Effectiveness of Facial Mask Non-Invasive Ventilation in Adults Under General Anesthesia: Two-Hand C-E vs V-E Techniques. A Double-Blind Randomized Trial
Phase: NA
Conditions: General Anesthetics
Sponsor: Universidad de Antioquia

 
 
 
 
 
 
 
 
COMPARISON OF EFFECTIVENESS OF NON-INVASIVE 
VENTILATION WITH A FACE MASK  IN ADULT PATIENTS 
UNDERGOING GENERAL ANESTHESIA: TWO HANDED 
VENTILATION TECHNIQUE C-E VS TWO HANDED VENTILATION 
TECHNIQUE  V-E 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
UNIVERSITY OF ANTIOQUIA 
ANESTHESIOLOGY AND REANIMATION SECTION  
 

 
  
 
 
 
 
 
 
 
 
 
Research team 
 
 
 
 
Postgraduate students 
Juan Pablo Vasquez Lainez 
Aldair Sayed Vides Villamizar 
 
 
 
Thesis Advisors 
Mario Andrés Zamudio Burbano 
 
 
 
 
Co-Researchers  
- 
 
 
 
March, 2024 
 
 
 
 
 
 
 
 
 
 
 
 
Pág. 
2 
Versión. 01 
 

 
  
TABLE OF CONTENTS 
  
I. Administrative information 
​
1. Title  
​
2. Study registration 
2.a. Study identifier and registry name  
2.b. Items of  “World Health Organization Trial Registration Data Set” 
​3. Protocol version 
​
4. Funding 
​
5. Roles and  responsibilities 
5.a Names, affiliations, and roles of protocol contributors 
5.b Name and contact information of the study sponsor 
II. Introduction 
​
6. Theoretical Framework 
6.a. Background and Justification  
​
7. Objectives and Hypotheses  
​
8. Study Design and Description 
III. Methods: Participants, Interventions, and Outcomes  
​
9.  Description of Study Characteristics  
​
10. Inclusion and Exclusion Criteria for Participants 
​
11. Interventions  
​
12. Primary and Secondary Outcomes 
​
13. Participant Timeline  
​
14. Sample Size 
​
15. Recruitment 
IV. Methods: Assignment of Interventions  
​16. Assignment  
16.a .Sequence Generation 
16.b. Allocation Concealment Mechanism 
Pág. 
3 
Versión. 01 
 

 
  
16.c. Implementation 
​
17. Blinding  
V. Methods: Data Collection, Management, and Analysis  
​
18. Data Collection Methods 
​
19.  Data Management 
​
20. Statistical Analysis 
VI.  Methods: Monitoring  
​
21. Data Monitoring 
​
22. Harms  
​
23. Auditing 
VII. Ethics and Dissemination  
​
24. Ethics Committee Approval 
​
25. Protocol Amendments  
​
26. Informed Consent  
​
27. Confidentiality 
​
28. Declaration of Conflicts of Interest  
​
29. Access to Data 
​
30. Post-Study Care 
​
31. Dissemination Policy 
VIII. Appendices 
​
32. Informed Consent 
 
 
 
 
 
 
 
 
 
 
 
Pág. 
4 
Versión. 01 
 

 
  
I. Administrative Information  
1.​ Title: 
Comparison of the Effectiveness of Non-Invasive Ventilation with a Facial Mask in Adult 
Patients Undergoing General Anesthesia: Two-Hand C-E Ventilation Technique vs. 
Two-Hand V-E Ventilation Technique. Double-Blind Randomized Clinical Trial  
2.​ Protocol Registration  
2a Protocol Registration: To be completed in Clinical Trial once finalized  
2b Data Registration according to World Health Organization recommendations in Table 1. 
Table 1. Data Registration according to WHO  
Data 
Information 
Registration and Identification 
Number 
 
Registration Date  
 
Secondary Registration Number  
 
Funding Sources 
Authors. Hospital Alma Máter de Antioquia. 
Primary Sponsor 
Hospital Alma Máter de Antioquia. 
Secondary Sponsor  
University of Antioquia, Faculty of Medicine 
Public Contact  
Aldair Sayed Vides Villamizar. 
Scientific Contact:  
Juan Pablo Vásquez Lainez. 
Public title  
VENTMASK 1 
Scientific title  
Comparison of the Effectiveness of Non-Invasive 
Ventilation with a Facial Mask in Adult Patients 
Undergoing General Anesthesia: Two-Hand C-E 
Ventilation Technique vs. Two-Hand V-E Ventilation 
Technique. Double-Blind Randomized Clinical Trial 
Recruitment Country  
Colombia. 
Study Problem 
Comparison of the Effectiveness of Non-Invasive 
Ventilation with a Facial Mask in Adult Patients 
Undergoing General Anesthesia: Two-Hand C-E 
Ventilation Technique vs. Two-Hand V-E Ventilation 
Technique. Double-Blind Randomized Clinical Trial  
Interventions 
Two-Hand V-E Maneuver Facial Mask Ventilation. 
Two-Hand C-E Maneuver Facial Mask Ventilation. 
Inclusion and Exclusion Criteria 
Inclusion Criteria  
Inclusion Criteria  
-​
Adult patients over 18 years old 
-​
Scheduled for elective surgery 
-​
Require general anesthesia 
-​
Consent to participate in the study 
Pág. 
5 
Versión. 01 
 

 
  
  
Exclusion Criteria 
-​
Presence of predictors of difficult ventilation: 
presence 
of 
a 
beard, 
obstructive 
sleep 
apnea/hypopnea syndrome  
-​
Anticipated difficult airway 
-​
Classified as ASA IV or higher 
-​
Oxygen saturation less than 92% upon admission 
-​
Requirement for supplemental oxygen 
Study Type 
Controlled clinical trial with two parallel groups, 
randomized 1:1, superiority design, blinded to the patient 
and data analyst. 
 
Recruitment Start Date 
 
Target Sample Size 
206 patients 
Study Status 
Protocol Development 
Primary Outcome 
Determine if the V-E technique is superior to the C-E 
technique for two-hand facial mask ventilation in adults 
undergoing general anesthesia with neuromuscular 
relaxation. 
 
Secundary outcomes 
Determine if there are statistically significant differences 
between the intervention and control groups in: 
○​ Mean end-tidal CO2 in mmHg 
○​ Proportion of ineffective ventilation 
○​ Mean ventilation in milliliters 
○​ Operator satisfaction 
○​ Operator’s perception of ease 
●​ Estimate if there is an interaction effect for the 
pre-planned subgroups of oropharyngeal cannula use, 
sex, age, and body mass index. 
●​ Estimate if there are statistically significant differences 
in hypoxemia. 
●​ Describe adverse events by group. 
 
 
3.  Versión de Protocolo Tabla 2. 
Version 
Date 
Modifications 
Responsible 
1 
March 2024  
 Initial version 
ASV, JPV, MAZ 
 
Pág. 
6 
Versión. 01 
 

 
  
4.  Funding 
Support will be sought from entities that promote research, including the Hospital Alma 
Máter de Antioquia.. 
5. Roles y responsibilities 
5.a Tabla 3 
Name 
Assignment 
Contributions 
Aldair Sayed Vides Villamizar 
Principal Investigator 
Protocol development, 
dissemination of results. 
Juan Pablo Vásquez Lainez 
Co investigator 
Protocol development, 
dissemination of results. 
Mario Andrés Zamudio Burbano 
Co investigator 
Protocol development, statistical 
analysis, dissemination of results. 
 
 
Roles del personal adjunto investigación 
Name 
Assignment  
Contributions 
Anesthesiologists HAMA 
(Hospital Alma Máter de 
Antioquia) 
Research 
Collaborator 
Conducting both interventions 
 
 
 
II. Introduction 
 
6. Theoretical Framework 
6.a Background and Justification 
 
Globally, 312 million surgeries are performed annually, which equates to one operation for 
every 25 people (Weiser 2015). In Colombia, 695,974 medical and surgical procedures 
were carried out in 2021, and it is estimated that around 60% of these involve general 
anesthesia (INS 2022). During the induction of general anesthesia, anesthetic drugs provide 
different levels of sedation and anesthesia. As the patient progresses to deeper planes, 
airway reflexes and spontaneous ventilation are lost (ASA 2018), making positive pressure 
ventilation essential. 
 
Difficult mask ventilation, defined by the ASA (American Society of Anesthesiologists) as 
"the inability to administer adequate ventilation (e.g., confirmed by the detection of 
end-tidal carbon dioxide) due to one or more of the following issues: inadequate mask seal, 
excessive gas leak, or excessive resistance to gas entry and exit" (Apfelbaum, J. L. 2022), 
has an incidence between 1.4% and 2.2%, as found in two studies (Kheterpal 2006; 
Pág. 
7 
Versión. 01 
 

 
  
Kheterpal 2009), which included 22,660 and 50,000 patients, respectively. Although rare, 
complications arising from airway management are associated with morbidity and mortality 
outcomes, such as the "can't oxygenate, can't ventilate" scenario, which occurs in 
approximately 1 in every 50,000 general anesthesias and accounts for around 25% of 
anesthesia-related deaths (Cook, T. M; 2012). Other outcomes, such as brain damage, 
occurred in 14.3% of patients during anesthesia (Cook, T. M. 2011). 
 
Therefore, it is essential to have backup airway management tools to prevent the 
aforementioned outcomes. This is where non-invasive airway management takes center 
stage, with mask ventilation being the main technique. Although often considered intuitive 
(DuCanto, J; 2023), mask ventilation has been shown to be difficult to learn and apply in 
both hospital and out-of-hospital settings. This is evident in a survey conducted among 
emergency medicine residents, pediatric residents, and pediatric medicine programs, where 
the goal was to assess residents' knowledge of bag-mask ventilation (BMV) and identify 
predictors of a well-developed mental model of BMV. Emergency medicine residents 
scored higher (mean (SD)) than the other two groups on a scale of 6 (2.71 (1.26) vs. 2.01 
(1.07), P = 0.004) and were significantly more likely to identify certain maneuvers: oral 
airway (81% vs. 52%, P = 0.006), nasal airway (57% vs. 29%, P = 0.006), and the 
two-person technique (14% vs. 3%, P = 0.042). Only 15% of all residents were able to 
identify 4 or more essential maneuvers (Eppich, W. J. 2010). 
There are different methods to hold the mask during face mask ventilation: the one-hand 
method and the two-hand method. Although the one-hand method is the most commonly 
used, the two-hand method is superior, as demonstrated by a randomized crossover study of 
42 patients. The minute ventilation with one hand was 6.32 ± 3.24 L/min, and with two 
hands, it was 7.95 ± 2.70 L/min; tidal volume was 6.80 ± 3.10 mL/kg PBW with one hand 
and 9.60 ± 2.31 mL/kg PBW with two hands, with a significant difference of 1.63 (95% CI, 
1.16-2.10) L/min and 1.80 (95% CI, 1.29-2.32) mL/kg PBW, respectively (Joffe, A.M. 
2010). 
Two techniques are described for two-hand ventilation: the bilateral C-E maneuver and the 
V-E maneuver. Some studies comparing both maneuvers in special populations observed 
better performance with the V-E maneuver. For example, Jain.D et al (2021) compared both 
maneuvers in edentulous populations, with the main outcome being expired tidal volume. 
They found a difference of -161 mL (-188 to -135; 95% CI, P < 0.001) in favor of the V-E 
maneuver. Similarly, Bharadwaj, M. S et al (2022) studied an obese population, comparing 
expired tidal volume per kilogram (kg) of predicted (ideal) and actual weight. They found a 
mean for current weight in the C-E group of 6.5 ± 0.9 mL/kg, while for the V-E maneuver, 
it was 9.0 ± 0.9 mL/kg (P < 0.001); for predicted weight, it was 8.7 ± 1.5 mL/kg and 12.3 ± 
1.9 mL/kg (P < 0.001), also in the obese population. Fei.M et al found a higher failure rate 
of 44% for the C-E maneuver, while it was 0% for the V-E maneuver, with a greater 
expired tidal volume (371 vs. 720 mL, P < 0.001) and no difference in peak airway 
pressure. Additionally, the efficacy of these maneuvers was evaluated when performed by 
inexperienced personnel in a prospective crossover study designed by Gerstein, N.S et al 
Pág. 
8 
Versión. 01 
 

 
  
(6). Using pairwise analysis, they found a difference in expired tidal volume for the V-E 
maneuver of 110 mL: V-E: 379 mL vs. C-E: 269 mL (95% CI; 65-157, P < 0.0001). 
Most of the mentioned studies were included in a meta-analysis conducted by Piedrahita, P 
et al (8), where it was corroborated, with low-quality evidence, that the difference found so 
far in expired tidal volume showed a mean difference between the groups of 2.52 mL/kg 
(95% CI, 0.18-4.85; P=0.035) in favor of the V-E maneuver. Additionally, a lower failure 
rate in ventilation with the V-E maneuver was demonstrated, though with high 
heterogeneity. 
The meta-analysis by Piedrahita, P et al not only demonstrated the differences between the 
two maneuvers but also identified possible variables that could potentially impact the 
results, such as the use of neuromuscular relaxants, which was not applied in any of the 
studies conducted so far. However, it is established that to define difficult mask ventilation, 
optimal conditions for the technique are required, including neuromuscular relaxation, as 
evidenced by Soltész, S. et al (2017). They sought to evaluate the influence of complete 
neuromuscular blockade in patients who had 3 or more risk factors for difficult mask 
ventilation. They measured tidal volume before and after the application of the 
neuromuscular relaxant, finding that 30 seconds after the administration of rocuronium, 
tidal volume increased by 48%, from a baseline of 350 mL (interquartile range 260-492 
[range 80-850]) to 517 mL (interquartile range 373-667 [range 100-1250]) (P < 0.001). 
There is still no knowledge about whether ventilating patients with one or the other mask 
maneuver under neuromuscular relaxation would make a difference. 
Additionally, it was observed that in most studies, the intervention was performed by 
trainees, with only one study involving anesthesiologists, which could impact or reduce the 
gap between both maneuvers when performed exclusively by experienced personnel 
(Piedrahita, P 2022). Therefore, there is still uncertainty as to whether the V-E technique is 
superior to the C-E technique for face mask ventilation in patients undergoing general 
anesthesia. 
Justification 
Airway management is a routine part of an anesthesiologist's work when subjecting patients 
to different degrees of sedation, eventually reaching general anesthesia. It is also crucial in 
emergency care, where general practitioners, emergency physicians, and prehospital care 
technicians/technologists (APH) manage the airway, each with varying degrees of training 
and experience. In these scenarios, the doctor or APH provider will determine whether to 
maintain the airway using invasive or non-invasive methods to achieve proper ventilation. 
Factors such as patient characteristics, which may predict difficult mask ventilation 
combined with difficult laryngoscopy, include: Mallampati classification III or IV, obesity 
(BMI over 30 kg/m²), presence of teeth, history of obstructive sleep apnea, short 
thyromental distance, limited mandibular protrusion, cervical mass, limited neck extension, 
Pág. 
9 
Versión. 01 
 

 
  
presence of a beard, male gender, or age over 46 years (Langeron, O, 2000; Kheterpal, 
2013). 
However, it has been observed that predictions about difficult mask ventilation or difficult 
intubation only correspond to actual difficult airway scenarios 25% of the time (Nørskov, 
A. K., 2015). Furthermore, difficult intubation and difficult mask ventilation were 
unanticipated in 93% and 94% of cases, respectively. Other factors that influence patient 
outcomes include the patient's current condition based on the context, such as elective 
surgery versus an emergency scenario. This can be the same patient at two different times, 
but the approach may vary depending on the physician’s training and experience 
(Rosenblatt, W. H., 2023), whether it is an APH technician/technologist, a general 
practitioner, an emergency physician, or an anesthesiologist. These decisions are also 
influenced by the availability of equipment. 
Mask ventilation is often considered intuitive (DuCanto, J, 2023), but it has been 
demonstrated to be difficult to learn and apply in both hospital and prehospital settings 
(Eppich, W. J., 2010). In such scenarios, the face mask should always be available and 
serves as the initial approach before invasive airway management or rescue if intubation or 
a supraglottic device fails (Frerk, C., 2015). Therefore, proper training in face mask 
ventilation skills, including the two-hand technique, is necessary to improve the seal, 
mandibular protrusion, and neck extension, targeting the determinants of difficult mask 
ventilation as defined by the ASA: "The inability to provide adequate ventilation (e.g., 
confirmed by detection of end-tidal carbon dioxide) due to any of the following: inadequate 
mask seal, excessive gas leak, or excessive resistance to gas entry or exit" (Apfelbaum, J. 
L., 2022). 
For two-handed mask ventilation, two techniques have been described: the C-E technique, 
in which the thumb and index fingers of each hand form a "C" around the mask while the 
third, fourth, and fifth fingers pull the jaw towards the mask in an "E" shape, and the V-E 
technique, in which the thumbs and thenar eminence of each hand press against the sides of 
the mask in a "V" shape while the rest of the fingers perform the "E" jaw traction 
(Piedrahita, P., 2022). 
Current evidence points to better performance of the V-E maneuver compared to the C-E 
maneuver (Piedrahita, P., 2022). However, the performance of these maneuvers has not 
been uniformly evaluated with the use of adjuncts to face mask ventilation, such as the 
Guedel airway, or in patients under neuromuscular blockade. 
Given the lack of scientific evidence, the results of our research would not only impact the 
work of anesthesiologists but also extend to emergency services and prehospital settings. 
This would lead to improved patient outcomes by enhancing knowledge of two-hand mask 
ventilation and raising the quality of care provided to patients 
 
Pág. 
10 
Versión. 01 
 

 
  
7. Research Objectives and Hypotheses  
 
Objectives 
Primary Objective 
-​
Determine if the V-E technique is superior to the C-E technique for two-hand facial 
mask ventilation in adults undergoing general anesthesia. 
 
Secondary Objectives 
-​
Determine if there are statistically significant differences between the intervention 
and control groups in: 
○​ Mean end-tidal CO2 in mmHg 
○​ Proportion of ineffective ventilation 
○​ Mean ventilation in milliliters 
○​ Operator satisfaction 
○​ Operator’s perception of ease 
-​
Estimate if there is an interaction effect for the pre-planned subgroups of 
oropharyngeal cannula use, sex, age, and body mass index. 
-​
Estimate if there are statistically significant differences in hypoxemia. 
-​
Describe adverse events by group. 
 
 
Hypotheses 
 
Operational Hypothesis: Non-invasive two-hand facial mask ventilation using the V-E 
technique is superior to the C-E technique in adult patients undergoing general anesthesia 
in terms of effectiveness, measured in milliliters per kilogram..  
 
8. Study Design 
 
Controlled clinical trial with two parallel groups, randomized 1:1, superiority design, 
blinded to the patient and data analyst. 
 
III Methods: Participants, Interventions, and Outcomes  
 
9.Description of Study Characteristics 
 
Study Setting 
The study will be conducted at the Hospital Alma Máter de Antioquia, a 660-bed institution 
that performs 1200 surgeries per month, providing a sufficient sample size. Approximately 
40% of these surgeries are performed under general anesthesia, ensuring access to the target 
population. Additionally, the intervention administrators consider this a routine practice in 
their professional activities. This institution does not attend to obstetric patients 
Pág. 
11 
Versión. 01 
 

 
  
Study Type 
Randomized clinical trial 
Population 
Patients over 18 years old undergoing general anesthesia. 
Reference Population 
Patients from the Hospital Alma Máter de Antioquia, Medellín-Antioquia, over 18 years 
old undergoing general anesthesia.. 
Study Population 
Patients from the Hospital Alma Máter de Antioquia, Medellín-Antioquia, over 18 years 
old undergoing general anesthesia, who consent to the V-E and C-E facial mask ventilation 
interventions during anesthetic induction  
Sample 
 
Patients from the study collection who undergo general anesthesia during the study 
collection period 
 
10.  Eligibility Criteria 
 
Inclusion Criteria  
-​
Adult patients over 18 years old 
-​
Scheduled for elective surgery 
-​
Require general anesthesia 
-​
Consent to participate in the study 
  
 
Exclusion Criteria​
 
-​
Presence of predictors of difficult ventilation: presence of a beard, obstructive sleep 
apnea/hypopnea syndrome 
-​
Anticipated difficult airway 
-​
Classified as ASA IV or higher 
-​
Oxygen saturation less than 92% upon admission 
-​
Requirement for supplemental oxygen 
 
​
 
 
 
Pág. 
12 
Versión. 01 
 

 
  
 
 
11. Interventions 
 
A patient over 18 years old who is scheduled for general anesthesia surgery at the Hospital 
Alma Máter de Antioquia will be identified. After validating the inclusion and exclusion 
criteria, the patient will be approached and asked to participate in the study, with a detailed 
explanation of the study’s objective and procedures. Upon confirming their acceptance and 
signing the informed consent (see appendices), they will be randomly assigned in equal 
proportion to one of the two comparison groups: V-E facial mask ventilation maneuver or 
C-E facial mask ventilation maneuver. Before starting the intervention, the anesthesiologist 
in charge will be shown an explanatory video on how to perform the assigned maneuver 
according to the randomization. 
The V-E maneuver is achieved by placing the thumbs and thenar eminence of each hand on 
the sides of the mask, creating a “V” shape, while the rest of the fingers perform a jaw 
thrust described as an “E” shape. This will be performed after anesthetic induction when 
the patient is unconscious and apneic. The C-E maneuver is achieved by placing the thumb 
and index finger of each hand on the mask in a “C” shape, while the third, fourth, and fifth 
fingers of both hands perform a jaw thrust towards the mask in an “E” shape. This will also 
be performed after anesthetic induction when the patient is unconscious and apneic. 
 
 
Once the patient arrives in the operating room, basic ASA monitoring will be performed, 
including a 5-lead electrocardiogram, pulse oximetry, blood pressure, and capnography. 
Prior to this, it will be verified that the anesthesia machine is functioning properly, the 
oropharyngeal cannula is the appropriate size for the patient (measured from the labial 
commissure to the external auditory meatus), and the mask is the appropriate size for the 
patient, covering from the nasal bridge to the chin. Preoxygenation will be performed with 
8 forced vital capacities using an oxygen flow of 10 liters per minute. Rocuronium will be 
used as a muscle relaxant at a dose of 0.3 mg/kg or higher, considering this is the effective 
dose 95 of the drug, and a minimum of 2 minutes will be waited before starting the 
intervention. Ventilation will be performed through the anesthesia machine ventilator with 
the following ventilatory parameters: pressure-controlled mandatory ventilation with a peak 
inspiratory pressure of 20 cmH2O, respiratory rate of 12, PEEP of 5, and inspiratory time 
of 2 seconds. The intervention will be evaluated according to the previously noted 
objectives, visualizing the parameters of interest on the screen. A video will be recorded 
capturing these parameters for later review by the outcome evaluator. 
 
After monitoring the patient, performing preoxygenation, induction, and muscle relaxant 
time, the intervention will be initiated by the anesthesiologist in charge of the case 
according to the maneuver to which the patient has been randomized (either V-E or C-E). 
The intervention will end after 7 ventilations have been performed. Following this, the 
intervention will be repeated with the oropharyngeal cannula, again performing 7 
ventilations, which will be recorded, and the intervention will be concluded. 
 
Pág. 
13 
Versión. 01 
 

 
  
Subsequently, the anesthesiologist will be evaluated after the procedure using a global 
satisfaction scale of the LIKERT type, for ease and comfort of the intervention: 
 
1: Very dissatisfied  
2: Dissatisfied  
3: Neutral  
4: Satisfied  
5: Very satisfied 
 
12. Outcomes 
 
Primary Outcome 
 
Average ventilation in milliliters per kilogram of body weight for seven ventilations 
recorded on the anesthesia machine at the end of expiration. 
 
Specific Outcomes 
 
Average CO2 in mmHg for seven ventilations recorded on the anesthesia machine at the 
end of expiration. 
Proportion of ineffective ventilation, defined as ventilation less than 1.5 ml/kg. 
Operator satisfaction. 
Operator's perceived ease of use, on a Likert scale from 1 to 5, with 1 being very easy and 5 
being very difficult. 
Interaction effect for preplanned subgroups: use of oropharyngeal airway, sex, age, and 
body mass index. 
Hypoxemia, defined as SpO2 less than 92%. 
Adverse events by group. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Pág. 
14 
Versión. 01 
 

 
  
13. Participants' timeline. Figure 1 
 
Pág. 
15 
Versión. 01 
 

 
  
14. Sample Size 
Considering the primary outcome of facial mask ventilation, defined as ml/kg of weight, 
and based on the meta-analysis conducted by Piedrahita and collaborators, we found an 
expected mean for the control group of 1 ml/kg with a standard deviation of 2.4, and for the 
intervention group, a mean of 1.4 with a standard deviation of 2.4 
With a superiority approach, an alpha error of 0.5, and a beta error of 20%, expecting a 
difference of at least 0.8 ml/kg, we calculated a sample size of 99 patients per group. The 
sample size is adjusted for drop-in, considering that there may be cases where the patient 
does not ventilate with the C-E technique and requires a switch to the V-E technique, 
approximately 5%. The sample size is corrected with the following formula: 
 
  
𝑁
* =  𝑁 / 1 − 𝑅
0  − 𝑅
1
where (R_0) is the drop-in rate. Corrected sample size: 206, i.e., 103 per arm. 
 
15. Recruitment  
To complete the sample size, active follow-up will be conducted by the investigators of 
both the outpatient and inpatient surgical programs. The participant timeline is specified in 
Figure 1. 
Methods: Assignment of Interventions  
16. Assignment  
16.a Generation of the Random Allocation Sequence 
The sequence will be generated using the latest version of R software with permuted blocks 
of 2, 4, and 6 participants with variable block sizes, and one stratification variable: use of 
an oropharyngeal cannula. 
 
16.b Allocation Concealment Mechanism  
The allocation will be kept in an opaque envelope that does not allow the assigned group to 
be seen.  
 
16.c   Implementation 
The envelope will be opened only by one of the investigators after completing the inclusion 
criteria and signing the informed consent   
 
17.Blinding  ​  
 
Patient: Will be blinded as they will be under general anesthesia 
Outcome Evaluator  Will be blinded as their analysis will be conducted on videos recorded 
by the research team 
 
V. Methods: Data Collection, Management, and Analysis 
Pág. 
16 
Versión. 01 
 

 
  
 
18. Data Collection Methods  19. Data Management 
 
The plan for data management, entry, coding, security, and storage to ensure data quality 
will be as follows: 
 
- Collection:: One of the anesthesiologist investigators will record the data on pre-designed 
physical forms, ensuring the security, confidentiality, and permanence of the data for 
subsequent analysis. 
 
- Data Submission: Once the data is collected, it will be entered into a platform in the 
Google Docs system, ensuring proper randomization and patient information. 
 
- Coding: The data will be entered via magnetic media into the Google Drive platform with 
a license provided by the University of Antioquia. 
 
-Security: Access to the collected information will be through an email password known 
only to the investigators. Periodic backups will be made to ensure data security. 
 
- Storage: The completed folder in the drive system will be deleted ten years after the study 
is concluded. 
 
- Analysis: Once the information is fully collected, it will be sent to the investigators who 
will analyze the data, completely blinded to the intervention groups. 
 
 
20.  Statistical Analysis 
The statistical analysis will be conducted in two phases. First, descriptive statistics will be 
performed, with qualitative variables presented as frequencies and percentages, and 
quantitative variables described according to their nature after normality tests. If the data 
are normally distributed, participants will be described using means and standard 
deviations; otherwise, medians and interquartile ranges will be used. 
 
In a second phase, we will conduct Bayesian statistical inference tests with non-informative 
priors according to Table 4 
 
 
 
 
 
 
 
 
 
 
Pág. 
17 
Versión. 01 
 

 
  
Table 4 Statistical analysis by outcome 
 
Outcome 
Hypothesis 
Measure of 
association 
Statistic 
Facemask 
ventilation: defined 
as ml/kg of body 
weight 
 
Ha: 
μintervention>  
μcontrol 
Ho: 
μintervention≤  
μcontrol 
Difference of means 
(95% 
Confidence 
Interval) 
Bayesian 
model 
based 
on 
Markov 
chains 
 
Mean CO2 in mmHg 
at the end of 
exhalation 
Ha: μintervention>≤ 
μcontrol 
Ho: 
μintervention≤  
μcontro 
Difference of means 
(95% 
Confidence 
Interval) 
Bayesian 
model 
based 
on 
Markov 
chains 
Proportion of 
ineffective 
ventilation 
Ha: Pintervention < 
Pcontrol 
Ho: Intervention ≥ 
Pcontrol 
Relative Risk RR  
Bayesian 
model 
based 
on 
Markov 
chains 
Mean ventilation in 
milliliters 
Ha: 
μintervention>  
μcontrol 
Ho: 
μintervention≤  
μcontro 
Difference of means 
(95% 
Confidence 
Interval) 
Bayesian 
model 
based 
on 
Markov 
chains 
Operator satisfaction 
Ha: 
μintervention>  
μcontrol 
Ho: 
μintervention≤  
μcontro 
Difference of means 
(95% 
Confidence 
Interval) 
Bayesian 
model 
based 
on 
Markov 
chains  
Pág. 
18 
Versión. 01 
 

 
  
Operator's 
perception of ease 
Ha: 
μintervention>  
μcontrol 
Ho: 
μintervention≤  
μcontro 
Difference of means 
(95% 
Confidence 
Interval) 
Bayesian 
model 
based 
on 
Markov 
chains  
Interaction effect for 
the pre-planned 
subgroups of 
oropharyngeal 
cannula use, sex, 
age, and body mass 
index  
Ha: There are no 
differences 
in 
the 
mean 
Ho: Intervention ≥ 
Pcontrol 
Interaction effect 
Bayesian 
multiple 
linear regression in 
the presence of the 
described factors 
Hypoxemia 
Ha: Pintervention < 
Pcontrol 
Ho: Intervention ≥ 
Pcontrol 
Relative Risk RR  
Bayesian 
model 
based 
on 
Markov 
chains 
Adverse events by 
group 
Ha: Pintervention < 
Pcontrol 
Ho: Intervention ≥ 
Pcontrol 
Relative Risk RR  
Bayesian 
model 
based 
on 
Markov 
chains 
 
Intention-to-Treat Principle 
The principle of intention-to-treat will be maintained for all analyses, meaning that if there 
is a “drop-in” from the control group to the intervention group, the analysis will be 
conducted according to the group assigned during randomization. Therefore, the 
denominator will remain the same number for all analyses. 
 
 
VI. Methods: Monitoring 
21. Data Monitoring​
A data monitoring committee will not be established. 
Pág. 
19 
Versión. 01 
 

 
  
22. Harms – Adverse Events​
All adverse events occurring during the study follow-up—up to the recording of the 
primary outcome, which marks the end of the interventions—will be reported in accordance 
with the Good Clinical Practice guidelines. Reporting will take place within the first 24 
hours after the event occurs. 
23. Audit​
Data quality audits will be conducted at 25%, 50%, and 75% of the sample, without 
performing hypothesis testing to avoid multiplicity of hypothesis tests. 
 
III. ETHICS AND DISSEMINATION 
24. Ethical Approval of the Research​
This clinical trial engages in a critical investigation designed to evaluate the ethical 
considerations associated with comparing the effectiveness of two non-invasive ventilation 
maneuvers using facial masks in adults undergoing general anesthesia. Since this study 
involves real patients, it is crucial to recognize the direct impact on the participants' health 
and to carefully address a series of key ethical issues. 
We consider that this clinical un research holds significant value, as it evaluates a potential 
intervention that could improve patients' clinical outcomes, not only in controlled 
environments such as operating rooms but also in other contexts, such as emergency 
services and prehospital care. 
Regarding patient selection, it will be based primarily on scientific and methodological 
grounds. Patients classified as ASA I and II without the presence of predictors of difficult 
airway or difficult ventilation will be included, as these could have a substantially higher 
risk of harm or experiencing more severe complications. Additionally, patients who do not 
meet the aforementioned scientific criteria will not be excluded. 
In accordance with the guidelines set forth in Resolution No. 8430 of 1993 by the Ministry 
of Health of Colombia (Ministerio de Salud, 1993) and the Declaration of Helsinki of 2013 
(World Medical Association, 2013) regarding the ethical aspects of health research 
involving human beings, this study is considered a Type C research: studies with greater 
than minimal risk. For this study, approval will be sought from the Ethics Committee of 
Hospital Alma Máter de Antioquia. 
The principle of respect for individuals' autonomy, especially regarding participation in the 
study, will be ensured through the completion of informed consent and respect for the 
participant's autonomy. Participants will be explicitly informed about the voluntary nature 
of their participation in the research, as well as the possibility of withdrawal if they decide 
to do so at any time they deem appropriate. 
Pág. 
20 
Versión. 01 
 

 
  
Accurate information will be provided to each participant about the purpose and scope of 
the research. The investigator will explain the content of the informed consent, which must 
be read and signed beforehand. 
Regarding the principle of beneficence, this research seeks to promote the well-being of the 
research participants with minimal risk and harm, determining strategies that optimize both 
acute and chronic pain control in this pathology. 
The principle of non-maleficence is taken into account for the proper handling of 
participants' data and the standardization of the proposed analgesic techniques, which are 
common in clinical anesthetic practice. Additionally, the confidentiality and custody of 
participants' data will be ensured during the data collection, processing, and analysis 
processes through the encoding of formats at all stages of the research and during the report 
preparation and publication of results. 
Identity information (identification, name) and contact details of the participants will be 
presented with general sample data. Furthermore, in reports and publication of results, the 
personal identity of the participants will be protected. 
The research has an academic, non-profit purpose. Participation is entirely voluntary and 
does not involve any economic obligation for the participants. Participants will be informed 
of these conditions before any activity begins. 
According to the American Medical Association, the 7 requirements for clinical research in 
human beings will be met (Emanuel EJ et al., 2000): 
1.​ Scientific Value: The proposed interventions are part of the usual clinical practice 
of anesthesiology, will be carried out by expert personnel, and adhere to all required 
biosafety standards. These interventions aim to determine the best facial mask 
ventilation maneuver. 
2.​ Scientific Validity: All scientific norms and protocols, including the scientific 
research method, are considered. 
3.​ Fair Selection of Participants: Selection will involve randomization with 
concealment of interventions. 
4.​ Risk/Benefit Ratio: The objective is to identify the best facial mask ventilation 
technique, additionally measuring the impact of the use of adjuvants and the effect 
of neuromuscular relaxation, which has proven to be of vital importance when 
addressing the airway, gaining prominence in difficult airway scenarios in various 
settings such as emergencies, prehospital, and operating rooms. 
5.​ Independent Review: External anesthesiologists and subject matter experts will 
review the research protocol and its methodology, and all their recommendations 
will be considered. 
6.​ Informed Consent: As previously outlined. 
Pág. 
21 
Versión. 01 
 

 
  
7.​ Respect for the Patient and Their Decisions: The patient will receive cordial and 
respectful treatment at all times, questions will be resolved, and the patient's wish 
not to participate in the study or to withdraw from it will be accepted if required. 
Finally, the potential benefits that could be obtained from the research outweigh the 
associated risks, given that facial mask ventilation is a common practice in operating rooms 
performed by anesthesiologists who will carry out the intervention. Additionally, as 
mentioned earlier, patients presenting criteria for difficult airway management, which could 
increase the risk in these patients, will be excluded. 
25. Protocol Amendments​
The development of the protocol will facilitate its adoption and review, which will help 
minimize changes. However, in the event of an unforeseen situation or circumstance that 
significantly impacts the study, a discussion and review will be conducted to determine the 
necessity of modifications. Any changes will be subject to prior notification and 
communication with the Ethics Committee of Hospital Alma Máter de Antioquia, ensuring 
that no amendments are made without the committee's prior approval. 
26. Informed Consent​
For this study, a specific informed consent document was designed, detailing the research 
objectives, clearly explaining its purpose, and establishing the voluntary participation of 
each patient. All participants will have the opportunity to read, ask questions, and complete 
the informed consent before undergoing the surgical procedure, following an appropriate 
explanation in language tailored to each patient. This consent form will also be reviewed by 
the Ethics Committee of Hospital Alma Máter de Antioquia and will be included in the 
appendices. 
27. Confidentiality​
All data collected during the study, both written and digital, will be reserved for research 
purposes and kept strictly confidential. Data may only be disclosed in cases of force 
majeure as requested by the Ethics Committee or the patient themselves. Digital 
information will be securely stored in databases accessible only to the principal 
investigators. Written data, including informed consent forms, will be kept in locked 
cabinets with no access granted to unauthorized individuals. 
28. Declaration of Interest​
The investigators have no conflicts of interest regarding this study. The implementation and 
use of facial mask ventilation are entirely detached from any political interests, focusing 
solely on improving ventilation across various scenarios. The sole purpose of the study is to 
generate and disseminate scientific knowledge relevant to anesthetic practice. 
29. Data Access​
Researchers will have access to the collected data once the study is completed. This data 
will be stored in a database coded to prevent revealing participants' identities and to avoid 
Pág. 
22 
Versión. 01 
 

 
  
compromising the study's methodological design. Access credentials will only be available 
to research assistants. 
30. Additional Care and Post-Study​
No participant will receive financial compensation for participating in the study. 
32. 33. Dissemination Policy and Expected Impacts and Outcomes of the Research 
Data Analysis and Results Release:​
Data analysis will be performed by one of the principal investigators with training in 
clinical epidemiology. The findings will then be compiled into a report with conclusions, 
approximately three months after data collection from the last participant. 
The research findings are planned to be published in an indexed scientific journal. The 
publication will aim to: 
 
1.​ Knowledge Generation 
 
Expected Outcome/Product 
 
Indicator 
 
Beneficiary 
 
Determine if two-hand facial 
mask ventilation using the V-E 
technique is better compared to 
the two-hand C-E technique. 
 
Submitted for scientific 
publication 
 
National and International 
Scientific Community 
 
 
 
2.​ Social Responsibility 
 
Expected Outcome/Product 
 
Indicator 
Beneficiary 
-​
Better Ventilation 
-​
Less Hypoxemia 
-​
Greater Operator Comfort  
 
Tidal volume measured 
in ml/kg 
Oxygen saturation 
Perception of comfort 
Likert scale 
 
 
Patient 
Anesthesiologists, 
Emergency physicians, 
General practitioners 
working in emergency 
services, technicians, and 
technologists in 
prehospital care. 
 
Pág. 
23 
Versión. 01 
 

 
  
3.​ Strengthening of care at the Hospital Alma Máter de Antioquia. 
 
Expected Outcome/Product 
 
Indicator 
 
Beneficiary 
Create a care protocol at the 
Hospital Alma Máter de 
Antioquia 
 
Care protocol 
 
Patients of the Alma 
Máter Hospital of 
Antioquia. 
 
 
4.​ Social appropriation of knowledge 
 
Expected Outcome/Product 
 
Indicator 
 
Beneficiary 
 
Dissemination of knowledge. 
 
Results dissemination 
in the academic 
community of the Alma 
Máter de Antioquia 
Hospital. 
Academic community and 
academic staff of the Alma 
Máter de Antioquia 
Hospital 
 
 
 
 
 
IV. ADMINISTRATIVE ASPECTS 
 
20. Products and deliverables generated from the research 
 
21. Activity Schedule (Table). 
 
Number 
Activity 
Start 
End 
Time 
1 
Literature Review 
1 
3 
Months 
2 
Development of the protocol 
2 
3 
Months 
Pág. 
24 
Versión. 01 
 

 
  
3 
Submission of the protocol to the 
program committee 
3 
4 
Months 
4 
Submission of the protocol to the 
ethics committee of HAMA  
4 
5 
Months 
5 
Development of data collection 
form and databases 
5 
7 
Months 
6 
Data collection 
7 
17 
Months 
7 
Data analysis 
17 
19 
Months 
8 
Preparation of final report and 
publication article 
19 
21 
Months 
 
22. Presupuesto (Tabla) 
 
 
ITEMS 
VALUE 
SOURCE 
Scientific Staff 
  
  
Field Researcher 
5.000.000 
Own Resources 
Thesis Supervisor 
15.650.000 
University of Antioquia 
Operating Expenses 
  
  
Pág. 
25 
Versión. 01 
 

 
  
Statistical 
Software 
and 
Databases 
1.000.000 
Perioperative 
Medicine 
Research Group 
Stationery 
200.000 
Perioperative 
Medicine 
Research Group 
Computing equipment 
2.500.000 
Own Resources 
Academic events 
  
  
Attendance at conferences 
6.000.000 
Own Resources 
Publication 
  
  
Writing and editing of the 
publication article 
2.500.000 
Perioperative 
Medicine 
Research Group 
TOTAL 
32.850.000 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Pág. 
26 
Versión. 01 
 

 
  
V. ANNEXES (Mandatory) 
a. Table of variables 
 
Variable 
Operational 
definition 
Type 
Scale 
Unit or Code 
X 1 
Age 
Continuous 
quantitative 
Ratio 
Years 
X 2 
Sex 
Qualitative 
Nominal 
0. Man 1. Woman 
X 3 
Weight 
Continuous 
quantitative 
Ratio 
Kilograms 
X 4 
Height 
Continuous 
quantitative 
Ratio 
Centimetres 
X 5 
Body Mass Index 
(BMI) 
Quantitative 
Interval 
1.​ Low weight 
(<18,5)  
2.​ Normal (18,5 
a 24,9) 
3.​ Overweight 
(25 a 29,9) 
4.​ Grade I 
Obesity (30 a 
34,9) 
5.​ Grade II 
Obesity (35 a 
39,9) 
6.​ Grade III 
Obesity (>40) 
 
X 6 
Types of Surgery 
Qualitative 
Ordinal 
1.​ Orthopedics 
2.​ General 
Surgery 
3.​ Gynecology 
4.​ Vascular 
5.​ Otorhinolaryn
gology 
6.​ Neurosurgery 
7.​ Urology 
8.​ Plastic 
Surgery 
X 7 
Identification number 
Qualitative 
Nominal 
Identification number 
X 8 
Case number 
Qualitative 
Ordinal 
Number from 1 to 
206 
X 9 
Functional class 
Qualitative 
Ordinal 
1.​ I 
2.​ II 
Pág. 
27 
Versión. 01 
 

 
  
3.​ III 
4.​ IV 
X 10 
ASA Classification 
Qualitative 
Ordinal 
1.​ I 
2.​ II 
3.​ III 
4.​ IV 
X 11 
Presence of a beard 
Qualitative 
Nominal 
0.Yes 1. No 
X 12 
Presence of 
obstructive sleep 
apnea 
Qualitative 
Nominal 
0.Yes 1. No 
X 13 
Upper lip bite test 
Qualitative 
Ordinal 
1.​ Clase I 
2.​ Clase II 
3.​ Clase III 
X 14 
Mallampati 
Qualitative 
Ordinal 
1.​ I 
2.​ II 
3.​ III 
4.​ IV​
 
X 15 
Thyromental distance 
Qualitative 
Nominal 
0. Greater than or 
equal to 6 centimeters 
1. Less than 6 
centimeters 
X 16 
Sternomental distance 
Qualitative 
Nominal 
0. Greater than or 
equal to 13 
centimeters 
1.Less than 13 
centimeters 
 
X 17 
Rheumatoid arthritis 
Qualitative 
Nominal 
0.Yes 1. No 
X 18 
Arterial Hypertension 
Qualitative 
Nominal 
0.Yes 1. No 
X 19 
Diabetes mellitus 
Qualitative 
Nominal 
0.Yes 1. No 
X 20 
Chronic Obstructive 
Pulmonary Disease 
Qualitative 
Nominal 
0.Yes 1. No 
X 21 
Heart Failure  
Qualitative 
Nominal 
0.Yes 1. No 
X 22 
Coronary Disease 
Qualitative 
Nominal 
0.Yes 1. No 
X 23 
Asthma 
Qualitative 
Nominal 
0.Yes 1. No 
X 24 
Operator's age 
Discrete 
quantitative 
Ratio  
Years 
X 25 
Operator's sex 
Qualitative 
Nominal 
0. Man 1. Woman 
X 26 
Years of experience in 
anesthesiology 
Discrete 
quantitative 
Ratio  
Years 
X 27 
Muscle relaxant dose 
Continuous 
quantitative 
Ratio 
Milligrams of the 
medication 
Pág. 
28 
Versión. 01 
 

 
  
X 28 
Muscle relaxant time 
Continuous 
quantitative 
Ratio 
Minutes 
X 29 
 
 
 
 
X 30 
Desaturation (Oxygen 
saturation less than 
90%) 
Qualitative 
Nominal 
0.Yes 1. No 
X 31 
Laryngospasm 
Qualitative 
Nominal 
0.Yes 1. No 
X 32 
Bronchospasm 
Qualitative 
Nominal 
0.Yes 1. No 
Outcome variables 
X33 
Operator satisfaction 
Quantitative  
Discrete 
1.Very dissatisfied 
2.Dissatisfied 
3.Neutral 
4.Satisfied 
5.Very satisfied 
X34 
Operator's perception 
of ease 
Quantitative 
Discrete 
1.Very difficult 
2.Difficult 
3.Neither  easy nor 
difficult 
4.Easy 
5.Very Easy 
X34 
Volume without 
oropharyngeal cannula 
(milliliters) No. 1 
Quantitative  
Continuous 
/ Ratio 
 Milliliters 
X35 
Carbon dioxide 
without oropharyngeal 
cannula (millimeters 
of mercury) No. 1 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
X36 
Volume without 
oropharyngeal cannula 
(milliliters) No 2 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X37 
Carbon dioxide 
without oropharyngeal 
cannula (millimeters 
of mercury) No.2 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
X38 
Volume without 
oropharyngeal cannula 
(milliliters) N°3 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X39 
Carbon dioxide 
without oropharyngeal 
cannula (millimeters 
of mercury) No.3 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
Pág. 
29 
Versión. 01 
 

 
  
X40 
Volume without 
oropharyngeal cannula 
(milliliters) N°4 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X41 
Carbon dioxide 
without oropharyngeal 
cannula (millimeters 
of mercury) No.4 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
X42 
Volume without 
oropharyngeal cannula 
(milliliters) N°5 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X43 
Carbon dioxide 
without oropharyngeal 
cannula (millimeters 
of mercury) No. 5 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
X44 
Volume without 
oropharyngeal cannula 
(milliliters) N°6 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X45 
Carbon dioxide 
without oropharyngeal 
cannula (millimeters 
of mercury) No. 6 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
X46 
Volume without 
oropharyngeal cannula 
(milliliters) N°7 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X47 
Carbon dioxide 
without oropharyngeal 
cannula (millimeters 
of mercury) No.  7 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
X48 
Volume with 
oropharyngeal cannula 
(milliliters) N°1 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X49 
Carbon dioxide with 
oropharyngeal cannula 
(millimeters of 
mercury) No.1 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
X50 
Volume with 
oropharyngeal cannula 
(milliliters) N°2 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X51 
Carbon dioxide with 
oropharyngeal cannula 
(millimeters of 
mercury) N°2 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
Pág. 
30 
Versión. 01 
 

 
  
X52 
Volume with 
oropharyngeal cannula 
(milliliters) N°3 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X53 
Carbon dioxide with 
oropharyngeal cannula 
(millimeters of 
mercury) No.3 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
X54 
Volume with 
oropharyngeal cannula 
(milliliters) N°4 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X55 
Carbon dioxide with 
oropharyngeal cannula 
(millimeters of 
mercury) N°4 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
X56 
Volume with 
oropharyngeal cannula 
(milliliters) N°5 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X57 
Carbon dioxide with 
oropharyngeal cannula 
(millimeters of 
mercury) N°5 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
X58 
Volume with 
oropharyngeal cannula 
(milliliters) N°6 
Quantitative  
Continuous 
/ Ratio 
Milliliters 
X59 
Carbon dioxide with 
oropharyngeal cannula 
(millimeters of 
mercury) N°6 
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
X60 
Volume with 
oropharyngeal cannula 
(milliliters) N°7 
Quantitative 
Continuous 
/ Ratio 
Milliliters 
X61 
Carbon dioxide with 
oropharyngeal cannula 
(millimeters of 
mercury) N°7  
Quantitative  
Continuous 
/ Ratio 
Millimeters of 
mercury 
 
 
 
 
 
 
 
 
 
Pág. 
31 
Versión. 01 
 

 
  
b. INFORMED CONSENT 
VERSION No: 002 – DATE: 17/05/2024​
PARTICIPANT No. _________________ out of 206 
PROJECT TITLE:​
“COMPARISON OF NON-INVASIVE VENTILATION WITH FACIAL MASK IN 
ADULT PATIENTS UNDERGOING GENERAL ANESTHESIA: TWO-HAND V-E 
VERSUS TWO-HAND C-E VENTILATION TECHNIQUES” 
PRINCIPAL INVESTIGATOR:​
Aldair Sayed Vides Villamizar​
Tel: 3017492294​
Email: aldair.vides@udea.edu.co​
Workplace: Universidad de Antioquia- Facultad de Medicina 
Study Site:​
Surgery Service, Hospital Alma Máter de Antioquia​
Supporting Entities:​
Hospital Alma Máter de Antioquia, Perioperative Medicine Research Group, Faculty of 
Medicine, Universidad de Antioquia​
Sponsoring Entity:​
Perioperative Medicine Research Group, Faculty of Medicine, Universidad de Antioquia 
Introduction 
The Perioperative Medicine Research Group, part of the Anesthesiology section of the 
Surgery Department at the Faculty of Medicine, Universidad de Antioquia, invites you to 
voluntarily participate in a study aimed at identifying the most effective technique for 
two-hand facial mask ventilation, comparing the V-E maneuver with the C-E maneuver. 
According to the guidelines outlined in Resolution No. 8430 of 1993 by the Colombian 
Ministry of Health and the 2013 Helsinki Declaration regarding the ethical aspects of health 
research with human beings, this is considered a type C investigation: research with greater 
than minimal risk. 
Two non-invasive airway management interventions will be carried out as part of standard 
anesthesiologist practice. These aim to improve the effectiveness of non-invasive lung 
ventilation using a two-hand facial mask, a technique that is important in difficult airway 
scenarios. 
The principal investigator believes you meet the inclusion criteria for the study, which are: 
being over 18 years old, scheduled for elective surgery, requiring general anesthesia, and 
consenting to participate in the study. 
Pág. 
32 
Versión. 01 
 

 
  
It is important to note that this study will not alter the routine care or management you will 
receive during your surgery, nor the perioperative care. The only change will be the 
technique used for facial mask ventilation after anesthetic induction. 
Purpose 
The aim is to determine if the V-E technique is superior to the C-E technique for two-hand 
facial mask ventilation in adults undergoing general anesthesia. We will define parameters 
such as CO2 levels at the end of expiration (in mmHg), proportion of ineffective 
ventilation, ventilation volume in milliliters, operator satisfaction, and ease of use as 
perceived by the operator. 
Participant Selection 
Based on the established inclusion criteria, and once the patient agrees to participate, a 
random selection will be made between the two facial mask ventilation techniques being 
compared. 
Type of Intervention 
If you choose to participate, on the day of your surgery, the study and its purpose will be 
explained to you, and you will be randomly assigned to one of the two comparison groups: 
the V-E facial mask ventilation maneuver or the C-E facial mask ventilation maneuver. 
Upon arrival in the operating room, you will undergo a complete monitoring of vital signs. 
Before the intervention, we will ensure that the anesthesia machine is functioning properly. 
During the procedure, an oropharyngeal airway device will be inserted, which will be 
measured to ensure it is appropriate for your size, along with the facial mask that will be 
fitted to your face. You will be instructed to breathe actively and "deeply" into the facial 
mask. Then, anesthesia drugs will be administered, after which the anesthesiologist will 
perform facial mask ventilation while the researcher collects the necessary data for the 
study. 
Voluntary Participation 
It is important to clarify that your participation is voluntary, meaning you are free to accept 
or refuse to participate in the study. You can withdraw at any time without needing to 
provide an explanation, and this will not affect your medical care. The research team is 
available to answer any questions and clarify any terms you may not understand. 
If you decide not to participate, this will have no impact on your surgical and anesthetic 
care, which will proceed as originally planned. 
 
 
Pág. 
33 
Versión. 01 
 

 
  
Duration 
The study will last approximately 24 months. Once the intervention has been received and 
the airway management has been defined with a different device, such as a laryngeal mask 
or endotracheal tube, no further follow-up will be required. 
Risks and Discomforts 
By participating in this research, you will be exposed to the risks of each ventilation 
technique, which are similar to those encountered in routine non-invasive ventilation. These 
risks include: 
●​ Bronchial aspiration 
●​ Laryngospasm 
●​ Bronchospasm 
●​ Hypoxemia 
●​ Hypercapnia 
●​ With the use of the oropharyngeal airway: 
○​ Dental trauma (loss of or fractured teeth) 
○​ Oral trauma 
○​ Bleeding 
However, the incidence of these risks is low. The benefits of providing effective lung 
ventilation and ensuring adequate oxygenation are notable. In case of any adverse effects, 
you will receive follow-up and treatment from the attending anesthesiologist, who will 
determine the appropriate course of action. 
Benefits 
The main benefit of the study is to contribute knowledge that may have an impact on health 
teams and, in turn, on future patient outcomes. Additionally, you will benefit from better 
ventilation, aiming to reduce the incidence of hypoxemia. Anesthesiologists will gain 
valuable insight into which technique is superior and how this can affect airway rescue 
scenarios. No financial incentives will be provided to you or your family. 
Confidentiality 
Your participation data will be protected and treated confidentially, using a code to identify 
each case without revealing your identity. At no point will data or results that could identify 
your participation be published. However, medical regulatory authorities and the Ethics 
Committee may request your records if necessary, always adhering to professional 
confidentiality. 
 
Pág. 
34 
Versión. 01 
 

 
  
Participant's Obligations 
You are not obligated to do anything other than authorize the use of relevant data for the 
study. 
Researcher's Obligations 
1.​ Collect the data from the intervention in an organized and appropriate manner. 
2.​ Address any issues that arise during the study period. 
3.​ Answer any questions related to the procedures, risks, benefits, and other study 
matters. 
4.​ Request evaluations from the relevant specialists or services as needed based on the 
anesthesia performed. 
5.​ Maintain patient confidentiality and protect their data. 
6.​ The study has been approved by the Ethics Committee of Hospital Alma Máter de 
Antioquia. The researchers are qualified medical professionals with valid 
certifications to practice. 
7.​ Communicate the results of the study once it is completed. 
Any complications resulting from the surgical procedure will be handled by the healthcare 
providers, as is standard practice. This is because the surgical intervention will not be 
modified for the purposes of this study. 
Signing this document does not waive any legal rights you may have. 
Expected Results 
The results will be published in a journal that can be accessed nationally and/or 
internationally. The dissemination of the results will encourage the widespread use of these 
techniques in the population, bringing benefits and reducing risks. 
Questions 
Before signing this document, you should read it thoroughly and ask the research team any 
questions until you are satisfied with the responses. If you have any doubts later, you can 
contact the principal investigator, Dr. Aldair Sayed Vides Villamizar at 3017492294. 
Before signing, please answer the following questions: 
DATE: Day ______ Month ______ Year ______ 
●​ Have you been informed about the study by the research team? ___ 
●​ Have you read and understood the entire document? ___ 
●​ If you had doubts, were all your questions answered? ___ 
Pág. 
35 
Versión. 01 
 

 
  
PARTICIPANT:​
Consent to Participate in the Study​
I, 
__________________________________________________, 
with 
ID 
number 
__________________ from _________________, confirm that I have read, been explained 
the information regarding the study, and had the opportunity to ask questions which have 
been answered. I understand that my participation is voluntary and that I can withdraw at 
any time without explanation, without affecting my medical care or legal rights. I 
understand that the researchers, the institutional ethics committee, and judicial authorities 
will be the only ones allowed to access my health records. I agree to the collection, 
processing, reporting, and transfer of the data collected during this study to locations 
chosen by the principal investigator, and that these data will only be used for this research. 
RESEARCHER:​
The study details, purpose, methodology, benefits, risks, and duration were explained to the 
participant, and any questions were addressed. 
 
Name and signature of researcher ID: _______________________ Medical 
Registration: ____________ 
WITNESS 1: 
 
Name and signature of witness ID: _______________________ 
WITNESS 2: 
 
Name and signature of witness ID: _______________________ 
 
 
c. Data collection formats 
 
https://docs.google.com/forms/d/1ks5Pepha1s-G4rGn2QTar7Y2cOctE8Yu4_HrOit31
Kk/edit?ts=6647d9f1 
 
External evaluator format 
https://docs.google.com/forms/d/157Ym14ETm66nTvyEKQ4ZBIh4G--P7Dk5ecWXf6
r46cI/edit 
 
 
 
Pág. 
36 
Versión. 01 
 

 
  
VI. REFERENCES 
 
1.​ Weiser, T. G., Haynes, A. B., Molina, G., Lipsitz, S. R., Esquivel, M. M., 
Uribe-Leitz, T., Fu, R., Azad, T., Chao, T. E., Berry, W. R., & Gawande, A. A. 
(2015). Estimate of the global volume of surgery in 2012: an assessment supporting 
improved health outcomes. Lancet (London, England), 385 Suppl 2, S11. 
https://doi.org/10.1016/S0140-6736(15)60806-6 
 
2.​ Instituto Nacional de Salud Dirección de Vigilancia y Análisis del Riesgo en Salud 
Pública Publicación en línea: ISSN 2357-6189  
https://doi.org/10.33610/23576189.2022.24 2020 
 
3.​ Apfelbaum, J. L., Hagberg, C. A., Connis, R. T., Abdelmalak, B. B., Agarkar, M., 
Dutton, R. P., Fiadjoe, J. E., Greif, R., Klock, P. A., Mercier, D., Myatra, S. N., 
O'Sullivan, E. P., Rosenblatt, W. H., Sorbello, M., & Tung, A. (2022). 2022 
American Society of Anesthesiologists Practice Guidelines for Management of the 
Difficult Airway. Anesthesiology, 136(1), 31–81. 
https://doi.org/10.1097/ALN.0000000000004002 
 
4.​ Kheterpal, S., Han, R., Tremper, K. K., Shanks, A., Tait, A. R., O'Reilly, M., & 
Ludwig, T. A. (2006). Incidence and predictors of difficult and impossible mask 
ventilation. Anesthesiology, 105(5), 885–891. 
https://doi.org/10.1097/00000542-200611000-00007 
 
5.​ Kheterpal, S., Martin, L., Shanks, A. M., & Tremper, K. K. (2009). Prediction and 
outcomes of impossible mask ventilation: a review of 50,000 anesthetics. 
Anesthesiology, 110(4), 891–897. https://doi.org/10.1097/ALN.0b013e31819b5b87 
 
6.​ Cook, T. M., & MacDougall-Davis, S. R. (2012). Complications and failure of 
airway management. British Journal of Anaesthesia, 109, i68-i85. 
https://doi.org/10.1093/bja/aes393 
 
7.​ DuCanto, J., Matioc, A., & Galgon, R. E. (2023). Noninvasive Management of the 
Airway. En C. Hagberg (Ed.), Hagberg and Benumof’s Airway Management (pp. 
323-341). https://doi.org/10.1016/B978-0-323-79538-8.00018-7 
 
8.​ Eppich, W. J., Zonfrillo, M. R., Nelson, K. L., & Hunt, E. A. (2010). Residents' 
mental model of bag-mask ventilation. Pediatric emergency care, 26(9), 646–652. 
https://doi-org.udea.lookproxy.com/10.1097/PEC.0b013e3181ef045a 
 
9.​ Jain, D., Sahni, N., Goel, N., Gandhi, K., & Sidhu, B. (2021). The C-E versus 
modified V-E hand positions for holding a face mask when ventilating an 
edentulous patient: A randomised crossover trial. European journal of 
anaesthesiology, 38(11), 1194–1196. 
https://doi.org/10.1097/EJA.0000000000001479 
Pág. 
37 
Versión. 01 
 

 
  
 
10.​Bharadwaj, M. S., Sharma, M., Purohit, S., & Joseph, A. (2022). Comparison of the 
Effectiveness of Two-Handed Mask Ventilation Techniques (C-E versus V-E) in 
Obese Patients Requiring General Anesthesia in an Indian Population. Anesthesia, 
essays and researches, 16(1), 167–171. https://doi.org/10.4103/aer.aer_59_22 
 
11.​Fei, M., Blair, J. L., Rice, M. J., Edwards, D. A., Liang, Y., Pilla, M. A., Shotwell, 
M. S., & Jiang, Y. (2017). Comparison of effectiveness of two commonly used 
two-handed mask ventilation techniques on unconscious apnoeic obese adults. 
British journal of anaesthesia, 118(4), 618–624. https://doi.org/10.1093/bja/aex035 
 
12.​Gerstein, N. S., Carey, M. C., Braude, D. A., Tawil, I., Petersen, T. R., Deriy, L., & 
Anderson, M. S. (2013). Efficacy of facemask ventilation techniques in novice 
providers. Journal of clinical anesthesia, 25(3), 193–197. 
https://doi.org/10.1016/j.jclinane.2012.10.009 
 
13.​Piedrahita P, Páramo M, Zamudio M. Técnica “CE” versus técnica “VE” para la 
ventilación con máscara facial  a dos manos: Revisión sistemática de la literatura y 
meta análisis. [Tesis] Medellín; Universidad de Antioquia. 2022 
https://hdl.handle.net/10495/29672  
 
14.​Soltész, S., Alm, P., Mathes, A., Hellmich, M., & Hinkelbein, J. (2017). The effect 
of neuromuscular blockade on the efficiency of facemask ventilation in patients 
difficult to facemask ventilate: a prospective trial. Anaesthesia, 72(12), 1484–1490. 
https://doi-org.udea.lookproxy.com/10.1111/anae.14035 
 
15.​Langeron, O., Masso, E., Huraux, C., Guggiari, M., Bianchi, A., Coriat, P., & Riou, 
B. (2000). Prediction of difficult mask ventilation. Anesthesiology, 92(5), 
1229–1236. https://doi.org/10.1097/00000542-200005000-00009 
 
16.​Kheterpal, S., Healy, D., Aziz, M. F., Shanks, A. M., Freundlich, R. E., Linton, F., 
Martin, L. D., Linton, J., Epps, J. L., Fernandez-Bustamante, A., Jameson, L. C., 
Tremper, T., Tremper, K. K., & Multicenter Perioperative Outcomes Group 
(MPOG) Perioperative Clinical Research Committee (2013). Incidence, predictors, 
and outcome of difficult mask ventilation combined with difficult laryngoscopy: a 
report from the multicenter perioperative outcomes group. Anesthesiology, 119(6), 
1360–1369. https://doi.org/10.1097/ALN.0000435832.39353.20 
 
17.​Nørskov, A. K., Rosenstock, C. V., Wetterslev, J., Astrup, G., Afshari, A., & 
Lundstrøm, L. H. (2015). Diagnostic accuracy of anaesthesiologists' prediction of 
difficult airway management in daily clinical practice: a cohort study of 188 064 
patients registered in the Danish Anaesthesia Database. Anaesthesia, 70(3), 
272–281. https://doi.org/10.1111/anae.12955 
 
Pág. 
38 
Versión. 01 
 

 
  
18.​Rosenblatt, W. H. (2023). Development of an Airway Management Plan. En C. 
Hagberg (Ed.), Hagberg and Benumof’s Airway Management (pp. 208-213). 
https://doi.org/10.1016/B978-0-323-79538-8.00010-2 
 
19.​Frerk, C., Mitchell, V. S., McNarry, A. F., Mendonca, C., Bhagrath, R., Patel, A., 
O'Sullivan, E. P., Woodall, N. M., Ahmad, I., & Difficult Airway Society intubation 
guidelines working group (2015). Difficult Airway Society 2015 guidelines for 
management of unanticipated difficult intubation in adults. British journal of 
anaesthesia, 115(6), 827–848. https://doi.org/10.1093/bja/aev371 
 
20.​American Society of Anesthesiologists (22 de octubre de 2019). Statement on 
​Continuum of Depth of Sedation: Definition of General Anesthesia and Levels of 
Sedation/Analgesia. Disponible en: 
https://www.asahq.org/standards-and-practice-parameters/statement-on-continuum-
of-depth-of-sedation-definition-of-general-anesthesia-and-levels-of-sedation-analge
sia 
 
21.​Aaron M. Joffe, Scott Hetzel, Elaine C. Liew; A Two-handed Jaw-thrust Technique 
Is Superior to the One-handed “EC-clamp” Technique for Mask Ventilation in the 
Apneic Unconscious Person. Anesthesiology 2010; 113:873–879 doi: 
https://doi.org/10.1097/ALN.0b013e3181ec6414 
 
22.​Matioc, A. The adult ergonomic face mask concept: historical and theoretical 
perspectives. Journal of Clinical Anesthesia (2009) 21, 300–304. DOI: 
10.1016/j.jclinane.2008.08.018 
 
23.​Fiona E. Wood, Colin J. Morley. Face mask ventilation – the dos and don'ts. 
Seminars in Fetal and Neonatal Medicine (2013), Volume 18, Issue 6, Pages 
344-351 DOI: https://doi.org/10.1016/j.siny.2013.08.009 
 
24.​Cook, T. M., Woodall, N., Frerk, C., & Fourth National Audit Project (2011). Major 
complications of airway management in the UK: results of the Fourth National 
Audit Project of the Royal College of Anaesthetists and the Difficult Airway 
Society. Part 1: anaesthesia. British journal of anaesthesia, 106(5), 617–631. 
https://doi.org/10.1093/bja/aer058 
 
25.​Hall, J. E., PhD, & Hall, M. E., MD, MS. (2021). Pulmonary Ventilation. En J. E. 
Hall PhD & M. E. Hall MD, MS (Eds.), Guyton and Hall Textbook of Medical 
Physiology (pp. 491-501). https://doi.org/10.1016/B978-0-323-59712-8.00038-2 
 
26.​Ministerio de Salud. Resolución 8430 de 1993. Ministerio de Salud y Protección 
Social República Colombia. 1993;1993(Octubre 4):1–19. 
 
Pág. 
39 
Versión. 01 
 

 
  
27.​Declaración de Helsinki de la Asociación Médica Mundial. Principios éticos para 
las investigaciones médicas en seres humanos. Fortaleza; 2013. 
28.​Emanuel EJ, Wendler D, Grady C. What Makes Clinical Research Ethical? J Am 
Med 
Assoc 
[Internet]. 
2000;283(20):2701–11. 
Available 
from: 
http://jama.ama-assn.org/cgi/doi/10.1001/jama.283.20.2701 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Pág. 
40 
Versión. 01