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September 1, 2013 Volume 77, Number 9
Videolaryngoscopy and the Difficult Airway Michael Aziz, M.D.


Videolaryngoscopy made its introduction to airway management more than 10 years ago. Since this time, we have learned much about the utility of the devices and have generated questions to guide future investigation. What is clear is that these tools generally provide an improved and magnified laryngeal view compared to direct laryngoscopy. Research has attempted to identify whether these benefits translate to an improvement in actual intubation difficulty and/or success rate. As success rates for tracheal intubation utilizing direct laryngoscopy in experienced hands is very high, there does not seem to be added benefit beyond improvement of laryngeal view for the undifferentiated airway across age spectrums.1,2 However, evidence has made it clearer that videolaryngoscopy eases intubation difficulty and increases first-attempt success rates in the airway predicted to be difficult to intubate by direct laryngscopy.3-5 These benefits are seen for patients who are obese, have a raised Mallampati score, and reduced cervical motion from pathology or cervical spine precautions.


The greatest benefit for videolaryngoscopy may be for the inexperienced provider. Compared to direct laryngoscopy, intubation success rates are higher with videolaryngoscopy than direct laryngoscopy.6,7 These benefits come both with devices that are video-assisted direct laryngoscopes as well as those with acutely curved indirect laryngoscopes. An instructor-guided laryngoscopy with a video device appears to accelerate even direct laryngoscopy skills.


Compared to awake fiberoptic intubation, awake video-laryngoscopy has been evaluated for the potential difficult airway.8 Findings demonstrated similar performance with both techniques. However, validity of the study findings is limited by sedation techniques and randomization exclusions.9 Despite these limitations, awake videolaryngoscopy may be a tool that is easier to learn and master than flexible fiberoptic intubation and likely has a future role in awake airway management.


One of the potential benefits of video technology is the capacity to record and archive pictures or video clips from the laryngoscopy. These records can be used to confirm tracheal tube placement, document laryngeal view, document absence of trauma and teach future laryngoscopists. Today’s anesthesia record contains a narrative describing the device, laryngeal view on the Cormack and Lehane scale, absence of trauma and confirmation of tube placement with various tools. Imagine the future electronic record as a single picture or video clip that tells the same story, and more! To date, anesthesia information management systems have not incorporated archiving of digital airway images as part of the anesthesia record, but this future seems feasible.


Early investigations in various clinical environments outside of the operating room suggest potential benefit. These environments contain both difficult airway scenarios and providers with less airway management experience than is often found in the operating room. In critical care and emergency medicine environments, videolaryngoscopy was associated with a higher intubation success rate in patients with predictors of difficult direct laryngoscopy.10-12 In the obstetric environment, videolaryngoscopy has been used for emergency airway management, potential difficult intubations and to rescue failure of direct laryngoscopy.13 Finally, in prehospital emergency medicine, videolaryngoscopy is associated with a reduction in the number of intubation attempts and shorter laryngoscopy time than direct laryngoscopy.14 However, these studies are retrospective in nature and interpretation of the results deserves some caution. Prospective, randomized studies are much more difficult to perform in these dynamic and emergent environments.


Despite these many benefits for the difficult airway, video- laryngoscopy can fail. One source of failure is an inability to achieve a laryngeal view. However, a frequent and more perplexing scenario is that of an adequate laryngeal view but inability to pass the tube into the trachea. This difficulty may occur with acutely curved indirect laryngoscopes, channeled videolaryngoscopes or even with video-assisted direct laryngoscopes. We have identified predictors of failure with one particular videolaryngoscope.15 The strongest predictor for failure is neck pathology from tumor, radiation or surgical scar. This evidence suggests that flexible techniques remain an important tool with which to master and maintain competency.


Many authors believe that videolaryngoscopy causes less patient stress than direct laryngoscopy. Indeed, less suspension pressure and extension of the cervical spine may be necessary to achieve an adequate laryngeal view. However, well designed clinical trials have been inconsistent in demonstrating that videolaryngoscopy is associated with less cervical traction than direct laryngoscopy when manual in-line stabilization is applied.16


Reports continue to confirm that pharyngeal injury is a problem with videolaryngoscopy. In particular, there are many reports of tracheal tubes passing through soft tissue of the pharynx during videolaryngoscopy.17 Obviously, the health care provider and tube cause this injury, not the device. However, despite some widespread knowledge of this potential problem, this complication occurs even in experienced hands. Caution is warranted when advancing a tracheal tube through the pharynx during videolaryngoscopy, especially if visual attention is distracted from the patient.


Future research is poised to address some key questions. In particular, very few studies have compared videolaryngoscope types and designs to determine the ideal device characteristics. Some limited data suggest that devices with channeled components (with a preloaded tube) result in faster and easier intubation than non-channeled devices.18 Furthermore, questions surrounding blade design continue to arise. For example, video-assisted direct laryngoscopes (i.e., Macintosh blade design) have the potential benefit of familiarity, simple tube passage and narrow blade profile. On the other hand, acutely curved blade designs may further augment laryngeal view for the truly difficult airway management. Future investigations will help guide the clinical scenarios for use, algorithm approaches and device designs.



Michael Aziz, M.D. is Associate Professor, Oregon Health & Science University, Portland, Oregon.



References:


1. Fiadjoe JE, Gurnaney H, Dalesio N, et al. A prospective randomized equivalence trial of the GlideScope Cobalt(R) video laryngoscope to traditional direct laryngoscopy in neonates and infants. Anesthesiology. 2012;116(3): 622-628.


2. Sun DA, Warriner CB, Parsons DG, Klein R, Umedaly HS, Moult M. The GlideScope Video Laryngoscope: randomized clinical trial in 200 patients. Br J Anaesth. 2005;94(3):381-384.


3. Malik MA, Subramaniam R, Maharaj CH, Harte BH, Laffey JG. Randomized controlled trial of the Pentax AWS, Glidescope and Macintosh laryngoscopes in predicted difficult intubation. Br J Anaesth. 2009;103(5):761-768.


4. Jungbauer A, Schumann M, Brunkhorst V, Borgers A, Groeben H. Expected difficult tracheal intubation: a prospective comparison of direct laryngoscopy and video laryngoscopy in 200 patients. Br J Anaesth. 2009;102(4):546-550.


5. Aziz MF, Dillman D, Fu R, Brambrink AM. Comparative effectiveness of the C-MAC video laryngoscope versus direct laryngoscopy in the setting of the predicted difficult airway. Anesthesiology. 2012;116(3):629-636.


6. Howard-Quijano KJ, Huang YM, Matevosian R, Kaplan MB, Steadman RH. Video-assisted instruction improves the success rate for tracheal intubation by novices. Br J Anaesth. 2008;101(4):568-572.


7. Nouruzi-Sedeh P, Schumann M, Groeben H. Laryngoscopy via Macintosh blade versus GlideScope: success rate and time for endotracheal intubation in untrained medical personnel. Anesthesiology. 2009;110(1):32-37.


8. Rosentock CV, Thogersen B, Afshari A, Christensen AL, Eriksen C, Gatke MR. Awake fiberoptic or awake video laryngoscopic tracheal intubation in patients with anticipated difficult airway management: a randomized clinical trial. Anesthesiology. 2012;116(6):1210-1216.


9. Todd MM, Bayman EO. Fiberoptic versus videolaryngoscopic management of the difficult airway: problems with postran-domization patient exclusion. Anesthesiology.2013;118(2):460.


10.Noppens RR, Geimer S, Eisel N, David M, Piepho T. Endotracheal intubation using the C-MAC(R) video laryngoscope or the Macintosh laryngoscope: a prospective, comparative study in the ICU. Crit Care. 2012;16(3):R103.


For a complete list of references, please refer to the back of the online version of the ASA NEWSLETTER at asahq.org or email communications@asahq.org.


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