Various guidelines for endotracheal intubation (insertion of breathing tube for mechanical ventilation) of Coronavirus Disease 2019 (COVID-19) patients recommend the use of videolaryngoscope (medical device used for intubation that has a camera to visualize the vocal cords between which the breathing tube will pass) over direct laryngoscope (conventionally-used medical device for intubation that depends on anesthetist's direct visualization of vocal cords). The reasons for this recommendation are to maximize the distance between the medical personnel and the patient's face during intubation to decrease the risk of viral particles transmission and to improve intubation success. For patients infected with COVID-19, Powered Air Purifying Respirator (PAPR) is recommended as an alternative to N95 masks during aerosol-generating procedures such as intubation because N95 masks may not fully protect medical personnel from viral transmission during intubation. There is no evidence to suggest that videolaryngoscope (VL) is superior to direct laryngoscope (DL) for intubation when PAPR is donned. The purpose of this study is to determine if McGrath VL is superior to DL for intubation when the anesthetist is wearing a PAPR. The investigators' hypothesis is that McGrath VL will decrease the time to intubation by 20 seconds and more compared to DL when PAPR is donned. The investigators also hope to learn if there is any difference in the difficulties encountered between the use of VL and DL.
Background:
17% of patients with Coronavirus Disease 2019 (COVID-19) may require endotracheal intubation
for mechanical ventilation due to respiratory failure.
Various guidelines for endotracheal intubation of COVID-19 patients recommend the use of
videolaryngoscope (VL) over direct laryngoscope (DL). The reasons for this recommendation are
to firstly, maximize the distance between the medical personnel and the patient's face during
intubation in order to decrease the risk of viral particles transmission and secondly, to
improve intubation success.
There is a lack of evidence to show that VL can decrease the risk of contact with aerosol
generated during intubation. Matthew T.V. Chan et al have shown that aerosol may be generated
up to 45cm away from the patient's face during intubation. In the investigators' own trial
run of an experimental set-up to study the difference in intubation between VL and DL when
PAPR is worn, the investigators found that it is not possible to maintain a distance of at
least 45cm during the intubation process because of the need to visualize the entry of the
laryngoscope blade into the patient's mouth in order to prevent injury to the oral
structures. The investigators' study is congruent with a recent study that reports the mean
distance from the patient's mouth to anesthetist's mouth was 35.6cm using VL and 16.4cm using
DL.
In routine intubations, VL is recommended over DL for endotracheal intubation as it may
provide a higher success and faster speed of intubation compared to DL. For patients infected
with COVID-19, PAPR is recommended as an alternative to N95 masks during aerosol-generating
procedures such as intubation because N95 masks may not fully protect medical personnel from
viral transmission during intubation. There is currently no evidence to suggest that VL is
superior to DL for intubation when PAPR is donned.
Proposed Study Design:
This study will be a randomized controlled trial. Informed consent to take part in the study
will be taken from patients who are planned for elective surgery requiring endotracheal
intubation and also from a group of anesthetists in the department.
Prior to a consented patient turning up for the operation, randomization will be done to
determine who from the selected group of anesthetists will be doing the intubation. The
randomly selected anesthetist will wear the PAPR and intubate the patient using either a DL
or McGrath VL that the anesthetist is randomized to.
Hypothesis and Objectives:
The hypothesis is that McGrath VL will decrease the time to intubation (TTI) by 20 seconds
and more compared to DL when PAPR is donned. The investigators will also study the secondary
outcomes between McGrath VL and DL which are first attempt success percentage, use of
adjuncts, success or failure at intubation using initial laryngoscope that the anesthetists
is randomized to, intubation difficulty scale (IDS), closest distance from patient's mouth to
anesthetist's mouth during intubation, adverse events and inability to intubate despite all
efforts by the anesthetist.
Sample size calculation:
The primary outcome of this study is the difference in time to complete intubation between DL
and VL with hooded PAPR. In a previous study reported by Dong et al in 2013, 21 the median
(IQR) time to complete tracheal intubation with suited VL was 18.2 (22.1 - 15.1 = 7.0)
seconds, whereas that for suited DL was 26.4 (35.2 - 23.1 = 12.1) seconds.
For a normal distribution, the IQR which covers the middle 50% of the whole distribution is
approximately equal to mean +/- 0.6 standard deviation (SD), or equivalently 1.2 SD. If time
to complete intubation is normally distributed, the SD for suited VL and suited DL are
approximately 5.8 and 10.1 seconds, respectively. To be conservative in calculating the
sample size, the larger SD of 10.1 seconds for suited DL is used. Moreover, the distribution
of time to complete intubation is unlikely normal but skewed, an inflated SD is assumed to
compensate for the violation of normal distribution. Hence, a SD of 18 seconds is used.
The minimal clinically important difference (MCID) for time to complete intubation in
comparing different laryngoscopes is not defined in the literature. MCIDs ranging between 10
and 20 seconds to compare intubation times using different laryngoscopes are commonly used,
in this study a difference of 20 seconds is assumed. Therefore, to detect a difference of at
least 20 seconds between the suited DL and suited VL groups, targeting a power of 80% and a
2-sided type I error of 5%, a sample size of 14 patients is required for each group (that is
a total of 28 patients for the study).
The investigators will attempt to recruit 50 patients at the Pre-operative Evaluation Clinic
(PEC) to account for a possible drop-out rate of 40% (either from patient refusal to take
part in the study on the day of operation or from other unforeseen reasons why
earlier-recruited patients will not be taking part in the study).
The investigators will recruit 10 anesthetists from the Division to increase the chance that
the randomly selected anesthetist is available on the day of operation for a patient who has
consented for the study.
Statistical analysis:
Data will be analyzed with an intention-to-treat analysis. To study the difference in TTI
between McGrath VL and DL, the investigators will compare the mean or median time of for
intubation with McGrath VL against DL using Mann-Whitney U test or Independent Samples T-test
depending on the normality of the distribution.
To study the difference in the first-attempt success rate, use of adjuncts at first attempt,
use of adjuncts at subsequent attempts, success or failure at intubation using initial
laryngoscope randomized to, adverse events (oxygen desaturation to less than 88%, oro-dental
injuries) and inability to intubate despite all measures between McGrath VL and DL,
Chi-square test will be used. The investigators will compare the mean or median IDS for
McGrath VL against that for DL and the mean or median of the closest distance between the
patient's mouth and the anesthetist's mouth during intubation for McGrath VL against that for
DL using Mann-Whitney U test or Independent Samples T-test depending on the normality of the
distribution.
Quality assurance plan:
All data will be monitored and reviewed by the PI or Co-investigators. Training will be given
to the clinical research coordinator for data extraction and entry to the case report forms
for analysis will be verified by a second person from the study team. Records for all
participants, including case report forms, all source documentation (containing evidence to
study eligibility, history and physical findings, laboratory data, results of consultations,
etc.) as well as Centralized Institutional Review Board (CIRB) records and other regulatory
documentation will be retained by the PI and be accessible for inspection and copying by
authorized authorities. The research data will be kept in the secure location within the
departmental office for 7 years before being destroyed.
Safety monitoring:
Serious adverse event (SAE) in relation to human biomedical research, means any untoward
medical occurrence as a result of any human biomedical research which:
- results in or contributes to death
- is life-threatening
- requires in-patient hospitalization or prolongation of existing hospitalization
- results in or contributes to persistent or significant disability/incapacity or
- results in or contributes to a congenital anomaly/birth defect
- results in such other events as may be prescribed Adverse event (AE) in relation to
human biomedical research means any untoward medical occurrence as a result of any human
biomedical research which is NOT serious. Adverse event can be any unfavorable and
unintended sign (including an abnormal laboratory finding), symptom, or disease
possibly/ probably/ definitely associated with the participant in the human biomedical
research.
Only related SAEs (definitely/ probably/ possibly) will be reported to CIRB. Related means
there is a reasonable possibility that the event may have been caused by participation in the
research.
The investigator is responsible for informing CIRB after first knowledge that the case
qualifies for reporting. Follow-up information will be actively sought and submitted as it
becomes available.
Related AEs will not be reported to CIRB. However, the investigator is responsible to keep
record of such AEs cases at the Study Site File.
Safety analyses and interim analyses will be done after 14 patients have completed the study
to determine the incidence of adverse events. If there are more than 3 patients with adverse
events, the investigators will review the safety of the study and decide if there is need to
improve on the study design or terminate the study prematurely.
Device: McGrath videolaryngoscope
A brand of a commonly-used videolaryngoscope which has a camera at the end of the laryngoscope to visualize the vocal cords
Device: Direct laryngoscope
Classic direct laryngoscope that depends on visualization of the vocal cords by the operator
Patients who attend the Pre-operative Evaluation Clinic (PEC) in Singapore General Hospital
(SGH) for pre-anesthesia assessment will be screened by a study team member for recruitment
if they meet the inclusion criteria.
Patients will be undergoing routine pre-anesthesia assessment (including review of medical
conditions and airway anatomy) by the anesthetists in the PEC prior to their planned
elective surgeries. During their routine pre-anesthesia assessment, they will also be
assessed by a study team member to confirm if they meet the eligibility criteria. If they
are eligible for enrollment, a qualified practitioner will take informed consent.
We will also recruit 10 anesthetists from the Division to perform the intubations. The 10
anaesthetists will have to self-report experience in both the use of McGrath
videolaryngoscope (VL) and direct laryngoscope (DL) for intubation (at least 20 successful
intubations with McGrath VL or DL).
Inclusion Criteria for patients:
- 21 years old and above
- Not pregnant
- ASA physical status I, II and III
- BMI less than 35kg/m2
- Elective surgical operations requiring general anesthesia and endotracheal intubation
- Able to give own informed consent
- No features of difficult airway which has to consist all of the following:
- Class I and II on the modified Mallampati classification
- Thyromental distance of 6.5cm and above
- Mouth opening of 3.5cm and above
- Sterno-mental distance of 12.5cm and above
Inclusion Criteria for Anesthetists:
- Qualified anesthetists (associate consultants and above)
- Experience with both the use of McGrath VL and DL for intubation (at least 20
successful intubations using McGrath VL)
- Willing to perform intubation with PAPR donned and using either the McGrath VL or DL
Exclusion Criteria for patients:
- Below 21 years old
- Pregnancy
- ASA status IV and above
- Poorly-controlled cardiorespiratory conditions (such as poorly-controlled asthma with
Asthma Control Test ≤ 19, chronic obstructive pulmonary disease GOLD 2 and above,
exertional angina, coronary artery disease with active symptoms, heart failure with
New York Heart Association Class III and above)
- Body Mass Index ≥ 35 kg/m2
- Emergency operation
- Unable to give own consent
- Any feature of difficult airway which is
- Class III and IV on the Modified Mallampati Classification
- Thyromental distance less than 6.5cm
- Mouth opening less than 3.5cm
- Sterno-mental distance less than 12.5cm
- History of difficult intubation
- Unstable cervical spine
Exclusion criteria for anesthetists:
- Non-specialist anesthetist
- Inexperience with both the use of McGrath VL and DL for intubation (less than 20
successful intubations using McGrath VL)
- Unwilling to perform intubation with PAPR donned using either the McGrath VL or DL
Singapore General Hospital
Singapore, Singapore
Qing Yuan Goh, M.Med (Anes), Principal Investigator
Singapore General Hospital