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ORIGINAL ARTICLE
Year : 2022  |  Volume : 20  |  Issue : 3  |  Page : 138-142

The incidence of trauma with the use of glidescope in anticipated difficult airway cases – A prospective observational study


1 Department of Anesthesia, Christian Medical College, Vellore, Tamil Nadu, India
2 Maidstone and Turnbridge Wells NHS TRUST, Kent, UK

Date of Submission29-Oct-2021
Date of Decision09-Mar-2022
Date of Acceptance23-Mar-2022
Date of Web Publication01-Aug-2022

Correspondence Address:
Dr. Mary Benita Jeyakumar
Christian Medical College, Vellore - 632 006, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/cmi.cmi_94_21

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  Abstract 


Background: Glidescope video-laryngoscope (GVL) is an invaluable equipment for patients with anticipated difficult intubations that aids in visualizing the vocal cords out of line-of-sight. However, despite the ease in the visualization and shortening of the time taken to visualise the cords, the intubation time is often prolonged and is associated with trauma. This study aims at identifying incidence of trauma with glidescope in anticipated difficult airway scenario and whether correct practice by experienced anesthesiologist can reduce trauma. Methodology: Eighty-nine adult patients with anticipated difficult airway who were intubated using GVL by experienced anesthesiologists in a tertiary care setting were studied. The time to visualize, the time to intubate, the difficulties encountered at intubation were documented, the incidence of trauma was reported. The factors associated with trauma were analyzed using PSPP software (psppire. exe 0.8.4-g012d99). Results: The incidence of airway trauma was 11.2%. It was higher in the group with technical difficulties (Gtd) (P < 0.001) and was less in the hands of an experienced anesthesiologist (P = 0.02). Conclusion: GVL intubation in anticipated difficult airway cases by experienced anesthesiologists using the right technique has lesser incidence of trauma, lesser than that is seen with Macintosh intubations in anticipated difficult airway scenario. Knowledge on techniques to troubleshoot technical difficulties with GVL may reduce the incidence of trauma further and needs to be studied more.

Keywords: Incidence, intubation, laryngoscopes


How to cite this article:
Jeyakumar MB, Abraham MA, Singh G, Chandy TT. The incidence of trauma with the use of glidescope in anticipated difficult airway cases – A prospective observational study. Curr Med Issues 2022;20:138-42

How to cite this URL:
Jeyakumar MB, Abraham MA, Singh G, Chandy TT. The incidence of trauma with the use of glidescope in anticipated difficult airway cases – A prospective observational study. Curr Med Issues [serial online] 2022 [cited 2022 Oct 6];20:138-42. Available from: https://www.cmijournal.org/text.asp?2022/20/3/138/352983




  Introduction Top


Glidescope video-laryngoscope (GVL) is an invaluable equipment for patients with anticipated difficult intubations that aid in visualizing the vocal cords out of line of sight.[1] It offers the advantage of minimal cervical spine movement and decreased force of application which results in lesser sympathetic response to intubation.[2],[3],[4],[5] Studies evaluating the efficacy of GVL confirm that despite the ease in visualization and shortening of the time taken to visualize, the intubation time was often prolonged in comparison with direct laryngoscopy using Macintosh blades.[6],[7] Furthermore, studies show increasing incidence of airway trauma with the use of GVL.[8],[9],[10],[11],[12] The image of the larynx which is out of line-of-sight,[1] blind spot in visualization (the tangent of the scope beyond the camera is not visualized),[13] and the mandatory use of the rigid stylet for intubation[14] have been implicated for the increased incidence of airway trauma. To overcome these technical difficulties, the glidescope comes with an instruction manual on the conduct of GVL scopy which is a 4-step technique[14] and this technique has a learning curve.[15]

The incidence of upper airway injuries with the use of glidescope has been reported in many studies. The incidence of trauma in the Xue et al.'s study was 3.4% (n = 91).[16] However, there was no mention of the sites of trauma and the reporting was made plainly based on the bloodstains on the GVL. The evidence for trauma was not actively sought after. Furthermore, the intubations were performed on mixed population with adequate airway and anticipated difficult airway. There were only 27 patients with difficult airway and if all the three cases with trauma were from this group, the incidence would be way higher. In a study by Pournajafian et al., a randomized controlled trial of GVL versus Macintosh, no injury was found in the GVL group.[6] The intubations were done by a single operator trained in the use of GVL on patients posted for elective surgery. Patients with anticipated difficult airway were excluded from the study. Aziz et al. report an incidence of 1.3% in 2004 patients with predicted difficult airway.[17] However, it was a retrospective evaluation of electronic medical records using certain select words to search for evidence of trauma. Greer et al. report an incidence of 0.0234% after a retrospective evaluation of 14,680 records inclusive of adequate airway and difficult airway cases.[18] Although such data are available, there is a paucity of data on the incidence of injuries with the use of GVL in predicted difficult airway cases.

Aims and objectives

The purpose of our study was to prospectively assess the incidence of trauma with the use of GVL in anticipated difficult airway cases and analyze whether correct practice by experienced anesthesiologists can decrease the incidence of trauma.


  Methodology Top


Study design and setting

This was an observational study done in a tertiary care teaching institute between November 2014 and August 2015.

Inclusion criteria and exclusion criteria

(1) Patients over 18 years of age, with anticipated difficult airway as assessed by the attending anesthesiologist based on Malampatti class (III/IV), neck extension (<80°), and body mass index (more than 30) with adequate mouth opening (limited mouth opening is a contraindication for GVL use), and planned for intubation with GlideScope® Cobalt (Verathon medical, Inc., Bothell, WA, USA) as the first attempt device were included in the study. (2) Patients intubated by experienced anesthesiologists were included (the Indian Society of Anesthesiologist definition of an experienced anesthesiologist: any anesthesiologist with more than 3 years of experience).

Patients who were intubated by inexperienced anesthesiologists (n = 16), patients who were intubated using alternative techniques (n = 21), and patients who had incomplete data collection forms (n = 34) were excluded from the study.

Variables and data collection

In the operating room, standard American Society of Anesthesiologists (ASA) monitoring was established. The conduct of anesthetic induction and the choice of endotracheal tube size were left to the discretion of the attending anesthesiologist.

The study protocol was as follows. A timer was turned on to estimate the time to visualize and time to intubate. Time to visualize was defined as the time taken from the time of insertion of scope to time of visualization of the cords. The time to intubate was defined as the time of visualization to time of satisfactory End-tidal CO2 (EtCO2) trace. The time to visualize and the time to intubate were noted down in seconds. The scope is then withdrawn while looking for evidence of trauma. The attending anesthesiologist documented the demographic details, ASA status, time to visualize, time to intubate, evidence of trauma, and the Intubation Difficulty Scale (IDS).

Statistical methods

The collected data were entered on Epidata and exported into Excel for further analysis using PSPP software (psppire. exe 0.8.4-g012d99). Descriptive statistics were reported using mean +/‒standard deviation, median with inter quartile range. Categorical variables were reported using frequency and percentage. Chi-square was used to check the association between outcome and the other variables. Risk factor analysis for the outcome was done using generalized linear models using stepwise method.

Bias

Hawthorne bias was one of the limitations of this study.

Sample size

Based on a pilot study on the incidence of airway trauma with GVL use in our institution, the sample size was calculated to be 190 with alpha error set at 10% and power at 80%. After obtaining the institutional review board approval, 150 patients who consented to the study were recruited. The final number of cases fulfilling the inclusion criteria in this study was 89.


  Results Top


The characteristics of the patients who participated in this study are presented in [Table 1]. The mean age of the study population was 51 ± 13 years. The male: female ratio was 7:3. Most of the patients were ASA II. The average time to visualize was 19 ± 17 s and the average time to intubate was 46 ± 26 s which is significantly longer than the time to visualize. The years of experience of the intubating anesthesiologists was 6 ± 3 years on an average (n = 86: Data were missing in three cases). Most patients had an IDS ≤5 (76/89). The data for the same are also presented in [Table 1].
Table 1: Patient characteristics and demographic details

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Technical difficulties were encountered in 21/89 cases (24%). The details are presented in [Table 2]. In some of the patients, multiple difficulties were encountered. The most common were difficulty in directing the tube toward the cords and decreased working space.
Table 2: Technical difficulties with the use of Glidescope Video-Laryngoscope

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The incidence of trauma was 11.2% in our study (10 out of 89 cases). All were minor trauma which did not require surgical management. There was no desaturation documented. Lip injury was the most common injury (50%). The other sites of injury were faucial pillars (10%), vallecula (10%), larynx (20%), and teeth (10%). Patients had lip injury when the anesthesiologist encountered difficulty in directing tube toward the cords and had less working space.

The group which had technical difficulties (Gtd) (n = 21) was compared with the group which had no technical difficulties (Gntd) (n = 68) and the same is presented in [Table 3]. The mean age was higher in the Gtd suggesting increasing prevalence of airway difficulty in the older age group.[19] The years of experience of the intubating anesthesiologist was significantly more in Gntd (P = 0.02). Finally, the incidence of trauma was seen to be significantly higher in the Gtd (P < 0.001).
Table 3: Comparison of group with technical difficulties versus group with no technical difficulties

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The analysis of trauma versus nontrauma cases, presented in [Table 4], shows that the mean age was relatively higher and the years of experience of the intubating anesthesiologist was slightly lesser in the trauma group. However, these observations were not statistically significant. Time to visualize and time to intubate were longer in the trauma group demonstrating difficulty which predisposes to trauma. In addition, the number of cases which had technical difficulties was significantly more in the trauma group (P < 0.001) as already mentioned. However, the incidence of trauma and IDS showed no significant association.
Table 4: Trauma versus nontrauma cases

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  Discussion Top


The statistics on upper airway trauma with laryngoscopy is as follows: Five percentage of all normal laryngoscopies, 17% in patients anticipated to have difficult intubation and 63% in patients with actual difficulty in intubation.[16] The results from our study is lesser than the estimated incidence of trauma with Macintosh laryngoscopes in patients with anticipated difficult airway cases. This may be due to the fact that all intubations in our study were performed by experienced anesthesiologists. However, the result is higher than the incidence seen in Aziz et al.'s study. One of the reasons could be that the search for trauma was based on retrospective search for certain specific words. This has a high probability of missing trauma cases if they were described using other words used for the search. Another reason for this could be that the final number of study participants was grossly low in our study.

The incidence of trauma was much less in the hands of the more experienced anesthesiologist and incidence of trauma was more in the hands of the less experienced anesthesiologist (P = 0.02). This confirms that there is a learning curve for GVL which is in par with existing literature.[20],[21]

Another finding was that 43% of patients in whom the anesthesiologist encountered a technical difficulty developed trauma (P < 0.001). The most common technical difficulty encountered was directing the tube toward the cord which is comparable to existing data on children.[22] The technical difficulties have not been clearly studied in adults although some practical suggestions for trouble shooting have been made.[23]

The success rate of intubation with GVL by experienced anesthesiologists in predicted difficult intubation was 100% in our study as opposed to Aziz et al.'s study which had a success rate of 98%.[17] This could be due to the Hawthorne's effect: This is one's reaction in response to the knowledge of the fact that one is under observation. The efficiency seems to be greater than usual while under observation. This observation bias was unavoidable in our study.

A major limitation of the study was that it is underpowered. Due to the limited number of glidescope, included patients were lost when induced simultaneously making our study grossly underpowered. In addition, the time to intubate was influenced by many factors such as zero calibration of the gas module (time to intubate was prolonged), bronchospasm (delayed EtCO2 trace due to bronchospasm therefore prolonged time to intubate). No significant predisposing factors could be identified in the trauma cases since the number of patients studied was too small.


  Conclusion Top


We conclude that GVL intubation in anticipated difficult airway cases by experienced anesthesiologists using the right technique has much lesser incidence of trauma, lesser than that is seen with Macintosh intubations in anticipated difficult airway scenario. Knowledge on techniques to troubleshoot technical difficulties with GVL may reduce the incidence of trauma further and needs to be studied more.

Research quality and ethics statement

All authors of this manuscript declare that this scientific study is in compliance with standard reporting guidelines set forth by the EQUATOR Network. The authors ratify that this study required Institutional Review Board/Ethics Committee review, and hence prior approval was obtained IRB Min. No. 9107 [OBSERVE] dated 06/10/2014). We also declare that we did not plagiarize the contents of this manuscript and have performed a Plagiarism Check.

Acknowledgments

We would lie to thank Dr. Divya Jacob (study topic selection).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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