a b s t r a c t

Objectives: Airway management during cardiopulmonary resuscitation is particularly important for patients with out-of-hospital cardiac arrest (OHCA). This study was performed to compare the efficacy of the most commonly used out-of-hospital airway management methods in increasing the survival to discharge in patients with OHCA. Methods: We screened all relevant literature from database inception to 21st January 2019 in PubMed, Web of Science, Embase, and the Cochrane Library. We included all Randomized controlled trials of airway management for OHCA in adults (>=16 years of age) with no limitations on publication status, publication date, or language. The primary outcome was survival to discharge. The secondary outcomes were the overall airway technique success rate, return of spontaneous circulation, and Survival to hospital admission.

Results: Overall, from 1986 to 2018, 9 RCTs involving 13,949 patients were included in the network meta- analysis, and the efficacy of six airway management methods for patients with OHCA were compared. However, none of the results were statistically significant.

Conclusions: As the gold standard of airway management for patients with out-of-hospital cardiac arrest in most countries, Endotracheal intubation has been widely used for many years. However, our systematic review and network meta-analysis showed that ETI is no better than other methods in increasing the survival to dis- charge. This is not directly proportional to the various preparations required before ETI. Additional randomized controlled trials are needed to identify more effective methods and improve patients’ outcome.

(C) 2023

1. Introduction

Cardiac arrest refers to the sudden loss of heart function and has var- ious causes [1]. Although the survival rate of cardiovascular disease has significantly improved during the past 30 years, the survival rate of out-of-hospital cardiac arrest (OHCA) has not shown a substantial in- crease worldwide [2,3]. OHCA has become a major Public health concern because of its high Morbidity and mortality rates. Statistics show that 5 million people worldwide develop OHCA each year, and only 7% of them survive [4,5]. As an important part of the “Chain of survival,” airway management has always been a major focus of research in recent years.

* Corresponding author at: Beijing Emergency Medicine Research Institute, Beijing emergency medical center, Qianmen West Street, No. 103, Xicheng District, Beijing 100031, China.

E-mail address: [email protected] (J. Zhang).

Airway management in OHCA has many methods, including manual maneuvers with bag valve mask ventilation (BM), endotracheal intuba- tion (ETI) and Supraglottic airway [6]. SGA methods commonly include the laryngeal tube (LT), laryngeal mask (LM), i-Gel and esopha- geal tracheal combitube (ETC) [7,8]. ETI has become the gold standard of airway management for patients with OHCA in most countries [9]. However, increasing numbers of studies have shown a high incidence of ETI-related complications (e.g., unrecognized Esophageal intubation, iatrogenic hyperventilation, and Aspiration pneumonia) [10-12]. Addi- tionally, the technical requirements for intubation methods are high, multiple attempts may be required, and chest compressions need to be stopped during the intubation process, resulting in postponement of cardiopulmonary resuscitation (CPR) [13,14]. ETI has become in- creasingly questioned as the first choice for airway management [15]. Thus, SGA during out-of-hospital CPR has been gradually used. SGA has the advantages of safe use, simple and fast operation, a high rate of successful implantation, a Good ventilation effect in various situa- tions, and no influence on chest compression during the implantation

https://doi.org/10.1016/j.ajem.2022.12.029

0735-6757/(C) 2023

process [8,16-18]. However, there are some shortcomings in the early stage of SGA placement, such as laryngeal spasm, air leakage, low lung compliance, invalid chest stiffness, and poor protection against gastric reflux [19-21]. BM is easier to initiate, and has been used many years as the primary airway management, but still has some problems too (e.g., regurgitation of gastric contents, aspiration, intragastric perfusion of oxygen) [22,23]. Based on the currently available evidence, the optimal airway management methods during OHCA is still debated. However, evidence derived from randomized trials is limited to few and small-scale studies. Previous reviews and meta-analyses have fo- cused only on pairwise comparison of various airway managements, and the most of clinical studies were observational studies [19,24].

Therefore, in this present systematic review and network meta- analysis of all completed randomized trials, we compared the outcomes of different airway management measures for patients with OHCA to provide a basis for clinical practice.

1. Methods
   1. Literature search strategy and selection criteria

This systematic review and network meta-analysis adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [25]. According to the previously developed retrieval strategy and inclusion criteria, two independent reviewers (L.J. and J.J.Z.) screened all relevant articles from database inception to 21st January 2019 in PubMed, Web of Science, Embase, and the Cochrane Library databases. The screening included but was not limited to the following search terms: “out of hospital” or “prehospital” and “airway” or “airway management” or “supraglottic airway” or “endotra- cheal intubation” or “cardiac arrest” (see appendix for specific search strategy).

Because each database uses different subject headings, the search strategy was modified for each database to include specific terms; each term was independently searched and cross-searched to avoid omitting any relevant articles. All RCTs of airway management for OHCA in adults (>=16 years of age) were included, with no limitations regarding the publication status, publication date, or language. Animal studies, manikin studies, case reports, reviews, trial protocols, abstracts, comments, and letters to the editor were excluded. We excluded publi- cations that did not specify the airway management methods or in which airway management data were unavailable as well as studies in- volving known pregnant women or known prisoners. We also hand- searched the reference lists of relevant articles and reviews and checked the US National Library of Medicine regulatory website (www. clinicaltrials.gov) to identify any unpublished trials.

Two investigators (L.J. and J.J.Z.) independently screened the titles and abstracts of all articles identified in the initial search and excluded articles that did not meet the inclusion criteria. A third investigator (S.J.T.) reviewed the titles and abstracts of all excluded articles to ensure the best capture of relevant articles. If the investigators had different opinions, the full text of the paper was retrieved; the differences were then reconsidered and discussed until a consensus was reached. If the differences could not be reconciled, a fourth investigator (X.Q.K.) was consulted.

• 1. Outcomes

We studied OHCA results according to the Utstein criteria. The pri- mary outcome was survival to discharge. The secondary outcomes were the overall airway technique success rate (efficient ventilation or

<=2 attempts airway management), return of spontaneous circulation

(ROSC), and survival to hospitalization.

• 1. Data extraction and quality assessment

Another two investigators (H.X.L. and X.Q.K.) extracted all data from the included articles according to previously developed criteria. The extracted data included the publication time of each article, experimen- tal location, study type, practitioner types, sample size, age, sex, etiology of cardiac arrest, witnessed arrest, bystander CPR, initial rhythm, adverse effects, primary and secondary outcomes, and relevant results. All differences were reconsidered and discussed until a consensus was reached. If the differences could not be reconciled, a third investigator (J.J.Z.) was consulted. If data or other research information was lacking, the corresponding authors of the individual studies were contacted (appendix tables 1-4).

Two reviewers (L.J. and J.J.Z.) independently assessed the risk of bias for each RCTs according to the Cochrane Handbook Systematic Reviews of Interventions. The risk of Bias assessment involved evaluation of selection bias (allocation concealment and random sequence genera- tion), performance bias (blinding of personnel and participants), detec- tion bias (blinding of outcome assessment), attrition bias (incomplete outcome data), reporting bias (selective reporting), and other types of bias. Each RCTs was classified as having unclear risk, low risk, or high risk. If the risk of bias was unknown, the RCTs was classified as having unclear risk. Any disagreements were resolved by a senior reviewer (X.Q.K.).

• 1. Statistical analysis

The outcomes analyzed in this review were the overall airway technique success rate (Efficient ventilation or <= 2 attempts airway management), ROSC, survival to hospital admission, and survival to hospital discharge. The main outcome was survival to hospital discharge. For patients who underwent two or more emergency treat- ment methods, the odds ratio (OR) was calculated with the adjusted data. When the adjusted data were not given in the paper, the OR was calculated according to the data given in the paper.

For indirect and mixed comparisons, we performed a random- effects network meta-analysis within a Bayesian hierarchical framework using R version 3.3.2 [26]. Model selection was performed using a trace plot and the deviance information criterion. The trace plot was used to diagnose convergence of the model by observing the Markov chain Monte Carlo (MCMC). A stable fused MCMC has the best convergence effect. After many experiments, the number of itera- tions for adaptation in the MCMC algorithm was 50,000, and the total number of iterations in each MCMC was 150,000. The model with the best fit was chosen as the primary analysis model. We estimated the relative ranking probability of each treatment and obtained the treatment hierarchy of competing interventions using rankograms. To determine the presence of inconsistency between direct and indirect comparisons, we compared the OR from the network meta-analysis with the corresponding OR from the traditional pairwise random- effects meta-analysis of direct comparisons. This study is registered with the International Prospective Register of Systematic Reviews (number CRD42019122451).

1. Results

In total, 7827 studies were identified by the initial searches of all databases, and 6735 studies remained after eliminating duplicates. After reviewing the research titles and abstracts, we identified 69 studies for full-text analysis. After excluding 20 studies for which data were not available, 38 studies with no airway management data, 1 study without primary outcome and 1 study in which the subjects were < 16 years old, 9 studies were finally included in the network meta-analysis (Fig. 1) [7,8,16-18,27-30]. Overall, from 1986 to 2018, 9 RCTs involving 13,949 patients, 63.7% (8869/13928) of whom were male, were included in the network meta-analysis and compared the

Fig. 1. Study selection flowchart.

efficacy of 6 airway management methods for patients with OHCA. Among them, one study compared LT with ETI [7], one study compared BM with ETI [27], one study compared i-gel with ETI [8], one study compared LM with LT [16], one study compared i-gel with LM and ETI [29], two studies compared BM with LT [17,28], and two studies compared ETI with ETC [18,30]. Six studies were conducted in Europe [8,17,18,27-29], two in the Americas [7,30], and one in Asia [16]. Practitioners of airway management included emergency medical tech- nicians, paramedics, and physicians. A total of 99.0% (13,408/13,549) of patients had OHCA from nonTraumatic causes, 73.0% (1991/2726) of pa- tients had OHCA from cardiac causes, 0.9% (131/13,549) of patients had OHCA from traumatic causes, and 10 patients had OHCA from unknown causes. The total rate of witnessed arrest for all included patients was 61.8% (8242/13,340), that of witnessed arrest by a bystander was 51.4% (6303/12,268), and that of witnessed arrest by emergency medical services personnel was 12.6% (1543/12,268). Arrest occurred at home in 77.0% (2097/2724) of patients. A bystander performed CPR in 58.1% (7721/13,292) of cases, and 10.9% (34/313) of bystanders administered shock by an Automated external defibrillator for patients with OHCA. Initial rhythm was achieved in 21.0% (2776/ 13,189) of patients with ventricular fibrillation, ventricular tachycardia, or delivery of an AED shock and in 78.7% (10,376/13,189) of patients with asystole, pulseless electrical activity, or an AED non-shockable

rhythm. A total of 95.7% (4777/4994) of patients with OHCA had used adrenaline before arriving at the hospital (appendix table 1-2). In terms of adverse events, the rate of difficult airway management (intubation difficulty Scale score >5 or >= 3 attempts airway manage- ment and BM difficulty was defined by Han scale score >2) using BM, LT, ETC, and ETI was 18.1% (186/1027), 4.5% (61/1353), 15.7% (14/89),

and 16.1% (382/2378), respectively. The rate of unsuccessful insertion at the first attempt using the LT, i-gel, LM, and ETI was 10.8% (162/ 1498), 20.8% (47/226), 24.7% (42/170), and 42.4% (634/1494), respec-

tively. The rate of regurgitation of gastric contents when using the BM, LT, i-gel, LM, and ETI was 15.1% (168/1109), 15.5% (11/71), 0.0%

(0/226), 1.7% (3/174), and 6.9% (75/1082), respectively. The rate of air- way misplacement or dislodgement when using the LT, i-gel, ETC, and ETI was 0.7% (10/1353), 10.7% (473/4436), 0.0% (0/174), and 4.8%

(252/5232), respectively. The Inadequate ventilation rate of the LT, i-gel, LM, and ETI was 1.8% (25/1353), 16.8% (38/226), 21.2% (36/170),

and 0.5% (8/1566), respectively. The oropharyngeal or hypopharyngeal injury rate of the BM, LT, i-gel, LM, ETC, and ETI was 0.1% (1/1068), 0.4% (2/495), 0.0% (0/226), 1.7% (3/174), 0.0% (0/89), and 0.5% (8/1749),

respectively (appendix table 4).

Fig. 2 summarizes the risk of bias judgments. The method of randomization was described in all included articles; however, two arti- cles did not mention the method of allocation concealment [17,18].

Fig. 2. Risk of bias.

Blinding of the participants to the airway management methods for OHCA was impossible because they would certainly know what airway management method was being performed during the resuscitation actions. One article showed that the research coordinators who ascertained the clinical outcomes were not blinded to the study inter- vention [7], and four articles did not mention whether blinding of the outcome assessment was performed [16,18,28,30]. Whether other biases were present in two articles could not be determined because

of incomplete information [18,30]. Most studies had a low risk of bias for most criteria.

Fig. 3 shows the evidence network that included all direct compari- sons. The size of the circular node represents the number of studies assessed for each treatment, and the thickness of the black edge is weighted by the inverse variance of each direct comparison.

In this network meta-analysis, all interventions were connected by at least one common therapy, allowing each intervention to be directly

Fig. 3. Network of available treatment comparisons for any type of cardiopulmonary re- suscitation strategy.

BM = bag valve mask, ETC = esophageal tracheal combitube, ETI = endotracheal intuba- tion, LM = laryngeal mask, LT = laryngeal tube.

compared with any other intervention through the primary circuit (Fig. 3).

Use of the LM performed best in terms of survival to hospital discharge, and the OR was 2.70 (95% credible interval [CI] 0.19-34.40),

1.01 (0.07-13.20), 1.72 (0.17-18.20), 1.16 (0.10-14.30), 1.55

(0.13-19.90) compared with BM, ETC, ETI, i-Gel and LT. The least effective method was the BM, and the OR was 0.37 (95% Cl 0.05-3.09),

0.65 (0.12-3.57), 0.45 (0.06-3.34), 0.37 (0.03-5.19), 0.58 (0.08-4.63)

compared with ETC, ETI, i-Gel, LM and LT (Table 1).

ETI was the most effective in terms of overall airway technique suc- cess rate, with the OR was 1.38 (95% Cl 0.18-9.10), 1.50 (0.20-9.42),

1.65 (0.05-17.40), 2.45 (0.19-21.80), 1.88 (0.38-6.70) compared with

BM, ETC, LM, i-Gel and LT; the least effective was the LM, with the OR was 0.59 (95% Cl 0.05-7.86), 0.63 (0.05-8.11), 0.41 (0.05-5.0.24), 0.72

(0.01-12.80), 0.79 (0.08-7.04) compared with BM, ETC, ETI, i-Gel and LT. The i-Gel method was the most effective in terms of ROSC, with the OR was 1.33 (95% Cl 0.29-5.79), 2.62 (0.23-37.20), 1.24

(0.31-5.19), 1.19 (0.23-6.92), 1.41 (0.32-5.60) compared with BM,

ETC, ETI, LM and LT; ETC was the least effective, with the OR were

0.51 (95% Cl 0.04-5.28), 0.49 (0.0.04-4.05), 0.38 (0.03-4.42), 0.46

(0.03-4.95), 0.53 (0.05-5.01) compared with BM, ETI, i-Gel, LM and LT. However, ETC was the most effective in terms of survival to hospital admission, with the OR was 1.63 (95% Cl 0.27-10.00), 1.31 (0.32-6.10),

1.53 (0.17-15.20), 1.93 (0.18-23.60), 1.80 (0.28-11.80) compared with

BM, ETI, i-Gel, LM and LT; the least effective was the LM, with the OR was 0.83 (95% Cl 0.07-9.66), 0.52 (0.04-5.63), 0.70 (0.07-6.49), 0.78

(0.05-14.00), 0.92 (0.08-11.90) compared with BM, ETI, ETC, i-Gel

and LT. However, based on assessment of the 95% CI, none of the results were statistically significant (Tables 2-4).

The airway management methods were ranked from best to worst

according to their effect of survival to hospital discharge: ETC = LM > i-gel > ETI > LT > BM. Their ranking in terms of overall airway tech- nique success rate was BM > ETI > ETC > LT > LM = i-gel. Their ranking

in terms of ROSC was i-gel = LM > ETI > BM > LT > ETC. Finally, their ranking in terms of survival to hospital admission was ETC > ETI > BM > LT > i-gel = LM (Fig. 4).

1. Discussion

In this systematic review and network meta-analysis, direct and indirect evidence from 9 RCTs involving 13,949 patients was combined to compare the effectiveness of 6 airway management methods during resuscitation of OHCA. However, no airway management methods for patients with OHCA was statistically more effective than the other methods in terms of survival to hospital discharge, overall airway tech- nique success rate, ROSC, and survival to hospital admission. Although a recent meta analysis showed that ETI demonstrated better in ROSC (OR = 1.44; 95% CI = 1.27 to 1.63; I² = 91%; p < 0.00001) and Survival to admission (OR = 1.36; 95% CI = 1.12 to 1.66; I² = 91%; p = 0.002)

than SGA devices. However, the sensitivity analyses of RCTs is same as our experimental results, which showed that no difference between ETI and SGA in regard to ROSC (OR = 0.90; 95% CI = 0.65 to 1.25; I² = 12%; p = 0.59), survival to admission (OR = 1.00; 95% CI = 0.68 to 1.47; I² = 0%; p = 0.99), and survival to discharge (OR = 0.90; 95% CI = 0.68 to 1.20; I² = 70%; p = 0.49) [24]. But, the meta-

analysis did not differentiate all the included SGA methods, which may affect the overall results. Therefore, our experiments grouped the SGA method to get more accurate results. However, the results are con- sistent, which may indicate that different SGA methods have no effect on the experimental results.In addition, most of the articles included in this study were retrospective studies and observational studies, and the quality of all the articles included was low (Serial = 16, Low = 5, Moderate = 8), and the research results were vulnerable to various con- founding factors. The inducement of cardiac arrest outside the hospital is an extremely complex process, which may be caused by various rea- sons. Therefore, in the early stage of the study, inclusion and exclusion should be strictly screened according to the research focus to avoid the impact of various confounding factors, so as to reduce the impact on the research results. Age and the cause of cardiac arrest are currently recognized factors to be considered. For example, the causes of trau- matic cardiac arrest and nonTraumatic cardiac arrest are fundamentally different. Therefore, these two types of cardiac arrest should not be clas- sified into the same category. Because of the limitations of the prehospi- tal rescue environment, patients with cardiac arrest outside the hospital should also be distinguished from patients with cardiac arrest in the hospital. In order to avoid the impact of the above reasons on the results of this study, all data were strictly screened during the inclusion and ex- clusion phase to improve the accuracy of the data.

In terms of adverse events, The BM showed poor results for the

difficult airway management rate in the present study (18.1%). As a relatively direct operation with fewer complications, almost every out-of-hospital emergency unit routinely carries a BM. However, this does not mean that operation of the BM is simple. Two medical person- nel operating simultaneously may be required to ensure patient ventila- tion. A recent study has shown that different manipulations also have an effect on ventilation [31]. Higher regurgitation of gastric contents rate (15.1%) also support to previous experimental results [32].

Table 1

Odds ratios of survival to hospital discharge of all six airway management methods.

BM
0.37 (0.05, 3.09)	ETC
0.65 (0.12, 3.57)	1.72 (0.32, 9.89)	ETI
0.45 (0.06, 3.34)	1.17 (0.15, 10.00)	0.68 (0.14, 3.47)	i-gel
0.37 (0.03, 5.19)	0.99 (0.08, 14.50)	0.58 (0.06, 5.88)	0.86 (0.07, 9.83)	LM
0.58 (0.10, 3.10)	1.56 (0.21, 12.70)	0.91 (0.19, 4.39)	1.33 (0.18, 10.20)	1.55 (0.13, 19.90)	LT

Table 2

Odds ratios of overall airway technique success rate of all six airway management methods.

BM
1.09 (0.10, 11.10)	ETC
0.72 (0.11, 5.45)	0.67 (0.11, 4.97)	ETI
1.25 (0.02, 19.40)	1.17 (0.02, 16.70)	1.65 (0.05, 17.40)	i-gel
1.70 (0.13, 20.60)	1.60 (0.12, 19.10)	2.45 (0.19, 21.80)	1.40 (0.08, 94.60)	LM
1.36 (0.20, 8.57)	1.23 (0.19, 8.64)	1.88 (0.38, 6.70)	1.05 (0.12, 44.70)	0.79 (0.08, 7.04)	LT

Methods are reported in alphabetical order. Data are presented as the ORs in the column-defining treatment compared with the ORs in the row-defining treatment. ORs of >1 favor the column-defining treatment. BM = bag valve mask, ETC = esophageal tracheal combitube, ETI = endotracheal intubation, LM = laryngeal mask, LT = laryngeal tube.

Table 3

Odds ratios of return of spontaneous circulation of all six airway management methods.

BM
1.98 (0.19, 26.00)	ETC
0.93 (0.29, 3.24)	0.49 (0.04, 4.05)	ETI
0.75 (0.17, 3.47)	0.38 (0.03, 4.42)	0.81 (0.19, 3.25)	i-gel
0.90 (0.21, 4.17)	0.46 (0.03, 4.95)	0.96 (0.27, 3.63)	1.19 (0.23, 6.92)	LM
1.04 (0.30, 3.85)	0.53 (0.05, 5.01)	1.13 (0.40, 3.14)	1.41 (0.32, 5.60)	1.16 (0.29, 4.32)	LT

Methods are reported in alphabetical order. Data are presented as the ORs in the column-defining treatment compared with the ORs in the row-defining treatment. ORs of >1 favor the column-defining treatment. BM = bag valve mask, ETC = esophageal tracheal combitube, ETI = endotracheal intubation, LM = laryngeal mask, LT = laryngeal tube.

ETI had a high rate of unsuccessful insertions at the first attempt (42.4%).This means, more than two attempts are required to complete ETI. However, other interventions often occur concurrently with ETI, such as chest compressions, defibrillation, establishment of intravenous access, or administration of medications. Therefore, frequent intubation may affect the smooth progress of other operations and affect the prognosis of patients [13]. ETI is a relatively complex operation; there- fore, emergency medicine residents, anesthesiology residents, and nurse anesthetist trainees are required to perform 50 to 150 ETI proce- dures before graduating from their respective training programs [33]. Moreover, clinical experience may be an important factor in maintain- ing ETI skills. Therefore, routine training is also essential to ensure the success rate of ETI and reduce the incidence of complications. The pres- ent study showed that although ETI may be relatively effective at ensur- ing ventilation (99.5%), out-of-hospital ETI may result in unintended hyperventilation, which may be deleterious in certain conditions [11].

LT placement has better performance in terms of the rates of difficult airway management (4.5%), unsuccessful insertion at the first attempt (10.8%), airway misplacement or dislodgement (0.7%), and inadequate ventilation (1.8%). However, the rate of regurgitation of gastric contents is relatively poor (15.5%). As a new type of airway management device that was first introduced in Europe in the 1990s, the LT has been widely used in out-of-hospital airway management because of its simple oper- ation, short training time, and minimal complications, and the device was a major competitor to the ETC. A previous study showed that non-professionals could complete LT placement in an average time of 129 s using illustrated instructions with additional written instructions, and the success rate of the first attempt was 53.3%. After the first at- tempt, correCT utilization of the LT was demonstrated to the

participants. The average time for the second attempt after this demon- stration was 12 s, and the success rate of the second attempt was 98% [34]. A recent study showed that the success rate of first-pass insertion of the LT by medical staff was 80.1% and that the success rate of overall- pass insertion was 92.6% [35]. These results are similar to our observa- tion. In terms of other SGA methods, the i-gel and LM have better performance with respect to the rate of regurgitation of gastric contents (0.0% and 1.7%, respectively). However, these devices have poor perfor- mance in terms of the rates of unsuccessful insertion at the first attempt (i-gel = 20.8%, LM = 24.7%), airway misplacement or dislodgement (i-gel = 10.7%), and inadequate ventilation (i-gel = 16.8%, LM = 21.2%). The ETC has better performance in the rate of airway misplace- ment or dislodgement (0.0%). However, its rate of difficult airway management (15.7%) is similar to that of the i-gel and LM. These results are similar to those of other adverse reactions associated with SGA devices [19-21].

1. Limitations

This study has several limitations. First, although a Comprehensive literature search was conducted, the number of included RCTs was small and a funnel plot for publication bias was not conducted. Second, owing to the particularities of airway management in patients with OHCA, it is impossible to implement a blinding method for the partici- pants. Although all included studies were of high quality, unblinded studies introduce unavoidable bias. Third, the emergency system of each country is different; thus, the first aid measures they provide and the practitioners who perform the first aid measures are also different. Although six airway management methods were studied in the present

Table 4

Odds ratios of survival to hospital admission of all six airway management methods.

BM
0.62 (0.10, 3.77)	ETC
0.83 (0.17, 3.75)	1.31 (0.32, 6.10)	ETI
0.94 (0.10, 10.10)	1.53 (0.17, 15.20)	1.12 (0.18, 9.19)	i-gel
1.20 (0.10, 15.00)	1.93 (0.18, 23.60)	1.44 (0.15, 14.50)	1.28 (0.07, 18.80)	LM
1.11 (0.17, 6.77)	1.80 (0.28, 11.80)	1.33 (0.29, 6.80)	1.18 (0.11, 10.80)	0.92 (0.08, 11.90)	LT

Fig. 4. Rankograms of airway management strategies during cardiopulmonary resuscitation for return of spontaneous circulation, survival to hospital admission, survival to hospital dis- charge, and overall airway technique success rate.

BM = bag valve mask, ETC = esophageal tracheal combitube, ETI = endotracheal intubation, LM = laryngeal mask, LT = laryngeal tube.

research, only nine RCTs were included. Because these articles did not include an influential factor analysis, we were unable to perform a subgroup analysis. Fourth, because of the different research focuses and experimental methods, some studies may have had missing data, which might have skewed the results of our meta-analysis. Therefore, all experimental results should be interpreted with caution.

In summary, we found that none of the airway management methods (BM, ETI, LT,LM, i-Gel and ETC) for patients with OHCA was statistically more effective than the other methods in terms of survival to hospital discharge, overall airway technique success rate, ROSC, and survival to hospital admission. Additional researches should be needed to identify which method is more effective.

Funding

This work was supported by the Beijing Municipal Science and Tech- nology Project (Z191100004419003) and the Capital’s Funds for Health Improvement and Research (2020-4-3031).

Contributions

LJ, JJZ, HML, WZZ conceived and designed the study. XQK, HXL selected the articles and extracted the data. SJT analyzed the data. LJ, JJZ, SJT wrote the first draft of the manuscript. LJ, JJZ, DP interpreted the data and contributed to the writing of the final version of the man- uscript. All authors read and approved the final version of the manu- script.

CRediT authorship contribution statement

Jing Lou: Writing – review & editing, Writing – original draft, Methodology, Data curation, Conceptualization. Sijia Tian: Writing – original draft, Formal analysis. Xuqin Kang: Writing – review & editing, Investigation, Data curation. Huixin Lian: Writing – review & editing, Investigation, Data curation. Hongmei Liu: Writing – review & editing, In- vestigation, Data curation. Wenzhong Zhang: Writing – review & editing, Methodology, Conceptualization. David Peran: Writing – review & editing, Writing – original draft, Data curation. Jinjun Zhang: Writing – review & editing, Writing – original draft, Methodology, Conceptualization.

Declaration of Competing Interest

There is no conflict of interest related to this study.

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi. org/10.1016/j.ajem.2022.12.029.

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