Techniques and Procedures TRACHEAL INTUBATION: THE PROOF IS IN THE BEVEL Anthony M.-H. Ho, MD, FRCPC, FCCP,* Adrienne K. Ho, MBBS,† and Glenio B. Mizubuti, MD, MSC* *Department of Anesthesiology and Perioperative Medicine, Queen’s University, Kingston, Ontario, Canada and †Department of Medical Oncology, Christie NHS Foundation Trust, Manchester, United Kingdom Reprint Address: Glenio B. Mizubuti, MD, MSC, Department of Anesthesiology and Perioperative Medicine, Queen’s University, Kingston General Hospital, Victory 2, 76 Stuart Street, Kingston, Ontario K7L 2V7, Canada , Abstract—Background: Efficient airway management is paramount in emergency medicine. Our experience teaching tracheal intubation has consistently identified gaps in the un- derstanding of important issues. Here we discuss the impor- tance of the endotracheal tube (ETT) bevel in airway management. Discussion: The ETT bevel orientation is the main determinant of which mainstem bronchus the ETT en- ters when advanced too distally, despite a common belief that attributes a higher incidence of right mainstem bronchial intubation to the straighter angle sustained by the right main- stem bronchus. Likewise, a bougie- or fiberscope-assisted tracheal intubation can be impeded by the ETT tip hooking onto laryngeal structures; a 90-degree counterclockwise turn of the ETT (such that the bevel is facing posteriorly) prior to advancing it toward the larynx produces a first- pass success rate of 100%. Similarly, a posterior-facing bevel is believed to improve the ease of passage through the back of the nasal cavity when performing nasotracheal intubation. If resistance is met after the ETT tip has reached the laryngeal vicinity, further counterclockwise rotation may change the plane and incident angle of the ETT tip, facilitating passage through the vocal cords. Clockwise twisting of the ETT re- duces the incident angle in the sagittal plane, thereby facili- tating videolaryngoscopy-assisted tracheal intubation. Finally, a posterior-facing ETT bevel is the least likely to intu- bate a tracheoesophageal fistula. Conclusions: Understanding the implications of the ETT bevel direction may significantly change the efficiency of deliberate endobronchial, nasal, and bougie/fiberscope-, and videolaryngoscope-assisted intuba- tions, and while managing the patient with a tracheoesopha- geal fistula. Ó 2018 Elsevier Inc. All rights reserved. , Keywords—airway management; tracheal intubation; ETT bevel; nasal intubation; fiberoptic intubation; videolar- yngoscopy INTRODUCTION When an endotracheal tube (ETT) is inserted, its asym- metrically tapered end is aligned with the laryngeal open- ing for ease of trespassing the larynx (Figure 1). The bevel is left-facing to avoid obscuring the laryngeal view during insertion from the right side of the mouth. The modern adult ETT has a bevel that is slightly less pointy at its tip, although a more pointy design can also often be found (Figure 2). Our experience teaching tracheal intubation has consistently identified gaps in the understanding of several important issues. These knowledge gaps nega- tively affect the efficiency of tracheal intubation and thus may increase patient discomfort, cause trauma, and delay the establishment of airway protection and proper ventilation. We herein discuss how the ETT bevel is our friend in airway management. Notably, our discussion stems from the anesthesiology literature (given the paucity of emergency medicine studies on the topic) and from several decades of anesthesia practice experi- ence. Nevertheless, the technical/procedural aspects out- lined herein are not unique to anesthesiology and are no doubt of interest to all airway management practitioners. RECEIVED: 6 January 2018; FINAL SUBMISSION RECEIVED: 2 August 2018; ACCEPTED: 1 September 2018 1 The Journal of Emergency Medicine, Vol. -, No. -, pp. 1–6, 2018 Ó 2018 Elsevier Inc. All rights reserved. 0736-4679/$ - see front matter https://doi.org/10.1016/j.jemermed.2018.09.001
Transcript
The Journal of Emergency Medicine, Vol. -, No. -, pp. 1–6, 2018� 2018 Elsevier Inc. All rights reserved.
0736-4679/$ - see front matter
https://doi.org/10.1016/j.jemermed.2018.09.001
RECEIVED: 6 JanACCEPTED: 1 Se
Techniquesand Procedures
TRACHEAL INTUBATION: THE PROOF IS IN THE BEVEL
Anthony M.-H. Ho, MD, FRCPC, FCCP,* Adrienne K. Ho, MBBS,† and Glenio B. Mizubuti, MD, MSC*
*Department of Anesthesiology and Perioperative Medicine, Queen’s University, Kingston, Ontario, Canada and †Department of MedicalOncology, Christie NHS Foundation Trust, Manchester, United Kingdom
Reprint Address: Glenio B. Mizubuti, MD, MSC, Department of Anesthesiology and Perioperative Medicine, Queen’s University, KingstonGeneral Hospital, Victory 2, 76 Stuart Street, Kingston, Ontario K7L 2V7, Canada
, Abstract—Background: Efficient airway management isparamount in emergency medicine. Our experience teachingtracheal intubation has consistently identified gaps in the un-derstanding of important issues. Here we discuss the impor-tance of the endotracheal tube (ETT) bevel in airwaymanagement. Discussion: The ETT bevel orientation is themain determinant of which mainstem bronchus the ETT en-ters when advanced too distally, despite a common belief thatattributes a higher incidence of right mainstem bronchialintubation to the straighter angle sustained by the rightmain-stem bronchus. Likewise, a bougie- or fiberscope-assistedtracheal intubation can be impeded by the ETT tip hookingonto laryngeal structures; a 90-degree counterclockwiseturn of the ETT (such that the bevel is facing posteriorly)prior to advancing it toward the larynx produces a first-pass success rate of 100%. Similarly, a posterior-facing bevelis believed to improve the ease of passage through the back ofthe nasal cavity when performing nasotracheal intubation. Ifresistance is met after the ETT tip has reached the laryngealvicinity, further counterclockwise rotation may change theplane and incident angle of the ETT tip, facilitating passagethrough the vocal cords. Clockwise twisting of the ETT re-duces the incident angle in the sagittal plane, thereby facili-tating videolaryngoscopy-assisted tracheal intubation.Finally, a posterior-facing ETT bevel is the least likely to intu-bate a tracheoesophageal fistula. Conclusions: Understandingthe implications of the ETT bevel direction may significantlychange the efficiency of deliberate endobronchial, nasal, andbougie/fiberscope-, and videolaryngoscope-assisted intuba-tions, and while managing the patient with a tracheoesopha-geal fistula. � 2018 Elsevier Inc. All rights reserved.
uary 2018; FINAL SUBMISSION RECEIVED: 2 Auguptember 2018
When an endotracheal tube (ETT) is inserted, its asym-metrically tapered end is aligned with the laryngeal open-ing for ease of trespassing the larynx (Figure 1). Thebevel is left-facing to avoid obscuring the laryngealview during insertion from the right side of the mouth.The modern adult ETT has a bevel that is slightly lesspointy at its tip, although a more pointy design can alsooften be found (Figure 2).
Our experience teaching tracheal intubation hasconsistently identified gaps in the understanding ofseveral important issues. These knowledge gaps nega-tively affect the efficiency of tracheal intubation andthus may increase patient discomfort, cause trauma, anddelay the establishment of airway protection and properventilation. We herein discuss how the ETT bevel is ourfriend in airway management. Notably, our discussionstems from the anesthesiology literature (given thepaucity of emergency medicine studies on the topic)and from several decades of anesthesia practice experi-ence. Nevertheless, the technical/procedural aspects out-lined herein are not unique to anesthesiology and are nodoubt of interest to all airway management practitioners.
Figure 1. The left-facing bevel makes it easier for the endo-tracheal tube to go through the larynx without obstructingthe view.
2 A. M.-H. Ho et al.
DISCUSSION
Selective Endobronchial Intubation
Left mainstem bronchial intubation may be unexpectedlyrequired, such as in cases of systemic air embolism afterright lung injury, pus or blood spilling from the right lung,right pneumothorax, and pneumatocele (1,2). In suchcases, and especially when there is already an ETT insitu, or a bronchial blocker or double-lumen tube is notreadily available (as would be the case in the emergencydepartment), the bevel orientation can be used to influ-ence the direction of the ETT when bronchial intubationis desired. Kubota et al. advanced the ETT beyond the ca-rina in 359 children and adults and found that 99% of thetime it entered the right mainstem bronchus (3). Whenthese authors rotated the ETT 180� immediately afterthe tip had passed the larynx, such that the bevel facedthe right, the ETT intubated the left mainstem 61% ofthe time (3). Baraka et al. found that in 10 children (1–6 years of age), the ETTs with bevel facing left (normalorientation) all entered the right mainstem, whereas theETTs with bevel facing right (turned 180�) all enteredthe left mainstem (4).
The ETT is typically inserted from the right mouthcorner slightly concave to the right. This favors the
ETT going into the right mainstem bronchus. To improvethe chance of left mainstem intubation, one technique isto turn the ETT 180� once the tip is through the larynx,such that the bevel faces right, as mentioned, and turnthe patient’s head to the right, such that the ETT is cominginto the mouth from the left. This latter maneuver simu-lates a left-handed intubation with the ETT now slightlyconcave to the left. Kubota et al. found with this tech-nique that the chance of a left mainstem intubation is92% in their cohort of 359 patients (3). These findingssuggest that the bevel orientation is the main determinantof which mainstem bronchus the ETT enters whenadvanced too far, and serve to debunk the myth that adistally placed ETT most frequently enters the rightmainstem bronchus because of its larger size andstraighter angle with the trachea. Indeed, the fact thatwe intubate with our right hand with the ETT slightlyconcave to the right is also contributory, whereas the cari-nal asymmetry and the fact that the right mainstem bron-chus is larger have only a small contribution. In ourexperience, one only needs to rotate the ETT by 180�
once the ETT tip has passed the larynx, and either turnthe head to the right (if no cervical spine concerns) orslightly turn the ETT so that it is slightly concave to theleft, to achieve left mainstem bronchial intubation.
Use of Gum Elastic Bougie or Fiberoptic Bronchoscopy
In difficult intubation, the gum elastic bougie or fiberscopeis sometimes used to guide the ETT into the trachea. Occa-sionally, the ETT tip is impeded at the epiglottis, cornicu-late, or cuneiform cartilages, the right vocal cord oraryepiglottic fold. Clinicians typically rotate the ETTclockwise and counterclockwise to try to ‘‘screw’’ theETT through the larynx. After a few trials they usually suc-ceed, but at the expense of increased trauma and patientdistress, not to mention the delay in securing the airway.Indeed, twisting the ETT or changing the direction of thebevel may help reduce (and thus, improve) the incidentangle of the ETT tip in relation to the airway structurethe tip is against. This may be true when the tip is twistedaway from the sagittal plane to a different plane. Twistingthe ETTmay also free the tip from the structure it has inad-vertently caught onto during advancement into the airway.In addressing this latter point, we suggest that the efficientway is to simply turn the ETT counterclockwise 90�, suchthat it is concave to the left, prior to advancing it toward thelarynx (5). Figure 2 shows how the overhanging tip of thebevel of an ETT before the 90-degree counterclockwisetwist can hook onto some of the laryngeal structures, asmentioned, and how the bevel of a rotated ETT hugs thecurvature (on the concave side) of the bougie or fiberscopeand has much less chance of catching some structure onthe way through the larynx. The first-pass success rate
Figure 2. Endotracheal tube tips are bevelled one way and may be pointy (right panel) or slightly rounded. The middle panel isseen from above a patient during a typical way of advancing the endotracheal tube (ETT) through a gum elastic bougie or fiber-optic bronchoscope that has already been passed into the trachea. Note the free-hanging tip of the ETT that can catch some up-per airway structure. After a 90-degree counterclockwise twist of the ETT prior to advancing it, the ETT tip hugs the bougie orbronchoscope on its way toward the trachea, thus reducing the chance of it catching some structure. The view shown in theleft bottom panel is from the side of the patient.
The Bevel in Tracheal Intubation 3
without the 90-degree twist is 44%, 73%, and 23%–46% instudies (6–8). With the bevel facing posteriorly after the90-degree counterclockwise twist, the first-pass successrate was 100% in a small (n = 27 adults) study (6).
Theoretically, it is even more important to use the 90-degree counterclockwise twist to facilitate placement ofETTs with a straight pointy tip.
Nasotracheal Intubation
Nasotracheal intubation is applicable in spontaneouslybreathingpatientswhomay have a difficult airway, possiblecervical spine injury, limitedmouth opening, or head injury.Smooth passage reduces stress and secures the airway effi-ciently. A dreaded complication of nasotracheal intubationis epistaxis, which can occur despite nasal instillation of avasoconstrictor and pre-softening of the ETT. Theoreti-cally, the pointier portion of the ETT tip causes moretrauma than the receding side of the bevel during advance-ment. On the one hand, the Kisselbach plexus, the mostcommon site of epistaxis, is in the nasal septum. Basedon that consideration, the bevel should be facing mediallyduring ETT insertion. On the other hand, trauma to the tur-binates in the lateral nasal wall has been described (9).Among emergency medicine textbooks, there is noconsensus on which direction the bevel should face, withexamples of those recommending the bevel to face medi-
ally, laterally, or having no recommendation (10–13).None provide any explanation or reference. No majoranesthesiology textbook has a recommendation on beveldirection either. Given the rarity of major epistaxis andthe lack of strong evidence, it is unknown which directionis safer. In our practice, we have the bevel facingmedially, which means a concave caudally orientation forthe ETT if going through the right nostril, and a concavetoward the forehead if through the left nostril.
Sometimes, the ETT meets considerable resistance atthe back of the nasal passage. Some practitioners opt totwist and turn and increase the force and eventually theETT gets through. Figure 3 illustrates how a posterior fac-ing bevel may improve the ease of negotiating the ETTaround the curve at the nasopharyngeal wall. In otherwords, a 90-degree counterclockwise twist shouldimprove the ease of passage through the back of the nasalcavity. Sugiyama et al. go one step further (14). Theyinsert a stylet that is bent 60� at the distal end into theETT to facilitate the passage and withdraw the styletonce the ETT tip has passed the back of the nasal passage.This is an option if there are indeed great difficulties andthe patient is not tolerating the discomfort.
Even after the ETT tip has reached the laryngeal vicin-ity, it may still be caught on the arytenoid cartilages (usu-ally the right one), the epiglottis, or the pyriform fossa(Figure 4) (15,16). When one meets resistance in this
Figure 3. The incident angle of the endotracheal tube (ETT) with the posterior pharynx can be reducedwith a 90-degree counter-clockwise turn of the ETT.
4 A. M.-H. Ho et al.
situation, one should rotate the ETT counterclockwise tochange the plane and the incident angle of the ETT tip (15).
Finally, even if the ETT tip has cleared the epiglottis, itcan still be unwilling to slide into the trachea because of ahigh incident angle. This happens usually when a McGillforceps is used to lift the tip of the ETT toward the trachealentrance when mouth opening allows (see Figure 5, leftpanel, which is an illustration also applicable to a similarsituation occasionally encountered in videolaryngoscopy,discussed below). At this point, rotating the ETT clock-wise such that the bevel faces anteriorly may reduce thatangle and improve the chance of success.
Figure 4. Structures that can be caught by the endotracheal tube
The Endotracheal Tube that Will Not Go into the TracheaDuring Videolaryngoscopy
This high incident angle, made worse as the stylet isremoved, is also one factor occasionally making it difficultto pass an ETTeven after its tip has already passed the lar-ynx (Figure 5, left panel). Readers are encouraged to exper-iment by loading an ETTwith a curved stylet and witnesshow the ETT rises at a steep angle as the stylet is removed.Theoretically, twisting the ETT by 180-degreewould alignthe path of the ETTwith that of the trachea when the styletis withdrawn but rotating the ETT by that amount is very
tip in the vicinity of the larynx.
Figure 5. The high incident angle of the endotracheal tube (ETT) to the trachea (left panel) occasionally makes it difficult to insertthe ETT. A 90-degree clockwise rotation may reduce the incident angle (right panel).
The Bevel in Tracheal Intubation 5
difficult, as is preloading an ETT that has not been pre-warmed with its curvature 180� opposite that of the stylet.Turning the bevel to face anteriorly (clockwise twist) hasthe advantage of reducing the incident angle (Figure 5,right panel), is less difficult to accomplish, and is superiorto random or counterclockwise twisting.
Tracheoesophageal Fistula
Emergency physicians may encounter patients with tra-cheoesophageal fistula (TEF). Because most congenitaland acquired TEFs are at the posterior aspect of the tra-
Figure 6. An example of a congenital tracheoesophageal fis-tula and a schematic of the trachea as viewed from the side.The size of the fistula opening is commonly similar to those ofthe mainstem bronchi. Unlike what is often depicted in text-books, the angle subtended by the fistula to the trachea isalso similar to those subtended by the mainstem bronchi.
chea, and some can be large and most have a slantedorientation (Figure 6), it is important to orientate theETT with the bevel facing posteriorly to minimize thechance of intubating the fistula, which has been describedbefore (17–20). Once the ETT tip is distal to the fistula,the ETT (one without a Murphy eye) can be rotated180�, if necessary, to avoid ventilating the fistula.Similar considerations apply whenever the ETTposition has to be adjusted.
CONCLUSIONS
The direction of the ETT bevel may significantly changethe efficiency of tracheal intubation in situations thatinclude deliberate endobronchial, nasal, and bougie/fiber-scope- and videolaryngoscope-assisted intubations, andin patients with a tracheoesophageal fistula.
REFERENCES
1. Ho AMH, Ling E. Systemic air embolism after lung trauma. Anes-thesiology 1999;90:564–75.
2. Ho AMH, Flavin MP, Fleming ML, Mizubuti GB. Selective leftmainstem bronchial intubation in the neonatal intensive care unit.Braz J Anesthesiol 2018;68:318–21.
3. Kubota H, Kubota Y, Toyada Y, Ishida H, Asada A, Matsuura H. Se-lective blind endobronchial intubation in children and adults.pdf.Anesthesiology 1987;67:587–9.
4. Baraka A, Akel S, Muallem M, et al. Bronchial inbubation in chil-dren: does the tube bevel determine the side of intubation? Anesthe-siology 1987;67:869–70.
5. Cossham P. Difficult intubation. Br J Anaesth 1985;57:239.6. BarakaA, RizkM,MuallemM, Bizri S, Ayoub C. Posterior-beveled
vs lateral-beveled tracheal tube for fibreoptic intubation. Can JAnaesth 2002;49:889–90.
7. Pandit JJ, Dravid RM, Iyer R, Popat MT. Orotracheal fibreopticintubation for rapid sequence induction of anaesthesia. Anaesthesia2002;57:123–7.
8. Hakala P, Randell T. Comparison between two fibrescopes withdifferent diameter insertion cords for fibreoptic intubation. Anaes-thesia 1995;50:735–7.
13. Kene M, Davis D. Airway management. In: Roppolo L, Davis D,Kelly S, Rosen P, eds. Emergency Medicine Handbook: ClinicalConcepts for Clinical Practice. Philadelphia: Mosby Elsevier;2007:25–44.
14. Sugiyama K, Manabe Y, Kohjitani A. A styletted tracheal tube witha posterior-facing bevel reduces epistaxis during nasal intubation: arandomized trial. Can J Anaesth 2014;61:417–22.
15. Marfin AG, Iqbal R, Mihm F, Popat MT, Scott SH, Pandit JJ. Deter-mination of the site of tracheal tube impingement during nasotra-cheal fibreoptic intubation. Anaesthesia 2006;61:646–50.
16. Katsnelson T, Frost E, Farcon E, Goldiner P. When the endotrachealtube will not pass over the flexible fiberoptic bronchoscope. Anes-thesiology 1992;76:151–2.
17. Ho AMH, Dion J, Wong J. Airway and ventilatory management op-tions in congenital tracheoesophageal fistula repair. J CardiothoracVasc Anesth 2016;30:515–20.
18. Alabbad SI, Shaw K, Puligandla PS, Carranza R, Bernard C,Laberge J. The pitfalls of endotracheal intubation beyond the fistulain babies with type C esophageal atresia. Semin Pediatr Surg 2009;18:116–8.
19. Buchino J, Keenan W, Pietsch J, Danis R, Schweiss J. Malposition-ing of the endotracheal tube in infants with tracheoesophageal fis-tula. J Pediatr 1986;109:524–5.
20. Goswami D, Kachru N. Difficult ventilation in a wide congenitaltracheoesophageal fistula. Can J Anaesth 2012;59:118–9.
