Elsevier

Annals of Emergency Medicine

Volume 54, Issue 5, November 2009, Pages 656-662.e1
Annals of Emergency Medicine

Emergency medical services/original research
Passive Oxygen Insufflation Is Superior to Bag-Valve-Mask Ventilation for Witnessed Ventricular Fibrillation Out-of-Hospital Cardiac Arrest

https://doi.org/10.1016/j.annemergmed.2009.06.011Get rights and content

Study objective

Assisted ventilation may adversely affect out-of-hospital cardiac arrest outcomes. Passive ventilation offers an alternate method of oxygen delivery for these patients. We compare the adjusted neurologically intact survival of out-of-hospital cardiac arrest patients receiving initial passive ventilation with those receiving initial bag-valve-mask ventilation.

Methods

The authors performed a retrospective analysis of statewide out-of-hospital cardiac arrests between January 1, 2005, and September 28, 2008. The analysis included consecutive adult out-of-hospital cardiac arrest patients receiving resuscitation with minimally interrupted cardiopulmonary resuscitation (CPR) consisting of uninterrupted preshock and postshock chest compressions, initial noninvasive airway maneuvers, and early epinephrine. Paramedics selected the method of initial noninvasive ventilation, consisting of either passive ventilation (oropharyngeal airway insertion and high-flow oxygen by nonrebreather facemask, without assisted ventilation) or bag-valve-mask ventilation (by paramedics at 8 breaths/min). The authors determined adjusted neurologically intact survival from hospital and public records and by telephone interview and mail questionnaire. The authors compared adjusted neurologically intact survival between ventilation techniques by using generalized estimating equations.

Results

Among the 1,019 adult out-of-hospital cardiac arrest patients in the analysis, 459 received passive ventilation and 560 received bag-valve-mask ventilation. Adjusted neurologically intact survival after witnessed ventricular fibrillation/ventricular tachycardia out-of-hospital cardiac arrest was higher for passive ventilation (39/102; 38.2%) than bag-valve-mask ventilation (31/120; 25.8%) (adjusted odds ratio [OR] 2.5; 95% confidence interval [CI] 1.3 to 4.6). Survival between passive ventilation and bag-valve-mask ventilation was similar after unwitnessed ventricular fibrillation/ventricular tachycardia (7.3% versus 13.8%; adjusted OR 0.5; 95% CI 0.2 to 1.6) and nonshockable rhythms (1.3% versus 3.7%; adjusted OR 0.3; 95% CI 0.1 to 1.0).

Conclusion

Among adult, witnessed, ventricular fibrillation/ventricular tachycardia, out-of-hospital cardiac arrest resuscitated with minimally interrupted cardiac resuscitation, adjusted neurologically intact survival to hospital discharge was higher for individuals receiving initial passive ventilation than those receiving initial bag-valve-mask ventilation.

Introduction

Out-of-hospital cardiac arrest is a leading cause of death in the United States, with estimates ranging from 166,000 to 310,000 events per year.1, 2 Long-term survival is typically less than 10%, but recent studies have shown that new emergency medical services (EMS) protocols can substantially improve survival for adult out-of-hospital cardiac arrest victims.3, 4, 5, 6, 7

New approaches to resuscitation emphasize chest compression continuity at the earliest stages of resuscitation. To achieve this goal, the latest protocols defer advanced airway interventions such as endotracheal intubation, substituting basic-level airway measures. One example was reported in a rural Wisconsin EMS system using cardiocerebral resuscitation, a strategy consisting of continuous chest compressions accompanied by initial passive ventilation only by nonrebreather mask.6, 7 In Arizona, we implemented a similar minimally interrupted cardiopulmonary resuscitation (CPR) protocol emphasizing continuous chest compressions with minimal interruptions, initial basic airway management, single defibrillation attempts, early epinephrine administration, and delayed endotracheal intubation.4 Under minimally interrupted cardiac resuscitation, paramedics in Arizona provide initial airway management with passive ventilation or standard bag-valve-mask ventilation.

Previous studies have linked assisted positive-pressure ventilation to impaired CPR coronary circulation and worsened patient neurologically intact survival.8 Aufderheide et al9 also showed that excessive ventilation is common during out-of-hospital cardiac arrest resuscitation. Passive ventilation offers a simpler approach to CPR oxygen delivery without positive pressure application. However, the relative merits of passive ventilation and bag-valve-mask ventilation remain unknown.

In this study, we compared outcomes of out-of-hospital cardiac arrest patients receiving minimally interrupted cardiac resuscitation with initial passive ventilation with those receiving minimally interrupted cardiac resuscitation with initial bag-valve-mask ventilation.

Section snippets

Setting and Selection of Participants

The state of Arizona encompasses 113,635 square miles and 15 counties. According to the 2006 census estimate, Arizona had a population of 6.2 million, yielding 45 persons per square mile. There were 3.1 million (50%) female residents and 3.1 million (50%) male residents. The median age was 34.6 years. Twenty-six percent of the population was younger than 18 years and 13% was older than 65 years. The median income of households in Arizona was $47,265. For people reporting one race alone, 77%

Results

Reports of 5,097 total EMS-attended out-of-hospital cardiac arrests were documented in the Arizona statewide Utstein-style EMS database from January 1, 2005, to September 28, 2008. For this analysis, we included the 1,019 cases receiving minimally interrupted cardiac resuscitation (Figure). Of these 1,019 arrests, 459 patients received passive ventilation and 560 received bag-valve-mask ventilation. There were no differences in age, sex, location of arrests, bystander CPR, witnessed arrests,

Limitations

An important limitation of this observational study is that the intervention was not tested in a randomized fashion. The results of our study may be subject to self-selection bias. Although we attempted to control for confounding variables, it is possible that there were characteristics of the out-of-hospital cardiac arrest victims or providers that led EMS personnel to select a particular ventilation method.

Our findings are also limited by the lack of CPR process data and our inability to

Discussion

For decades, the advanced cardiac life support guidelines for cardiac arrest have advocated positive-pressure ventilation, traditionally delivered through bag-valve-mask ventilation or endotracheal intubation.14 Yet Aufderheide et al9 suggest adverse consequences from excessive positive-pressure ventilation, including increased intrathoracic pressure and decreased coronary perfusion pressure. Advanced airway insertion efforts or bag-valve-mask ventilation may also disrupt CPR chest compression

References (26)

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Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article that might create any potential conflict of interest. The authors have stated that no such relationships exist. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement.

Supervising editor: Henry E. Wang, MD, MS

Author contributions: BJB, GAE, LC, RAB, ABS, TFV, RWH, and KBK conceived the study. All authors designed the study. BJB, GAE, and LC supervised the conduct of the analysis. BJB and LC supervised the data collection. BJB and LC recruited the participating EMS agencies. LC and VC managed the data including quality control. VC provided statistical advice on study design and performed the final analysis of the data. BJB, GAE, RAB, ABS, and TFV drafted the article and all authors contributed substantially to its revision. BJB takes responsibility for the paper as a whole.

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