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ORIGINAL ARTICLE
Year : 2020  |  Volume : 36  |  Issue : 4  |  Page : 483-488

Comparison of conventional C-MAC video laryngoscope guided intubation by anesthesia trainees with and without Frova endotracheal introducer: A randomized clinical trial


Department of Anesthesia and Critical Care, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, India

Date of Submission18-May-2020
Date of Acceptance12-Oct-2020
Date of Web Publication18-Jan-2021

Correspondence Address:
Dr. Priya Rudingwa
Department of Anesthesia and Critical Care, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry - 605 006
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/joacp.JOACP_263_20

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  Abstract 


Background and Aims: Successful intubation with video laryngoscopes necessitates good hand-eye coordination and the use of intubation adjuncts like bougie and stylet. We proposed this study to find whether using Frova introducer with C-MAC video laryngoscope will reduce the intubation time in trainee anesthesiologists.
Material and Methods: We enrolled 140 adults without any difficult airway predictors. They were randomly assigned to undergo C-MAC video laryngoscope guided intubation by anesthesia residents using tracheal tube preloaded over Frova introducer (n = 70) or without Frova introducer (n = 70). Primary outcome was the intubation time. Secondary outcomes were the number of redirections of tracheal tube or Frova introducer toward glottis, need for external laryngeal maneuvers (ELMs), first attempt intubation success rate, and ease of intubation.
Results: The median actual intubation time (IQR) in Frova and non-Frova group, respectively, were 25.46 (28.11–19.80) and 19.96 (26.59–15.52) s (P = 0.001). The number of redirections of TT or Frova introducer toward glottis, first attempt success rate, and ease of intubation were comparable. The need for ELMs [n (%)] was 15 (21.4) and 26 (37.1) in Frova and non-Frova group, respectively (P = 0.04).
Conclusion: Frova introducer guided endotracheal intubation with C-MAC videolaryngoscope in patients with normal airways had a marginally prolonged intubation time with a significant reduction in the need of external laryngeal manoeuvres but with a comparable number of redirections and attempts. Further research is needed to generalize these findings to patients with difficult airways.

Keywords: Bougie, C-MAC videolaryngoscope, frova tracheal tube introducer, novice learners, video-assisted intubation success, trainee anesthesia


How to cite this article:
Arasu M, Rudingwa P, Satyaprakash M V, Panneerselvam S, Kuberan A. Comparison of conventional C-MAC video laryngoscope guided intubation by anesthesia trainees with and without Frova endotracheal introducer: A randomized clinical trial. J Anaesthesiol Clin Pharmacol 2020;36:483-8

How to cite this URL:
Arasu M, Rudingwa P, Satyaprakash M V, Panneerselvam S, Kuberan A. Comparison of conventional C-MAC video laryngoscope guided intubation by anesthesia trainees with and without Frova endotracheal introducer: A randomized clinical trial. J Anaesthesiol Clin Pharmacol [serial online] 2020 [cited 2021 Jul 26];36:483-8. Available from: https://www.joacp.org/text.asp?2020/36/4/483/307194




  Introduction Top


Over the years, the C-MAC videolaryngoscope (VLS) C-blade has shown to enhance the laryngeal view during intubation.[1],[2],[3] Video-based intubation necessitates skilled hand-–eye coordination and intubating aids like bougie/stylet for successful intubation.[3],[4],[5] It is a well-known fact that the indirect view of glottis obtained with a videolaryngoscope doesnot always guarantee easier passage of tube inspite of a good Cormacke Lehane (CL) grade.[3] The manufacturer does not recommend the use of a stylet with standard C-MAC blade as it has a Macintosh like curvature, but it depends on individual preferences.[6],[7] In such situations, the Frova introducer with its bent tip and narrow diameter enables better maneuverability and passage through glottis. The optimal learning technique is unclear for the standard C-MAC VLS as intubation can be done with or without bougie/stylet.[2],[6],[7] We evaluated whether using Frova introducer with C-MAC VLS would reduce the intubation time especially in learners. The primary objective was to compare the intubation time. Secondary objectives were the number of redirections of tracheal tube or Frova introducer toward glottis, need for external laryngeal maneuvers, first attempt success rate, and ease of intubation.


  Material and Methods Top


After approval from the institute ethics committee (JIP/IEC/2017/0260) and registration in the clinical trials registry of India (CTRI/2017/09/009793), this randomized, parallel-arm, prospective, single-center clinical trial was undertaken from April 2018 to June 2019. After informed written consent, a total of 140 patients in the age group of 18–60 years of age, belonging to the American society of anesthesiologists physical status (ASA PS) I and II scheduled to undergo elective surgery with orotracheal intubation were included in this study. Patients who fulfilled the inclusion criteria of mouth opening more than 3 cm, full range of neck movements, thyromental distance more than 6 cm, Modified Mallampati (MMP) class less than or equal to two were included in the study. Any patient requiring rapid sequence induction or with anticipated difficult airway predictors was excluded from the study.

Randomization was done during the pre-anesthetic visit using a computer-generated random number table of varying block sizes by an investigator not involved in the study. Concealment to the group allocation was done using sequentially numbered opaque sealed envelope (SNOSE). The patients were randomly assigned in a 1:1 ratio to undergo intubation by anesthesia trainees with a tracheal tube (TT) preloaded over the Frova introducer (Group F) or TT alone, without Frova introducer (Group WF). The anesthesia trainees had at least 1 year of training in anesthesia and had practiced C-MAC VLS guided intubation for ten times in a manikin.

All patients underwent pre-anesthetic checkup a day before surgery and informed written consent was obtained. On the day of surgery in the operating room, standard ASA monitors like electrocardiogram, noninvasive blood pressure, pulse oximetry were attached and baseline vital parameters were recorded. The patients were positioned in sniffing position and preoxygenated with 100% oxygen followed by intravenous induction with propofol, fentanyl, and vecuronium. Mask ventilation was done for 3 min with isoflurane in 100% O2 to achieve a minimum alveolar concentration (MAC) of one. In both groups, the C-MAC C-blade (Karl Storz, Tuttlingen, Germany) of size three and appropriate size polyvinyl chloride TT were used for intubation.

The C-MAC Videolaryngoscope blade was inserted into the patient's oral cavity and the tongue was displaced to the left side in a manner similar to conventional direct laryngoscopy. Then the C-MAC VLS screen was observed for the CL grade obtained. On reaching the base of the tongue, the tip of the blade was kept in the vallecula and the epiglottis was lifted. After glottic visualization, in group F, intubation was attempted with the lubricated TT preloaded over a Frova intubating introducer without the stiffening stylet (14 Fr, 70 cm long, Cook Medical, Bloomington, USA). The lubricated TT was preloaded on the Frova introducer such that 30 cm length was free from the distal (patient) end as shown in [Figure 1]. After the distal tip of Frova introducer entered the glottis, the TT was railroaded over it till the intubation marker was at the level of vocal cords, while an assistant stabilized the introducer. Once the intubation marker just reached the glottis, the Frova introducer was withdrawn. In group WF, after glottic visualization, the trachea was intubated using TT separately without the aid of Frova introducer.
Figure 1: Tracheal tube preloaded on the Frova tracheal introducer (till the 30 cm mark from its distal tip)

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After the successful passage of TT beyond the glottis, the laryngoscope was removed and TT was connected to the anesthesia circuit. Anesthesia was maintained using isoflurane in air and oxygen mixture. The primary outcome was to compare the intubation time using a TT with Frova introducer vs TT alone. The total intubation time was regarded as the time interval between the introduction of the C-MAC C-blade into the patient's mouth to the appearance of the ETCO2 trace. The total laryngoscopy time was regarded as the interval between the introduction of the C-MAC C-blade into the patient's mouth to the best visualization of the glottis on the video screen. The total laryngoscopy time was subtracted from the total intubation time to derive the actual intubation time. This eliminated the confounding effect of a faulty laryngoscopy technique on the actual intubation time.

The secondary outcome parameters were the number of redirections of the TT or Frova introducer toward glottis, first attempt intubation success rate, CL grade observed, need for external laryngeal maneuvers (ELMs), and ease of intubation measured on a Likert scale (1- very easy passage of tube/bougie through glottis, 2- easy passage of tube/bougie through glottis, 3- moderately difficult to pass tube or bougie through glottis, 4- very difficult to pass tube/bougie through glottis). Any attempt that is taken to push the TT or the Frova introducer in the direction of the glottis was regarded as one redirection attempt. Passage of the TT (in group WF) or the Frova introducer (in group F) in the first attempt without redirection was considered as intubation success at the first attempt. External laryngeal maneuvers (ELMs) such as the thyroid manipulation were performed if required to facilitate glottic visualization for intubation and were noted. If the total duration of intubation took more than 120 s or if any adverse event like airway injury or desaturation (oxygen saturation <95%) occurred, the intubation attempt was considered as a failure and appropriate actions were initiated. All patients were blinded to the group allocation. Blinding of anesthetist performing intubation could not be done as they were informed about the technique to be used. All the study parameters were noted by a separate anesthesiologist not involved in the study except for the ease of intubation, which was reported by the intubator using an ordinal scale. The biased interpretation was eliminated by objectively defining the intubation time, laryngoscopy time, and the number of redirections toward glottis.

The sample size was calculated using the statistical formula for comparing two independent means based on the study done by Hodgetts V et al.[8] The sample size was estimated as n = 140 (n = 70 in each group) with a minimum expected mean difference in the time taken for intubation of 10 s, a standard deviation of 20 s, power of 80%, 5% level of significance and an attrition rate of 10%.The statistical analysis was done using SPSS software version 19 (IBM Corp Armonk NY). The distribution of categorical variables such as gender, need for ELMs, need for redirection of TT or Frova introducer toward glottis, first attempt success rate of intubation was expressed in terms of frequency or percentage and was compared using Chi-square test/ Fishers test as relevant.

The distribution of continuous and discrete variables such as age, weight, height, body mass index, total intubation time, laryngoscopy time, actual intubation time, and the number of attempts at redirection of the endotracheal tube was expressed in terms of the median with interquartile range or mean with standard deviation and analyzed with Mann–Whitney test or independent Student's t-test, respectively, based on the normality distribution of the data as estimated by Shapiro–Wilk test. The comparison of ordinal data such as MMP Class, Cormack-Lehane (CL) grade, ASA PS class, and the ease of intubation (ordinal scale) was done using Chi-square test or Fisher's exact test. All statistical tests were performed at a 5% level of significance.


  Results Top


A total of 162 patients were enrolled and assessed for eligibility. Out of these, 22 patients were excluded as they did not give consent to participate in the study. After obtaining written informed consent the remaining 140 patients were equally allocated to two groups as depicted. The demographic and airway characteristics were comparable as represented in [Table 1] and [Table 2].
Table 1: Patient demographic characteristics

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Table 2: Airway characteristics

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The median (IQR) actual intubation time was significantly higher in Group F 25.46 (28.1-19.8) s as compared to Group WF 19.96 (26.59-–15.52) s, P = 0.001. The median laryngoscopy time was comparable between the groups. The median (IQR) number of redirections toward glottis [1 (2-0) vs. 1 (3-0)] was comparable in both the groups. The passage of the Frova introducer through glottis in the first attempt without any redirection was 44.3% in group F and in group WF the passage of the TT through glottis in the first attempt without any redirection was 40%, which was not statistically different (P = 0.61). In group WF, there was a significantly increased need for ELMs than in group F (37.1% vs. 21.4%), P = 0.04. There was a significantly higher proportion of patients with CL II grade of laryngoscopy view in group WF (20% vs. 2.9%), P = 0.001 [Table 3].
Table 3: Intubation conditions and characteristics

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The perceived ease of intubation was comparable between the two groups, P = 0.67 [Table 4]. There was no airway injury, failed intubation, or incidence of desaturation in either of the groups.
Table 4: Comparison of ease of intubation (ordinal scale)

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  Discussion Top


The advent of video laryngoscope in 20th century has ushered a remarkable change in the approach toward difficult airways. The Difficult airway society (DAS) 2015 guidelines mention early use of VLS in plan A of unanticipated difficult intubation.[4] The C-MAC VLS has been found to enhance the glottic view by at least one CL grade, thus enabling easier intubation.[3],[9],[10],[11] As VLS might be the standard of care in future there is need for all trainees to familiarize with the equipment and to find an optimal technique of its use.

In our study, we found that the median total and actual intubation times were marginally prolonged by about 5 s when TT preloaded over Frova introducer was used for C-MAC VLS guided intubation by anesthesia residents, as compared to TT alone, in patients without any difficult airway predictors. The number of redirections toward glottis and the first attempt intubation success rate was similar in both the groups. The need for ELMs was significantly more in the non-Frova group. The ease of intubation on an ordinal scale was comparable in the two groups.

The Frova introducer because of its narrow diameter (4.7 mm) and a bent coude tip can be maneuvered toward glottis easily with less encroachment of glottic view compared to the TT with a greater diameter.[12],[13] Its stiffer nature enables it to be a good alternative to gum elastic bougie in various studies.[14],[15],[16] Though we hypothesized that the Frova introducer will reduce the intubation time by reducing the intubation attempts because of its easy maneuverability, there was no reduction in the intubation time with the use of Frova introducer in our study. The higher intubation time needed in the group F could be because of the time taken for railroading the TT over the introducer or because of the need for rotation of the TT if there was arytenoid impingement.

Though statistically significant, the difference of 5.11 and 5.5 s in the median total and actual intubation time respectively is of questionable clinical significance in healthy adult patients since the median intubation times were still found to be in near range with other studies involving experienced anesthetists.[12],[13],[17]

The comparable number of redirections and first attempt intubation success rate among the groups may be because of the involvement of patients without any difficult airway parameters. The advantage of Frova introducer guided tracheal intubation may be appreciated better in patients with difficult airway parameters where one may encounter difficulty in passing the tracheal tube despite a good laryngeal view noted on the video screen. In such scenarios, an endotracheal introducer can be easily passed through the glottis with lesser attempts by virtue of its narrower diameter and maneuverability.[12],[13],[18],[19],[20],[21],[22]

This feature of the Frova introducer could have also led to a decreased need for ELMs for the passage of Frova introducer toward glottis in group F. A significantly higher number of patients with CL grade II in the non-Frova group, could have also resulted in more need for ELMs to optimize the glottis visualization for TT passage in that group.

The preference for the intubation technique among the trainees between both the groups was similar, though we expected that the Frova introducer would be preferred because of its easy maneuverability as shown in other studies.[19] This could be explained because of the lack of familiarity with a pre-railroaded TT over the Frova introducer technique [Figure 1], as it is not routinely used by our residents.

The Frova tracheal tube introducer has an established role as a rescue intubation aid, especially in difficult airways.[18],[19],[20],[21] Sakles et al., Hasegawa et al., and Mort et al. have used bougie as a primary intubating aid routinely for all cases instead of using it as a rescue device for difficult airways.[22],[23],[24] This has shown to reduce the number of intubation attempts and hence decreased the airway morbidity in these studies.

The routine use of bougie for intubation has also shown an increased first attempt intubation success rate even in novices with less training.[12],[17],[18] Angerman et al. demonstrated a significantly increased success rate of intubation with the routine use of Frova introducer guided TT with C-MAC VLS for all cases in the emergency department irrespective of the airway examination of patients.[17] Driver et al. also noted a higher first attempt success rate of intubation using C-MAC VLS with bougie versus stylet in patients with or without difficult airway characteristics.[12] The higher first attempt success rate with bougie noted in these studies could be because of the enrolment of patients with at least one difficult airway predictor in which the use of bougie would have been more beneficial, whereas in our study, the potential benefit of bougie in reducing the intubation attempts was not seen which could be because of the enrolment of patients without any difficult airway parameters.

The study limitation entails the inclusion of patients without any difficult airway parameters hence the findings cannot be generalized to those with anticipated difficult airway parameters wherein Frova introducer guided intubation with video laryngoscopy could be of greater benefit potentially. This study was restricted to the single-use Frova TT introducer with a distal anterior curvature which may not be generalizable to other types of bougies that lack a stiff nature. Another limitation was the lack of familiarity with the technique of preloading the TT on the Frova introducer which could have influenced the ease of intubation score by the residents. Recording of the primary objective (total intubation time) from the introduction of CMAC C-blade into the patient's mouth till ETCO2 appearance could have led to a prolongation in group F due to the time taken to remove the introducer before connecting the breathing circuit. Instead, the usage of time until observation of TT/Frova introducer passage through glottis would have been a better parameter.


  Conclusion Top


Frova introducer guided endotracheal intubation with C-MAC C-blade VLS by trainee anesthesiologists in patients with normal airway parameters had a marginally prolonged intubation time but with a comparable number of redirections and first attempt success rate to that of intubation without Frova introducer. Hence Frova introducer may not serve as a superior intubating aid for anesthesia trainees using C-MAC videolaryngoscope in patients with normal airway parameters. Further studies are needed to generalize these findings to all patients undergoing routine anesthesia care including obese patients and difficult airways.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Piepho T, Fortmueller K, Heid FM, Schmidtmann I, Werner C, Noppens RR. Performance of the C-MAC video laryngoscope in patients after a limited glottic view using Macintosh laryngoscopy: C-MAC in limited glottic view. Anaesthesia 2011;66:1101-5.  Back to cited text no. 1
    
2.
Xue F-S, Li H-X, Liu Y-Y, Yang G-Z. Current evidence for the use of C-MAC videolaryngoscope in adult airway management: A review of the literature. Ther Clin Risk Manag 2017;13:831-41.  Back to cited text no. 2
    
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Frerk C, Mitchell VS, McNarry AF, Mendonca C, Bharath R, Patel A, et al. Difficult airway society 2015 guidelines for management of unanticipated difficult intubation in adults. Br J Anaesth 2015;115:827-48.  Back to cited text no. 4
    
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Kaplan MB, ward DS, Brerci G. A new video laryngoscope – An aid to intubation and teaching. J Clin Anaesth 2002;14:620-6.  Back to cited text no. 5
    
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Mc Elwain J, Malik MA, Harte BH, Flynn NH, Laffey JG. Determination of the optimal stylet strategy for the C-MAC video laryngoscope: Stylet use with C-MAC video laryngoscope. Anaesthesia 2010;65:369-78.  Back to cited text no. 6
    
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van Zunderty A, Maassen R, Lee R, Willems R, Timmerman M, Siemonsma M, et al. A Macintosh laryngoscope blade for videolaryngoscope reduces stylet use in patients with normal airways. Anesth Analg 2009;109:825-31.  Back to cited text no. 7
    
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Hodgetts V, Danha RF, Mendonca C. A randomized comparison of C-MAC videolaryngscope versus macintosh laryngoscope for tracheal intubation. J Anesth Clin Res 2011;2:163.  Back to cited text no. 8
    
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Kilicaslan A, Topal A, Tavlan A, Erol A, Otelcioglu S. effectiveness of the C-MAC video laryngoscope in the management of unexpected failed intubations. Rev Bras Anestesiol 2014;64:62-5.  Back to cited text no. 9
    
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Noppens RR, Geimer S, Eisel N, David M, Piepho T. Endotracheal intubation using the C-MAC video laryngoscope or the Macintosh laryngoscope: A prospective, comparative study in the ICU. Crit Care 2012;16:R103.  Back to cited text no. 10
    
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Shin M, Bai SJ, Lee KY, Oh E, Kim HJ. Comparing McGRATH® MAC, C-MAC®, and Macintosh laryngoscope operated by medical students: A randomized crossover, Manikin study. Biomed Res Int 2016;2016:18.  Back to cited text no. 11
    
12.
Driver BE, Prekker ME, Klein LR, Reardon RF, Miner JR, Fagerstrom ET, et al. Effect of use of a bougie vs endotracheal tube and stylet on first-attempt intubation success among patients with difficult airways undergoing emergency intubation: A randomized clinical trial. JAMA 2018;319:2179-89.  Back to cited text no. 12
    
13.
Kim Y, Kim JE, Jeong DH, Lee J. Combined use of a McGrath MAC video laryngoscope and Frova intubating introducer in a patient with Pierre Robin syndrome: A case report. Korean J Anesthesiol 2014;66:310-3.  Back to cited text no. 13
    
14.
Hodzovic I, Latto IP, Wilkes AR, Hall JE, Mapleson WW. Evaluation of Frova, single use intubation introducer, in a mannikin. Comaprison with Eschmann multiple use introducer and Portex single use introducer. Anaesthesia 2004;59;811-6.  Back to cited text no. 14
    
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Annamaneni R, Hodzovic I, Wilkes AR, Latto IP. A comparison of simulated difficult intubation with multiple use and single use bougies in a mannikin. Anaesthesia 2003;58:45-9.  Back to cited text no. 15
    
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Whitcombe A, Strang T. A comparison of multiple use and single use bougies. Anaesthesia 2005;60:407-21.  Back to cited text no. 16
    
17.
Angerman S, Kirves H, Nurmi J. A before-and-after observational study of a protocol for use of the C-MAC videolaryngoscope with a Frova introducer in pre-hospital rapid sequence intubation. Anaesthesia 2018;73:348-55.  Back to cited text no. 17
    
18.
Brazil V, Grobler C, Greenslade J, Burke J. Comparison of intubation performance by junior emergency department doctors using gum elastic bougie versus stylet reinforced endotracheal tube insertion techniques: Dose a bougie improve intubation? Emerg Med Australas 2012;24:194-200.  Back to cited text no. 18
    
19.
Rai MR. The humble bougie… forty years and still counting? Anaesthesia 2014;69:199-203.  Back to cited text no. 19
    
20.
Hodzovic I, Wilkes AR, Stacey M, Latto IP. Evaluation of clinical effectiveness of the Frova single-use tracheal tube introducer. Anaesthesia 2008;63:189-94.  Back to cited text no. 20
    
21.
Batuwitage B, Mc Donald A, Nishikawa K, Lythgoe D, Mercer S, Charters P. Comparison between bougies and stylet for simulated tracheal intubation with the C-MAC D blade video laryngoscope. Eur J Anaesthesiol 2015;32:400-5.  Back to cited text no. 21
    
22.
Sakles JC, Chiu S, Mosier J, Walker C, Stolz U. The importance of first-pass success when performing orotracheal intubation in the emergency department. Acad Emerg Med 2013;20:71-8.  Back to cited text no. 22
    
23.
Hasegawa K, Shigemitsu K, Hagiwara Y, Chiba T, Watase H, Brown CA, et al. Association between repeated intubation attempts and adverse events in emergency departments: An analysis of a multicenter prospective observational study. Ann Emerg Med 2012;60:749-54.  Back to cited text no. 23
    
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Mort TC. Emergency tracheal intubation: Complications associated with repeated laryngoscopic attempts. Anesth Analg 2004;99:607-13.  Back to cited text no. 24
    


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    Tables

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



 

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