|Year : 2015 | Volume
| Issue : 2 | Page : 66-72
Anticipated Difficult Tracheal Intubation: Comparison between conventional laryngoscope (Macintosh) and video laryngoscope TrueView EVO 2
Sheetal Dalal, Manas Manohar
Department of Anaesthesia, Government Medical College and Hospital, Nagpur, Maharashtra, India
|Date of Web Publication||16-Jul-2015|
Dr. Sheetal Dalal
13, Pub Cooperative Housing Society, Pratapnagar, Nagpur, Maharashtra
Source of Support: None, Conflict of Interest: None
Context: In patients with anticipated difficult airway, it is difficult to align the oropharyngolaryngeal axis to facilitate intubation by conventional laryngoscopy, which leads to failed intubation. The TruView EVO 2 laryngoscope is a device with a unique blade that provides an optical view "around the corner." The blade is a modiﬁed laryngoscope blade incorporating an unmagniﬁed optic side port with anterior fraction of 42 in the line of sight allowing indirect tracheal intubation. Aim: The aim of the study was to compare TrueView blade with Macintosh blade with respect to the (view of the glottis by (Cormack-Lehane grading); Time for tracheal Intubation, Attempts required for intubation, maneuvers to optimize the laryngeal view and success rate of intubation); Settings and Design: It was a prospective, randomized controlled single blind clinical study. Materials and Methods: Seventy ASA grade I and II, Mallampatti Grading (MPG), III and IV patients posted for elective surgery with restricted neck mobility such as post-burn contracture neck, cervical spine surgeries divided into Group 1-35 patients (Trueview) and Group 2-35 patients (Macintosh). All intubation was done by an expert anesthesiologist. Statistical Analysis: Tests used were Mann-Whitney U test, two independent sample t-tests, Chi-square test, and Fischer's exact t-test. Results: Cormack-Lehane Grade I was seen in 62.85% and O in Group 1 and Group 2, respectively. Grade II was seen in 37.14% and 28.57% in Group 1 and Group 2, respectively, and Grade III in 0 and 71.42% in Groups 1 and 2, respectively, which was statistically significant. Thus EVO 2 improved the view of glottis by 2 Grades. Both the techniques were comparable as far as time is concerned. A 94.2% patients in Group 1 intubated in 1 st attempt, 5% needed 2 nd attempt, whereas in Group 2 72.7% patients were intubated in 1 st attempt and 27.2% in 2 nd attempt. Maneuver BURP required more with conventional laryngoscopy. Success rate in Group 1 was 100% and in Group 2 it was 94.2%. Conclusion: The use of TrueView in patients with anticipated difficult airway considerably improved the view of glottis. With adequate experience, the number of attempts may be reduced and maneuver required for securing airway successfully could be optimized.
Keywords: Cormack-Lehane, difficult airway, Trueview EVO 2
|How to cite this article:|
Dalal S, Manohar M. Anticipated Difficult Tracheal Intubation: Comparison between conventional laryngoscope (Macintosh) and video laryngoscope TrueView EVO 2. J Health Res Rev 2015;2:66-72
|How to cite this URL:|
Dalal S, Manohar M. Anticipated Difficult Tracheal Intubation: Comparison between conventional laryngoscope (Macintosh) and video laryngoscope TrueView EVO 2. J Health Res Rev [serial online] 2015 [cited 2020 Feb 22];2:66-72. Available from: http://www.jhrr.org/text.asp?2015/2/2/66/160923
| Introduction|| |
The primary responsibility of the anesthesiologist is to safeguard the airway.  Inability to maintain and manage very difficult airways has been responsible for approximately 30% deaths totally attributable to anesthesia. In situations such as unusual anatomical configurations, intubation becomes challenging to the anesthesiologist. In patients with anticipated difficult airway, such as short neck or limited neck extension, it is difficult to align the oro-pharyngo-laryngeal axis to facilitate intubation by conventional laryngoscopy. Sometimes considerable technical difficulty is encountered when orotracheal intubation is attempted under direct vision by conventional methods. , In such situations, it becomes necessary to use rescue techniques like bougie, BURP maneuver, and so on. which results in increased time for intubation, increased stress response, and in some cases failed intubation. Various video laryngoscopes have been introduced to overcome the shortcomings of conventional laryngoscopy.
TruView EVO 2 Laryngoscope.The TruView EVO 2 laryngoscope (Truphatek International Ltd., Netanya, Israel) is a recently introduced device with a unique blade that provides an optical view around the corner [Figure 1].  The blade is a modified laryngoscope blade incorporating an unmagnified optic side port with anterior refraction of 35° in the line of sight allowing indirect tracheal intubation. 
It applies the optical principle of light refraction to provide a good view of a more anteriorly placed larynx. The TruView EVO 2 laryngoscope employs an inexpensive telescope angled at 42° approximately with the blade molded so that the glottis lying at the tip of the blade is best seen without any manipulation or tilt of the head, neck, instrument, or soft tissues. The scope helps improve laryngeal view by 1-2 grades.
A number of studies have been done using Trueview laryngoscope in patients with normal airway. ,, TruView EVO 2 laryngoscope has been claimed to be associated with a better glottis view, expressed by the Cormack-Lehane Grade ,,,, and reduced intubation time.
Taking into consideration the studies we conducted a study to compare and contrast the efficacy of the TruView EVO 2 against the Rigid Laryngoscope, in anticipated difficult airway with the following objectives:
- View of the glottis as per Cormack-Lehane grading system
- Time to intubation (TTI)
- Number of attempts required for intubation
- Optimizing maneuvers needed to facilitate intubation: BURP (backward upward rightward pressure) maneuver, use of bougie
- Success rate of the technique.
| Materials and Methods|| |
The present study was carried out during the period of October 2010 to October 2012 in the Department of Anesthesiology, a tertiary care center after approval by the Hospital ethics committee. Patients posted for various elective surgeries in General surgery, ENT, Plastic surgery, and Orthopedic surgery under general anesthesia was included. It was a prospective randomized controlled clinical study.
Adults aged 18-60 years of either gender. ASA Grade I and II patients with MPG-III and IV. Patients with restricted neck mobility, e.g., post-burn contracture neck, cervical spine injury, patients with a history of difficult intubation.
Patients with ASA grades III-V and age <18 years and >60 years, undergoing rapid sequence intubation, emergency patients, not NBM, mouth opening less than 2 cm, patients with difficult mask ventilation and at risk for aspiration.
The study population consisted of 70 patients. Randomization was done by picking up a chit. The patients were distributed into two groups of 35 (N = 35) each, Group 1: To be intubated with Trueview EVO 2 laryngoscope and Group 2: To be intubated with Macintosh laryngoscope.
A detailed preanesthetic evaluation, including history, general, and systemic examination, thorough airway assessment, and appropriate laboratory tests was carried out in each patient. Airway assessment included mouth opening, condition of teeth, temporomandibular joint mobility, neck movement, modified Mallampati grading (MPG), and atalantooccipital extension.
Study procedure including risks and benefits were explained, and written informed consent was taken from patients willing to participate in the study for anesthesia and surgery. Night prior to surgery, Tab. diazepam 5 mg and Tab. ranitidine 150 mg were given. Patients were kept fasting overnight. The patients were re-examined in operation theater. Monitors were attached and vital parameters such as heart rate, blood pressure, SPO 2 , and respiratory rate were noted. Before induction, difficult intubation tray was kept ready.
Premedication was given with i.v. ranitidine 50 mg and i.v. glycopyrrolate 0.004 mg/kg. Sedation was given with i.v. midazolam 0.02 mg/kg and i.v. post-burn contracture neck with fixed flexion deformity of the neck. Pentazocine 0.5 mg/kg. Patients were preoxygenated with 100% oxygen on mask for 3 min. Induction was done with i.v. propofol 2 mg/kg. Patients were assessed for ease of bag and mask ventilation, and those who could not be ventilated with ease were excluded from the study. Rest of the patients were paralyzed by i.v. succinylcholine 1.5 mg/kg and ventilated for 90 s.
In Group 1, patients were intubated with the head in neutral position using TruView EVO 2 , whereas the patients in Group 2 were placed in sniffing position with their head on pillow and were intubated with blade of size 3 or 4 of the standard Macintosh laryngoscope. On visualization of cords, Cormack-Lehane grade was noted. Endotracheal intubations were performed indirectly using size 7.0 or 7.5 mm Endotracheal Tube ETT (Endotracheal Tube) in females and 8.5 or 9.0 mm ETT in males. The ETT was mounted on preformed "J"-shape stylet. The anesthesiologist was allowed to apply external laryngeal pressure or use the bougie or change the blade in Group 2 patients to facilitate intubation. After successful intubation, the patients were mechanically ventilated for the surgical procedure and anesthesia was maintained with isoflurane/sevoflurane/halothane in a mixture of nitrous oxide and oxygen in a 1:1 ratio. Intubations in both the groups were performed by the same anasthesiologist who was experienced with both the techniques in managing difficult airways.
The time taken for intubation was measured from the time of insertion of the laryngoscope into the patient's mouth till the inflation of the cuff of the endotracheal tube. The number of attempts needed by anesthesiologist to correctly place the tube was recorded. If more than one attempt was required, the patient was ventilated with bag and mask between the attempts and the anesthesiologist was allowed to change the blade. Failure to intubate trachea after three attempts was considered as failure to intubate and alternative techniques were used to maintain airway. An independent observer noted the intubation time, number of attempts, type of technique used, and any external manipulation. All the observations done in the study were subjected to statistical analysis.
| Results|| |
Statistical analysis of continuous parameters was presented as Mean±SD.Categorical parameters were expressed in percentages.
- View of the glottis was analyzed using Mann-Whittney U test
- TTI was analyzed using two independent sample t-tests
- Number of attempts and optimizing maneuvers required were analyzed using Chi-square test
- Success rate was analyzed using Fischer's exact t test.
P value <0.05 was considered statistically significant.
The demographic data in both the groups were comparable with respect to age, gender, and weight distribution [Table 1] .
Both the groups had similar patient distribution with respect to difficulty level. In Group 1, 8.57% patients had a history of difficult intubation, whereas 2.85% patients in Group 2 had a history of difficult intubation. A 31.42% of the patients in Group 1 had limited neck extension as compared to 25.71% patients in Group 2. A 37.14% of the patients showed MPG III in Group 1 against 45.71% in Group 2. A 22.85% of the patients in Group 1 exhibited MPG IV as against 25.71% in Group 2 [Table 2] and [Figure 2] .
|Figure 2: Distribution of patients with respect to difficulty level in group 1 and group 2|
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|Table 2: Distribution of patients with respect to difficulty level in Group 1 and Group 2 |
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In Group 1, 11.42% of the patients were of ENT surgery, whereas in Group 2, 8.5% of the patients were of ENT surgery. Forty percent of the patients were of general surgery in Group 1, whereas 54.28% of the patients in Group 2 were of general surgery. In Group 1, 25.71% of the patients were of orthopedic surgery, whereas in Group 2, 14.28% of the patients were of orthopedic surgery. A 22.85% of the patients were of plastic surgery in both the groups. By using Fisher's exact test P > 0.05; hence both the groups are comparable to each other in terms of surgical procedures [Figure 3] .
Cormack-Lehane Grade I was seen in 62.85% and in no patient in Group 1 and Group 2, respectively, Cormack-Lehane Grade II was seen in 37.14% and 28.57% patients in Group 1 and Group 2, respectively, and Cormack-Lehane Grade III was seen in 0% and 71.42% patients in Group 1 and Group 2, respectively. These values were statistically significant. Also there was a significant difference in the median Cormack-Lehane grading in both the Groups. It was I in Groups 1 and II in Group 2. The view of the glottis improved by one Cormack-Lehane grade in patients with MPG IV and by two grades in patients with MPG III, limited neck extension and history of difficult intubation. Thus Trueview EVO 2 improved the view of the glottis by two grades as compared with Macintosh blade the median Cormack-Lehane Grade was I in Group 1 as compared with Grade III in Group 2. Hence, by using Mann-Whitney U test P < 0.05 therefore there is significant difference between median Cormack-Lahane grade in Group 1 and Group 2 [Table 3], [Table 4], [Table 5] and [Figure 4] .
|Figure 4: Comparison of patients with respect to Cormack grade in group 1 and group 2|
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|Table 4: Comparision with respect to median Cormack-Lehane grade in Group 1 and Group2 |
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|Table 5: Comparison of Cormack-Lahane in Group 1 and Group 2 with respect to difficulty level |
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TTI in Group 1 was 89.71 ± 66.59 s while the TTI was 104.09 ± 92.79 s in Group 2. This difference was not statistically significant and both the groups were comparable in terms of TTI [Table 6] and [Figure 5] .
The mean TTI in patients of Group 1 with limited neck extension was 104.64 ± 75.37 s, whereas it was 143 ± 106.15 s in patients of Group 2. The mean TTI in patients of Group 1 with MPG III was 67.15±3.91 s, whereas it was 94.33 ± 94.72 s in patients of Group 2. The mean TTI in patients of Group 1 with MPG IV was 110.50 ± 97.51 s, whereas it was 93.44 ± 81.80 s in patients of Group 2.
Hence by using two independent sample t-tests, P value is >0.05 therefore there is no significant difference between mean time required in Group 1 and Group 2 with respect to grade of difficulty [Table 7] and [Figure 6] .
|Figure 6: Comparision of time in group 1 and group 2 with respect to difficulty level|
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|Table 7: Comparison of time in Group 1 and Group 2 with respect to difficulty level |
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In Group 1, 94.2% of the patients were intubated in one attempt, whereas only 5% patients needed two attempts, but in Group 2, 72.7% of the patients were intubated in one attempt, whereas 27.2% of the patients needed two attempts. This difference was found to be statistically significant (P = 0.02). Thus, with Trueview EVO 2 blade less number of attempts were required for intubation as compared with those using Macintosh blade [Table 8] and [Figure 7] .
In Group 1 only 5.7% of the patients required BURP maneuver to facilitate intubation, whereas 94.3% of the patients did not require any optimizing maneuver. In Group 2, 68.5% of the patients required BURP maneuver, whereas 8.5% of the patients required BURP maneuver and bougie to facilitate intubation and only 22.8% of the patients were intubated without using any optimizing maneuvers. These findings were statistically significant. Thus the number of optimizing maneuvers required to facilitate intubation is significantly less with Trueview EVO 2 blade as compared with those using a Macintosh blade [Table 9] and [Figure 8] .
|Figure 8: Distribution of optimizing maneurer used in group 1 and group 2|
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Success rate was of 100% in Group 1 and 94.2% in Group 2. These values were not significant. Thus both the techniques were comparable to each other in terms of success rate of intubation [Figure 9] .
| Discussion|| |
The TruView EVO 2 has previously been reported to provide a better laryngeal appearance through the use of its optical system, which provides a 42° deflection view through a 15-mm eyepiece. It applies the optical principle of light refraction to provide a more anterior view of the larynx. The aim of this is to provide a better view in a greater proportion of patients and thus allow intubation to be performed under direct vision more frequently than is possible with a conventional laryngoscope. TruView EVO 2 reduces the problems associated with lens blurring by using a continuous O 2 flow system (4-5 L/min) attached to the laryngoscope. There are various reports of successful use of Trueview EVO 2 for endotracheal intubation in patients with normal airway as well as suspected difficult airways.
In our study, TruView EVO 2 and Macintosh blade laryngoscopes were compared by noting the Cormack-Lehane grades during laryngoscopy. Barak et al. (2007)  found that the TruView blade provided a better laryngoscopic view than the Macintosh blade, that is, in 100% patients with anticipated difficult intubation in TrueView Group the Cormack-Lehane grade was I, whereas in Macintosh Group only 14.2% of the patients had Cormack-Lehane grade I and 28.5% and 57.14% of the patients had Cormack-Lehane grades II and III, respectively, Timanaykar et al. (2011)  found that in patients with MPG III Trueview provided Cormack-Lehane Grade I in 68.48% cases, whereas Macintosh blade provided grade I in 22.22% of the cases. In patients with MPG IV no patients had Cormack-Lehane grade III/IV in TrueView Group while 50% patients in Macintosh Group had Cormack-Lehane III/IV. These results are similar to that of Li et al. (2007)  who reported that MPG determined prior to laryngoscopy was significantly related to the view of the glottis for both the Groups Tutuncu et al. (2009)  found that only 3.3% of the patients in TrueView Group had Cormack-Lehane Grade III, whereas 33.3% of the patients in Macintosh Group had Cormack-Lehane Grade III. In our study we also observed that the median Cormack-Lehane grade in Group 1 was I, whereas in Group 2 it was III. This difference was statistically significant. Thus our study showed that TrueView EVO 2 improved the glottic view by two Cormack-Lehane grades as compared with Macintosh blade. Singh et al. (2007)  stated that 93.75% of the patients showed improvement in glottic view by one Cormack-Lehane grade, whereas 76.47% of the patients showed improvement by two grades. Li et al. (2007)  also found that the view of the glottis improved by 1 or 2 Cormack-Lehane grade in 52.5% of the patients. Tutunku et al. (2011)  found that median Cormack-Lehane grade in Macintosh Group was II and it was I in TrueView Group. Recently, a better visualization of the glottis with TrueView was also reported by Joseph et al. (2012)  and Bag et al. (2015)  in patients with difficult airway.
Our study reveals the improvement in Cormack-Lehane grade with respect to the difficulty. We found that the view improved by two Cormack-Lehane grades in patients with MPG III and limited neck extension, whereas it improved by one Cormack-Lehane grade in patients with MPG IV. The results were similar to that of Li et al. (2007).  Conventional laryngoscopes require the alignment of oral and pharyngeal axis to view the glottic opening. This is a difficult skill to be acquired successfully and maintained. TruView laryngoscope is a modified Macintosh blade with an exaggerated distal curvature and viewing lens. It gives a view of the glottis without the need to align the oral and tracheal axis and therefore simplify intubation. In our study, TTI was noted from the insertion of the laryngoscope in the patients' mouth till the inflation of the cuff. , This time was noted by an independent observer in both the groups. Li et al. (2007)  observed that the overall TTI was 34 s (95% confidence interval (CI) 32-37) in the Macintosh Group and 51 s (95% CI 48-53) in the TruView Group. Barak et al. (2007)  also observed an increase in the TTI with increasing Cormack-Lehane grade in the Macintosh Group but not in the TruView Group. Ramesh et al. (2011)  reported that TTI was 23.11 s in the Macintosh Group and 33.62 s in the TrueView Group. He stated that in laryngoscopy, intubation is performed in an indirect manner with TrueView. Seeing the tube and the cords through the lens, the anesthesiologist looks through the TrueView lens and focuses on the cords, then passes the endotracheal tube blindly till the tip enters the TrueView visual field. Performing this maneuver requires good hand-eye coordination and some practice. Anesthetists experience considerable difficulty in advancing the tracheal tube toward the view of the lens; this may be the reason for increased TTI with TrueView. Torun et al. (2011)  observed in their study that the time for intubation in Macintosh Group was 23 s and in TrueView Group it was 42 s, which was statistically significant. Singh et al. (2011)  observed that in their study the mean TTI in TrueView Group was 28.6 s. The average time taken for negotiation of ETT was much less than that reported by other authors. , Considering difficulty involved in all the cases, the recorded average time for tracheal intubation was significantly quicker. On the other hand, TTI did not bear much difference whether it was Cormack and Lehane Grade I or II. They experienced requirement of certain manipulative movements while negotiating the endotracheal tube under TruView EVO 2 vision even when the best of the laryngeal view was available. This was the reason for requirement of longer time for tracheal intubation under TruView vision as compared with conventional laryngoscopy. Hence it is noteworthy that it involves probably a little longer learning curve but becomes handy with repeated use. The findings of our study are in agreement with the findings of Barak et al. (2008),  Li et al. (2007),  and Bag et al. (2015).  Other studies that observed a significant difference in the two groups with respect to time were conducted in patients with normal airway. Thus in our study, although the time in Group 1 was less than that in Group 2, this difference was not significant. In our study we also compared the number of attempts required to intubate the patients. One attempt at laryngoscopy was considered as one attempt. If the anesthesiologist had to change the blade in Group 2, it was also counted as an attempt. If the patient could not be intubated after three attempts, it was considered as failure of intubation. Jungbauer et al. 2009  found that with video laryngoscopy, 99% patients were intubated in the first attempt, whereas with Macintosh 92% were intubated in the first attempt. This was statistically significant. The findings of this study are in agreement with the findings of our study. Studies by Malik et al. (2008),  Torun et al. (2011),  Barak et al. (2007), and Timnayakar et al. (2011)  found no significant difference in the number of attempts with both the techniques. Although our findings differ from the findings of the above-mentioned studies, we feel that in our study the number of attempts were less in Group 1 because in Group 1 there was a significant improvement in the view of the glottis and the anesthesiologist in our study was experienced in using TrueView EVO 2 blade in difficult intubation cases. In our study, we compared the optimizing maneuvers such as BURP and gum elastic Bougie required to facilitate intubation with both the techniques. As results suggested the number of optimizing maneuvers required to facilitate intubation is significantly less with TrueView EVO 2 blade as compared with Macintosh blade. These findings were statistically significant. Malik et al. (2008)  had similar findings.
We found a success rate of 100% in Group 1 and of 94.2% in Group 2, which was insignificant. Two patients of Group 2 of post-burn contracture neck with fixed flexed deformity could not be intubated with Macintosh blade even after three attempts. Patients managed with LMA and surgeons were asked to release a part of the contracture and after achieving some amount of neck extension, patients were intubated using Macintosh blade with the help of stylet. Singh et al. (2007),  Malik et al. (2008),  Li et al. (2007),  Torun et al. (2011),  Timanayakar et al. (2011),  and Barak et al. (2008)  found in their studies that there was no difference in both the techniques with respect to success rate of intubation.
| Conclusion|| |
It can be concluded that the TruView EVO 2 laryngoscopy offered a better view of the glottis by 1-2 Cormack-Lehane Grades as compared with Macintosh blade in patients with anticipated difficult airway. Also less attempts and rescue techniques were required with the use of TruView EVO 2 laryngoscopy. So, we recommend the use of TrueView in patients with anticipated difficult airway, as it considerably improves the view of the glottis with adequate experience may reduce the number of attempts and optimizing maneuvers required for securing the airway successfully.
Limitation of our study
We could not double blind the study as both the laryngoscopes were conspicuously different. We could not assess parameters of difficult airway such as thyromental distance and sternomental distance as we had included patients of post-burn contracture neck in our study and it is not possible to measure these distances in such patients.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9]