing laryngeal exposure. Remember to lift in a manner that avoids over-extension of the neck, otherwise you will push the base of tongue and epiglottis backward, limiting mouth opening and decreasing the hypopharyngeal space. Keeping the face plane parallel to the ceiling is an easy reference. Expanding the viewing space also increases the space for tube delivery.

3. Tilt the optics away from the target (toward the ET tube)
In preparation for tube delivery, airway managers handling an imaging device must appreciate that maximizing target visualization may impede tube delivery. This is certainly so with the hyperangulated devices (i.e. those devices that have a curve more acute than a standard curved blade laryngoscope). Using the Glidescope, for instance, keep the larynx in the northern hemisphere (upper half) of the monitor. This then permits the southern hemisphere for tube delivery. If the imaging lens of a hyperangulated device is tilted too close to the target there is no space for tube delivery and no viewing of the tube [images 1 and 2]. Since the tube must be placed with imaging (i.e., no direct view), the operator cannot determine how to adjust tube delivery to get it to the target. Tilting the optics toward the ET tube allows visualization of tube delivery, but it also has a secondary benefit. It lessens the acuity of the angle between the viewing axis (the device retractor) and the tracheal axis [image 3]. The imaging lens of hyperangulated devices look up toward the larynx, but the trachea follows the cervical and thoracic spine, diving posteriorly. By tilting the imaging toward the ET tube, this angle difference is lessened, making it easier to drive the tip of the tube into the larynx.

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The blade is right of midline instead of straight on. The blade has been pivoted so far towards the target that the target takes up the whole image.  There is no space to view tube insertion, making it very difficult to delivery the tube to the larynx.  Rotating the device in this far also exaggerates the angle between the blade and the trachea, making tube delivery into the trachea more difficult.

4. Two stage tube delivery
When actually bringing the tube toward the target using an imaging device, advance the tube slowly, until the tip comes into view. Then adjust your insertion angle and direction as needed to get to the second stage of tube delivery (i.e. insertion into the larynx). Do not plunge the tube up and down, hoping it will go into the larynx. Since you’re working off the monitor exclusively, you need the visual feedback of where the tube tip is (and where it’s pointing) before adjusting the direction. With the Glidescope, Doreges blade C-Mac, or King Vision (non-channeled version) the tube will be placed using a hyperangulated stylet. With channeled devices (AirTraq, King Vision with a channel, or Pentax AWS) there is no stylet; the tube is advanced down a channel alongside the retractor. Regardless of whether a stylet is used or not, when working off an imaging device, advance the tip slightly until you see it, then modify your insertion as needed. With the Glidescope, the King Vision (non-channeled) and other hyperangulated non-channeled devices, I follow the curvature of the blade, hugging the blade itself, as I rotate the tip of the tube down to the end of the retractor (blade) until I see the tip on the monitor.

Depending upon the type of device used and whether there is a stylet needed for tube insertion, tube insertion into the trachea may need to be modified. I consider this a major advantage of the direct-video laryngoscopes like the C-Mac, McGrath Mac, or Glidescope Direct Trainer. These devices have tube delivery similar to direct laryngoscopy (straight-to-cuff 35 degree stylet shape, or even no stylet if you prefer—but I always use a stylet). When using the GlideRite stylet which has a 70 degree bend, or other hyperangulated stylet, the side-to side dimension is too big to insert into the trachea, and the tip of the styletted tube will catch on the cricoid cartilage or high tracheal rings, preventing tub insertion. One option to overcome this mechanical impediment, is “STOP, POP and DROP.” Stop stylet insertion after the tip is through the cords, pop the stylet out of the tube, and then drop the now partially non-styletted tube into the trachea. Another option is to rotate the hyperangulated stylet to the right 90 degrees (clockwise). Instead of the tip pointing upwards, the tip of the rotated tube now is better aligned with the tracheal axis and can be further advanced before the stylet is withdrawn. I prefer Parker Medical’s ski-tip tube design when using video or imaging devices. These tube tips tend to catch less on the rings than standard left-facing beveled tracheal tubes.
 

Dr. Levitan teaches emergency medicine at Jefferson Medical College and at the Univ. of Maryland and helps run a monthly airway management course involving specially prepared cadavers: jeffline.jefferson.edu/jeffcme/Airway

Comments   

# Pre-Loaded VL devicesRic Todhunter 2013-09-12 19:58
Thanks for a great post with good advice.
If I might be so bold as to comment that I think the omission of new geometry blades, in particular those with a pre-loaded ETT in your discussion was a shame. These devices (such as the Pentax Airway Scope - www.ambu.com/corp/products/anaesthesia/product/pentax_airway_scope_(aws)_video_laryngoscope_and_pentax_single_patient_use_blade_(pblade)-prod13584.aspx) require a different but (in my opinion) simpler technique than the types of VL your are describing above. The fact that visualisation of the cords in the "cross-hairs" of the Pentax = correct position for simply sliding the ETT into place completely alleviates the need as you have described in part 4 to reposition the scope before insertion of the ETT between the cords.
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