How to reduce two of the most common errors of direct laryngoscopy, tube delivery issues, and failing to plan for the epiglottis-only view.
Tube Delivery Issues
Tracheal tubes should always be inserted from below the line of sight, using the right hand corner of the mouth, initially placing the tube behind the maxilla. With a proper shape (straight-to-cuff, 35 degree bend angle at the proximal cuff), the distal tip is advanced from below the line of sight to the larynx, then toggled up over the posterior cartilages and interarytenoid notch by pivoting the proximal portion of the tube. The right side of the mouth provides room for maneuvering the tube and is the lowest point of the dental arch [see Figure 1]. In restricted visualization situations, inserting devices into small body cavities, it is important to understand the optical advantage of a long narrow axis with a slight distal deflection [Figure 2]. This is the same shape as alligator forceps, laryngeal mirrors, etc.
It is important to note that the malleable stylet should never extend beyond the tip of the tracheal tube. I believe it should not extend beyond the distal cuff of the tube. This makes the last few centimeters of the tube less rigid and is also safer.
If the tracheal tube and stylet are bent at too steep an angle, or sometimes if the patient’s neck is hyper-extended (something that should always be avoided), the tip of a left-facing beveled tube can catch the tracheal rings. Tracheal tubes with a bend angle exceeding 35 degrees have a high rate of mechanical impaction [Levitan RM, Pisaturo JT, Kinkle WC, Butler K, Everett WW. Stylet bend angles and tracheal tube passage using a straight-to-cuff shape. Acad Emerg Med, 2006; 13: 1255-8.].
This is especially true of straight cut tubes. A shrouded tip has a rounded leading edge. The least likely tubes to catch on the tracheal rings anteriorly is a Parker ski-tip shaped tube [see Figure 3]. This tube design is now sold by the maker of the Glidescope and labeled as the GlideRite tube. The tip of a tracheal tube often interacts with the tracheal rings at a steep angle when using a video laryngoscope and this design makes tube insertion easier.
If a tube will not advance into the trachea (even though it is through the cords), the first response should be to turn the tube rightward. This lowers the leading edge of the tube, turns the bevel upward, and disengages the tip of the tube from the tracheal rings [see Figure 4]. The stylet can also be withdrawn by an assistant while maintaining the tube in position within the trachea.
1. Insertion of tracheal tube using a straight-to-cuff styletted tube and the extreme right corner of the mouth. Toggling the proximal tube backward brings the distal tip of the tube over the interarytenoid notch.
2. Ideal shape for tracheal tube is straight-to cuff, with bend at proximal cuff of 35 degrees (top and left in images). An accurate shape has a large long axis shape, does not pass easily in the restricted space of laryngoscopy, and blocks the line of sight to the larynx.
3. Tube tips from left to right: straight cut, shrouded, and Parker (a.k.a. GlideRite).
4. The tip of a left–facing beveled tube can catch the tracheal rings (round dots) after passing through the vocal cords (line). Turning tube rightward (clockwise) lowers the leading edge, rotates bevel upward, and disengages tube tip from rings allowing it to pass into the trachea.
5. Bimanual laryngoscopy links fine movements on the patient’s neck with immediate observation of laryngeal view by the operator. An assistant can take over for the operator, maintaining pressure at the right location, if needed – allowing operator to pass the tracheal tube.
No plan for the epiglottis-only view.
The vast majority of emergency intubations are done with a curved blade which indirectly elevates by pressure at the vallecula (where the tongue and epiglottis meet) and the underlying hyoepiglottic ligament. Practitioners must have a plan for the epiglottis-only view that involves modifications in technique as well as appropriate equipment.
The immediate response to an epiglottis-only view is to optimize the position of the blade tip in the vallecula. The fastest and easiest way to do this is by using bimanual laryngoscopy. This is not cricoid pressure, done by an assistant at the cricoid cartilage. It is also not BURP, or backward-upward-rightward-pressure (also done by an assistant). Bimanual laryngoscopy involves using your right hand to reach around the neck and apply pressure in the direction opposite to the force direction at the end of the blade (which is in the vallecula) [see Figure 5]. Bimanual laryngoscopy advances the tip of the blade fully into the vallecula, in a manner similar to the advancement of a key into a lock. Unless the key (i.e. the tip) is fully advanced, it is impossible to turn the lock (i.e., lift the epiglottis). Bimanual laryngoscopy is usually applied at the thyroid cartilage (more than 90% of cases); it is not necessary to be precise about your hand placement. By connecting manipulations of your right hand on the neck with immediate observation of effect, fine positioning and amount of force can be quickly adjusted to optimize the laryngeal view. [Levitan RM, et. al. Laryngeal View During Laryngoscopy: A Randomized Trial Comparing Cricoid Pressure, BURP, and Bimanual Laryngoscopy. Ann Emerg Med. 2006; 47: 548-55.]
Bimanual laryngoscopy works through two mechanisms: the first is improved mechanics (tip position); the second is by pushing the larynx posteriorly into the line of sight. In about 10% of cases, it is beneficial to have an assistant’s hand ready to apply position at the optimal location, in order to maintain this downward pressure, so the operator can use their freed right hand for tube delivery. Some clinicians find that this is easiest by performing bimanual with the assistant’s hand at the outset, while others only involve the assistant as needed after they have applied bimanual themselves.
The next response to improving view if bimanual has been applied but the epiglottis is still blocking the view is to lift the head higher [not in cervical spine precautions]. Increasing head elevation improves the line of sight, and improves the mechanics of jaw distraction. [Levitan RM, et. al.. Head Elevated Laryngoscopy Positioning (HELP): Improving laryngeal exposure during laryngoscopy by increasing head elevation. Ann Emerg Med 2003;41: 322-30.]
Finally, if the view cannot be further optimized, the next step is to address the challenge and achieve intubation despite a suboptimal view. This may be done with a straight-to-cuff styletted tube (carefully placed under the epiglottis), a tube introducer (a.k.a., a “bougie”), or an optical stylet.
A bougie, originally designed with a 38 degree bend at its distal tip, has an optical advantage over a tube in that it has a smaller outer diameter (5 mm). For it to be used effectively it should be shaped straight to the distal deflection, and gripped like a pencil about half way along it’s length. If the bougie has been stored in a curled up position, then it will be very difficult to direct to the larynx and have a great deal of rotational movement as it is inserted.
The bougie is inserted into the trachea and the distal rounded tip of the device will move over the anterior tracheal rings like a car’s tire passing over a rumble strip. This palpable detection of the tracheal rings is felt in 65-95% of cases; if the distal tip of the bougie is deflected posteriorly, along the membranous trachea, the rings will not be felt. The bougie will stop between 24 and 40 cm if it is in the trachea, as it passes into the narrowing bronchi. Care should be taken not to forcefully insert the device. A tracheal tube is advanced over the bougie to the proper depth, and the bougie removed.
When using a large tracheal tube, i.e., 8.0, 8.5 mm ID, the gap between the OD of the bougie (5.0 mm) and the ID of the tube can create a mechanical problem as the tube passes over the bougie and the leading edge of a left-facing beveled tube catches the right side of the laryngeal inlet. If resistance is felt at 14-16 cm as the tube is advanced, turn the tube on the bougie in a strong counter-clockwise or leftward direction. This will close this gap and allow the tube to pass.
The bougie is not a heat-seeking missile. It does not magically find the trachea and should never be inserted in a Hail Mary attempt when no landmarks are seen. If inserted in an epiglottis-only situation, the distal tip should hug the underside of the epiglottis, making sure it is oriented anteriorly. Ideally, the operator should visualize at least the interarytenoid notch and see the tip pass over this important divide between the trachea anteriorly and the esophagus posteriorly.
An optical stylet is perhaps the most powerful device for the epiglottis only view, but it requires knowledge of fiberoptic principles and an appreciation of landmarks from a fiberoptic perspective; this requires a separate column to review.
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