Efficacy of Laryngeal Tube versus Bag Mask Ventilation by Inexperienced Providers

Abstract

Introduction:
Bag mask ventilation (BMV) and extraglottic devices (EGDs) are two common methods of providing rescue ventilation. BMV can be difficult to perform effectively, especially for inexperienced providers and in patients with difficult airway characteristics. There is some evidence that the laryngeal tube (LT) can be successfully placed by inexperienced providers to provide effective ventilation. However, it is unclear whether ventilation provided by LT is superior to that of BMV, especially in the hands of inexperienced airway providers. Therefore, we aimed to compare ventilation efficacy of inexperienced airway providers with BMV versus LT by primarily measuring tidal volumes and secondarily measuring peak pressures on a simulated model.

Methods:
We performed a crossover study first year emergency medicine residents and third and fourth year medical students. After a brief instructional video followed by hands on practice, participants performed both techniques in random order on a simulated model for two minutes each. Returned tidal volumes and peak pressures were measured.

Results:
Twenty participants were enrolled and 1200 breaths were measured, 600 per technique. The median ventilation volumes were 194 milliliters (mL) for BMV, and 387 mL for the laryngeal tube, with a median absolute difference of 170 mL (95% confidence interval [CI] 157-182 mL) (mean difference 148 mL [95% CI, 138-158 mL], p<0.001). The median ventilation peak pressures were 23 centimeters of water (cm H2O) for BMV, and 30 cm H2O for the laryngeal tube, with a median absolute difference of 7 cm H2O (95% CI, 6-8 cm H2O) (mean difference 8 cm H2O [95% CI, 7-9 cm H2O], p<0.001).

Conclusion:
Inexperienced airway providers were able to provide higher ventilation volumes and peak pressures with the LT when compared to BMV in a manikin model. Inexperienced providers should consider using an LT when providing rescue ventilations in obtunded or hypoventilating patients without intact airway reflexes. Further study is required to understand whether these findings are generalizable to live patients.

Full text

UC Irvine
Western Journal of Emergency Medicine: Integrating Emergency
Care with Population Health
Title
Efficacy of Laryngeal Tube versus Bag Mask Ventilation by Inexperienced Providers
Permalink
https://escholarship.org/uc/item/8cp7f85r
Journal
Western Journal of Emergency Medicine: Integrating Emergency Care with Population
Health, 21(3)
ISSN
1936-900X
Authors
Hart, Danielle
Driver, Brian
Kartha, Gautham
et al.
Publication Date
2020
Supplemental Material
https://escholarship.org/uc/item/8cp7f85r#supplemental
License
https://creativecommons.org/licenses/by/4.0/ 4.0
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Western Journal of Emergency Medicine 688 Volume 21, no. 3: May 2020
Brief research report
Efcacy of Laryngeal Tube versus Bag Mask Ventilation by
Inexperienced Providers
Danielle Hart, MD, MACM
Brian Driver, MD
Gautham Kartha, MD
Robert Reardon, MD
James Miner, MD
Section Editor: Juan F. Acosta, DO, MS
Submission history: Submitted November 10, 2019; Revision received February 28, 2020; Accepted March 8, 2020
Electronically published April 16, 2020
Full text available through open access at http://escholarship.org/uc/uciem_westjem
DOI: 10.5811/westjem.2020.3.45844
Hennepin Healthcare, Department of Emergency Medicine, Minneapolis, Minnesota
Introduction: Bag mask ventilation (BMV) and extraglottic devices (EGDs) are two common methods
of providing rescue ventilation. BMV can be difcult to perform effectively, especially for inexperienced
providers and in patients with difcult airway characteristics. There is some evidence that the laryngeal
tube (LT) can be successfully placed by inexperienced providers to provide effective ventilation.
However, it is unclear whether ventilation provided by LT is superior to that of BMV, especially in
the hands of inexperienced airway providers. Therefore, we aimed to compare ventilation efcacy
of inexperienced airway providers with BMV versus LT by primarily measuring tidal volumes and
secondarily measuring peak pressures on a simulated model.
Methods: We performed a crossover study rst year emergency medicine residents and third and
fourth year medical students. After a brief instructional video followed by hands on practice, participants
performed both techniques in random order on a simulated model for two minutes each. Returned tidal
volumes and peak pressures were measured.
Results: Twenty participants were enrolled and 1200 breaths were measured, 600 per technique. The
median ventilation volumes were 194 milliliters (mL) for BMV, and 387 mL for the laryngeal tube, with a
median absolute difference of 170 mL (95% condence interval [CI] 157-182 mL) (mean difference 148
mL [95% CI, 138-158 mL], p<0.001). The median ventilation peak pressures were 23 centimeters of
water (cm H2O) for BMV, and 30 cm H2O for the laryngeal tube, with a median absolute difference of 7
cm H2O (95% CI, 6-8 cm H2O) (mean difference 8 cm H2O [95% CI, 7-9 cm H2O], p<0.001).
Conclusion: Inexperienced airway providers were able to provide higher ventilation volumes and peak
pressures with the LT when compared to BMV in a manikin model. Inexperienced providers should
consider using an LT when providing rescue ventilations in obtunded or hypoventilating patients
without intact airway reexes. Further study is required to understand whether these ndings are
generalizable to live patients. [West J Emerg Med. 2020;21(3)688–693.]
INTRODUCTION
Rescue ventilation, performed for apneic or hypoventilating
patients and after failed intubation attempts, is an important
skill for emergency airway management. Bag mask ventilation
(BMV) and the use of extraglottic devices (EGDs) are two
common methods of providing rescue ventilation.
BMV, long the gold standard, can be difcult to perform
effectively and requires proper technique to ensure sufcient
ventilation.1–5 In a study of rst-year anesthesia residents, only
17% were able to provide effective BMV on anesthetized
patients following a traditional 36-hour BMV and endotracheal
intubation (ETI) course.2 BMV can prove to be especially

Volume 21, no. 3: May 2020 689 Western Journal of Emergency Medicine
Hart et al. Efcacy of Laryngeal Tube vs Bag Mask Ventilation
difcult in patients with older age, obesity, lack of teeth, a
beard, a higher Mallampati class, or history of snoring.6,7
EGDs provide similar ventilation to endotracheal tubes,8–10
are easy to place, and are often used for emergency ventilation.
The laryngeal tube (LT), a type of EGD, can be successfully
placed by inexperienced providers to provide effective
ventilation.3,11–13 However, there is conicting evidence on
whether ventilation provided by LT is superior to that of BMV,
and it is unknown whether an efcacy difference exists in
the hands of inexperienced airway providers or those who
infrequently perform emergency ventilation, a group that
requires an easy and effective method to maintain oxygenation.
Proper BMV may require skill acquisition and maintenance
that would be difcult for providers that rarely perform the
procedure; however, training and skill acquisition for both
BMV and EGD placement is important. Studies examining
minute ventilation as well as those using a subjective outcome
of “adequate ventilation” as judged by the care provider have
yielded conicting results when examining the efcacy of LT
versus BMV.3,8,14,15
We therefore aimed to compare ventilation efcacy of
inexperienced airway providers with BMV versus LT on a
simulated model. Our primary outcome was measured tidal
volume, and our secondary outcome was peak pressure. We
hypothesized that LT would produce higher tidal volumes and
peak pressures than BMV.
METHODS
We performed a crossover study, including rst year
emergency medicine (EM) residents and third and fourth
year medical students. Twenty participants were enrolled, all
inexperienced in airway management: 12 medical students,
seven rst year EM residents, and one paramedic student.
We chose these participants because they were largely
inexperienced in basic airway management. The local
institutional review board declared this study exempt from
review; all participation was voluntary.
To teach the basics of BMV and LT insertion, participants
listened to a brief introductory lecture discussing basic airway
management and watched a standardized, four-minute video
that described best practices for BMV and LT insertion and use.
The two-handed thenar eminence (TE) BMV technique was
taught due the superiority of this technique when compared
to the one-handed or two-handed E-C technique;16,17 in this
technique, the thenar eminences rest on the mask, and the
ngers lift the ramus of the mandible upward into the mask to
create a seal (Appendix). For LT insertion, participants were
instructed to perform a jaw lift, insert the LT deeply, then
withdraw the tube slowly during ventilation, until adequate
ventilation was achieved.
After a period of unstructured hands-on practice (which
included the same length of time, manikins, airway equipment,
and instructor availability for all participants), participants
performed both techniques in random order. They were given
a standard adult size facemask and a #4 King LT. We used
a manikin to compare the effectiveness of each technique
(TruCorp AirSim Combo X; Belfast, Ireland); the esophagus
and cricothyroid membrane apertures were taped closed; a 3
liter reservoir bag (Intersurgical; East Syracuse, NY) was used
to simulate ination and deation of a lung. The manikin was
inspected for any tears or disruptions prior to data collection
to ensure there were no detectable areas that would result in
an air leak. A mechanical ventilator, connected with standard
ventilator tubing to the facemask or laryngeal tube, (Viasys LTV
1200; Vyaire Medical, Mettawa, IL), delivered a tidal volume
of 500 milliliters (mL) at 15 breaths per minute, and measured
peak pressure and returned tidal volumes. We used a ventilator
rather than manual bagging in order to standardize the volume
delivered, allowing comparisons between devices
After LT insertion or establishing a facemask seal, ve
breaths were administered to inate the reservoir bag; then, the
participants performed each technique for two minutes. The
LT or mask position could be adjusted at any time to maintain
the best possible ventilation. Participants were able to see the
reservoir bag inating and deating during the ventilation;
no other real-time feedback or assistance was provided.
We recorded the tidal volume and peak pressure for each
ventilation. This essentially compared the ability of subjects
to achieve an airway seal with a two-hand thenar eminence
technique on a mask compared to placement of the LT.
The primary outcome was returned tidal volume; the
secondary outcome was peak pressure. These parameters are
indicative of the effectiveness of the airway technique and have
been used in prior research.17 Assuming delivered volumes of
about 400 mL (with a standard deviation of approximately 75
mL), we estimated 20 subjects would be required to detect a
50 mL difference in volumes delivered by the two techniques.
Using the Shapiro-Wilk normality test, we determined that
neither tidal volume and peak pressure values were normally
distributed. Therefore, we compared the volumes and pressures
for the two techniques by calculating the median difference
between groups. The mean values are also presented. We used
Stata (version 15.1, College Station, TX) for all data analysis.
RESULTS
All participants performed both techniques; 1200 breaths
were measured, 600 per technique. The median ventilation
volumes were 194 mL for BMV, and 387 mL for the laryngeal
tube, with a median absolute difference of 170 mL (95%
condence interval [CI], 157-182 mL) (mean difference 148 mL
[95% CI, 138-158 mL], p<0.001). The median ventilation peak
pressures were 23 centimeters of water (cm H2O) for BMV,
and 30 cm H2O for the laryngeal tube, with a median absolute
difference of 7 cm H2O (95% CI, 6-8 cm H2O) (mean difference
8 cm H2O [95% CI, 7-9 cm H2O], p<0.001). Volumes and
pressures achieved by training level are displayed in the Table.
Performance of each participant in each technique is presented
in Figure 1.

Western Journal of Emergency Medicine 690 Volume 21, no. 3: May 2020
Efcacy of Laryngeal Tube vs Bag Mask Ventilation Hart et al.
Table. Median and mean volume delivered, by training level and technique.
Training level Laryngeal tube Bag-mask ventilation
Volume (mL)
First year resident 398 (318 to 402); 367 (54) 194 (161 to 232); 194 (53)
Medical student 382 (370 to 405); 382 (26) 227 (143 to 347); 243 (109)
Pressure delivered (cm H2O)
First year resident 29 (26 to 31); 29 (3) 23 (22 to 25); 23 (1.6)
Medical student 36 (28 to 42); 35 (8) 25 (17 to 35); 26 (9)
mL, milliliters; cm H2O, centimeters of water.
All values are median (interquartile range); mean (standard deviation).
Figure 1. Tidal volume and peak pressure. This gure displays each tidal volume (panel A) and peak pressure (panel B) measurement
for the 1,200 breaths administered, sorted in ascending order and by group.
mL, milliliters; cm, centimeters; BVM, bag mask ventilation.

Volume 21, no. 3: May 2020 691 Western Journal of Emergency Medicine
Hart et al. Efcacy of Laryngeal Tube vs Bag Mask Ventilation
DISCUSSION
Although BMV is often the rst-line method of
emergency ventilation, there is growing evidence supporting
the use of LTs and other EGDs in airway management,
including those with out of hospital cardiac arrest (OHCA),
and those requiring advanced airway management in the
out-of-hospital setting, ED, or during general anesthesia.
Prior literature suggests that the LT has a high rate of
successful placement and adequate ventilation. 3,18–21 What
is less clear is how the LT compares to BMV in the hands of
inexperienced providers.
In our study, we found signicantly higher ventilation
volumes and peak pressures when using the LT compared to
BMV for medical students and rst year EM residents. This
supports previous work of Kurola, who found signicantly
higher minute ventilation with LT compared to BMV in
a simulation model with emergency medical technician
(EMT) students, and of Roth, who found that the LT was
subjectively more effective than BMV in OHCA patients
managed by volunteer EMTs.3,8 There are, however, a
few studies that have not found differences in ventilation
provided by LT versus BMV. Kurola later found that both
LT and BMV were equally effective in ventilating and
oxygenating anesthetized patients in the controlled setting
of the operating room (OR) in the same study population as
his simulation-based study. In addition, Fiala et al found no
difference between BMV and the LT for ventilating OHCA
patients in a multicenter randomized study of EMT-led
airway management.14,15
Considering other EGDs, our ndings are also
consistent with multiple prior studies of inexperienced
providers using laryngeal mask airways (LMA), all of which
concluded that inexperienced airway providers (including
nurses, nursing students, dental students, and other
volunteers with no prior experience) can provide better
ventilation with the LMA than with BMV (with or without
a concomitant oropharyngeal airway).5,22–26 One study
looking specically at obese patients found that medical
students were able to establish effective ventilation more
quickly with the LMA than with BMV.27 A few studies that
contradict these ndings used more experienced providers,
highlighting the need for experience and practice in order to
ventilate with BMV effectively.2,28–30
EGDs are essential for emergency ventilation in
patients who are known to have difcult mask ventilation,
such as those with beards, morbid obesity, or a history of
snoring.6,7,27 In cardiac arrest patients, EGDs result in a
lower incidence of gastric insufation and regurgitation
than BMV.3,5,26,31 With prior conicting results regarding the
efcacy of LT versus BMV in providing superior ventilation,
our results add support to the assertion that the LT may be
a better choice than BMV in obtunded or hypoventilating
patients without intact airway reexes for inexperienced
providers who have not developed effective BMV
techniques.1–5 Knowing that LMAs have also shown to result
in superior ventilation to BMV in the hands of inexperienced
providers, it is possible that when an inexperienced provider
encounters a patient who requires emergency ventilation, an
EGD may be preferred to BMV, because this device requires
less practice and skill, and likely allows higher tidal volume
and peak pressure, enabling better overall ventilation.
Further study is required to determine whether the ndings
in our study of LT being superior to BMV for inexperienced
providers is generalizable to live patients.
LIMITATIONS
Our study included a convenience sample of subjects,
who may have volunteered for our study due to their
perceived increased or decreased skill compared to
their overall cohort. There are also inherent differences
between manikins and actual patients, including a taped-
off esophagus. While this differs from human anatomy,
closing off the esophagus was necessary to accurately
measure delivered and returned tidal volumes and pressures
for this study. While a human model would be preferred,
unfortunately there is no practical way to compare BMV
with LT insertion for inexperienced providers during
actual emergency airway management. Therefore, these
data should serve as a surrogate that reects the increased
difculty in obtaining a mask seal compared to inserting an
EGD in the clinical environment. Although further human
study in emergency airway management may not be feasible
in an emergency setting, further study of inexperienced
medical students and residents could be performed in the
more controlled environment of the operating room. This
could then account for additional variables that may occur
in live patients, such as variations in human anatomy and
differences in lung compliance. Similarly, use of a ventilator
rather than a resuscitation bag does not mirror real-world
practice, but enabled standardization of tidal volumes
between groups, so that differences in measured volume
and pressure were due to differences in laryngeal tube or
BMV technique rather than differences in bag squeezing.
We did not measure skill retention, which could be an area
of future exploration. Finally, we had a small sample size of
20 participants; although this sample size provided power
to detect a 50 mL difference, a larger sample size would
provide further mitigation of type 2 error.
CONCLUSION
Inexperienced airway providers were able to provide
higher ventilation volumes and peak pressures with
the LT when compared to BMV in a manikin model.
Inexperienced providers should consider using an LT
when providing rescue ventilations in obtunded or
hypoventilating patients without intact airway reexes.
Further study is required to understand whether these
ndings are generalizable to live patients.

Western Journal of Emergency Medicine 692 Volume 21, no. 3: May 2020
Efcacy of Laryngeal Tube vs Bag Mask Ventilation Hart et al.
Address for Correspondence: Danielle Hart, MD, MACM, Hennepin
Healthcare, Department of Emergency Medicine, 701 Park Ave,
Minneapolis, MN 55415. Email: danielle.hart@hcmed.org.
Conicts of Interest: By the WestJEM article submission
agreement, all authors are required to disclose all afliations,
funding sources and nancial or management relationships that
could be perceived as potential sources of bias. No author has
professional or nancial relationships with any companies that are
relevant to this study. There are no conicts of interest or sources of
funding to declare.
Copyright: © 2020 Hart et al. This is an open access article
distributed in accordance with the terms of the Creative Commons
Attribution (CC BY 4.0) License. See: http://creativecommons.org/
licenses/by/4.0/
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