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| A study has shown that a change in the type of breathing tube paramedics use to resuscitate patients with sudden cardiac arrest can improve the odds of survival. (Photo/VBM Medical) |
Study: Laryngeal tubes could increase cardiac arrest survivalA study has shown that a change in the type of breathing tube paramedics use to resuscitate patients with sudden cardiac arrest can improve the odds of survival
By Wendy Holdren
The Register-Herald
WASHINGTON — A new National Institutes of Health (NIH) study has shown that a change in the type of breathing tube paramedics use to resuscitate patients with sudden cardiac arrest can significantly improve the odds of survival and save thousands of lives.
The release said more than 90 percent of Americans who experience sudden cardiac arrest die before, or soon after, reaching a hospital. Usually caused by a heart attack, sudden cardiac arrest occurs when the heart suddenly or unexpectedly stops beating, cutting off blood flow to the brain and other vital organs.
"During resuscitation, opening the airway and having proper access to it is a key factor for the survival of someone who goes into cardiac arrest outside of a hospital," said George Sopko, M.D., M.P.H., program director in the NHLBI's Division of Cardiovascular Sciences and coauthor of the study.
"But one of the burning questions in prehospital emergency care has been, 'Which is the best airway device?'"
Funded by the National Heart, Lung, and Blood Institute (NHLBI), part of the NIH, this study is the largest of its kind to test oxygen delivery methods used by firefighters, emergency medical service (EMS) providers and paramedics. It is the first to show that a particular airway intervention can positively affect patient survival rates.
"This study demonstrated that just by managing the airway well in the early stage of resuscitation, we could save more than 10,000 lives every year," Sopko said.
EMS providers treat the majority of the 400,000 out-of-hospital cardiac arrests each year. For more than three decades, their standard-of-care technique for resuscitation has been endotracheal intubation—the insertion of a plastic tube into the trachea to maintain an open airway. They use this technique in hopes that mirroring the care given by in-hospital physicians will produce better patient outcomes.
"While identical to techniques used by doctors in the hospital, intubation in these severe and stressful prehospital settings is very difficult and fraught with errors," said the study's lead author, Henry E. Wang, M.D., professor and vice chair for research in the Department of Emergency Medicine at McGovern Medical School at The University of Texas Health Science Center at Houston.
Today, however, new devices such as laryngeal tubes, offer simpler alternatives to opening and accessing an airway. These tubes are easier to use, and the trial showed that cardiac arrest patients treated with this alternative had a higher survival rate.
The findings from the study, the Pragmatic Airway Resuscitation Trial, were published online in the Journal of the American Medical Association.
Copyright 2018 The Register-Herald https://www.ems1.com/intubation/articles/390247048-Study-Laryngeal-tubes-could-increase-cardiac-arrest-survival/?platform=hootsuite
Key Points
Question What is the effect of an initial airway management strategy using laryngeal tube insertion, compared with endotracheal intubation, on survival among adults with out-of-hospital cardiac arrest?
Findings In this cluster-crossover randomized trial of 3004 adults with out-of-hospital cardiac arrest, 72-hour survival was 18.3% for laryngeal tube insertion and 15.4% for endotracheal intubation, a significant difference.
Meaning A strategy of initial laryngeal tube insertion, compared with endotracheal intubation, was associated with greater likelihood of 72-hour survival, but given limitations in study design and findings, additional research is warranted.
Abstract
Importance Emergency medical services (EMS) commonly perform endotracheal intubation (ETI) or insertion of supraglottic airways, such as the laryngeal tube (LT), on patients with out-of-hospital cardiac arrest (OHCA). The optimal method for OHCA advanced airway management is unknown.
Objective To compare the effectiveness of a strategy of initial LT insertion vs initial ETI in adults with OHCA.
Design, Setting, and Participants Multicenter pragmatic cluster-crossover clinical trial involving EMS agencies from the Resuscitation Outcomes Consortium. The trial included 3004 adults with OHCA and anticipated need for advanced airway management who were enrolled from December 1, 2015, to November 4, 2017. The final date of follow-up was November 10, 2017.
Interventions Twenty-seven EMS agencies were randomized in 13 clusters to initial airway management strategy with LT (n = 1505 patients) or ETI (n = 1499 patients), with crossover to the alternate strategy at 3- to 5-month intervals.
Main Outcomes and Measures The primary outcome was 72-hour survival. Secondary outcomes included return of spontaneous circulation, survival to hospital discharge, favorable neurological status at hospital discharge (Modified Rankin Scale score ≤3), and key adverse events.
Results Among 3004 enrolled patients (median [interquartile range] age, 64 [53-76] years, 1829 [60.9%] men), 3000 were included in the primary analysis. Rates of initial airway success were 90.3% with LT and 51.6% with ETI. Seventy-two hour survival was 18.3% in the LT group vs 15.4% in the ETI group (adjusted difference, 2.9% [95% CI, 0.2%-5.6%]; P = .04). Secondary outcomes in the LT group vs ETI group were return of spontaneous circulation (27.9% vs 24.3%; adjusted difference, 3.6% [95% CI, 0.3%-6.8%]; P = .03); hospital survival (10.8% vs 8.1%; adjusted difference, 2.7% [95% CI, 0.6%-4.8%]; P = .01); and favorable neurological status at discharge (7.1% vs 5.0%; adjusted difference, 2.1% [95% CI, 0.3%-3.8%]; P = .02). There were no significant differences in oropharyngeal or hypopharyngeal injury (0.2% vs 0.3%), airway swelling (1.1% vs 1.0%), or pneumonia or pneumonitis (26.1% vs 22.3%).
Conclusions and Relevance Among adults with OHCA, a strategy of initial LT insertion was associated with significantly greater 72-hour survival compared with a strategy of initial ETI. These findings suggest that LT insertion may be considered as an initial airway management strategy in patients with OHCA, but limitations of the pragmatic design, practice setting, and ETI performance characteristics suggest that further research is warranted.
Trial Registration ClinicalTrials.gov Identifier: NCT02419573
Introduction
Out-of-hospital cardiopulmonary arrest (OHCA) affects more than 350 000 adults in the United States each year, with less than 10% surviving to hospital discharge in 2016.1 In the United States and countries with advanced emergency medical services (EMS) systems, paramedics commonly perform endotracheal intubation (ETI) on patients with cardiac arrest to provide a direct conduit to the lungs, facilitate controlled oxygenation, and protect the lungs from aspiration of vomitus.
ETI plays a central but controversial role in contemporary EMS care. More than 30 years ago, ETI became a standard US paramedic practice under the assumption that it would improve OHCA outcomes. However, numerous studies have highlighted the challenges of paramedic ETI, including significant rates of unrecognized tube misplacement or dislodgement, need for multiple ETI attempts, and ETI insertion failure.2-4 ETI has also been associated with iatrogenic hyperventilation and chest compression interruptions.5,6 Furthermore, opportunities for EMS ETI training and skills maintenance are limited in the United States, with many paramedics performing only 1 live procedure annually.7
Alternatives to ETI include supraglottic airway (SGA) devices including the laryngeal mask airway, esophageal-tracheal combitube, i-gel, and laryngeal tube (LT). Compared with ETI, SGA insertion is rapid, simple, and requires less training, while offering ventilatory characteristics that are similar to ETI.8 While traditionally reserved for contingency use in the event of unsuccessful ETI efforts, SGA insertion has been incorporated by many EMS agencies as the primary method of ventilation during OHCA resuscitation. However, multiple observational studies reported better outcomes associated with ETI compared with SGAs.9-11
To date, few randomized clinical trials have compared ETI with other airway techniques in OHCA.12-14 This Resuscitation Outcomes Consortium Pragmatic Airway Resuscitation Trial (PART) compared the effectiveness of initial LT and initial ETI strategies on outcomes in adult OHCA.
Methods
Design
We conducted a multicenter cluster-crossover randomized trial. The trial methods have been previously reported, and the trial protocol is available in Supplement 1.15 The institutional review boards of the participating institutions approved the trial under federal rules for conduct of emergency research under Exception From Informed Consent (21 CFR 50.24). Participating sites satisfied all requirements for this, including community consultation, public disclosure, and notification of patient, family members, or legally authorized representatives of enrollment.
Funding
The trial was funded by a National Heart, Lung, and Blood Institute (NHLBI) program supporting large-scale, low-cost pragmatic clinical trials.16 This required following stipulated pragmatic trial principles, the use of existing research infrastructure, adherence as much as possible to existing clinical practice, and focus on describing outcomes rather than explanatory mechanisms. The Pragmatic-Explanatory Continuum Indicator Summary 2 (PRECIS-2)17 wheel for the trial is provided in eAppendix 1 in Supplement 2. The capped funding amount constrained the potential number of enrolled patients.
Data and Safety Monitoring
A trial-appointed study monitoring committee monitored EMS agency and regional center protocol compliance and data reporting. An NHLBI-appointed data and safety monitoring board approved the protocol, monitored the safety and interim results of the trial, and made recommendations for its continuation or suspension.
Study Setting and Organization
The trial included 27 EMS agencies associated with US sites of the Resuscitation Outcomes Consortium, a North American multicenter network funded by the NHLBI to conduct clinical trials of therapies for OHCA and major trauma (eTable 1 in Supplement 2). The University of Alabama at Birmingham and the University of Washington Clinical Trials Center functioned as the respective clinical and data coordinating centers for the trial.
Selection of Patients
The trial included adults (age ≥18 years or per local interpretation) with nontraumatic OHCA treated by participating EMS agencies and requiring anticipated ventilatory support or advanced airway management (eAppendix 2 in Supplement 2). Patients who received initial clinical care by EMS agencies with ETI or SGA insertion capabilities and that were not affiliated with the trial were excluded.
Interventions
The trial randomized EMS agencies to either of 2 initial advanced airway management strategies: initial LT insertion or initial orotracheal ETI (eFigure 1 in Supplement 2). Although a variety of SGA devices are available, only LT insertion was allowed because it is the most commonly used SGA in the United States. The protocol allowed the use of neuromuscular blocking agents or video laryngoscopy but not other techniques (eg, nasotracheal intubation) for initial intubation efforts.
The protocol did not prescribe or limit the number of initial LT or ETI insertion attempts. If the initial LT/ETI insertion efforts were unsuccessful, EMS personnel performed rescue airway management using any available airway technique, including bag-valve-mask (BVM) ventilation, ETI (including alternate ETI techniques such as nasal or digital intubation), insertion of LT or another SGA device, or needle jet ventilation or cricothyroidotomy. EMS personnel followed local protocols for confirmation of airway placement and management of OHCA, including field termination of resuscitation efforts. Patients receiving BVM ventilation only (without any LT or ETI attempts) were retained in their assigned treatment group per intention-to-treat principles. The trial did not prescribe clinical care at the receiving hospitals, including the use or replacement of the EMS airway, the provision of targeted temperature management, percutaneous coronary intervention, or the timing of withdrawal of life-sustaining therapy.18
While ETI is almost exclusively an advanced life support skill, basic life support clinicians at the Milwaukee and Portland sites had been trained in LT insertion.19,20 When these EMS agencies were assigned to LT, select basic life support–only clinicians performed initial LT insertion. When assigned to ETI, these clinicians performed BVM ventilation until advanced life support arrival.
Randomization
The trial used cluster randomization with crossover. We grouped the 27 EMS agencies into 13 randomization clusters. Each cluster selected an a priori crossover interval of 3 or 5 months. Based on each cluster’s selected crossover interval and projected duration of trial participation, the lead statistician created a detailed a priori randomization plan (complete with crossover dates and assigned interventions), with the goal of achieving balance within and across sites at the end of the trial. Within each cluster, treatment assignments for consecutive intervals were computer-randomized in blocks of 2 to ensure balanced exposure to both airway groups. Crossovers between study groups could occur more than once.
Practical factors influenced the execution of the randomization. We provided crossover notifications to each cluster at least 1 month prior to the scheduled crossover date, aiming to initiate crossovers on the first day of a calendar month. We allowed EMS agencies to align crossover dates with training sessions, avoid weekends, and avoid crossovers during the last month of the trial. Some clusters experienced delays in start-up, which required adjustments of planned crossover dates (but not randomization groups). If clinicians from more than 1 participating EMS agency were present on scene, the first arriving unit determined the study treatment assignment.
Among the 56 random cluster treatment group assignments, we made 2 crossover adjustments to achieve balanced enrollment between study groups. Enrollment in 1 cluster exceeded projections; we instructed this cluster to carry out 1 additional crossover. One agency ended participation in the trial prior to study completion; to compensate, we instructed another cluster to defer its final crossover. These decisions regarding changes to cluster crossover timings were made without knowledge of outcome data by randomization cluster.
Outcomes
The primary outcome was survival to 72 hours after the index arrest, determined from hospital or (in cases of field termination of resuscitation) EMS records (eTable 2 in Supplement 2). We chose this outcome because it requires a smaller sample size than traditional outcomes (eg, survival to hospital discharge) and accommodated key elements of standard postarrest care such as therapeutic hypothermia (targeted temperature management), early percutaneous coronary intervention, and delay of neurological assessment.18,21 Secondary trial outcomes included (1) return of spontaneous circulation (presence of palpable pulses on emergency department arrival), (2) survival to hospital discharge, and (3) favorable neurological status on hospital discharge (Modified Rankin Scale score ≤3). Other secondary outcomes included EMS airway management course and hospital adverse events. Research coordinators ascertaining clinical outcomes were not blinded to the study intervention.
While postulated mechanisms influencing OHCA outcomes following advanced airway management include chest compression interruptions and hyperventilation, the pragmatic nature of the trial precluded the formal collection and analysis of chest compression and ventilation data.6,22,23
Study Compliance Benchmarks
Benchmarks used by the study monitoring committee for assessing EMS agency performance in the trial are listed in eAppendix 3 in Supplement 2.
Data Analysis
We estimated the sample size based on the expected frequency of 72-hour survival (eAppendix 4 in Supplement 2). Because we could not identify any prior reports of 72-hour survival after OHCA, we used data from the ROC PRIMED trial.24,25 After limiting this analysis to US sites with active use of SGA, we estimated baseline 72-hour survival rates of 16.2% for ETI and 11.1% for SGA, suggesting a potential effect size of 5.1%. By study team consensus, we selected a more conservative value of 4.5% as the difference to power the study.
To account for patients receiving BVM only, we increased the baseline LT survival rate to 13.7%. We designed the trial to have 85% power to detect a 4.5% difference in 72-hour survival, assuming an overall 2-sided α = .05, adjusting for number of analyses (3 interim and 1 final) and accommodating up to a 5% loss of precision due to cluster randomization with crossover. While the projected minimum sample size was 2612 patients (1306 per group) to allow for exclusions, loss to follow-up, and patients treated with BVM only, we aimed to enroll a total of 3000 patients. Trial-stopping boundaries followed asymmetric 2-sided designs based on the unified family of group sequential stopping rules.26,27
We analyzed the primary and secondary outcomes on intention-to-treat bases. In cases where rescuers used only BVM (without ETI or LT insertion), we retained the patient in their assigned randomization. To quantify the treatment effect, we used generalized estimating equations (GEEs) with an identity link and robust standard errors, accounting for randomization cluster and number of interim analyses.
We assessed whether the association of airway management strategy with the primary outcome differed by a priori–defined subgroups, including initial cardiac rhythm, bystander-witnessed arrest, EMS response time, basic life support unit capability of LT insertion, time of airway placement after first rescuer arrival on scene, use of neuromuscular blocking agents before or during airway insertion efforts, age, use of video laryngoscopy, use of BVM ventilation only, and airway placement after return of spontaneous circulation. We assessed the influence of these factors by evaluating each (intervention by subgroup) interaction term in the primary model.
To assess the effect of deviations from random assignment, we conducted a per-protocol analysis, retaining only cases in compliance with their assigned airway group (eg, assigned to ETI and received ETI or BVM). We considered instances of BVM only to be compliant with the protocol because the expected course of airway management may entail BVM ventilation.
To assess the effect of unbalanced randomization within clusters, we conducted post hoc GEE analyses of the intention-to-treat and per-protocol populations, adjusting for age, sex, bystander- or EMS-witnessed arrest, time to EMS arrival, bystander chest compressions, and initial cardiac rhythm. We repeated post hoc analysis of the intention-to-treat population with a hierarchical model (patients nested within EMS agency and EMS agency nested within randomization cluster) and a model with randomization cluster as a fixed effect. We examined the effect of randomization order (LT first vs ETI first) by fitting a treatment by order interaction term. We also conducted as-treated analyses, classifying each case to 1 of 3 groups according to airway technique received: LT, ETI, and BVM or other. We limited as-treated comparisons to LT vs ETI.
Missing data were flagged on data entry and reviewed by data entry staff for accuracy. We treated “unknown” variable categories as informative and included these as separate factors in the GEE models. We considered missing baseline data to be missing completely at random for post hoc GEE models; we did not impute values. Patients with missing data in any of the adjustment variables were excluded from the model. We used 2-sided tests with an α of .05 as the threshold for statistical significance. We conducted all analyses using the statistical package R version 3.2.5 (The R Foundation).
Results
Patient Characteristics
The trial enrolled patients from December 1, 2015, through November 4, 2017. The duration of enrollment for each cluster ranged from 11 to 23 months (eFigure 2 in Supplement 2). Enrollment clusters crossed over between interventions 1 to 6 times. Of 3840 screened patients, 3004 were included; 1505 assigned to initial LT and 1499 assigned to initial ETI (Figure). The proportion of LT and ETI assignments varied across randomization clusters (eFigure 3 in Supplement 2).
Baseline patient and airway management characteristics are provided in Table 1 and eTable 3 in Supplement 2. LT and ETI protocol compliance (initial attempt with assigned airway or use of BVM only) were 95.5% and 90.7%, respectively. Elapsed time from first EMS arrival to airway start was shorter for LT than ETI (median, 9.8 vs 12.5 minutes). Initial LT and ETI success rates (excluding BVM) were 90.3% and 51.6%. Overall LT and ETI airway success rates (initial + rescue airway attempts) were 94.2% and 91.5%, respectively. Clinicians at receiving emergency departments converted 64.4% of EMS LT to ETI. Among patients receiving successful EMS ETI, emergency department clinicians performed repeat ETI in 33.1%. Outcomes of initial and rescue airway interventions are presented in eFigure 4 in Supplement 2.
A total of 352 patients received BVM only without any advanced airway insertion efforts. Reported reasons for the use of BVM only included the patient regaining consciousness (29.3%), death prior to airway insertion attempts (14.2%), jaw clenching (trismus, 11.9%), adequate ventilation with BVM (9.9%), arrival at emergency department prior to airway insertion efforts (7.7%), and other (8.8%) (eTable 4 in Supplement 2).
Primary Outcome
Seventy-two–hour survival was unknown for 4 patients (0.1%). Among the remaining patients, 72-hour survival was 18.3% in the LT group vs 15.4% in the ETI group; accounting for randomization cluster and interim analyses, this difference was 2.9% (95% CI, 0.2%-5.6%; P = .04; relative risk, 1.19 [95% CI, 1.01-1.39]) (Table 2).
Secondary Outcomes
Secondary outcomes in the LT group vs ETI group were return of spontaneous circulation (27.9% vs 24.3%; adjusted difference, 3.6% [95% CI, 0.3%-6.8%]; P = .03), hospital survival (10.8% vs 8.1%; adjusted difference, 2.7% [95% CI, 0.6%-4.8%; P = .01), and favorable neurological status at discharge (7.1% vs 5.0%; adjusted difference, 2.1% [95% CI, 0.3%-3.8%] P = .02). There were no statistically significant differences in treatment effects in 72-hour survival among a priori–defined subgroups (eFigure 5 in Supplement 2).
Additional Analyses
In the per-protocol group, 72-hour survival was greater for LT than ETI (18.3% vs 15.4%; risk difference, 2.9% [95% CI, 0.1%-5.7%]; P = .045).
Adverse events are summarized in Table 3. Compared with LT, patients in the ETI group were more likely to experience 3 or more airway insertion attempts (18.9% vs 4.5%). Unsuccessful initial airway insertion was higher for ETI than LT (44.1% vs 11.8%). Unrecognized airway misplacement or dislodgement was higher for ETI than LT (1.8% vs 0.7%). EMS personnel reported inadequate ventilation more often in LT than ETI (1.8% vs 0.6%). Pneumothoraces (7.0% vs 3.5%) and rib fractures (7.0% vs 3.3%) were more common with ETI than LT. There were no significant differences in oropharyngeal or hypopharyngeal injury (0.2% vs 0.3%), airway swelling (1.1% vs 1.0%), or pneumonia or pneumonitis (26.1% vs 22.3%) in the LT vs ETI groups.
Post-Hoc Analyses
In the intention-to-treat population, after post hoc adjustment for age, sex, initial cardiac rhythm, response time, witnessed status, and bystander chest compressions, the difference in 72-hour survival between LT and ETI was not statistically significant (adjusted difference, 2.1% [95% CI, −0.5% to 4.8%]; P = .11; Table 2). In a hierarchical model with patients nested within agency and agency nested within randomization cluster and applying independent correlation structure, the difference in 72-hour survival between LT and ETI was 1.8% (95% CI, −0.9% to 4.5%). In a linear regression model with randomization cluster included as a fixed effect, the difference in 72-hour survival between LT and ETI was 1.5% (95% CI, −1.2% to 4.3%).
When stratifying by order of randomization (LT first or ETI first), the differences in 72-hour survival were 2.5% (95% CI, −0.9% to 5.9%) for LT first and 3.6% (95% CI, −0.9% to 8.2%) for ETI first (interaction P = .69). After post hoc multivariable adjustment, the difference in 72-hour survival in the per-protocol analysis was not statistically significant (adjusted difference, 2.3% [95% CI, −0.4% to 5.1%]; P = .09; Table 2).
In the as-treated analysis, the initial airway devices used on enrolled patients were ETI in 1224 patients, LT in 1423, and BVM or other in 354; there was no significant difference in 72-hour survival between those receiving initial LT and initial ETI (16.0% vs 13.5%; P = .07) (eTable 5 in Supplement 2).
Treatment effects varied among randomization clusters (eFigure 6 in Supplement 2) and EMS agencies (eFigure 7 in Supplement 2) and showed a tendency toward favoring LT only in clusters with lower baseline ETI survival.
The primary outcome (72-hour survival) was missing for 4 of 3004 enrolled patients (0.1%), all assigned to ETI. Because of the low number of missing cases, we did not apply multiple imputation. Among the 4 patients with missing 72-hour outcome, there were 16 possible combinations of 72-hour survival; only 1 (all 4 patients surviving to 72 hours) would have altered the primary trial results. Given the observed 15.4% 72-hour survival rate in the ETI group, the probability of all 4 cases surviving to 72 hours was 0.06%.
Discussion
In this trial of 3004 adults with OHCA, a strategy of initial LT was associated with modest but significantly greater 72-hour survival than a strategy of initial ETI. There were also statistically significant associations with survival to hospital discharge and favorable neurological status at hospital discharge that favored the LT group. The trial offers preliminary observations that may potentially guide EMS airway management practices and serve as the basis for future research.
The trial demonstrated the effectiveness of an LT-based strategy of advanced airway management, not the efficacy of the LT airway device. OHCA resuscitation requires the careful coordination of multiple interventions, including initiation and maintenance of chest compressions, controlled ventilation, vascular access, drug administration, and defibrillation. The simpler LT technique may better integrate with and facilitate these other treatments. Although the 2 groups reported similar procedural duration, the elapsed time from EMS arrival to first airway attempt was 2.7 minutes shorter in the LT than ETI group. Also, LT required fewer insertion attempts than ETI. This pragmatic trial did not assess mechanisms underlying the effect of airway type on chest compression quality (in particular, chest compression continuity), which may potentially influence OHCA outcomes.5,28
The ETI success rate of 51% observed in this trial is lower than the 90% success rate reported in a meta-analysis.29 The reasons for this discordance are unclear. Prior reports of higher success rates may be susceptible to publication bias. Another possibility is that some medical directors encourage early rescue SGA use to avoid multiple unsuccessful intubation attempts and to minimize chest compression interruptions.5 Few of the study EMS agencies had protocols limiting the number of allowed intubation attempts, so the ETI success rate was not the result of practice constraints. While the ETI proficiency of study clinicians might be questioned, the trial included a diverse range of EMS agencies and likely reflects current practice. It is not clear whether clinicians with more advanced ETI skills or experience would have altered these results. However, this pragmatic trial highlights the outcomes of care resulting from existing EMS airway clinical and training practices; supplementing the trial with specialized airway management training would have limited the generalizability of the findings.
Some limitations of a cluster-crossover design include imbalance in patient allocation, group baseline characteristics, and variations in within-cluster treatment effects. Post hoc adjustment for these factors influenced the observed associations with 72-hour survival, underscoring the importance of even small imbalances. Post hoc analyses also suggested that the benefit of LT may have been amplified in clusters with lower baseline ETI 72-hour survival. The reasons for these intercluster differences are unknown. Post hoc analyses are extremely difficult to interpret in the context of a clinical trial. While cluster-crossover designs have been successfully used in trials enrolling patients with OHCA, additional study must evaluate the nuances of this approach in the context of airway management.24,30
These results contrast with prior studies of OHCA airway management. Observational studies have reported higher survival with ETI than SGA, but they were nonrandomized, included a range of SGA types, and did not adjust for the timing of the airway intervention.9,10,31-34 A trial of 830 children found no difference in survival or neurological outcomes between those randomized to BVM-only ventilation vs BVM+ETI, but the study occurred in 1994-1997, used clinicians who were newly trained in pediatric ETI, and included a range of medical conditions in addition to OHCA.12 A recent trial of 2043 adult OHCA cases in France and Belgium found no OHCA survival differences between BVM and ETI, but care was rendered by physician-staffed EMS units, a model less common in the United States and countries with similar paramedic-based EMS systems.35 In the United Kingdom, enrollment has been completed in Airways-2, a trial comparing i-gel SGA with ETI on OHCA outcomes.36 The current trial focused on LT, which is more commonly used in the United States.
While prior studies suggest higher survival with BVM than with advanced airway devices, similar inferences should not be made based on the as-treated analysis of this trial. The BVM-only group exhibited higher rates of witnessed arrest, bystander chest compressions, and shockable rhythms than LT or ETI, and almost a third regained consciousness prior to advanced airway intervention, suggesting influence from resuscitation time bias.37 These and other biases cannot be overcome by post hoc analytic techniques. A randomized trial comparing BVM and LT would be needed to assess their relative efficacy.
Limitations
This study has several limitations. First, the pragmatic trial evaluated strategies of LT and ETI under existing clinical protocols and educational practices without additional training or quality improvement monitoring. Second, the stipulations of the grant award influenced many elements of the study design such as limiting the available sample size. Third, the trial could not assess the influence of chest compression or ventilation quality. Fourth, the trial focused on LT use and not other SGAs. Fifth, many elements of the trial were not blinded, including the interventions, allocation, crossover timings, and outcomes ascertainment, and adjustments were made to the crossover plan to balance allocation. Sixth, these results pertain to the out-of-hospital environment and may not apply to the in-hospital setting.
Conclusions
Among adults with OHCA, a strategy of initial LT insertion was associated with significantly greater 72-hour survival compared with a strategy of initial ETI. These findings suggest that LT insertion may be considered as an initial airway management strategy in patients with OHCA, but limitations of the pragmatic design, practice setting, and ETI performance characteristics suggest that further research is warranted.
Accepted for Publication: May 4, 2018.
Concept and design: Wang, Daya, Stephens, Herren, Richmond, Sternig, May, Weisfeldt, Nichol.
Acquisition, analysis, or interpretation of data: Wang, Schmicker, Daya, Idris, Carlson, Colella, Herren, Hansen, Richmond, Puyana, Auderheide, R. Gray, P. Gray, Verkest, Owens, Brienza, May, Sopko, Weisfeldt, Nichol.
Drafting of the manuscript: Wang, Schmicker, Daya, Stephens, Carlson, Auderheide, May, Weisfeldt, Nichol.
Critical revision of the manuscript for important intellectual content: Wang, Schmicker, Daya, Idris, Carlson, Colella, Herren, Hansen, Richmond, Puyana, Auderheide, R. Gray, P. Gray, Verkest, Owens, Brienza, Sternig, May, Sopko, Weisfeldt, Nichol.
Statistical analysis: Schmicker, May.
Obtained funding: Wang, Stephens, Idris, Herren, May, Weisfeldt, Nichol.
Administrative, technical, or material support: Wang, Daya, Stephens, Idris, Colella, Herren, Richmond, Puyana, Verkest, Owens, Brienza, Sternig, May, Weisfeldt, Nichol.
Supervision: Wang, Daya, Stephens, Idris, Carlson, Colella, Hansen, Richmond, May, Nichol.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Wang reported receiving grants from the National Institutes of Health (NIH)/National Heart, Lung, and Blood Institute (NHLBI) and providing research consultation for Shire Inc. Mr Schmicker; Drs Daya, Aufderheide, and May; and Mrs Herren reported receiving grants from the NHLBI. Dr Idris reported receiving grants from the NIH, University of Alabama, and HeartSine Inc and being an uncompensated member of HeartSine Inc’s scientific advisory board. Dr Carlson reported receiving grants from the NHLBI and American Heart Association for intubation research. Dr Sopko reported being an employee of the NIH. Dr Nichol reported receiving salary support from Medic One Foundation; grants from NIH, Agency for Healthcare Research and Quality, and US Food and Drug Administration; and contracts from Abiomed, GE Healthcare, and ZOLL Medical Corp, and providing consultancy to ZOLL Circulation. No other disclosures were reported.
Funding/Support: This study was supported by award UH2/UH3-HL125163 from the NHLBI. The Resuscitation Outcomes Consortium institutions participating in the trial were supported by a series of cooperative agreements from the NHLBI, including 5U01 HL077863 (University of Washington Data Coordinating Center), HL077866 (Medical College of Wisconsin), HL077871 (University of Pittsburgh), HL077873 (Oregon Health and Science University), HL077881 (University of Alabama at Birmingham), and HL077887 (University of Texas Southwestern Medical Center/Dallas). Ambu Inc provided laryngeal tube airways to replace equipment used by emergency medical services (EMS) agencies during the trial.
Role of the Funder/Sponsor: The NHLBI had the following roles in the study: design and conduct of the study; review, advising, and approval of study design; participation in monitoring enrollment progress, assembly of data and safety monitoring board; preparation, review, or approval of the manuscript (participation of coauthor Dr Sopko); and decision to submit the manuscript for publication (formal approval of the final manuscript by the institute). Ambu Inc had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Disclaimer: The content is solely the responsibility of the authors and does not necessarily represent the official views of the NHLBI or the NIH.
Meeting Presentation: This study was presented at the Society for Academic Emergency Medicine Annual Meeting; May 16, 2018; Indianapolis, Indiana.
Additional Information: A list of the individuals and entities that were involved in the study is available in Supplement 2.
References
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