Abstract

The goal of this meta-analysis is to evaluate and compare the effectiveness of endotracheal intubation (ETI) and supraglottic airway (SGA) devices in airway management during out-of-hospital cardiac arrest events.

Study was designed as a systematic review and meta-analysis and was conducted according to the 2020 PRISMA guidelines. Relevant studies published up to January 2024 were searched systematically using the following databases: PubMed, EMBASE, Scopus, Web of Science, and Cochrane Library. Pooled effect sizes were calculated using a random-effects model and reported as the odds ratios and 95% confidence intervals.

Out of 4218 records initially identified, 25 eligible studies were selected for inclusion in a meta-analysis. Survival to hospital admission was 26.8% for ETI and 14.5% for SGA (p<0.001). Survival rates among patients treated with ETI vs. SGA varied and amounted to: 25.5% vs. 17.6% for 24-h survival rate (p<0.001); 13.4% vs. 15.1% (p=0.002); and 8.6% vs. 6.0% for survival to hospital discharge/30-d  survival (p=0.09). Survival with favorable neurological outcomes occurs in 5.3% in ETI group, compared to 3.8% in SGA group (p=0.35).

Our analysis reveals the nuanced and context-dependent nature of airway management in prehospital emergency care. The high heterogeneity across studies suggests that factors such as provider experience, patient characteristics, and the specific emergency context significantly influence outcomes.

Keywords: Endotracheal intubation, supraglottic airway device, airway management, out-of-hospital cardiac arrest, survival rate

Introduction

Airway management is a cornerstone of resuscitation in out-of-hospital cardiac arrest (OHCA), a critical medical emergency with low survival rates globally (1, 2). The primary goal during resuscitation is to ensure adequate oxygenation and ventilation to support the heart and brain until spontaneous circulation can be restored (3, 4). Over the years, the strategies for airway management in OHCA have evolved from basic methods like mouth-to-mouth respiration to advanced techniques involving endotracheal intubation (ETI) and supraglottic airway (SGA) devices. These advancements reflect the ongoing efforts to improve patient outcomes by optimizing the airway management approach during the critical minutes following cardiac arrest.

ETI has long been considered the gold standard for securing the airway in emergency medicine, given its ability to provide a secure airway, protect against aspiration, and enable controlled ventilation (5, 6). ETI, however, requires significant skill and experience to perform successfully, especially in the challenging conditions encountered during OHCA. Studies, including those by Bartos et al. (7) have explored the impact of ETI in OHCA, with a focus on the procedure’s success rates, its influence on survival outcomes, and potential complications arising from its use in the ETI setting.

On the other hand, SGA devices have emerged as a viable alternative to ETI for airway management in OHCA. SGAs are designed to be easier to insert and require less skill and training than ETI. They have gained popularity due to their simplicity and the potential for rapid deployment, which is crucial in time-sensitive scenarios like OHCA. The literature, including studies by Becker et al. (8), Benger et al. (9), and others, has examined the efficacy of SGAs compared to ETI, assessing metrics such as insertion success rates, ventilation quality, and the impact on patient outcomes including survival to hospital discharge (SHD) and neurological status.

The debate between the use of ETI and SGA devices in OHCA management centers around several key issues. These include the skill level required for effective implementation, the impact on patient outcomes, and the operational challenges faced by emergency medical services in different regions. Factors such as the availability of skilled personnel, training programs, and the specific circumstances of each cardiac arrest case (e.g., etiology of arrest, patient anatomy, presence of bystanders) play critical roles in determining the most appropriate airway management strategy.

The evolution of airway management strategies reflects a broader trend in emergency medicine towards evidence-based practice. Randomized controlled trials and observational studies have provided valuable insights into the relative benefits and drawbacks of ETI and SGA devices. For instance, research has shown that while ETI may offer superior airway protection, the technical challenges and potential for procedural complications can adversely affect outcomes. Conversely, the ease of use associated with SGA devices might lead to faster airway control but could be associated with increased rates of improper placement and inadequate ventilation in some cases.

The goal of this meta-analysis is to evaluate and compare the effectiveness of ETI and SGA devices in airway management during OHCA events. This work aims to integrate available data from studies comparing these two methods with respect to key outcome indicators, such as survival to hospital admission (SHA), SHD, and the neurological status of patients who survived the cardiac arrest.

Materials and Methods

This study was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines (10) and the Cochrane Handbook for Systematic Review of Interventions (11). The review protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO-CRD42024500150). This study did not require ethical approval and informed consent as it was a systematic review and meta-analysis of previously published studies.

Search Strategy

We did a systematic review and network meta-analysis. We searched the PubMed, EMBASE, Scopus, Web of Science, and Cochrane Library databases from the date of their inception to January 31, 2024, with restriction to English language.

We used the search terms compilation “endotracheal intubation” OR “intubation” OR “direct laryngoscope” OR “direct intubation” OR “Macintosh laryngoscope” OR “laryngoscope” OR “MAC” AND “supraglottic airway device” OR “SGA” OR “i-gel” OR “IGEL” OR “laryngeal mask airway” OR “laryngeal tube” OR “LMA-Classic” OR “LMA-Proseal” OR “LMA” OR “SoftSeal” OR “air-Q” OR “cobra perilaryngeal airway” OR “self-pressurised air-Q” OR “Ambu Aura-I” OR “Ambu AuraGain”  OR “Ambu AuraOnce” AND “heart arrest” OR “cardiac arrest” OR “out-of-hospital cardiac arrest” OR “OHCA” OR “OOHCA” OR “OH-CA” OR “prehospital cardiac arrest” OR “sudden cardiac death”. We also checked the reference lists of included studies.

Study Selection

Two researchers (M.D. and M.P.) independently screened titles and abstracts of the identified papers in order to select relevant and not-relevant papers. Each citation was reviewed with full-text retrieval of any citation considered potentially relevant. All studies meeting the following PICOS criteria were included in our analysis: adult (aged 18 years or older) patients with OHCA (P); airway management with ETI (I); airway management with SGA devices (C); return of spontaneous circulation (ROSC), SHA with sustained ROSC; SHD, with good neurological outcome defined as a score 1 or 2 according to Cerebral Performance Categories (CPC) Scale (O); randomized controlled trial as well as non-randomized trials (S). We excluded trials focusing on pediatric population or conducted among simulation or animal model, systematic reviews, reviews, commentaries/editorials, letter to editors, and literature reviews, as well as studies not addressing our review question.

Data Extraction and Data Retrieval

After identifying those studies meeting inclusion criteria, two members (M.D. and D.K.) of our team should have independently reviewed and assessed each of the included studies. Any disagreement on both study selection and data extraction was planned to be solved by discussion with a further author (L.S.) or by contacting the corresponding author.

The following information was collected: first author, year of the study, country, study design, type of SGA device, total number of patients per group, sex and age. Furthermore, we collected: witnessed arrest and bystander cardiopulmonary resuscitation, ROSC, SHA with sustained ROSC; SHD with good neurological outcome defined as a CPC 1-2. If data were missing, a request was sent by e-mail to the corresponding author of the study. If no response was received after our initial request, a second request was sent seven days later.

Quality Assessment and Certainty of Evidence Assessment

Two researchers (M.D. and M.P.) independently evaluated the quality of included RCTs by using the risk of bias (RoB) 2 Tool (12) and for non-RCT by using ROBINS-I Tool (13). Disagreements were resolved by discussion with a third researcher (B.C.).

RoB 2 Tool assesses study quality and RoB  by exploring five domains (bias arising from the randomization process, bias due to deviations from intended interventions, bias due to missing outcome data, bias in the measurement of the outcome, bias in the selection of the reported result) and each domain is judged on a three-grade scale (low RoB, high RoB or some concerns).

In contrast, in the case of the ROBINS-I tool, the following domains were assessed: bias due to confounding; bias due to the selection of participants; bias in the classification of intervention; bias due to deviations from the intended interventions; bias due to missing data; bias in the measurement of outcomes; bias in the selection of the reported result.

An overall RoB among both tools was expressed based on the above domains on a three-grade scale (low RoB, high RoB or some concerns).

Both the single domains and the overall judgement are based on the criteria reported in the RoB 2 Tool (14).

Statistical Analysis

Statistical analyses utilized Review Manager software (v5.4, by the Nordic Cochrane Centre of the Cochrane Collaboration) and Stata software (v18, from StataCorp in College Station, TX, USA) for computations. We conducted all statistical comparisons as two-tailed, setting the threshold for significance at p<0.05. The analysis employed (OR) with 95% confidence intervals (CIs) for binary outcomes, and mean differences with 95% CIs for continuous outcomes. When studies reported continuous outcomes using medians and ranges, we derived means and standard deviations using Hozo et al.’s (15) method. A random-effects model underpinned all analyses, with heterogeneity quantified by I² statistics, categorizing it as low (<25%), moderate (25-50%), or high (>50%). To detect publication bias, we applied Egger’s test and constructed funnel plots, specifically examining asymmetry in analyses involving more than ten studies. Finally, in sensitivity analyses, leave-one-out analysis was performed.

Results

Study Selection

Our literature search identified a total of 4218 studies; the process of study selection is summarized in Figure 1. We excluded 1171 duplicates and 3022 citations after title and abstract screening. We identified 25 trials (with 160,071 participants) to include in this meta-analysis (7-9,16-37). Baseline characteristics of the included studies were provided in Table 1. Of the included articles, eight were conducted in the US, three each in Germany, Taiwan, Korea and Japan, two in England, and two in Austria. In addition, one study was an international survey covering Belgium, the Czech Republic and Sweden. Both prospective and retrospective studies had low RoB (Supplementary Figures 1-4).

Summary of Studies

Our analysis included data from 160,071 out-of-hospital cardiac arrest cases. Among them, 57,921 airways were protected with ETI, while in 102,150 cases with SGA. Patient characteristics are shown in Table 2. In the analysis of airway management outcomes, the odds of being male were marginally lower in the ETI group (62.2%) compared to the SGA group (63.1%), with an odds ratio of 0.94 (95% CI, 0.92 to 0.97, p<0.001) and low study heterogeneity (I²=23%). Age did not significantly differ between ETI and SGA groups, with specifics on mean and standard deviation not provided. Witnessed arrests occurred in 47.5% of ETI cases versus 46.6% for SGA, with an OR of 1.04 (95% CI, 0.97 to 1.11, p=0.23) and moderate heterogeneity (I²=75%). Bystander CPR was provided in 39.2% of ETI cases against 33.5% in SGA, with an OR of 1.12 (95% CI, 0.98 to 1.27, p=0.09) and high heterogeneity (I²=94%). These findings suggest that demographic factors and prehospital interventions like witnessed arrest and bystander CPR show no significant differences between the ETI and SGA groups, despite varying levels of heterogeneity across studies.

Meta-analysis Outcomes

Prehospital ROSC was assessed in 6 studies involving 7,712 participants for ETI and 42,330 for SGA (Figure 2). The event rate was 33.1% for ETI compared to 35.4% for SGA. The odds ratio (OR) was 1.25, with a 95% CI of 0.87 to 1.79, indicating no significant difference between the groups (p=0.23). Heterogeneity across trials was high (I²=88%).

SHA was evaluated in 17 studies with 49,218 participants for ETI and 59,989 for SGA, revealing an event rate of 26.8% for ETI and 14.5% for SGA (Figure 3). The OR was 1.37 (95% CI, 1.32 to 1.42), with a p value of less than 0.001, suggesting a significant difference favoring ETI. However, heterogeneity remained high (I²=94%).

24-hour survival rate among patients treated with ETI and SGA varied and amounted to 25.2% and 17.6% respectively (OR=1.56; 95% CI: 1.38 to 1.77; p<0.001; Figure 4).

For the 72-hour survival rate, 5 studies with 9,189 participants for ETI and 10,071 for SGA showed an event rate of 13.4% for ETI and 15.1% for SGA. The OR was 0.85 (95% CI, 0.77 to 0.94), with moderate heterogeneity (I²=27%) and a p value of 0.002, favoring SGA.

SHD/30-day survival rate was reported in 21 studies including 57,425 participants for ETI and 101,791 for SGA. The event rate was 8.6% for ETI and 6.0% for SGA, with an OR of 1.13 (95% CI, 0.98 to 1.30). Despite high heterogeneity (I²=85%), the difference was not statistically significant (p=0.09).

SHD with CPC 1-2 was assessed in 15 studies with 49,834 participants for ETI and 92,270 for SGA. The event rate was 5.3% for ETI compared to 3.8% for SGA. The OR was 1.13 (95% CI, 0.87 to 1.46), and the p value was 0.35, indicating no significant difference, with very high heterogeneity (I²=90%).

Discussion

This meta-analysis compares the efficacy of ETI versus SGA devices in the prehospital setting, focusing on various survival outcomes. Our findings present mixed results, highlighting the complexity of choosing the optimal airway management technique in emergency situations.

In our analysis for prehospital ROSC, the difference between ETI and SGA was not statistically significant. While a slightly higher event rate was observed for SGA, the OR did not indicate significant differences between the groups. The high degree of heterogeneity (I²=88%) may reflect variations in study protocols, patient populations, or techniques used for both procedures. Regarding SHA the significant difference favoring ETI suggests that under certain clinical conditions, intubation may provide better outcomes. Nevertheless, the extremely high heterogeneity (I²=94%) underscores the need for cautious interpretation of these results. The SHD/30-day  survival rate did not show a statistically significant difference between ETI and SGA, despite high heterogeneity (I²=85%). This finding suggests that the immediate benefits of airway management techniques may not translate into long-term survival advantages, highlighting the importance of comprehensive post-resuscitation care. Furthermore, when assessing SHD with CPC of 1-2, no significant difference was observed, indicating that the choice of airway management technique may not significantly impact neurological outcomes, although very high heterogeneity (I²=90%) was noted. The importance of securing airway patency in prehospital emergency care cannot be overstated, as it is a critical determinant of successful resuscitation outcomes. Both ETI and SGA devices play pivotal roles in ensuring airway management, yet they offer distinct advantages that cater to different emergency scenarios. Isolating the airway through either ETI or SGA is crucial for preventing aspiration, a common and potentially fatal complication during cardiac arrest and other emergencies. Furthermore, these airway management techniques facilitate the delivery of high-quality, uninterrupted chest compressions by allowing for asynchronous resuscitation. This approach, wherein ventilation and chest compressions are not temporally linked, can maximize cerebral and coronary perfusion by eliminating pauses in chest compressions, which are known to negatively impact survival and neurological outcomes.

The ability to provide asynchronous resuscitation underscores the strategic importance of choosing the appropriate airway management device in the prehospital setting. ETI, with its direct access to the trachea, offers a definitive airway that is most beneficial in scenarios requiring long-term ventilation, protection against aspiration, and in situations where advanced airway management skills are readily available.

ETI is recognized as a technically demanding procedure that requires a high level of skill and practice to achieve proficiency. The learning curve for ETI is steep, indicating that a significant number of attempts are needed to reach a level of competency where the success rate stabilizes. Studies suggest that to achieve a high success rate in ETI, practitioners often need to perform a substantial number of intubations under supervision. The complexity of the procedure, variability in patient anatomy, and the emergent nature of situations requiring ETI contribute to this challenging learning curve. As such, continuous training and regular practice are imperative for maintaining proficiency, particularly for providers in the prehospital setting where conditions can be unpredictable and resources limited. In contrast, the learning curve for SGA devices is generally less steep compared to ETI. SGAs are designed for ease of use, allowing for rapid and reliable airway management with minimal interruption to resuscitation efforts. The simpler insertion technique and lower skill threshold needed for effective use make SGAs an attractive option in emergency settings, especially for providers who may not perform airway management procedures frequently. However, while SGAs can be easier to learn and implement, understanding the nuances of proper placement, seal, and potential complications is essential for optimizing patient outcomes.

Study Limitations

This meta-analysis also has several limitations. The included studies showed substantial heterogeneity, which might be attributed to differences in research protocols, patient groups, or procedures. Second, significant imprecision and inconsistency lowered trust in evidence for a range of outcomes. Furthermore, there are questions regarding protocol adherence, since not all patients may get the course of care to which they were allocated. This might be explained by resuscitation time bias, which occurs when patients who fail tracheal intubation get an SGA and are predicted to have a poorer result.

Conclusion

Our analysis reveals the nuanced and context-dependent nature of airway management in prehospital emergency care. The high heterogeneity across studies suggests that factors such as provider experience, patient characteristics, and the specific emergency context significantly influence outcomes. Future research should aim to identify these moderating factors and evaluate the cost-effectiveness of ETI and SGA in various prehospital settings. Additionally, training protocols and guidelines may need to be adapted to reflect the complex decision-making process in choosing the most appropriate airway management technique.

Ethics

Ethics Committee Approval and Informed Consent: This study did not require ethical approval and informed consent as it was a systematic review and meta-analysis of previously published studies.

Authorship Contributions

Surgical and Medical Practices: M.D., Concept: M.D., Design: M.D., Data Collection or Processing: M.D., P.W., M.P., L.S., Analysis or Interpretation: M.D., Literature Search: M.D., P.W., M.P., L.S., Writing: M.D., P.W., B.C., D.K., M.P., L.S.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: The authors declared that this study received no financial support.