Comparison of Comparison of McGrath Videolaryngoscopy and Direct Laryngoscopy for Rapid Sequence Intubation: an International, Multicenter Randomized Trial
Phase: NA
Conditions: Surgery
Sponsor: The Cleveland Clinic

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Study protocol 
Version 9; June 24th,2022 
 
Comparison of McGrath Videolaryngoscopy and Direct Laryngoscopy for Rapid 
Sequence Intubation: an international, multicenter randomized trial 
 
Kurt Ruetzler, MD1,2, , Yasin Tire, MD3,  
Gokhan Sertcakacilar, MD4, Elyad Ekrami, MD1, Edward Mascha, PhD1,5,  
and colleagues 
 
1. Department of OUTCOMES RESEARCH, Anesthesiology Institute, Cleveland Clinic, 
Cleveland, USA  
 
2. Department of General Anesthesiology, Anesthesiology Institute, Cleveland 
Clinic, Cleveland, USA 
 
3. The University of Health Science, Konya City Hospital, Konya Turkey 
 
4. The University of Health Science, Bakırköy Dr. Sadi Konuk Education, and 
Research Hospital, Istanbul, Turkey 
 
5. Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, USA 
 
 
 
Address correspondence to:  Kurt Ruetzler, M.D.; Department of OUTCOMES 
RESEARCH; Anesthesiology Institute; Cleveland Clinic; 9500 Euclid Avenue, P-77; 
Cleveland, Ohio, 44195; Telephone: (216)-445-9857, fax (216) 444-6135; E-mail: 
kr@or.org  
On the World Wide Web: www.OR.org 

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BACKGROUND 
Securing the airway is a fundamental priority in the treatment of critically ill or injured 
patients. In the regular OR setting, direct laryngoscopy is the primary method for 
performing endotracheal intubation. But even in experienced hands, along with regular 
training and practice, successful endotracheal intubation sometimes requires additional 
tools to assist endotracheal intubation.1-3 Airway complications are rare but may lead to 
severe complications, such as brain damage and even death4. Set aside the “cannot 
ventilate and cannot intubation” scenario, difficult intubation has been associated with 
significant patient morbidity. For example, repeated intubation attempts are associated 
with respiratory and hemodynamic complications, including hypoxemia, cardiac arrest, 
regurgitation, aspiration, and airway trauma — along with bradycardia and cardiac 
arrest in emergency settings5 6.  
 
Rapid Sequence Intubation (RSI) is indicated when patients are not fully conscious or 
are otherwise at increased risk of gastric regurgitation and aspiration.7 The main 
objective of this technique is to minimize the time interval between loss of protective 
airway reflexes and tracheal intubation with a cuffed endotracheal tube. The period 
between induction of general anesthesia and securing the airway is most critical since 
aspiration of gastric content is then most likely.8 However, rapid sequence induction is 
associated with, hemodynamic instability and oxygen desaturation.9-11 It‘s therefore 
crucial to minimize the number of intubations attempts and the time to intubation, as 
both prolonged time to intubation and multiple intubation attempts significantly attribute 
to perioperative morbidity and mortality. 
 
Videolaryngoscopes were introduced into clinical practice approximately two decades 
ago and have gained wide acceptance in the elective OR setting.12 Videolaryngoscopes 
can facilitate endotracheal intubation by improving visualization of the larynx, thereby 
facilitating direct observation of the tracheal tube during passage through the vocal 
cords.13-17 Consequently, videolaryngoscopy may decrease intubation difficulties and 
ultimately increase first-attempt and overall intubation success rate.13-17 However, 

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available literature is heterogeneous in study design, patient characteristics, and 
intubation provider experience.  
 
Several trials demonstrated that videolaryngoscopes improve vocal cord visualization, 
but not first-pass intubation success.18,19 Interestingly, in a trial with ICU patients, 
videolaryngoscopy did not improve first-attempt intubation success and was associated 
with severe complications including death, cardiac arrest, cardiovascular collapse and 
hypoxemia.19 In contrast, other trials reported improved glottis visualization, improved 
first-pass success16 and no difference in rate of complications compared with direct 
laryngoscopy.20 In a recent Cochrane review of more than seven thousand patients with 
and without difficult airways, videolaryngoscopy was associated with fewer 
complications (e.g., laryngeal or airway trauma, postoperative hoarseness, hypoxia), 
fewer failed intubations, and no increase in the time required for intubation.21 The extent 
to which videolaryngoscopes might facilitate intubation in patients undergo RSI is 
unclear.  
 
The McGrath (Medtronic, Minneapolis, MN) is an FDA-approved and commercially 
available videolaryngoscope that includes a Macintosh blade and a camera which 
provides an indirect view of the glottis. The McGrath has been tested in a variety of 
settings22-24 and consistently provides better glottis visualization than direct 
laryngoscopy in patients with difficult airways.25,26 However, its suitability in the context 
of RSI has yet to be formally evaluated, and whether results from previous trials apply to 
these patients remains unknown. 
 
 

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Objectives and Hypothesis 
Our goal is to compare conventional direct laryngoscopy using a Macintosh blade with 
the McGrath videolaryngoscope for rapid sequence endotracheal intubation. 
Specifically, we propose to test the primary hypothesis that videolaryngoscopy improves 
visualization of the vocal cords, defined using the modified Cormack and Lehane 
classification (primary outcome), versus direct laryngoscopy. 
   
We will also test the secondary hypotheses that McGrath videolaryngoscopy decreases 
number of intubation attempts and the number of intubation failures. We hypothesize 
that the McGrath videolaryngoscopy reduces both, the number of intubation attempts 
and the number of intubation failures.  
We will also assess the following exploratory outcomes: 
1. Ease of intubation; 
2. Glottis opening score (POGO) score; 
3. Duration of intubation. 
We will also assess the following safety outcomes: 
1.  Incidence of cut lips, airway injury, or dental injury; 
2. Incidence of postoperative coughing;  
3. Incidence or severity of postoperative sore throat; 
4. Incidence or severity of postoperative hoarseness. 
 
 

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METHODS 
Design 
We propose a patient-blind multi-center randomized trial that will be coordinated 
by the Department of Outcomes Research at the Cleveland Clinic, Main Campus. 
 
Patients 
We will enroll up to 800 (including 25 – 50 pilot) consenting adults, with American 
Society of Anesthesiologists (ASA) physical status 1-3, who are scheduled for elective 
non-cardiac surgery requiring endotracheal intubation with rapid sequence induction for 
general anesthesia. Written informed consent will be obtained. Participating study 
centers will be:  
• Cleveland Clinic, Main Campus, Cleveland OH 
• Tabriz University of Medical Sciences, Tabriz, Iran 
• The University of Health Science, Konya City Hospital, Konya, Turkey 
• The University of Health Science, Bakırköy Dr. Sadi Konuk Education, and 
Research Hospital, Istanbul, Turkey 
 
Inclusion criteria 
1. Age between 18 and 99 years; 
2. American Society of Anesthesiologists (ASA) physical status 1-3; 
3. Elective surgery requiring oral endotracheal intubation for general anesthesia; 
4. Any clinical indication for rapid sequence induction as determined by the 
attending anesthesiologist; 
5. Anticipated extubation in the operating room. 
 
Exclusion criteria 
1. Refusal of participation by attending anesthesiologist; 
2. Indicated fiberoptic awake intubation 

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3. Body Mass index (BMI) > 45 kg/m2. 
 
Protocol 
In the preoperative period, airway details for participating patients will be 
recorded by a research coordinator or anesthesia provider. Patients will be positioned 
supine and in a standardized ramped position on the OR table. Patients will be pre-
medicated with midazolam, as clinically appropriate. All patients will be pre-oxygenated 
until the fraction of expired oxygen exceeds 80%.  
 
Rapid sequence induction will be induced as preferred by the attending 
anesthesiologist, usually with a combination of lidocaine 1 mg/kg, propofol 2-5 mg/kg, 
fentanyl 1-3 µg/kg, and succinylcholine 1.5 mg/kg or rocuronium 1.0 mg/kg. Complete 
muscle relaxation will be confirmed by absence of palpable twitches in response to 
supra-maximal train-of-four stimulation of the ulnar nerve at the wrist.  
 
Patients will be randomized 1:1 before induction, stratified for primary anesthesia 
providers (experienced – specialist, attending vs. unexperienced – trainees) to: 
- 
Direct laryngoscopy using an appropriately sized Macintosh blade (usually size 3 
or 4); 
- 
McGrath videolaryngoscope in an appropriate size (usually blade size 3 or 4). 
 
Randomization will be based on computer-generated codes accessed from the Redcap 
system.  
 
Intubations will be performed with a regular endotracheal tube of adequate diameter, 
usually 7.0 mm to 8.0 mm. Endotracheal tubes will be equipped with a hockey-stick-
shaped stylette, which will be prepared by the anesthesiologist in advance. The 
McGrath or the Macintosh blade will be introduced into oral cavity according to 
manufacturer recommendations and clinical practice. Minor airway manipulation 
procedures including BURP or Sellick maneuvers will be allowed to improve 

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visualization of the vocal cords. If initial intubation attempts fail, the endotracheal tube 
will be removed. Minor adjustments of patient’s position and/or tube stylette will be used 
as clinically appropriate. Up to two intubation attempts will be made as necessary. 
Further airway management will follow clinical assessment of the anesthesiologist. The 
anesthesiologist will be permitted to terminate study participation and switch to an 
alternative method.   
 
Once intubation is achieved, the endotracheal tube will be connected to the anesthesia 
circuit, and the endotracheal cuff pressure will be measured placed between 25 and 30 
cm H2O. 
 
Mechanical ventilation with O2 and air will be adjusted to maintain end-tidal PCO2 
between 32 and 35 mmHg as clinically necessary. Maintenance of general anesthesia 
will be provided, as clinically indicated.  
 
At the end of the surgical procedure, patients will be extubated and transferred to 
the post anesthesia care unit (PACU). Patients will then be assessed for postoperative 
complications 2 hours following extubation, or at PACU discharge. 
 
Measurements 
Demographic and morphometric characteristics will be collected from electronic 
medical records.  
1. Age 
2. Sex 
3. Race 
4. BMI  
5. ASA status 
6. Airway examination 
a. History of obstructive sleep apnea (yes/no) 
b. History of snoring (yes/no) 

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c. History of CPAP (yes/no) 
d. History of difficult airway (yes/no) 
e. Mobility of cervical spine (0, 15, 30, and 45 degrees) 
f. Mouth opening (cm)  
g. Inter-incisor gap (cm)  
h. Mandibular protrusion test (Class A, B, C) 
i. Thyro-mental distance (cm)  
j. Thyro-mental height (cm) 
k. Sterno-mental distance (cm)  
l. Neck circumference (cm)  
m. Upper lip bite test (Class I, II, III) 
n. Mallampati score (1/2/3/4) 
o. Teeth status (Edentulous, missing frontal teeth or full dentition)  
 
Outcomes 
Primary outcome: 
Best glottis visualization, defined as visualization according to the modified 
Cormack and Lehane classification27 
 
 
 

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Secondary Outcomes: 
• Intubation attempts, defined as introducing the endotracheal tube into oral cavity 
to perform endotracheal intubation (1, 2, 3, etc.) 
 
• Intubation failure, defined as  
- 
Failure to intubate within 3 intubation attempts 
- 
Need to switch intubators or intubation device  
- 
Need to stop study per anesthesiologist’s discretion  
 
Exploratory outcomes: 
- 
Portion of glottis opening score (POGO) score, defined as estimation of the 
glottis, which is visible during laryngoscopy (0, 25, 50, 75, 100%)28,29 
 
- 
Time to intubation, defined as the time between the laryngoscope introduced into 
oral cavity and cuff inflation (RSI definition) and to the first appearance of end-
tidal CO2. 
 
- 
Ease of intubation, defined as subjective evaluation of the anesthesiologist after 
finishing the intubation procedure: (1) very easy; (2) easy; (3) moderate; 
(4) difficult; and, (5) impossible.30,31 
Safety outcomes: 
- 
Any apparent airway or dental injury including bleeding, airway trauma, dental 
fracture, aspiration, or bronchospasm. 
 
- 
Incidence and severity of postoperative cough, assessed 2 hours after extubation 
in the PACU, and defined as continuous throat pain and rated as mild (less than 
a common cold), moderate (similar to a common cold), or severe (more than a 
common cold).30,31 
 

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- 
Incidence and severity of postoperative sore throat, assessed after 2 hours of 
extubation in the PACU, defined as an acoustic quality that was different from the 
previous voice quality of the patients and rated as mild (less than a common 
cold), moderate (similar to a common cold), or severe (more than a common 
cold).30,31 
 
- 
Incidence and severity of postoperative hoarseness, assessed after 2 hours of 
extubation in the PACU, and rated as noticed by the patient only, apparent to an 
observer, or aphonia.30,31 
 
Data analysis: 
Statistical Analysis 
We will assess the balance of two randomized groups (McGrath videolaryngoscopy vs. 
direct laryngoscopy) on baseline and demographic characteristics using the absolute 
standardized difference (ASD), defined as the absolute difference in means, mean 
ranks, or proportions divided by the pooled standard deviation. Any characteristics with 
ASD > maximum of 0.10 and 1.96
1 2
1
2
(
)x(
)
n n
n
n
+
 will be considered imbalanced and 
will be adjusted for in the primary and secondary analyses. 
  
All primary and secondary analyses will be completed using the modified intent-to-treat 
principle, thus including all randomized patients in whom intubation was attempted in 
the analyses.  We will conservatively assign all missing outcome values as the highest 
possible score in the control group (direct laryngoscopy) and the lowest possible score 
in the treatment group (McGrath videolaryngoscopy) for all primary and secondary 
analyses. 
 
Primary outcome: 
Wilcoxon-Mann-Whitney test will be used to formally compare categorical outcome of 
glottis visualization (Cormack and Lehane classification) at the 5% significance level 
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between the two study groups; this test accounts for the ordinal nature of the outcome. 
If adjustment for imbalanced baseline covariates is required, we will attempt a 
proportion odds logistic regression model to compare randomized groups, reporting an 
odds ratio indicating the estimated odds of being better using videolaryngoscopy versus 
direct. 
 
If the proportional odds assumption does not hold after testing and also visualizing with 
further modeling, the outcome will be assessed using either an adjacent logit analysis or 
by combining categories and using chi-square test or binary logistic regression, as 
appropriate. The distribution of patients in each glottis visualization class will be 
reported for each randomized group.  
 
Secondary outcomes: 
Randomized groups will be compared on the secondary outcome of Intubation failure 
(yes/no) via chi-square test and the associations reported using relative risk [97.5% 
confidence interval (CI)].   Randomized groups will be compared on the count of number 
of intubation attempts using either Wilcoxon-Mann-Whitney test or negative binomial 
regression, as appropriate. A Bonferroni correction will be applied and a significance 
criterion of 0.05/2=0.025 to control the overall Type I error at 5% level for two secondary 
hypotheses.  
 
The exploratory and safety outcomes will be reported by study groups without formal 
statistical testing of the difference. 
 
Interim analyses to assess efficacy and futility will be conducted at each 25% of the 
maximum planned enrollment.  We will use a gamma spending function with gamma 
parameter= -4 for efficacy and -1 for futility.    
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implementation and diagnostics. 
 
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function. 
Commented [WP3R2]: Response MUST be an 
ordered factor. Returns an object of class vglmff to be 
used by vgam/vglm 
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Sample size considerations.  Sample size is based on the primary outcome of glottis 
visualization (Cormack and Lehane classification) and the Wilcoxon-Mann-Whitney test.  
From the literature we assume a distribution of scores for the Direct Laryngoscopy 
group such that the proportion of patients in categories 1, 2a, 2b, 3 and 4 are 0.50, 0.30, 
0.15, 0.04, 0.01, and that for the videolaryngoscopy the proportions are improved to 
0.65, 0.25, 0.07, 0.02, 0.01.  We would thus need a total of 384 patients to detect this 
difference or larger with 90% power at the 0.05 significance level.  Incorporating a 
maximum of 3 interim analyses and a final analysis with the above-detailed spending 
functions will require a maximum of N=438 patients. Simulations indicate that if the 
specified difference is a good estimate of the true effect, the expected sample size is 
about 78% of the maximum sample size, or N=342.  In such a case, the study will have 
a very good chance of crossing an efficacy boundary at interim looks 2 or 3. 
 
Because our estimates of laryngeal view are uncertain, we plan to enroll a maximum of 
800 patients in case the treatment effect is somewhat less than anticipated.   
 
Pilot patients: We will enroll 5-10 pilot patients prior to the start of the study at each 
study center to familiarize the study team with the protocol and identify any systematic 
issues that might result in protocol modifications. Pilot patients will be randomized either 
to McGrath videolaryngoscopy or direct laryngoscopy group in the same manner as it is 
planned for the study. Pilot patients will not be included in the statistical analysis. 
 
Funding: 
This study is an investigator-initiated study.  
 
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REFERENCES 
 
1. 
Wang HE, Seitz SR, Hostler D, Yealy DM: Defining the learning curve for 
paramedic student endotracheal intubation. Prehosp Emerg Care 2005; 9: 156-62 
 
2. 
Garza AG, Gratton MC, Coontz D, Noble E, Ma OJ: Effect of paramedic 
experience on orotracheal intubation success rates. J Emerg Med 2003; 25: 251-6 
 
3. 
Deakin CD, King P, Thompson F: Prehospital advanced airway 
management by ambulance technicians and paramedics: is clinical practice sufficient to 
maintain skills? Emerg Med J 2009; 26: 888-91 
 
4. 
Cook TM, MacDougall-Davis SR: Complications and failure of airway 
management. Br J Anaesth 2012; 109 Suppl 1: i68-i85 
 
5. 
Hasegawa K, Shigemitsu K, Hagiwara Y, Chiba T, Watase H, Brown CA, 
3rd, Brown DF: 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.e2 
 
6. 
Mort TC: Emergency tracheal intubation: complications associated with 
repeated laryngoscopic attempts. Anesth Analg 2004; 99: 607-13, table of contents 
 
7. 
El-Orbany M, Connolly LA: Rapid sequence induction and intubation: 
current controversy. Anesth Analg 2010; 110: 1318-25 
 
8. 
Olsson GL, Hallen B, Hambraeus-Jonzon K: Aspiration during 
anaesthesia: a computer-aided study of 185,358 anaesthetics. Acta Anaesthesiol Scand 
1986; 30: 84-92 
 
9. 
Gebremedhn EG, Mesele D, Aemero D, Alemu E: The incidence of 
oxygen desaturation during rapid sequence induction and intubation. World J Emerg 
Med 2014; 5: 279-85 
 
10. 
Higgs A, McGrath BA, Goddard C, Rangasami J, Suntharalingam G, Gale 
R, Cook TM: Guidelines for the management of tracheal intubation in critically ill adults. 
Br J Anaesth 2018; 120: 323-52 
 
11. 
Ahmed A, Azim A: Difficult tracheal intubation in critically ill. J Intensive 
Care 2018; 6: 49 

Study protocol McGrath in patients having RSI  
 
14 | P a g e  
 
 
12. 
Weiss MS, U.; Gerber, AC.: Video-Intubating Laryngoscopy – A New 
concept four Routine and Difficult Tracheal Intubation Management. Anesthesiology 
1998; Suppl. 3A, SEE9 
 
13. 
Aziz MF, Abrons RO, Cattano D, Bayman EO, Swanson DE, Hagberg CA, 
Todd MM, Brambrink AM: First-Attempt Intubation Success of Video Laryngoscopy in 
Patients with Anticipated Difficult Direct Laryngoscopy: A Multicenter Randomized 
Controlled Trial Comparing the C-MAC D-Blade Versus the GlideScope in a Mixed 
Provider and Diverse Patient Population. Anesth Analg 2015 
 
14. 
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. Anaesthesia 2011; 66: 1101-5 
 
15. 
Sakles JC, Mosier J, Chiu S, Cosentino M, Kalin L: A comparison of the C-
MAC video laryngoscope to the Macintosh direct laryngoscope for intubation in the 
emergency department. Ann Emerg Med 2012; 60: 739-48 
 
16. 
Aziz MF, Dillman D, Fu R, Brambrink AM: Comparative Effectiveness of 
the C-MAC Video Laryngoscope versus Direct Laryngoscopy in the Setting of the 
Predicted Difficult Airway. Anesthesiology 2012; 116: 629-36 
 
17. 
Jungbauer A, Schumann M, Brunkhorst V, Borgers A, Groeben H: 
Expected difficult tracheal intubation: a prospective comparison of direct laryngoscopy 
and video laryngoscopy in 200 patients. Br J Anaesth 2009; 102: 546-50 
 
18. 
Sulser S, Ubmann D, Schlaepfer M, Brueesch M, Goliasch G, Seifert B, 
Spahn DR, Ruetzler K: C-MAC videolaryngoscope compared with direct laryngoscopy 
for rapid sequence intubation in an emergency department: A randomised clinical trial. 
Eur J Anaesthesiol 2016; 33: 943-8 
 
19. 
Lascarrou JB, Boisrame-Helms J, Bailly A, Le Thuaut A, Kamel T, Mercier 
E, Ricard JD, Lemiale V, Colin G, Mira JP, Meziani F, Messika J, Dequin PF, Boulain T, 
Azoulay E, Champigneulle B, Reignier J: Video laryngoscopy vs direct laryngoscopy on 
successful first-pass orotracheal intubation among icu patients: A randomized clinical 
trial. Jama 2017; 317: 483-93 
 
20. 
Taylor AM, Peck M, Launcelott S, Hung OR, Law JA, MacQuarrie K, 
McKeen D, George RB, Ngan J: The McGrath(R) Series 5 videolaryngoscope vs the 

Study protocol McGrath in patients having RSI  
 
15 | P a g e  
 
Macintosh laryngoscope: a randomised, controlled trial in patients with a simulated 
difficult airway. Anaesthesia 2013; 68: 142-7 
 
21. 
Lewis SR, Butler AR, Parker J, Cook TM, Smith AF: Videolaryngoscopy 
versus direct laryngoscopy for adult patients requiring tracheal intubation. Cochrane 
Database Syst Rev 2016; 11: Cd011136 
 
22. 
Kwak HJ, Lee SY, Lee SY, Cho SH, Kim HS, Kim JY: McGrath Video 
Laryngoscopy Facilitates Routine Nasotracheal Intubation in Patients Undergoing Oral 
and Maxillofacial Surgery: A Comparison With Macintosh Laryngoscopy. J Oral 
Maxillofac Surg 2016; 74: 256-61 
 
23. 
Hyuga S, Sekiguchi T, Ishida T, Yamamoto K, Sugiyama Y, Kawamata M: 
Successful tracheal intubation with the McGrath((R)) MAC video laryngoscope after 
failure with the Pentax-AWS in a patient with cervical spine immobilization. Can J 
Anaesth 2012; 59: 1154-5 
 
24. 
Foulds LT, McGuire BE, Shippey BJ: A randomised cross-over trial 
comparing the McGrath((R)) Series 5 videolaryngoscope with the Macintosh 
laryngoscope in patients with cervical spine immobilisation. Anaesthesia 2016; 71: 437-
42 
 
25. 
Noppens RR, Mobus S, Heid F, Schmidtmann I, Werner C, Piepho T: 
Evaluation of the McGrath Series 5 videolaryngoscope after failed direct laryngoscopy. 
Anaesthesia 2010; 65: 716-20 
 
26. 
Shippey B, Ray D, McKeown D: Use of the McGrath videolaryngoscope in 
the management of difficult and failed tracheal intubation. Br J Anaesth 2008; 100: 116-
9 
 
27. 
Yentis SM, Lee DJ: Evaluation of an improved scoring system for the 
grading of direct laryngoscopy. Anaesthesia 1998; 53: 1041-4 
 
28. 
Biro P, Ruetzler K: The reflective intubation manoeuvre increases success 
rate in moderately difficult direct laryngoscopy: A prospective case-control study. Eur J 
Anaesthesiol 2015; 32: 406-10 
 
29. 
Cormack RS, Lehane JR, Adams AP, Carli F: Laryngoscopy grades and 
percentage glottic opening. Anaesthesia 2000; 55: 184- 

Study protocol McGrath in patients having RSI  
 
16 | P a g e  
 
 
30. 
Ruetzler K, Grubhofer G, Schmid W, Papp D, Nabecker S, Hutschala D, 
Lang G, Hager H: Randomized clinical trial comparing double-lumen tube and EZ-
Blocker for single-lung ventilation. Br J Anaesth 2011; 106: 896-902 
 
31. 
Ruetzler K, Guzzella SE, Tscholl DW, Restin T, Cribari M, Turan A, You J, 
Sessler DI, Seifert B, Gaszynski T, Ganter MT, Spahn DR: Blind intubation through self-
pressurized, disposable supraglottic airway laryngeal intubation masks: An international, 
multicenter, prospective cohort study. Anesthesiology 2017; 127: 307-16