Video laryngoscopy does not improve the intubation outcomes in emergency and critical patients – a systematic review and meta-analysis of randomized controlled trials
Jiang et al. Critical Care
Video laryngoscopy does not improve the intubation outcomes in emergency and critical patients - a systematic review and meta-analysis of randomized controlled trials
Jia Jiang 1
Danxu Ma 1
Bo Li 2
Yun Yue 1
Fushan Xue 0
0 Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College , Beijing 100144 , China
1 Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University , Beijing 100020 , China
2 Beijing Hospital of Traditional Chinese Medicine, affiliated with Capital Medical University, Beijing Institute of Traditional Chinese Medicine , Beijing 100010 , China
Background: There is significant controversy regarding the influence of video laryngoscopy on the intubation outcomes in emergency and critical patients. This systematic review and meta-analysis was designed to determine whether video laryngoscopy could improve the intubation outcomes in emergency and critical patients. Methods: We searched the Cochrane Central Register of Controlled Trials, PubMed, Embase, and Scopus databases from database inception until 15 February 2017. Only randomized controlled trials comparing video and direct laryngoscopy for tracheal intubation in emergency department, intensive care unit, and prehospital settings were selected. The primary outcome was the first-attempt success rate. Review Manager 5.3 software was used to perform the pooled analysis and assess the risk of bias for each eligible study. The GRADE (Grading of Recommendations Assessment, Development and Evaluation) system was used to assess the quality of evidence for all outcomes. Results: Twelve studies (2583 patients) were included in the review for data extraction. Pooled analysis did not show an improved first-attempt success rate using video laryngoscopy (relative risk [RR], 0.93; P = 0.28; low-quality evidence). There was significant heterogeneity among studies (I2 = 91%). Subgroup analyses showed that, in the prehospital setting, video laryngoscopy decreased the first-attempt success rate (RR, 0.57; P < 0.01; high-quality evidence) and overall success rate (RR, 0.58; 95% CI, 0.48-0.69; moderate-quality evidence) by experienced operators, whereas in the in-hospital setting, no significant difference between two devices was identified for the first-attempt success rate (RR, 1.06; P = 0.14; moderate-quality evidence), regardless of the experience of the operators or the types of video laryngoscopes used (P > 0.05), although a slightly higher overall success rate was shown (RR, 1.11; P = 0.03; moderatequality evidence). There were no differences between devices for other outcomes (P > 0.05), except for a lower rate of esophageal intubation (P = 0.01) and a higher rate of Cormack and Lehane grade 1 (P < 0.01) when using video laryngoscopy. Conclusions: On the basis of the results of this study, we conclude that, compared with direct laryngoscopy, video laryngoscopy does not improve intubation outcomes in emergency and critical patients. Prehospital intubation is even worsened by use of video laryngoscopy when performed by experienced operators.
Airway management; Laryngoscope; Tracheal intubation; Randomized controlled trial
Securing the airway with tracheal intubation (TI) is a
fundamental treatment for emergency and critical care
patients with respiratory dysfunction or decreased airway
protection. Direct laryngoscopy (DL) is the primary
method for TI, but it can be challenging when performed
in emergencies because the patient often is in
lifethreatening condition and has the factors that make TI
difficult, such as limited mouth opening, unstable cervical
spine, blood or secretions in the airway, and facial trauma,
and in addition the expertise of available practitioners
]. The first-attempt success rate of urgent TI in
emergency and critical patients is relatively low [
unsuccessful or prolonged TI can be life-threatening and
may result in severe complications [
Video laryngoscopy (VL) is a new device that contains
a miniaturized camera at the blade tip to visualize the
glottis indirectly. This method was developed at the
beginning of the 21st century [
]. It has been shown that
VL improves laryngeal visualization compared with DL
] and provides some advantages in surgical
patients, especially those with difficult airways [
The use of VL in emergent and critical situations has
also been tested in several observational studies, which
have shown that VL can lead to better intubation
4, 5, 20, 21
]. A recent meta-analysis of intensive
care unit (ICU) patients demonstrated that, compared
with DL, VL reduces difficult intubation and increases
the first-attempt success rate [
]. Of the nine studies
included in that meta-analysis, however, only three (n =
157 subjects) were randomized controlled trials (RCTs)
]. An observational study, whether prospective,
nonrandomized, or retrospective in design, does not
control for the operators’ experience with each device or
for patients’ conditions and thus may bias the
determination of the efficacy of different airway devices.
Recently, the performance of VL and DL in patients
needing emergency TI was compared in several RCTs,
and some of them showed no benefit regarding success
rate or intubation time with VL [
]. In view of
this, we performed a systematic review and
metaanalysis that included only RCTs comparing the
performance of VL and DL for emergency TI with
respect to the intubation outcomes and complications.
Our review is registered with PROSPERO (http://
The Cochrane Central Register of Controlled Trials
(CENTRAL), PubMed, Embase, and Scopus databases
were searched from inception of the databases until 15
February 2017. The PubMed search strategy provided in
Additional file 1 was applied to search other electronic
databases. For literature without full text, the
corresponding author of the study was contacted by
email. The reference lists of all eligible trials and reviews
were screened for additional citations. No language
restriction was imposed.
RCTs or quasi-RCTs comparing VL and DL for TI in
emergency or critical care patients were included.
Manikin studies, cadaveric studies, and retrospective or
observational studies were excluded. Participants were
nonsurgical patients needing emergent TI in the
inhospital or prehospital setting. Patients with suspected
laryngeal trauma or extensive maxillofacial injury
requiring an immediate surgical airway, supraglottic airway, or
awake fiberoptic intubation were excluded. The primary
outcome was the first-attempt success rate. The
secondary outcomes were overall success rate; duration of
intubation; and complications, including esophageal
intubation, aspiration, severe low oxygen saturation, and
in-hospital mortality. The rate of Cormack and Lehane
grade 1 classification was also recorded. The definitions
of the outcomes are shown in Additional file 2: Table S1.
The titles and abstracts were independently screened
by two of the present review’s authors (JJ and DM). After
retrieving the full texts of any potentially relevant
studies, the studies’ eligibility was determined. Any
disagreements between the two review authors were
resolved by discussion with the other authors until a
consensus was obtained. A Preferred Reporting Items
for Systematic Review and Meta-Analysis (PRISMA)
flow diagram was completed to record the selection
process in sufficient detail [
Data extraction and risk of bias assessment
The data were independently extracted by two review
authors (JJ and DM). For continuous data, mean, SD,
and sample size were extracted. Data such as median or
CI that cannot be used directly were converted to SD by
using a formula provided in the Cochrane Handbook
]. For dichotomous variables, the number of events
that had occurred and the sample size were extracted.
The corresponding author of the study was contacted if
the data were unavailable.
The risk of bias for each eligible study was
independently assessed by two review authors (JJ and DM) using
the “risk of bias” assessment tool of the Cochrane
]. If all seven domains were assigned a low risk
of bias, the study was classified as “low risk”; if one or
more domains were assigned to the “unclear risk” of bias
category, the study was classified as “unclear risk”; if one
or more domains were assigned to a high risk of bias,
the study was classified as “high risk” [
the criteria of the Grading of Recommendations
Assessment, Development and Evaluation (GRADE)
system (study limitations, consistency of effect, imprecision,
indirectness, and publication bias) were used to assess
the quality of the body of evidence associated with all
]. Then we developed a grade evidence
profile table using the GRADE software
(www.guidelinedevelopment.org) to rate these outcomes as being of
high, moderate, low, or very low quality. If serious or
very serious deficiencies in these criteria were
considered, the quality of evidence was downgraded by one
or two levels.
The weighted mean difference (WMD) and 95% CI were
used for continuous data. Relative risk (RR) and 95% CI
were used for dichotomous data. A P value less than
0.05 was considered statistically significant. RevMan 5.3
software (Cochrane Collaboration, London, UK) was
used to perform the pooled analysis for the outcomes
from more than one study. A chi-square test with the I2
statistic was used to quantify heterogeneity. An I2 value
less than 40% was considered as low heterogeneity, and
a fixed-effect model was used; otherwise, a
randomeffect model was used. In the presence of statistical
heterogeneity (I2 ≥ 40%) or an indication of clinical
heterogeneity, subgroup analysis was planned for the primary
outcomes according to the following possible
heterogeneous factors: (a) different settings: in-hospital (ICU and
emergency room) and prehospital; (b) operators’
experience: experienced (certified anesthesiologist, emergency
medical service technician with more than 3 years of
clinical experience, performed > 50 TIs, or according to
the judgment of the study authors) or inexperienced;
and (c) different devices: channeled, Macintosh and
angulated VLs. Sensitivity analysis was conducted to
explore other potential sources of heterogeneity if
necessary. Reporting bias was assessed using funnel plots if
the result of the primary outcome was derived from at
least ten trials [
Using our search strategy, a total of 1380 papers were
identified. Of them, 1313 were excluded during title and
abstract screening because they were duplicates or
irrelevant to our research question. Sixty-seven studies
were selected for full-text assessment using our
inclusion and exclusion criteria. Fifty-two further studies were
removed because of having non-RCT characteristics,
lacking relevant data, including surgical participants,
and/or being duplicates. Authors of three studies were
contacted for their full-text articles to confirm their
eligibility: One [
] proved to be a meeting report that
was part of another included study [
]; one was an
observational study [
]; and another was qualified, but its
full text could not be obtained to do the risk of bias
]. Thus, all three of these studies were
excluded. One study author was contacted for additional
]. Eventually, 12 studies (n = 2583) were included
in the review for data extraction [
23–32, 41, 42
study selection process is shown in Fig. 1.
Description of included studies
Characteristics of included studies are listed in Table 1.
Among 12 included studies, 10 were RCTs, and the
S o o ll ll ll
R N M A A A
ce re ed sn
i()rrrtsxcaeeeeeonppO iii()rssxcycaeeeePnnhpd iirrtssSEeeeonndD i)(rtsxceeeeonpdm iirtttssaaEeeennnnddgdD iiii()rtsssxyccaeeeenonnhpdpm iiii()rrrsxccvveeeeeeonnopddpN iliilrrrtyccaaaaTeunonndpdm iilliif(rrsxccaeeeeeeenonndpwm ii(rrttsxcaEeee05unnopdb> lIf)ssssccTeuu .ii()rxca31e1eee86840nnnpdd% ii(rrtttssxcaeeeeunnoodbpm ii)rxceeeennpd iliilrrrtycccaaaaaTeunonndpdm iilliif()rsxcceeeeeeenonnddpwm ili(rtttssssxccaaeeeeeuhonnnnpA iliiirttsssssycaSEeehooohngpAM i)(rxceeeendp iii()rssxyccaSEeeeehnnppdM ilirrttssssyaEeeeeonhoongdD i)(rxceeeenpd ,iilirtrrscyavaaeeuuoonnpdCmPRC
.svD .LD .(98 .)4% .LD .svD
e L L sv C (1 sv C
p D D A A
co .s .s ep M ep ep M
s S v v co th co co th
ice ya CA CA Se ra Se Se ra
ve irw -M -M lid cG ild L ild cG
D A C C G M G D G M
iiffc lcu o o o se o
D in N N N Y N
L L L ,t
D D D n
. . . e
s s s
v L L v v tm
e .D .D e e ra
p s s p p p
o v v o o e
c c c d
Se CA raq Se Se cy
ild -M irt ild ild en
G C A G G g
se o o o o le o
Y N N N N o e
ska tu ed co yp
ithw ithw rtem leudd ithow lxcud izedm itonb
ts ts fa xc ts ts ts e od ra
n n e n n n ts n tu
ite ite 2% n ite ite ite en aR sa
ap ap 9 ito ap ap ap ita TC en
lt lt <2 ilta lt lt lt p R g
u R u R O n u R u u R ,s xy
d P d P p e d P d d P e O
A C A C S v A C A A C ad 2
s s s s
r s r r
a t a ra t a
s e n e e se e
tn y ite y y rr y
a 8 a 6 6 a 8
1 p 1 1 c 1
ic ≥ lt ≥ ≥ ia ≥
rt e u e eg rad eg
a g d g
P A A A A c A
d s p
e g s
d in o
lu t e U U
c Se rP ED ED IC IC
4 ] ] seq lin d
[1052 31 [4111 [6132 25 iapd caaeh ttcaeon
,.llirrtavee2egb .,llrtsae1062eu ,.llirtaee20mm ,.llirtaee20mm .,ltttsaaee1032 R:iiItrsveSoaRbbn ,rrscyyToognpIT trscaaeouhhw
S S T T Y A laaT
remainder were quasi-RCTs; 3 were carried out in the
prehospital setting and 9 in the ICU or emergency
department (in-hospital setting). Most intubations in seven
studies were performed by experienced operators, and
five were performed mostly by inexperienced operators.
The angulated VL (GlideScope; Verathon, Seattle, WA,
USA) was used in six studies, the Macintosh-type VL in
four (C-MAC, Karl Storz, Tuttlingen, Germany; or
McGrath MAC, Aircraft Medical, Edinburgh, Scotland),
and the channeled VL in two (Pentax Airway Scope,
Pentax Lifecare/Hoya, Tokyo, Japan; or Airtraq,
Prodol Meditec, Las Arenas, Spain). Five in-hospital
studies excluded patients with cardiac arrest, and one
enrolled only patients with cardiac arrest. Rapid
sequence induction (RSI) with sedatives or narcotics
and neuromuscular blockades (NMBAs) were chosen
for all participants or as appropriate by choice of
physicians in most included studies. Three studies did
not use any NMBAs [
24, 26, 29
The overall risk of bias of the included studies was
relatively low. Eight of them could be classified as
low-risk studies and three as high-risk studies.
Detailed information regarding the risk of bias of the
included studies is shown Fig. 2 and summarized in
Additional file 3: Table S2. A funnel plot obtained
from the primary outcome is shown in Additional file
4: Figure S1. The GRADE system showed that the
quality of most evidence was low or moderate for
inconsistency owing to a moderate or high level of
heterogeneity. The results of the evidence of outcomes
are listed in Additional file 5: Table S3.
First-attempt success rate
The data on the first-attempt success rate for all 12
included studies were available. Pooled analysis showed no
significant difference in the first-attempt success rate
between VL and DL (12 studies; RR, 0.93; 95% CI, 0.82–
1.06; n = 2583; P = 0.28; low-quality evidence). There was
significant heterogeneity among studies (P < 0.01; I2 =
91%) (Additional file 6: Figure S2).
Subgroup analysis according to different settings
identified a significant difference for the prehospital setting
(three studies; RR, 0.57; n = 647; P < 0.01; high-quality
evidence) but no significant difference for the in-hospital
setting (nine studies; RR, 1.06; n = 1936; P = 0.14;
moderate-quality evidence). Prehospital intubation was
performed mostly by experienced operators, and two
kinds of VLs (channeled [
] or angulated  VLs)
were used. Given that different settings would introduce
principal heterogeneity and only three studies in the
prehospital setting were included, subgroup analyses based
on the experience of operators and different devices
used were performed only in the in-hospital setting. No
significant difference was found when TI was performed
by experienced operators (four studies; RR, 1.03; n =
1108; P = 0.37) or by inexperienced operators (six studies
with seven comparisons; RR, 1.16; n = 924; P = 0.05). No
significant difference was found for intubation with
angulated VLs (GlideScope; five studies with six
comparisons; RR, 1.16; n = 1016; P = 0.04) or with
Macintoshtype VLs (C-MAC/McGrath MAC; five studies; RR, 1.03;
n = 1016; P = 0.43) (Fig. 3). The study by Silverberg et al.
] had a much higher first-attempt success rate when
using VL than that in other studies, and it was the only
study performed in non-cardiopulmonary resuscitation
(non-CPR) patients without using any NMBAs. Thus, a
sensitivity analysis excluding this study in the in-hospital
setting was conducted. The results were not altered;
however, no evidence of heterogeneity could be found in all
subgroups that originally included this study (I2 < 40%).
Results of secondary outcomes, including overall
success rate, duration of intubation, esophageal
intubation rate, in-hospital mortality, aspiration, severe low
oxygen saturation, and Cormack and Lehane grade 1
classification, are summarized in Table 2 and
Additional file 7: Figure S3, S4, S5, and S6.
To our knowledge, this is the first meta-analysis and
systematic review of available RCTs comparing VL and DL
for TI in emergency and critical care patients, including
the quality of evidence. In this analysis, the first-attempt
success rate was used as the primary endpoint because
multiple intubation attempts performed outside the
operating room can significantly increase the risk of
lifethreatening complications [
6, 43, 44
improving the first-attempt success rate has been regarded
as the main goal of emergency TI [
]. Our results show
that laryngeal visualization was improved by using VL.
This is consistent with findings for surgical patients in
the operating room [
]. However, better visualization
did not translate into an improved first-attempt success
rate or other intubation outcomes or complications,
except for a lower rate of esophageal intubation.
Prehospital intubation outcomes were even worsened with
lower first-attempt and overall success rates with VL
when TI was performed by experienced operators.
Evidence derived from surgical patients shows that VL
is associated with better intubation outcomes, especially
for inexperienced operators and patients with difficult
16, 28, 46
]. This is because TI in the operating
room is controllable, such as with the common use of
RSI and NMBAs, patients’ fasting state, and favorable
oxygenation, as well as appropriate light or intubation
position. For highly experienced anesthesiologists, it
seems unlikely that a single device will show superiority
unless a difficult airway is encountered [
for novices who have not yet received long-term DL
training, visualization of the airway on a video screen
can allow their supervisors to directly assist them in
completing an intubation themselves, thus reducing the
number of attempts and improving the safety of airway
]. However, emergent TI is quite
another thing. Although TI in the emergency department
or ICU is frequently performed by paramedics or
emergency medicine physicians who do not practice TI with
DL on a daily basis [
], and although the patients often
have a higher risk of difficult airways [
operators may not benefit from using VL as novices in the
operating room. There are several uncontrollable factors
that may explain this difference. First, critically ill
patients with a poor oxygen reserve capacity are more
subject to hypoxia, which makes it more likely that
operators will turn to alternatives such as DL, a flexible or
rigid bronchoscope, or at least further mask
oxygenation. If TI is not completed within the allowed time,
inexperienced operators will be replaced by more
experienced operators earlier, making the first-attempt success
rate much lower. Second, secretions or blood in the
airway might impair laryngeal visualization with VLs [
]. Third, RSI and NMBAs will be chosen with caution
owing to circulation compromise, certain airway
problems, operators’ experience, or accessibility of medicine.
Prehospital intubation is more challenging, owing to
additional risk factors such as ambient light, limited
workspace, special positioning, and chest compression
during CPR [
]. Under chest compression, increased
intrathoracic pressure can cause reflux of gastric
Abbreviations: C&L Cormack and Lehane, IV Inverse variation, M-H Mantel-Haenszel, WMD Weighted mean difference
contents, resulting in more attempts and longer
intubation time with the VL. Prolonged intubation time
and subsequent hypoxemia have been identified as
major reasons for increased mortality in patients
undergoing prehospital intubation [
]. In addition, in
prehospital care, DL is more accessible, and most
operators are experienced in using it.
It must be emphasized that performance of VL is
different between devices owing to various designs and
]. Even a slight design modification may
significantly change the success rate, intubation time,
and use of adjunct maneuvers . Some types of VLs
have their own design-related deficiencies that may
dwarf their results. For example, the A.P. Advance™ VL
(Venner Medical International, St Helier, Jersey, UK),
with a large video screen, shows the plastic part of the
blade tip instead of the relevant airway, contributing to
its poor performance [
]. Studies included in our
analysis used three types of VLs (angulated, Macintosh, or
channeled), including five different devices (GlideScope,
C-MAC, McGrath MAC, Airwayscope, and Airtraq). In
the prehospital setting, two of three included studies
used channeled VL. The channeled VL, with its
integrated design, might be more portable in the prehospital
setting, but it is bulkier and may require other team
members to maneuver the tracheal tube [
]. It should
be noted that the poor performance of the VL is due
mainly to the prehospital setting itself rather than to the
devices chosen. We therefore did a related subgroup
analysis only in the in-hospital setting. No difference
was identified between VLs and DLs, regardless of the
devices used. Although an angled blade design was
assumed to facilitate laryngeal visualization and thus to
lead to a better intubation outcome, it may afford less
room for tracheal tube insertion and increase stylet use
in patients with a normal airway, resulting in increased
procedural difficulty and prolonged intubation time [
]. In addition, pooling of results from studies
evaluating different VLs may lead to intrinsic inconsistencies.
An especially important issue neglected in the design of
the five included studies comparing the Macintosh-type
VL and DL is that the Macintosh-type VL can provide
the two options of DL and VL in one device. When one
attempt fails, the operators can immediately switch to
another option to successfully complete the TI without
having to make a second attempt [
]. This unique
feature of Macintosh-type VLs is significantly different from
DLs and angulated VLs, which can provide only one
option. Thus, definition of laryngoscopy attempts used in
these studies is desirable for DLs but not for
Macintoshtype VLs [
The results of some studies indicate that VLs should
be used with caution in critical patients because of a
prolonged intubation time and subsequent possible
higher incidence of severe life-threatening complications
23, 25, 30
]. Our review shows that incidences of
aspiration, severe low oxygen saturation, and in-hospital
deaths did not differ between VLs and DLs. However,
these results remain unreliable owing to the limited
number of participants included. Our review shows a
lower rate of esophageal intubation using VLs than that
in another study [
]. This might be somewhat
meaningful because “even a single episode of recognized
esophageal intubation is associated with desaturation, increased
risk of aspiration, and cardiac arrest” [
]. Moreover, an
important and promising finding in one of our
included studies and another observational study is that
the use of a VL has a higher first-attempt success rate
with fewer chest compression interruptions in the
emergency department [
Our study included only RCTs and quasi-RCTs.
Although blinding was not adopted in most studies, we
judged “no blinding” as low risk because it seems
impossible to blind personnel in urgent situations at times. In
the prehospital setting, moreover, there is never time for
allocation concealment, and even randomization using a
common method such as a random number table is
impractical. Risk assessment of bias for the included
studies showed that 7 of 12 studies could be classified as
low-risk studies. Therefore, in general, this supports the
quality of our study. The funnel plot, with its visually
symmetrical distribution, qualitatively indicates a low
risk of publication bias. Given that the quality of most
evidence was low or moderate owing to a moderate or
high level of heterogeneity, subgroup analysis and
sensitivity analysis based on some potential clinical
heterogeneous factors also were performed in our review.
There are some limitations of our review. First,
although subgroup analyses were performed, there were
still other clinical heterogeneities in subgroups, such as
patients having different conditions, use of various
intubation strategies, and use of any adjacent tool or
maneuver. Whether patients with predicted difficult airways
were enrolled was another important heterogeneous
factor. However, for emergency or critical care patients, the
traditional predictors of difficult airways, such as
thyromental distance, Mallampati score, or neck mobility,
cannot be recorded, because all intubations are
performed so urgently that there is never a chance to
make predictions or subsequent grouping before
randomization. One observational study showed that
VLs significantly increased the intubation success rate in
emergency patients with difficult airways [
]. In the
absence of a difficult airway, however, the use of VLs may
even bring some disadvantages [
anesthetics were used and the choice of medication can also
introduce heterogeneity. RSI with sedatives, narcotics,
and NMBAs has been shown to facilitate TI and
decrease intubation-related complications in reasonable
]. Because most of the studies included
in our review did not have strict protocols regarding
medication, subgroup analysis according to medications seemed
impossible. Anyway, the study by Silverberg et al. 
demonstrated a much higher first-attempt success rate using
VLs. Sensitivity analysis excluding this study did not alter the
results, but the heterogeneities within the subgroups
disappeared, indicating that this study may be the main factor
leading to heterogeneity. The effect of the NMBAs on the
result was unclear. It may be the negative influence of
alternating of devices that use different configurations on the
learning curve of operators with the DLs that led to a lower
success rate with DLs. Second, owing to ethical
considerations, some patients had to be excluded on enrollment,
such as patients with low oxygen saturation [
], those with
an immobilized cervical spine, and patients with predicted
difficult airways, or those excluded owing to attending
physicians’ discretion and unavailability of devices at the time of
eligible patient arrival [
]. It is unclear whether these
excluded patients would benefit from one of the interventions.
Third, the classification of the operators’ qualifications and
the definition of intubation time or overall success rate used
in our analysis were based on previous papers or our own
judgment, and this might somehow be arbitrary.
This review does not reveal any improvements in
intubation outcomes with the use of VLs compared with DLs
in emergency and critical care patients, except for a
lower rate of esophageal intubation with VLs. In the
prehospital setting, intubation outcomes may be worsened
by the VL when intubation is performed by experienced
operators. Further studies are still needed to determine
whether the VL is beneficial for emergency and critical
care patients with difficult airways, regardless of the
operator’s experience, and should be focused more on the
impact of VLs on prognostic outcomes such as severe
complications, length of hospital stay, and mortality.
Additional file 1: The PubMed search strategy. (DOC 23 kb)
Additional file 2: Table S1. Definitions of some outcomes. (DOC 28 kb)
Additional file 3: Table S2. Description of the risk of bias for 12
included studies. (DOC 88 kb)
Additional file 4: Figure S1. Funnel plot of comparison for the primary
outcome: first-attempt success rate. (DOC 32 kb)
Additional file 5: Table S3. GRADE evidence profile of all outcomes.
(DOC 94 kb)
Additional file 6: Figure S2. VL vs. DL for first-attempt success rate.
Abbreviations: VL Video laryngoscope, DL Direct laryngoscope. (DOC 35 kb)
Additional file 7: Figures S3, S4, S5, and S6 VL vs. DL for overall
success rate. Abbreviations: VL Video laryngoscope, DL Direct
laryngoscope. (DOC 97 kb)
C&L: Cormack and Lehane; CENTRAL: Cochrane Central Register of Controlled
Trials; CPR: Cardiopulmonary resuscitation; DL: Direct laryngoscopy;
ED: Emergency department; EMS: Emergency medical service;
GRADE: Grading of Recommendations Assessment, Development and
Evaluation; ICU: Intensive care unit; IV: Inverse variation; M-H:
MantelHaenszel; NMBA: Neuromuscular blockade; PRISMA: Preferred Reporting
Items for Systematic Review and Meta-Analysis; RCT: Randomized controlled
trial; RR: Relative risk; RSI: Rapid sequence induction; SpO2: Oxygen saturation
by pulse oximetry; TI: Tracheal intubation; VL: Video laryngoscopy;
WMD: Weighted mean difference
The authors acknowledge the Cochrane Collaboration for guidance on
implementing this review. The authors acknowledge Professor J. Salkes,
Professor M. Silverberg, Professor E. Goksu, Professor H. Trimmel, and
Professor D. E. Griesdale for providing additional information.
There was no special funding support provided for this work.
Availability of data and materials
JJ and FX had full access to all the data in the study and take responsibility
for the integrity of the data and the accuracy of the data analysis.
JJ and DM significantly contributed to the design and implementation of the
study, as well as analysis and interpretation, and they drafted the manuscript.
BL participated substantially in data acquisition and interpretation. YY
contributed considerably to the conception and design of the study,
supervised implementation of the study, performed data analysis and
interpretation, and wrote and critically revised the manuscript. FX
significantly contributed to the conception of the study, performed data
analysis and interpretation, and critically revised the manuscript. All authors
saw the original study data, reviewed the analysis of the data, and read and
approved the final manuscript.
Ethics approval and consent to participate
Consent for publication
All authors declare (1) receiving no support from any organization for the
submitted work, (2) having no financial relationships with any organizations
that might have an interest in the submitted work in the previous 3 years,
and (3) having no other relationships or activities that could appear to have
influenced the submitted work.
Springer Nature remains neutral regarding jurisdictional claims in published
maps and institutional affiliations
Submit your next manuscript to BioMed Central
and we will help you at every step:
1. Agro F , Barzoi G , Montecchia F . Tracheal intubation using a Macintosh laryngoscope or a GlideScope in 15 patients with cervical spine immobilization . Br J Anaesth . 2003 ; 90 : 705 - 6 .
2. Jaber S , Amraoui J , Lefrant JY , Arich C , Cohendy R , Landreau L , Calvet Y , Capdevila X , Mahamat A , Eledjam JJ. Clinical practice and risk factors for immediate complications of endotracheal intubation in the intensive care unit: a prospective, multiple-center study . Crit Care Med . 2006 ; 34 : 2355 - 61 .
3. Healy DW , Maties O , Hovord D , Kheterpal S. A systematic review of the role of videolaryngoscopy in successful orotracheal intubation . BMC Anesthesiol . 2012 ; 12 : 32 .
4. Kory P , Guevarra K , Mathew JP , Hegde A , Mayo PH . The impact of video laryngoscopy use during urgent endotracheal intubation in the critically ill . Anesth Analg . 2013 ; 117 : 144 - 9 .
5. Lakticova V , Koenig SJ , Narasimhan M , Mayo PH . Video laryngoscopy is associated with increased first pass success and decreased rate of esophageal intubations during urgent endotracheal intubation in a medical intensive care unit when compared to direct laryngoscopy . J Intensive Care Med . 2015 ; 30 : 44 - 8 .
6. Cook TM , Woodall N , Harper J , Benger J . 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 2: intensive care and emergency departments . Br J Anaesth . 2011 ; 106 : 632 - 42 .
7. De Jong A , Molinari N , Terzi N , Mongardon N , Arnal JM , Guitton C , Allaouchiche B , Paugam-Burtz C , Constantin JM , Lefrant JY , Leone M , Papazian L , Asehnoune K , Maziers N , Azoulay E , Pradel G , Jung B , Jaber S . Early identification of patients at risk for difficult intubation in the intensive care unit: development and validation of the MACOCHA score in a multicenter cohort study . Am J Respir Crit Care Med . 2013 ; 187 : 832 - 9 .
8. Frerk C , Mitchell VS , McNarry AF , Mendonca C , Bhagrath R , Patel A , O'Sullivan EP , Woodall NM , Ahmad I. Difficult Airway Society 2015 guidelines for management of unanticipated difficult intubation in adults . Br J Anaesth . 2015 ; 115 : 827 - 48 .
9. Griesdale DE , Bosma TL , Kurth T , Isac G , Chittock DR . Complications of endotracheal intubation in the critically ill . Intensive Care Med . 2008 ; 34 : 1835 - 42 .
10. Martin LD , Mhyre JM , Shanks AM , Tremper KK , Kheterpal S. 3 , 423 emergency tracheal intubations at a university hospital: airway outcomes and complications . Anesthesiology . 2011 ; 114 : 42 - 8 .
11. Schwartz DE , Matthay MA , Cohen NH . Death and other complications of emergency airway management in critically ill adults: a prospective investigation of 297 tracheal intubations . Anesthesiology . 1995 ; 82 : 367 - 76 .
12. Nouruzi-Sedeh P , Schumann M , Groeben H . Laryngoscopy via Macintosh blade versus GlideScope: success rate and time for endotracheal intubation in untrained medical personnel . Anesthesiology . 2009 ; 110 : 32 - 7 .
13. Parasa M , Yallapragada SV , Vemuri NN , Shaik MS . Comparison of GlideScope video laryngoscope with Macintosh laryngoscope in adult patients undergoing elective surgical procedures . Anesth Essays Res . 2016 ; 10 : 245 - 9 .
14. Sun Y , Lu Y , Huang Y , Jiang H . Pediatric video laryngoscope versus direct laryngoscope: a meta-analysis of randomized controlled trials . Paediatr Anaesth . 2014 ; 24 : 1056 - 65 .
15. Aziz MF , Dillman D , Fu R , Brambrink AM . Comparative effectiveness of the C-MAC video laryngoscope versus direct laryngoscopy in the setting of the predicted difficult airway . Anesthesiology . 2012 ; 116 : 629 - 36 .
16. Griesdale DEG , Liu D , McKinney J , Choi PT . GlideScope® video-laryngoscopy versus direct laryngoscopy for endotracheal intubation: a systematic review and meta-analysis . Can J Anaesth . 2012 ; 59 : 41 - 52 .
17. Kelly FE , Cook TM . Seeing is believing: getting the best out of videolaryngoscopy . Br J Anaesth . 2016 ; 117 Suppl 1 : i9 - 13 .
18. Niforopoulou P , Pantazopoulos I , Demestiha T , Koudouna E , Xanthos T . Video-laryngoscopes in the adult airway management: a topical review of the literature . Acta Anaesthesiol Scand . 2010 ; 54 : 1050 - 61 .
19. Zaouter C , Calderon J , Hemmerling TM . Videolaryngoscopy as a new standard of care . Br J Anaesth . 2015 ; 114 : 181 - 3 .
20. Mosier JM , Whitmore SP , Bloom JW , Snyder LS , Graham LA , Carr GE , Sakles JC . Video laryngoscopy improves intubation success and reduces esophageal intubations compared to direct laryngoscopy in the medical intensive care unit . Crit Care . 2013 ; 17 : R237 .
21. Noppens RR , Geimer S , Eisel N , David M , Piepho T. Endotracheal intubation using the C-MAC® video laryngoscope or the Macintosh laryngoscope: a prospective, comparative study in the ICU . Crit Care . 2012 ; 16 : R103 .
22. De Jong A , Molinari N , Conseil M , Coisel Y , Pouzeratte Y , Belafia F , Jung B , Chanques G , Jaber S. Video laryngoscopy versus direct laryngoscopy for orotracheal intubation in the intensive care unit: a systematic review and meta-analysis . Intensive Care Med . 2014 ; 40 : 629 - 39 .
23. Griesdale DE , Chau A , Isac G , Ayas N , Foster D , Irwin C , Choi P. Videolaryngoscopy versus direct laryngoscopy in critically ill patients: a pilot randomized trial . Can J Anaesth . 2012 ; 59 : 1032 - 9 .
24. Silverberg MJ , Li N , Acquah SO , Kory PD . Comparison of video laryngoscopy versus direct laryngoscopy during urgent endotracheal intubation: a randomized controlled trial . Crit Care Med . 2015 ; 43 : 636 - 41 .
25. Yeatts DJ , Dutton RP , Hu PF , Chang YW , Brown CH , Chen H , Grissom TE , Kufera JA , Scalea TM . Effect of video laryngoscopy on trauma patient survival: a randomized controlled trial . J Trauma Acute Care Surg . 2013 ; 75 : 212 - 9 .
26. Arima T , Nagata O , Miura T , Ikeda K , Mizushima T , Takahashi A , Sakaida K . Comparative analysis of airway scope and Macintosh laryngoscope for intubation primarily for cardiac arrest in prehospital setting . Am J Emerg Med . 2014 ; 32 : 40 - 3 .
27. Goksu E , Kilic T , Yildiz G , Unal A , Kartal M. Comparison of the C-MAC video laryngoscope to the Macintosh laryngoscope for intubation of blunt trauma patients in the ED . Turk J Emerg Med . 2016 ; 16 : 53 - 6 .
28. Janz DR , Semler MW , Lentz RJ , Matthews DT , Assad TR , Norman BC , Keriwala RD , Ferrell BA , Noto MJ , Shaver CM , Richmond BW , Zinggeler Berg J , Rice TW . Randomized trial of video laryngoscopy for endotracheal intubation of critically ill adults . Crit Care Med . 2016 ; 44 : 1980 - 7 .
29. Kim JW , Park SO , Lee KR , Hong DY , Baek KJ , Lee YH , Lee JH , Choi PC . Video laryngoscopy vs. direct laryngoscopy: which should be chosen for endotracheal intubation during cardiopulmonary resuscitation? A prospective randomized controlled study of experienced intubators . Resuscitation . 2016 ; 105 : 196 - 202 .
30. Lascarrou JB , Boisrame-Helms J , Bailly A , Le Thuaut A , Kamel T , Mercier E , Ricard JD , Lemiale V , Colin G , Mira JP , Meziani F , Messika J , Dequin PF , Boulain T , Azoulay E , Champigneulle B , Reignier J . Video laryngoscopy vs direct laryngoscopy on successful first-pass orotracheal intubation among ICU patients: a randomized clinical trial . JAMA . 2017 ; 317 : 483 - 93 .
31. Sulser S , Ubmann D , Schlaepfer M , Brueesch M , Goliasch G , Seifert B , Spahn DR , Ruetzler K. C-MAC videolaryngoscope compared with direct laryngoscopy for rapid sequence intubation in an emergency department: a randomised clinical trial . Eur J Anaesthesiol . 2016 ; 33 : 943 - 8 .
32. Trimmel H , Kreutziger J , Fitzka R , Szuts S , Derdak C , Koch E , Erwied B , Voelckel WG . Use of the GlideScope Ranger video laryngoscope for emergency intubation in the prehospital setting: a randomized control trial . Crit Care Med . 2016 ; 44 : e470 - 6 .
33. Shamseer L , Moher D , Clarke M , Ghersi D , Liberati A , Petticrew M , Shekelle P , Stewart LA . Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) 2015 : elaboration and explanation . BMJ . 2015 ; 349 : g7647 .
34. Higgins JPT , Green S , editors. Cochrane handbook for systematic reviews of interventions. Version 5.1 [updated March 2011 ]. The Cochrane Collaboration . http://handbook-5 -1 .cochrane.org/. Accessed 15 Jun 2015 .
35. Guyatt G , Oxman AD , Akl EA , Kunz R , Vist G , Brozek J , Norris S , Falck-Ytter Y , Glasziou P , DeBeer H , Jaeschke R , Rind D , Meerpohl J , Dahm P , Schunemann HJ . GRADE guidelines: 1. Introduction-GRADE evidence profiles and summary of findings tables . J Clin Epidemiol . 2011 ; 64 : 383 - 94 .
36. Guyatt GH , Oxman AD , Kunz R , Vist GE , Falck-Ytter Y , Schunemann HJ . What is “quality of evidence” and why is it important to clinicians? BMJ. 2008 ; 336 : 995 - 8 .
37. Egger M , Davey Smith G , Schneider M , Minder C. Bias in meta-analysis detected by a simple, graphical test . BMJ . 1997 ; 315 : 629 - 34 .
38. Silverberg M , Li N , Kory P . Efficacy of video laryngoscopy vs. direct laryngoscopy during urgent endotracheal intubation: a randomized controlled trial [abstract] . Chest . 2013 ; 144 ( 4 Suppl) : 580A .
39. Sakles J , Mosier J , Cosentino M , Kalin L . The CMAC videolaryngoscope for difficult airway management in the emergency department [abstract 433] . Acad Emerg Med . 2012 ; 19 ( 4 Suppl 1 ): S232 .
40. Miner JR , Moore J , Rischall M , Beste R , Maddy N , Joing S , McGill JW , Biros MH , Reardon RF . Randomized controlled trial of endotracheal intubation using the C-MAC videolaryngoscope versus standard laryngoscopy in patients undergoing emergent endotracheal intubation in the emergency department [abstract 428] . Acad Emerg Med . 2012 ; 19 ( 4 Suppl 1 ): S229 .
41. Trimmel H , Kreutziger J , Fertsak G , Fitzka R , Dittrich M , Voelckel WG . Use of the Airtraq laryngoscope for emergency intubation in the prehospital setting: a randomized control trial . Crit Care Med . 2011 ; 39 : 489 - 93 .
42. Driver BE , Prekker ME , Moore JC , Schick AL , Reardon RF , Miner JR . Direct versus video laryngoscopy using the C-MAC for tracheal intubation in the emergency department, a randomized controlled trial . Acad Emerg Med . 2016 ; 23 : 433 - 9 .
43. Bowles TM , Freshwater-Turner DA , Janssen DJ , Peden CJ . Out-of-theatre tracheal intubation: prospective multicentre study of clinical practice and adverse events . Br J Anaesth . 2011 ; 107 : 687 - 92 .
44. Simpson GD , Ross MJ , McKeown DW , Ray DC . Tracheal intubation in the critically ill: a multi-centre national study of practice and complications . Br J Anaesth . 2012 ; 108 : 792 - 9 .
45. Natt BS , Malo J , Hypes CD , Sakles JC , Mosier JM . Strategies to improve first attempt success at intubation in critically ill patients . Br J Anaesth . 2016 ; 117 Suppl 1 : i60 - 8 .
46. Agro FE , Doyle DJ , Vennari M . Use of GlideScope® in adults: an overview . Minerva Anestesiol . 2015 ; 81 : 342 - 51 .
47. Jungbauer A , Schumann M , Brunkhorst V , Borgers A , Groeben H . Expected difficult tracheal intubation: a prospective comparison of direct laryngoscopy and video laryngoscopy in 200 patients . Br J Anaesth . 2009 ; 102 : 546 - 50 .
48. Komasawa N , Ueki R , Nomura H , Itani M , Kaminoh Y. Comparison of tracheal intubation by the Macintosh laryngoscope and Pentax-AWS (Airway Scope) during chest compression: a manikin study . J Anesth . 2010 ; 24 : 306 - 8 .
49. Malik MA , Subramaniam R , Churasia S , Maharaj CH , Harte BH , Laffey JG . Tracheal intubation in patients with cervical spine immobilization: a comparison of the Airwayscope, LMA CTrach, and the Macintosh laryngoscopes . Br J Anaesth . 2009 ; 102 : 654 - 61 .
50. Malik MA , Subramaniam R , Maharaj CH , Harte BH , Laffey JG . Randomized controlled trial of the Pentax AWS, GlideScope, and Macintosh laryngoscopes in predicted difficult intubation . Br J Anaesth . 2009 ; 103 : 761 - 8 .
51. Marrel J , Blanc C , Frascarolo P , Magnusson L . Videolaryngoscopy improves intubation condition in morbidly obese patients . Eur J Anaesthesiol . 2007 ; 24 : 1045 - 9 .
52. Paolini JB , Donati F , Drolet P . Review article: video-laryngoscopy: another tool for difficult intubation or a new paradigm in airway management? Can J Anaesth . 2013 ; 60 : 184 - 91 .
53. Timmermann A , Eich C , Russo SG , Natge U , Brauer A , Rosenblatt WH , Braun U . Prehospital airway management: a prospective evaluation of anaesthesia trained emergency physicians . Resuscitation . 2006 ; 70 : 179 - 85 .
54. Platts-Mills TF , Campagne D , Chinnock B , Snowden B , Glickman LT , Hendey GW . A comparison of GlideScope video laryngoscopy versus direct laryngoscopy intubation in the emergency department . Acad Emerg Med . 2009 ; 16 : 866 - 71 .
55. Wang HE , Simeone SJ , Weaver MD , Callaway CW . Interruptions in cardiopulmonary resuscitation from paramedic endotracheal intubation . Ann Emerg Med . 2009 ; 54 : 645 - 52 .
56. Davis DP , Dunford JV , Poste JC , Ochs M , Holbrook T , Fortlage D , Size MJ , Kennedy F , Hoyt DB . The impact of hypoxia and hyperventilation on outcome after paramedic rapid sequence intubation of severely headinjured patients . J Trauma . 2004 ; 57 : 1 - 10 .
57. Kleine-Brueggeney M , Buttenberg M , Greif R , Nabecker S , Theiler L . Evaluation of three unchannelled videolaryngoscopes and the Macintosh laryngoscope in patients with a simulated difficult airway: a randomised, controlled trial . Anaesthesia . 2017 ; 72 : 370 - 8 .
58. Kleine-Brueggeney M , Greif R , Schoettker P , Savoldelli GL , Nabecker S , Theiler LG . Evaluation of six videolaryngoscopes in 720 patients with a simulated difficult airway: a multicentre randomized controlled trial . Br J Anaesth . 2016 ; 116 : 670 - 9 .
59. Sakles JC , Patanwala AE , Mosier J , Dicken J , Holman N. Comparison of the reusable standard GlideScope® video laryngoscope and the disposable cobalt GlideScope® video laryngoscope for tracheal intubation in an academic emergency department: a retrospective review . Acad Emerg Med . 2014 ; 21 : 408 - 15 .
60. van Zundert A , Pieters B , Doerges V , Gatt S. Videolaryngoscopy allows a better view of the pharynx and larynx than classic laryngoscopy . Br J Anaesth . 2012 ; 109 : 1014 - 5 .
61. Sakles JC , Mosier JM , Patanwala AE , Arcaris B , Dicken JM . The utility of the C-MAC as a direct laryngoscope for intubation in the emergency department . J Emerg Med . 2016 ; 51 : 349 - 57 .
62. Xue FS , Li HX , Liu YY , Yang GZ . Current evidence for the use of C-MAC videolaryngoscope in adult airway management: a review of the literature . Ther Clin Risk Manag . 2017 ; 13 : 831 - 41 .
63. Mort TC . Esophageal intubation with indirect clinical tests during emergency tracheal intubation: a report on patient morbidity . J Clin Anesth . 2005 ; 17 : 255 - 62 .
64. Park SO , Baek KJ , Hong DY , Kim SC , Lee KR . Feasibility of the videolaryngoscope (GlideScope®) for endotracheal intubation during uninterrupted chest compressions in actual advanced life support: a clinical observational study in an urban emergency department . Resuscitation . 2013 ; 84 : 1233 - 7 .
65. Ahmadi K , Ebrahimi M , Hashemian AM , Sarshar S , Rahimi-Movaghar V . GlideScope video laryngoscope for difficult intubation in emergency patients: a quasi-randomized controlled trial . Acta Med Iran . 2015 ; 53 : 738 - 42 .
66. Lossius HM , Roislien J , Lockey DJ . Patient safety in pre-hospital emergency tracheal intubation: a comprehensive meta-analysis of the intubation success rates of EMS providers . Crit Care . 2012 ; 16 : R24 .
67. Wilcox SR , Bittner EA , Elmer J , Seigel TA , Nguyen NT , Dhillon A , Eikermann M , Schmidt U . Neuromuscular blocking agent administration for emergent tracheal intubation is associated with decreased prevalence of procedurerelated complications . Crit Care Med . 2012 ; 40 : 1808 - 13 .