A Comparative Study of Glottis Visualization According to the Method of Lifting the Epiglottis in Video Laryngoscopy: Indirect and Direct Lifting Methods

Anesth Pain Med 2021;16:196-200 https://doi.org/10.17085/apm.20073 Clinical Research pISSN 1975-5171 • eISSN 2383-7977

A comparative study of glottis visualization according to the method of lifting the epiglottis in video laryngoscopy: indirect and direct lifting methods

Ji Youn Oh, Ji Hye Lee, Yu Yil Kim, Seung Min Baek, Da Wa Jung, and Ji Hun Park Received September 11, 2020 Revised January 4, 2021 Department of Anesthesiology and Pain Medicine, Presbyterian Medical Center, Jeonju, Accepted January 14, 2021 Korea

Background: The direct entry of the camera under the epiglottis may provide a better view of the glottis than the indirect lifting of the epiglottis by placing the Macintosh blade tip on the vallecula when using the video laryngoscope. This study aimed to compare the efficiency of two different methods of lifting the epiglottis during the visualization of glottis using video laryngoscopy in the same patient. Methods: This prospective study enrolled 60 patients who underwent general anesthesia with tracheal intubation. In each patient, glottic views were obtained by directly (group DE) and indirectly lifting the epiglottis (group IE). These two methods were compared using the modified Cormack and Lehane grade and the percentage of glottis opening (POGO) score as assessment parameters. Results: Modified Cormack and Lehane grade showed a significant difference between the Corresponding author groups DE and IE (P = 0.004). The difference in the POGO score between the groups DE and Ji Hye Lee, M.D. Department of Anesthesiology and IE was also statistically significant (87.5% and 64.4%, respectively; P < 0.001). Pain Medicine, Presbyterian Medical Conclusions: Our results, therefore, revealed that the method of directly lifting epiglottis was Center, 365, Seowon-ro, Wansan-gu, better at exposing glottis than the method of indirectly lifting epiglottis using a video laryngo- Jeonju 54987, Korea scope. Tel: 82-63-230-1591 Fax: 82-63-230-8919 E-mail: [email protected] Keywords: Endotracheal intubation; Epiglottis; Glottis; Laryngoscopes; Lifting; Visualization.

INTRODUCTION laryngoscopes (DLs) are commonly used for the alignment of the oral, pharyngeal, and laryngeal axes, and for the ele- Tracheal intubation, in which an appropriate endotra- vation of the epiglottis. Among the methods that employ cheal tube is inserted into the trachea through the oral or DLs, despite the enormous progress in anesthetic practice, nasal cavity to secure the airway, is the most important exposing the glottis by indirect elevation of epiglottis using routine practice for anesthesiologists. During the process a Macintosh blade (Macintosh method) developed by RR of tracheal intubation, it is imperative to overcome the an- Macintosh in 1943 [1] is still the most used method world- atomical characteristics presented by the angled airway to wide. ensure a line of sight to the glottis. To achieve this, direct Recently, the method of intubation has changed from

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196 KSAM ------197 ] and ] and 12 [ ]. Laryngoscopy ]. Laryngoscopy 11 [ Patient’s demographic data was collected, was and airway data as demographic Patient’s neither glottis nor epiglottis visible) visible) nor epiglottis neither glottis performed who did not was an anesthesiologist by grading perform video laryngoscopy. secondary The was outcome (POGO) opening of glottis the percentage score and asystole, or bradycardia severe as such events adverse of POGO landmark The was laryngospasm recorded. were interarytenoid and (anterior) commissure anterior the during the indirect method. In the direct method, attempts method, attempts the direct method. In during the indirect limited to were under the epiglottis the blade enter to video laryngoscopy The performed was an expe by three. of experience 5 years than rienced (more anesthesiologist of the video laryngos results The as an anesthesiologist). based on the method two groups divided into were copy of glottis; the epi in which used for the exposure the group in DE) and the group (group lifted directly was glottis The IE). (group indirectly lifted was epiglottis the which cap the using twothe in groups compared was view glottic images. tured Measurement thy opening, mouth class, Mallampati including sessment performed. mobility was and neck The distance, romental primaryof video laryngoscopy outcome the modified was (grade view glottic the of Lehaneand grade (CL) Cormack 2a; grade 1; full view of the glottis, partial view of the glottis, 2b; arytenoidsgrade or posterior cords part of the vocal 4; grade visible, epiglottis 3; only grade visible, just only 1–2 mg/kg propofol, 0.8 mg/kg rocuronium, and remifent rocuronium, mg/kg 0.8 propofol, 1–2 mg/kg count TOF “zero” When infusion). (target-controlled anil administration the after twice continuously recorded was was view the glottic agent, blocking of a neuromuscular directly two the epiglottis methods of lifting obtained by Korea) Co., Acemedical (AceScope, VL using and indirectly with a curved was of the VL blade use). The (single blade shape and the inserted of the tongue, the midline along for the confirmed. was First, of the epiglottis and location placed under the epiglottis method, was the blade direct Second,for the indirect and lifted expose to the glottis. and the tip of the blade back pulled method, was blade the and lifted epi base (vallecula) placedthe tongue on was minimize to order In expose to the glottis. indirectly glottis performed both methods were in a the patient, the harm to laryngeal external manipulation No process. sequential performed.was for each taken view was best glottic The performed was a stylet method, using and intubation ------]. 10 – 2 [ Glottic visualization using VL using visualization Glottic MATERIALS AND METHODS MATERIALS Non-invasive blood pressure, electrocardiogram, pulse pulse electrocardiogram, blood pressure, Non-invasive This study was conducted as a prospective study after after study conducted a prospective as was study This Thus, we hypothesized that the direct entry the direct of the cam that we hypothesized Thus, www.anesth-pain-med.org formed as standard monitoring in all patients. Glycopyrro monitoring in all patients. formed as standard induc before intravenously administered was (0.2 mg) late induced with was General anesthesia tion of anesthesia. oximetry, index, bispectral and monitoring of neuromus per were ratio) (TOF four of with train blocking cular Method ry history risk intubation, of aspiration, of difficult diseases, this study. from excluded conditions were and poor dental were scheduled for general anesthesia with tracheal intu with scheduled anesthesia tracheal for general were written informed consent provided All the patients bation. or respirato with cardiovascular patients The the study. to were recruited from a single medical center. All the patients All the patients center. medical a single from recruited were American Soci and had of age 18 years over were enrolled patients 1–2. These status physical ety of Anesthesiologists 2020-04-015) and included 60 patients. This study was reg was study This 2020-04-015) and included 60 patients. All patients KCT0005170). (no. ClinicalTrials.gov at istered approval from the Institutional Review Board (IRB no. (IRB no. Board Review the Institutional from approval ization of glottis using VL in the same patient. in the same VL using of glottis ization blade tip in the vallecula in the VL. We compared the indi compared in the VL. tip in the vallecula blade We for visual the epiglottis methods of lifting and direct rect era under the epiglottis may provide a better glottic view view glottic a better provide may under the epiglottis era the placing by of the epiglottis lifting the indirect than uses the indirect glottic view of the camera close to the the close to camera the of view glottic usesindirect the the epi lifting by the glottis the method of exposing glottis, appropriate. be more may directly glottis because of the camera position in the pharynx. the position in the camera the of of because Most method the Macintosh VLs of recommend manufacturers VL considering that However, indirectly. lift epiglottis to structures such as epiglottis through the oral cavity, the the cavity, oral the through epiglottis as such structures video laryngoscopy observe can the laryngeal structures location of the glottis on an external monitor via a camera a camera via monitor on an external of the glottis location di when the Even the middle or tip of the blade. in located the laryngeal identify laryngoscopy directly rect cannot bation success rate, reduction in intubation attempts and and attempts in intubation reduction rate, success bation laryngoscopes direct to compared complications confirm view can glottis the uses an indirect that VL The that involving a direct glottic view to an indirect glottic view glottic indirect an to view glottic direct a involving that video laryngoscopesbecause advantages several (VL) have intu higher a visualization, of glottis as improvement such Anesth Pain Med notch (posterior). POGO score was based on the subjectiv- DE and group IE was also statistically significant (87.5% ity of the estimator, and measured on a scale of 0–100% in and 64.4, %respectively; P < 0.001). The superiority of glot- steps of 10%. The scoring was performed by three anesthetic view (Fig. 1) by POGO score in the same patient was 43 siologists, and the mean of the assigned scores were used. (71.7%) and 8 (13.3%) in group DE and group IE, respectively (Table 2). There were no cases where the blade failed Study sample size and statistical analysis to enter under the epiglottis in the group DE. In addition, there were no cases of laryngospasm or cardiac arrhyth- When the pilot study (n = 26) was conducted, the differ- mias related to laryngoscopy. ence in incidence of modified CL grade 1 in the two groups (direct elevation group: 96.2%, indirect elevation group: DISCUSSION 69.2%) was 27%. When the sample size was calculated at an α level of 0.05 and a power of 0.8 based on this result of the In this study, we assessed the efficacy of two different pilot study, each group was estimated to have 54 cases. It methods of lifting the epiglottis (direct and indirect) for vi- was decided to include 60 cases in each group (total 120 sualization of the glottis in the same patient using VL. Our cases) by adding 10% of cases to compensate for dropout results revealed that the method of directly lifting the epi- rates. Since each procedure was performed serially on the glottis was better at exposing the glottis than the method of same patient, the study was conducted in a total of 60 pa- indirectly lifting epiglottis using a VL. In addition, upon tients. Statistical analysis was performed using SPSS ver. 23 (IBM Co., USA) Patient demographic and airway assessment data are expressed as mean (95% confidence inter- A a val). The two methods were performed sequentially in same patient, but because each method was independent, modified CL grade was analyzed using the chi-squared test and POGO score was analyzed using the t-test. A P value < 0.05 was considered to be statistically significant.

RESULTS B b The demographic and airway assessment data of the patients are as shown in Table 1. Modified CL grade showed significant difference between group DE and group IE (P = 0.004). The difference in the POGO scores between group

Table 1. Patients Demographic and Airway Assessment Data Variable Value (n = 60) Sex (M/F) 13/47 Age (yr) 45.6 (42.1–48.7) C c Height (cm) 160.6 (158.5–162.9) Weight (kg) 64.6 (61.7–68.1) Body mass index (kg/m2) 25.0 (24.1–26.1) Mallampati class (I/II/III/IV) 45/14/1/0 (75/23.3/1.7/0) Mouth opening (cm) 4.4 (4.2–4.6) < 3 cm 0 Thyromental distance (cm) 8.3 (8.0–8.7) < 6 cm 2 Fig. 1. Paired glottic view in the same patient (A-a, B-b, C-c). The Neck extension (degrees) 44.1 (42.7–45.7) capital letter is a method of lifting the epiglottis directly, and the < 35 degrees 2 small letter is a method of lifting the epiglottis indirectly in the same Values are presented as mean (95% confidence interval) or number patient. The glottic view obtained by lifting the epiglottis directly (%). shows superiority.

198 www.anesth-pain-med.org KSAM ------199 001 001 004 . . . 0 0 0 P value < < ) 0 / 7 . 1 / 3 . ) 13 4 / . 7 . 72 ) 3 – 36 . 3 / . 3 13 . ( 56 8 ( 48 Group IE 4 ( . 0 / 64 1 / 8 / ]. Since the VL is evolving rapidly and has has and rapidly evolving is VL the Since ]. CONFLICTS OF INTEREST CONFLICTS 22 / 16 , 29 9 DATA AVAILABILITY STATEMENT AVAILABILITY DATA – 3 [ The datasets generated during and/or analyzed during during during and/or analyzed generated datasets The The limitation of this study is that the study related to in to related the study is that of this study limitation The when ex that demonstrated results our conclusion, In this article to relevant conflict of interest potential No was reported. was au corresponding the from available are study current the request. thor on reasonable further investigations to determine the most appropriate determine to appropriate the most further investigations VL.method for using these investiga this study, to Similar the followings: address tions should visualization glottis VL,using the en use whether to when entering the stylet and the form the stylet, properly to or how tube dotracheal on the blade. usefulness channel of the not be method conduct each could to according tubation performed the in ed bothas methods were simultaneously the superiority addition, because In of glottis patient. same the superiority does not indicate in intuba visualization in that intubation to related tion, further investigations and intubation, time to rate, success the intubation volve method in each will be needed.complications a VL, using the glottis posing lifting the method of directly the in a superior view than glottic provided the epiglottis method. direct Macintosh laryngoscope. In many studies, VL has been re has VL studies, laryngoscope. many In Macintosh intubation increase visualization, glottis ported improve to pressure reduce attempts, intubation reduce rate, success com complications and reduce on laryngeal structures, laryngo those to observedpared the Macintosh on using scope laryngoscope,it is con Macintosh over advantages various in airway practice will VL becomea routine that sidered of the Macintosh in place during anesthesia management conduct to is important It laryngoscope future. in the near ) 0 / 0 / ) 5 6 / . ------) 15 90 7 / . – 2 . 80 71 ( ( 80 0 ( / 43 Group DE ]. Most of of ]. Most 7 0 Glottic visualization using VL using visualization Glottic . / 3 15 85 , / ]. In contrast, contrast, ]. In 9 / 14 13 [ [ 48 ) 4 / 3 b/ 2 a/ 2 / ]. VL uses a blade as in a direct laryndirect a uses in as VL ]. blade a 1 4 – 2 [ Variable Glottis Visualization Glottis Superiority of the glottic view glottic the of Superiority POGO score Modified CL grade ( CL grade Modified Macintosh method, developed in 1943, has been method, developed used in 1943, has as Macintosh The VL developed for difficult airway management in the in developedVL airway for difficult The management POGO scores of patients. Group DE: directly elevation of epiglottis, Group IE: indirectly elevation of epiglottis, CL: Cormack and Lehane, POGO: Lehane, and CL: Cormack epiglottis, of elevation indirectly IE: Group epiglottis, of elevation directly DE: Group patients. of POGO scores opening. glottis of percentage Values are presented as mean (95% confidence interval) or number (%). The superiority of glottic view was evaluated by comparing the the comparing by evaluated was view glottic of superiority (%). The number or interval) confidence (95% as mean presented are Values www.anesth-pain-med.org the VL studies compared glottis visualization, intubation intubation visualization, glottis compared studies the VL in to time attempt, first the and/or overall at rate success with those observed complication, and tubation, the using a standard method for tracheal intubation for decades, and for decades, intubation methodtracheal for a standard used, used popularly this is still as the VLsalthough are other devices in evaluating gold standard less affected by the anatomy of the larynx. the anatomy affectedless by by laryngeal anatomy cannot be avoided. However, the the However, be avoided. cannot laryngealby anatomy the posterior aspect enter easily of the can of VL camera be to considered therefore, and this method is, epiglottis, the Macintosh method is recommended mainly for most of for most mainly method is recommended Macintosh the method is also used in video When the Macintosh the VLs. offered laryngoscope hindrance the elevation, for epiglottis barrier concealing the glottis from the camera’s view. Even view. Even the camera’s barrier from the glottis concealing laryngoscope fundamen are and Macintosh the VL though the glottis, in the methods used approach to different tally alignment of the airway axes is not important. Therefore, it Therefore, of the airway is not important. axes alignment is the final which the epiglottis, raise to important is most gidity, and the relationship with connected structures such such with connected structures gidity, and the relationship ligament bone and hyoepiglottic as hyoid in the pharynx, is located in the VL the camera because the as an indirect method of applying force on the vallecula on the vallecula force method of applying as an indirect the affected by method is significantly base). This (tongue ri shape, as size, such variety of the epiglottis anatomical simultaneously to expose the glottis. For epiglottis eleva epiglottis For expose to the glottis. simultaneously laryngoscope used commonly most is Macintosh the tion, ing direct glottis view, the two steps including the align view, the two glottis including steps direct ing of the epi airway and the elevation axes of the three ment be performed method, should or indirect direct by glottis goscope. However, VL uses an indirect glottic view that view that glottic uses VL an indirect However, goscope. through monitor external an on glottis the identify to helps laryngoscopy us direct In blade. the on located camera a early 2000s combines the advantages of DLs and fiberoptic of DLs and fiberoptic the advantages 2000s combines early bronchoscopes ods on the same patient, we observed us cases most ods patient, on the same that method showed superior view. glottic the direct ing evaluation of the glottic view using each of the two each meth view using of the glottic evaluation Table 2. Table Anesth Pain Med

AUTHOR CONTRIBUTIONS intosh laryngoscope vs. Pentax-AWS video laryngoscope: com- parison of efficacy and cardiovascular responses to tracheal Conceptualization: Yu Yil Kim. Data curation: Ji Youn Oh, intubation in major burn patients. Korean J Anesthesiol 2012; Seung Min Baek, Da Wa Jung, Ji Hun Park. Writing - origi- 62: 119-24. nal draft: Yu Yil Kim. Writing - review & editing: Yu Yil Kim. 8. Arulkumaran N, Lowe J, Ions R, Mendoza M, Bennett V, Dunser Supervision: Ji Hye Lee. MW. Videolaryngoscopy versus direct laryngoscopy for emergency orotracheal intubation outside the operating room: a ORCID systematic review and meta-analysis. Br J Anaesth 2018; 120: 712-24. Ji Youn Oh, https://orcid.org/0000-0003-3082-9402 9. Liu DX, Ye Y, Zhu YH, Li J, He HY, Dong L, et al. Intubation of Ji Hye Lee, https://orcid.org/0000-0003-3269-3844 non-difficult airways using video laryngoscope versus direct Yu Yil Kim, https://orcid.org/0000-0003-3455-9251 laryngoscope: a randomized, parallel-group study. BMC Anes- Seung Min Baek, https://orcid.org/0000-0003-0290-0208 thesiol 2019; 19: 75. Da Wa Jung, https://orcid.org/0000-0002-1566-7903 10. Avidan A, Shapira Y, Cohen A, Weissman C, Levin PD. Difficult Ji Hun Park, https://orcid.org/0000-0003-3897-7151 airway management practice changes after introduction of the GlideScope videolaryngoscope: a retrospective cohort study. REFERENCES Eur J Anaesthesiol 2020; 37: 443-50. 11. Yentis SM, Lee DJ. Evaluation of an improved scoring system 1. Macintosh RR. A new laryngoscope. Lancet 1943; 241: 205. for the grading of direct laryngoscopy. Anaesthesia 1998; 53: 2. Cooper RM. Use of a new videolaryngoscope (GlideScope) in 1041-4. the management of a difficult airway. Can J Anaesth 2003; 50: 12. Levitan RM, Ochroch EA, Kush S, Shofer FS, Hollander JE. As- 611-3. sessment of airway visualization: validation of the percentage 3. Sun DA, Warriner CB, Parsons DG, Klein R, Umedaly HS, of glottic opening (POGO) scale. Acad Emerg Med 1998; 5: 919- Moult M. The GlideScope video laryngoscope: randomized 23. clinical trial in 200 patients. Br J Anaesth 2005; 94: 381-4. 13. Nakao H. The Macintosh laryngoscope: the mechanism of la- 4. Cooper RM, Pacey JA, Bishop MJ, McCluskey SA. Early clinical ryngeal exposure and the optimal maneuver. J Curr Surg 2018; experience with a new videolaryngoscope (GlideScope) in 728 8: 1-6. patients. Can J Anaesth 2005; 52: 191-8. 14. Mihai R, Blair E, Kay H, Cook TM. A quantitative review and 5. Griesdale DE, Liu D, McKinney J, Choi PT. Glidescope® vid- meta-analysis of performance of non-standard laryngoscopes eo-laryngoscopy versus direct laryngoscopy for endotracheal and rigid fibreoptic intubation aids. Anaesthesia 2008; 63: 745- intubation: a systematic review and meta-analysis. Can J An- 60. aesth 2012; 59: 41-52. 15. Scott J, Baker PA. How did the Macintosh laryngoscope become 6. Sakles JC, Mosier J, Chiu S, Cosentino M, Kalin L. A compari- so popular? Paediatr Anaesth 2009; 19 Suppl 1: 24-9. son of the C-MAC video laryngoscope to the Macintosh direct 16. Gordon JK, Bertram VE, Cavallin F, Parotto M, Cooper RM. Di- laryngoscope for intubation in the emergency department. rect versus indirect laryngoscopy using a Macintosh video la- Ann Emerg Med 2012; 60: 739-48. ryngoscope: a mannequin study comparing applied forces. 7. Woo CH, Kim SH, Park JY, Bae JY, Kwak IS, Mun SH, et al. Mac- Can J Anaesth 2020; 67: 515-20.

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