Advancing Airway Management: Channeled Laryngoscopes
In a previous article we explored the different tools utilized for endotracheal intubation. This article focuses on channeled laryngoscopes, both optical and video, that assist with achieving safe and rapid intubation of the trachea. The two systems discussed are the Airtraq optical device and King Systems’ King Vision video laryngoscope.
The Airtraq received FDA approval in November 2006 and was initially marketed as an MRI-compatible intubating device. It utilizes a set of reflective prisms with a distal light source to enable the airway manager to view around the tongue without requiring its displacement. A channel on the right side of the device holds an endotracheal tube (ETT) at the ready. Once an appropriate view of the glottis is obtained, the ETT is gently slid forward through the channel into the trachea. Once in position, it is gently disconnected laterally from the Airtraq, and the device is removed from the patient’s mouth.
A PubMed literature review for the Airtraq reveals numerous articles describing its utilization in normal and predicted difficult airway cases. In 2006 a team led by Chrisen Maharaj, MD, BSc, described a comparison of the Airtraq versus the Macintosh laryngoscope (direct laryngoscopy) in routine airway management of 60 patients. All patients were intubated successfully, and only one patient in the Macintosh control group required additional attempts. Modest improvements in ease of use and less hemodynamic variation during the intubation occurred with the Airtraq. This article supported the Airtraq in routine airway management with similar success to DL.
Several studies also evaluated the Airtraq in predicted or known difficult airways. In 2008 Dr. Serge Ndoko, et al, presented a comparison between the Macintosh and the Airtraq in 106 morbidly obese patients. Patients were randomly assigned to either a Macintosh #3 or the Airtraq. In addition, if intubation could not be performed with the randomized device within 120 seconds, then the alternative device was attempted. Results showed that intubation via the Macintosh #3 blade occurred on the first attempt 49 of 53 times (92%), required some alternative technique 17/53 times (32%) and needed external manipulation of the larynx 31/53 times (58%). Alternatively the Airtraq was successful on the first attempt 53 out of 53 times, required some alternative technique zero times, and needed external manipulation of the larynx 4/53 times (8%). This particular study showed a clear benefit to using the Airtraq in the predicted difficult airway of the morbidly obese patient.
A similar study was published in 2012 by Dr. Dante Ranieri, Jr., et al, in which intubating conditions and success of intubation were evaluated in 128 obese patients undergoing bariatric surgery. This study found that, using the Cormack-Lehane (CL) scoring for glottic visualization, the Macintosh produced a grade 3 or 4 view (no direct view of the glottic opening) in 7/64 patients (11%). One patient in this group could not be intubated successfully with the Macintosh and was subsequently intubated with the Airtraq. The Airtraq was evaluated utilizing the same CL scoring system and produced a grade 3 or 4 view in 0/64 patients. Additionally it was noted that the Airtraq scored significantly better in CL grade 2 views (in which only part of the glottic structure is visualized) compared to the Macintosh (Airtraq 3 vs. Macintosh 20). This article further supports use of the Airtraq in the morbidly obese patient population. Exercise caution, though, as factors beyond morbid obesity affect intubation difficulty.
The King Vision channeled video laryngoscope is similar to the Airtraq but uses video technology to see around the tongue and display the glottic structures on the attached video screen. A review in PubMed did not reveal any studies published on the King Vision thus far, though it is being widely adopted.
Airway practitioners find similar factors that challenge the use of both the Airtraq and the King Vision. One factor that leads to airway management difficulty is soiling of the airway by blood and/or vomit, both common in trauma patients. Few published studies have evaluated the incidence and complications associated with management of these soiled airways when an optical or video channeled device is used. A clear problem associated with optical and video devices in soiled airways is obscured lenses, which prevent clear images of the glottic structures. Although techniques to deal with this complication, such as suctioning ahead of the device, are becoming more common, it remains a significant problem.
Another factor that leads to difficulties with channeled optical and video devices is the facilitation of tube placement once the glottic structure is visualized. In DL, a line of sight (and ETT advancement) is created between the airway manager’s vision and the glottic opening. Once the glottic opening is visualized, placement of the ETT into the trachea is straightforward. Channeled devices that look “around” the tongue require the device to be placed in the optimum position to achieve tube placement, since the tube can only be minimally directed while in the channel. A common occurrence is excellent visualization of the glottic structures (CL grade 1 view) but an inability to advance the ETT into the trachea. For channeled devices this is usually rectified by slightly withdrawing the device and assuring the target glottis is in the middle of the viewing screen. Once this view is obtained, the ETT can be advanced into the trachea and intubation completed.
The Airtraq and King Vision are two of many new advanced imaging devices that have been added to the airway armamentarium. At this point it is impossible to say which device is the best, but there is evidence to show the Airtraq improves first-pass success compared to traditional direct laryngoscopy in difficult intubations, particularly for obese patients. Since the King Vision is a similar device, it may well show the same success when the Airtraq studies are replicated. In our next article, we will examine the use of non-channeled scopes, and a future issue will evaluate the cost per procedure of some common devices. Until then, happy intubating.
Maharaj CH, O’Croinin D, Curley G, Harte BH, Laffey JG. A comparison of tracheal intubation using the Airtraq or the Macintosh laryngoscope in routine airway management: A randomized, controlled clinical trial. Anaesthesia, 2006 Nov; 61(11): 1,093–9.
Ndoko SK, Amathieu R, Tual L, et al. Tracheal intubation of morbidly obese patients: a randomized trial comparing performance of Macintosh and Airtraq laryngoscopes. Br J Anaesth, 2008 Feb; 100(2): 263–8.
Ranieri D Jr., Filho SM, Batista S, do Nascimento P Jr. Comparison of Macintosh and Airtraq laryngoscopes in obese patients placed in the ramped position. Anaesthesia, 2012 Sep; 67(9): 980–5.
Lu Y, Jiang H, Zhu YS. Airtraq laryngoscope versus conventional Macintosh laryngoscope: a systematic review and meta-analysis. Anaesthesia, 2011 Dec; 66(12): 1,160–7.
Kevin M. Franklin, CFRN, BS, EMT-P, is a flight nurse with West Michigan Air Care in Kalamazoo, as well as the service’s utilization review coordinator and credentialing coordinator. He is the Midwest regional course director for The Difficult Airway Course: EMS and Fundamentals of Airway Management.
Jan Eichel, CFRN, BA, EMT-P, is director of clinical operations and a flight nurse with West Michigan Air Care. She is Southeast regional course director for The Difficult Airway Course: EMS.