Comparison of Direct and Video Laryngoscopes during Different Airway Scenarios Performed by Experienced Paramedics: A Randomized Cross-Over Manikin Study

Introduction. Airway management plays an essential role in anaesthesia practice, during both elective and urgent surgery procedures and emergency medicine. Aim The aim of the study was to compare Macintosh laryngoscope (MAC), McGrath, and TruView PCD in 5 separate airway management scenarios. Methods This prospective cross-over simulation study involved 93 paramedics. All paramedics performed intubation using direct laryngoscope (MAC), McGrath, and TruView PCD video laryngoscopes. The study was performed in 5 different scenarios: (A) normal airway, (B) tongue oedema, (C) pharyngeal obstruction, (D) cervical collar stabilization with tongue oedema, and (E) cervical collar stabilization with pharyngeal obstruction. Results In scenario A, the success rate was 99% with MAC, 100% with McGrath, and 94% with PCD. Intubation time was 17 s (IQR: 16–21) for MAC, 18 s (IQR: 16–21) for McGrath, and 27 s (IQR: 23–34) for PCD. In scenario B, the success rate was 61% with MAC, 97% with McGrath, and 97% with PCD (p < 0.001). Intubation time was 44 s (IQR: 24–46) for MAC, 22 s (IQR: 20–27) for McGrath, and 39 s (IQR: 30–57) for PCD. In scenario C, the success rate with MAC was 74%, 97% with McGrath, and 72% with PCD (p < 0.001). Intubation time was 44 s (IQR: 24–46) for MAC, 22 s (IQR: 20–27) for McGrath, and 39 s (IQR: 30–57) for PCD. In scenario C, the success rate with MAC was 74%, 97% with McGrath, and 72% with PCD (p < 0.001). Intubation time was 44 s (IQR: 24–46) for MAC, 22 s (IQR: 20–27) for McGrath, and 39 s (IQR: 30–57) for PCD. In scenario C, the success rate with MAC was 74%, 97% with McGrath, and 72% with PCD (p < 0.001). Intubation time was 44 s (IQR: 24–46) for MAC, 22 s (IQR: 20–27) for McGrath, and 39 s (IQR: 30–57) for PCD. In scenario C, the success rate with MAC was 74%, 97% with McGrath, and 72% with PCD ( Conclusions The McGrath video laryngoscope proved better than Truview PCD and direct intubation with Macintosh laryngoscope in terms of success rate, duration of first intubation attempt, number of intubation attempts, Cormack-Lehane grade, percentage of glottis opening (POGO score), number of optimization manoeuvres, severity of dental compression, and ease of use.


Introduction
Advanced airway management is crucial in the treatment of severely injured or sick patients [1]. Endotracheal intubation is considered the preferable technique to secure and protect an airway, especially in the out-of-hospital emergency setting. Endotracheal intubation might be challenging, especially if performed by relatively inexperienced providers and prolonged intubations lead to a higher risk of adverse respiratory events and increased risk of airway injuries [1][2][3]. Unrecognized esophageal intubation is associated with even worse clinical outcomes and may cause even death [1,3,4].
Endotracheal intubation in the out-of-hospital setting is especially challenging, as paramedics have to deal with difficult circumstances and suboptimal positions [1]. Direct laryngoscopy using a Macintosh blade (MAC) is the widely used standard technique for endotracheal intubation, but this technique requires a high level of training and personal skills [1,2,4,5]. Video laryngoscopy was introduced into clinical practice to ease endotracheal intubation and might be especially useful in less experienced providers like paramedics. Video laryngoscopes are equipped with a camera on the tip of the blade, enabling better visualization of the airway anatomy and ultimately making it easier to visualize the entrance to the larynx [3,6]. Several video laryngoscopes have recently been developed and are currently commercially available [3].
e McGrath video laryngoscope (Aircraft Medical, Edinburgh, United Kingdom) is a portable video laryngoscope with Macintosh-style blades for paediatric and adult patients. It is in clinical use for many years now and is widely used in both in-hospital and out-of-hospital settings [7,8].
e Truview PCD (referred to in this paper as PCD) system consists of a set of optical blades for neonates, paediatric patients, and adults with a built-in cleaning system, handles, blades with a dedicated Truview PCD camera, and a monitor with photo and video recording capabilities [9][10][11]. e Truview PCD offers a unique blade that provides a wide angle optical view and, using a prismatic lens, enables visualization of the larynx entrance (without requiring the alignment of the oral, pharyngeal, and tracheal axes) and confirmation of correct introduction and position of the endotracheal tube [9][10][11]. e aim of the study was to compare MAC, McGrath, and PCD in 5 different simulated airway management scenarios. Our hypothesis was that the video laryngoscopes are superior in terms of intubation success rate compared to MAC if used by paramedics in a manikin setting.

Material and Methods
e study protocol was approved by the institutional review board of the Polish Society of Disaster Medicine (approval no. 21.09.2018.IRB). After obtaining written informed consent, 93 paramedics were enrolled in the study. e inclusion criteria were as follows: more than 5 years of professional work experience, previous experience with endotracheal intubation using MAC, and no previous experience with any type of video laryngoscopes.

Study Protocol.
All paramedics participating in the study underwent a 45-minute lasting lecture covering basic aspects of airway management using direct laryngoscopy and video laryngoscopy. Afterwards, paramedics were allowed to familiarize themselves with the McGrath and TruView PCD laryngoscopes and were asked to perform at least one successful intubation with each device. All intubations were performed on a MegaCode Kelly advanced life support manikin (Laerdal Medical, Stavanger, Norway).
Paramedics were then randomly assigned to 1 out of 3 groups. Randomization was based on the Research Randomizer (http://www.randomizer.org) software.
e airway of the manikin as well as the tubes was well lubricated. e tubes were equipped with a hockey-stick-shaped stylet, prepared by an experienced researcher. All study participants were allowed to adjust the stylet as desired. After randomization, paramedics were asked to perform 5 intubations in 5 subsequent airway scenarios.
(1) Scenario A: normal airway. Once the paramedic completed the initial 5 scenarios, the paramedic was asked to perform another 5 airway scenarios with an alternate technique in the same manner as described above. After the completion of all airway scenarios using the second airway technique, paramedics performed the final five airway scenarios with the third and remaining airway technique.
All scenarios were limited to a maximum of 1 intubation attempt and each intubation attempt was limited to a maximum of 60 seconds. To avoid any teaching bias, all paramedics performed the intubations alone and were not allowed to observe one another.

Measurements.
e primary endpoint was the overall success rate. e secondary endpoints included duration of intubation attempt, Cormack-Lehane grade, POGO score, number of optimization manoeuvres, severity of dental compression, and ease of use. e duration of an intubation attempt was defined as the time from grasping the airway device until the first successful ventilation of the lungs. Ease of use was assessed with a visual analogue scale score ranging within 1-100, with 1 indicating "extremely easy" and 100 indicating "extremely difficult." e number of optimization manoeuvres was assessed and documented by observation by an independent researcher. POGO score and Cormack-Lehane classification were assessed by asking the paramedics after each intubation attempt [12].

Statistical Analysis.
e sample size was based on expected differences of time to intubation and calculated with G × Power 3.1 using a two-tailed t-test (Cohen's d � 0.8, alpha error � 0.05, power � 0.95). With the minimum of 80 participants necessary, 93 paramedics were included to compensate for potential doubts. e statistical analysis was performed with the Statistica software version 13.3EN for Windows (Tibco Inc., Tulsa, USA). e level of significance was set at the value of p < 0.05. Data are presented as number (percentage), mean ± standard deviation (SD), or median (interquartile range [IQR]), as appropriate. Nonparametric tests were used for the data that did not have normal distribution, which was tested with the Lilliefors test and the Shapiro-Wilk test. All statistical tests were two-sided. e one-way ANOVA on ranks was applied to compare the different times and to determine the statistical difference for each group (post hoc Bonferroni correction was used to counteract the problem of multiple comparisons).

Results
Ninety-three paramedics with a median of 8.5 years [IQR: 5.5-11] of experience participated in this study. All of the paramedics had a previous experience with direct laryngoscopy guided endotracheal intubation (median 54 intubations (IQR: 42-77)) and none had any experience with any video laryngoscope. Endotracheal intubation with McGrath was associated with the fewest optimization manoeuvres in comparison with MAC (p < 0.001) and PCD (p < 0.001). McGrath also had the fewest number of tooth compressions in comparison with MAC (p < 0.001) and PCD (p < 0.001).      e best POGO score was obtained for McGrath and for PCD (100% each), and the worst for MAC (80%).

Scenario
Endotracheal intubation with McGrath was associated with the fewest optimization manoeuvres in comparison with MAC (p � 0.021) and PCD (p < 0.001).
McGrath also had the fewest number of tooth compressions in comparison with MAC (p � 0.006) and PCD (p < 0.001).

Scenario D: Cervical Collar Stabilization and Tongue
Oedema. Detailed results obtained in scenario D are presented in Table 4. e success rate with MAC was 32%, compared to 69% for McGrath and 58% for PCD.

Scenario E: Cervical Collar Stabilization and Pharyngeal
Obstruction. Detailed results of the parameters obtained in scenario E are presented in Table 5

Discussion
e most important finding of our randomized cross-over simulation study is the superiority of the McGrath video laryngoscope compared to conventional Macintosh laryngoscope intubation, considering the overall success rate, duration of intubation attempt, Cormack-Lehane grade, POGO score, number of optimization manoeuvres, severity of dental compression, and ease of use in all 5 tested scenarios of normal and difficult airways.
Overall, the success rate for MAC ranged between 15% in scenario E and 99% in scenario A. While the success rate in the normal airway is acceptable, a success rate of only 15% is far from acceptable. Consequently, MAC should not serve as the first airway intubation device for paramedics. For PCD, the success rate varied between 57 and 97% in the several airway scenarios. It is worth noting that, in all difficult airway scenarios, the overall success rate for McGrath was between 69% and 94%. We noticed that paramedics performed endotracheal intubation with best results when using McGrath as compared with PCD and MAC. In contrast to our results, Altun et al., in a simulation study on Macintosh, McGrath, McCoy, and C-MAC laryngoscopes among 41 anaesthesiology residents, revealed that McGrath offered the longest intubation time, especially in a difficult airway (tongue oedema) scenario [11]. In an observational study in a prehospital setting, the McGrath MAC video laryngoscope first-pass success rate did not change when compared with the previous period of using Macintosh laryngoscope; however, the post-rapid sequence induction first-pass success rate was significantly higher. e authors concluded that gastric content, blood, or secretion in the airway resulted in reduced vision when using the McGrath MAC video laryngoscope [13]. Choi et al. in a manikin study compared tracheal intubation by novice users applying the McGrath series 5 video laryngoscope versus the Macintosh laryngoscope in a cervical immobilized manikin and revealed that the first-attempt success rate was higher for the McGrath compared with the Macintosh laryngoscope in cervical immobilizations (84% versus 48%, resp.; p � 0.019). In our study in scenario D: cervical collar stabilization and tongue oedema, the values of 69% versus 32% (p < 0.001) were obtained for McGrath and Macintosh laryngoscope [14]. e duration of the intubation attempt is a clinically important factor and differences of 15 seconds or more can be clinically important, especially in severe hypoxia or cardiac arrest patients. In our study, the shortest time of intubation attempt among all difficult airway scenarios was obtained for McGrath intubation; however, only in normal airway the time was not statistically significantly shorter (17 seconds versus 18 seconds for MAC and McGrath; p � 0.899). In the presented study, in some difficult airway scenarios, the time of intubation attempt was shorter as compared with MAC (scenarios B and D). is finding is generally supported by other studies. Bag et al. found the mean time necessary for intubation equaled 21.10 ± 5.64 seconds for Truview and 15.79 ± 2.76 seconds for Macintosh [11]. A clinical study conducted by Bhola et al. comparing McGrath and Truview PCD reported that the time to successful intubation was shorter with the McGrath video laryngoscope when compared with Truview (30.02 seconds versus 38.72 seconds) but there was no significant difference between the laryngoscopic views obtained in both groups [15]. Singh et al. published the results of their study on intubation using Truview PCD, C-MAC, and Macintosh laryngoscopes in paediatric patients. ey concluded that the intubation time was 19.2 seconds for Truview PCD and 10.7 s for Macintosh [16].
From a clinical point of view, each intubation attempt is important, with repeated intubation attempts leading to an increased risk of complications including bleeding and oedema of the airways, which reduce the chance of successful endotracheal intubation [17]. Alvis  McGrath was superior to Macintosh in terms of glottic visualization [19].
In our study, POGO score was better for McGrath compared with MAC and PCD. is finding is concordant with other studies. Singh et al. published the results of their study on intubation using Truview PCD, C-MAC, and Macintosh laryngoscopes in paediatric patients. ey concluded that POGO scores were significantly better with Truview PCD than with Macintosh laryngoscopes (94.7 ± 12.9 versus 85.1 ± 17.1; p < 0.01). e number of necessary external manoeuvres was fewer in the Truview PCD than in the Macintosh group [16].
As a limitation, higher success rates and shorter intubation times obtained with MAC compared with video laryngoscopes may be due to greater experience with MAC. Expertise with standard direct laryngoscopy does not translate to that with video laryngoscopy, and separate training and experience with video laryngoscopy are required. Our study included only paramedics experienced with MAC, with no prior experience in any video laryngoscopes. We enrolled paramedics because this group of medical personnel must provide airway management including endotracheal intubation in out-of-hospital settings with no support from experienced personnel, for example, anaesthesiologists.
A further limitation is the nature of any manikin study. Results of any manikin study need to be confirmed in clinical studies, which is extremely challenging due to ethical concerns, especially if investigated by less experienced providers like paramedics. However, manikin studies are generally considered reliable. Another limitation is the potential of bias, as it is impossible to blind participating paramedics. e POGO score and ease of use were subjective measures. e application of manikins allows for enough statistical power while performing cross-over studies with no risk for humans.
In conclusion, in this randomized cross-over simulation study performed among a group of paramedics, the McGrath video laryngoscope was demonstrated to be superior to the Truview PCD video laryngoscope and direct laryngoscopy guided intubation using a Macintosh laryngoscope in terms of success rate, duration of intubation attempt, Cormack-Lehane grade, POGO score, number of optimization manoeuvres, severity of dental compression, and ease of use.

Data Availability
e data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest
e authors declare no conflicts of interest regarding the publication of this paper.