Endotracheal intubation versus supraglottic airway placement in out-of-hospital cardiac arrest

© Gary Wilson/ Pre-hospital Research Forum

© Gary Wilson/ Pre-hospital Research Forum

Resuscitation: August 2015, Volume 93, Pages 20–26

Overall survival from out-of-hospital cardiac arrest (OHCA) is less than 10%. After initial bag-valve mask ventilation, 80% of patients receive an advanced airway, either by endotracheal intubation (ETI) or placement of a supraglottic airway (SGA). The objective of this meta-analysis was to compare patient outcomes for these two advanced airway methods in OHCA patients treated by Emergency Medical Services (EMS).


A dual-reviewer search was conducted in PubMed, Scopus, and the Cochrane Database to identify all relevant peer-reviewed articles for inclusion in the meta-analysis. Exclusion criteria were traumatic arrests, paediatric patients, physician/nurse intubators, rapid sequence intubation, video devices, and older airway devices. Outcomes were (1) return of spontaneous circulation (ROSC), (2) survival to hospital admission, (3) survival to hospital discharge, and (4) neurologically intact survival to hospital discharge.


From 3,454 titles, 10 observational studies fulfilled all criteria, representing 34,533 ETI patients and 41,116 SGA patients. Important covariates were similar between groups. Patients who received ETI had statistically significant higher odds of ROSC (odds ratio [OR] 1.28, 95% confidence interval [CI] 1.05–1.55), survival to hospital admission (OR 1.34, CI 1.03–1.75), and neurologically intact survival (OR 1.33, CI 1.09–1.61) compared to SGA. Survival to hospital discharge was not statistically different (OR 1.15, CI 0.97–1.37).

The authors’ meta-analysis of 10 studies shows that ETI is associated with improved outcomes after OHCA when compared to SGA. Despite the effect sizes being small, they were consistent across outcomes after OHCA, including proximal outcomes occurring minutes after cardiac arrest (e.g., ROSC) and distal outcomes that are not apparent until days to weeks after the cardiac arrest event (e.g., neurologically intact survival to hospital discharge.)

The authors explained that the mechanisms behind these associations are poorly understood. “Although not common, multiple complications can occur during and after SGA insertion including pulmonary aspiration, pneumothorax, upper airway bleeding, oesophageal laceration, subcutaneous emphysema, tongue oedema, tracheal injury, and pneumomediastinum. In addition, the airway is not secure after SGA insertion, so head and neck position can lead to significant oropharyngeal air leaks, and most patients will still undergo ETI after arrival in the Emergency Department. Finally, decreased carotid blood flow has been seen in a porcine model of SGA use in cardiac arrest, however this has yet to be demonstrated in humans. These complications may result in worse outcomes for SGA patients despite the concern that ETI is more difficult to perform in the pre-hospital environment.”


Patients with OHCA who receive ETI by EMS are more likely to obtain ROSC, survive to hospital admission, and survive neurologically intact when compared to SGA.

As the research is a meta-analysis of existing data and no randomized controlled trials exist comparing these two airway interventions, resulting in an overall low quality of evidence, the authors do recommend a randomized controlled trial be undertaken.


STEMI identification algorithm

An algorithm for identification of ST-elevation myocardial infarction patients by emergency medicine services

© Gary Wilson/ Pre-hospital Research Forum

© Gary Wilson/ Pre-hospital Research Forum

American Journal of Emergency Medicine. Volume 31, Issue 7 , Pages 1098-1102, July 2013

ST-elevation myocardial infarction (STEMI) identification by emergency medicine services (EMS) leading to pre-hospital catheterization laboratory (CL) activation shortens ischemic time and improves outcomes. The authors examined the incremental value of addition of a screening clinical tool (CT), containing clinical information and a Zoll electrocardiogram (ECG)-resident STEMI identification program (ZI) to ZI alone.

All EMS-performed and ZI-analyzed ECGs transmitted to a percutaneous coronary intervention hospital from October 2009 to January 2011 were reviewed for diagnostic accuracy. ZI performance was also compared to ECG interpretations by 2 experienced readers The CT was then retrospectively applied to determine the incremental benefit above the ZI alone. The CT required  the answer to be yes to all to the following questions for CL activation:

  • Computer interprets ECG as ***ACUTE MI***?
  • Ongoing chest pain or other symptoms suggestive of cardiac ischemia for > 15 min & < 12 h?
  • Paramedic confirmation of quality of ECG tracing and presence of ST-elevation ≥ 1 mm in at least 2 anatomically contiguous leads?
  • Patient alert and able to give a history?
  • Absence of active bleeding?
  • Absence of acute trauma?
  • Absence of signs of acute stroke?
  • Absence of treatment limiting comorbidity?

ST-elevation myocardial infarction was confirmed in 23 (7.5%) of 305 patients. ZI was positive in 37 (12.1%): sensitivity: 95.6% and specificity: 94.6%, positive predictive value (PPV), 59.5%, negative predictive value (NPV), 99.6%, and accuracy of 93.8%. Moderate agreement was observed among the readers and ZI. CT criteria for CL activation were met in 24 (7.8%): 20 (83.3%) were confirmed STEMIs: sensitivity: 86.9%, specificity: 98.5%, a PPV: 83.3%, and NPV: 98.6%, accuracy of 97.7%. CT + ZI increased PPV and specificity (P<0.003) by reducing false positive STEMI identifications from 15 (4.9%) to 4 (1.3%).

In an urban cohort of all EMS transmitted ECGs, ZI has high sensitivity and specificity for STEMI identification. Whereas the PPV was low, reflecting both low STEMI prevalence and presence of STEMI-mimics, the NPV was very high. These findings suggest that a simplified CT combined with computer STEMI interpretation can identify patients for pre-hospital CL activation.  These findings suggest that the addition of the CT to the ZI results in a modest increase in STEMI diagnostic accuracy and a significant reduction in the number of potential false CL activations. Confirmation of these results could improve the design of STEMI care systems.


Computer algorithms for STEMI identification

Prehospital Electrocardiographic Computer Identification of ST-segment Elevation Myocardial Infarction

Prehospital Emergency Care: Posted online on October 15, 2012.

Identifying ST-segment elevation myocardial infarctions (STEMIs) in the field can decrease door-to-balloon times. Paramedics may use a computer algorithm to help them interpret prehospital electrocariograms (ECGs). It is unknown how accurately the computer can identify STEMIs.

The aim of the research was to determine the sensitivity and specificity of prehospital ECGs in identifying patients with STEMI.

Retrospective cross-sectional study of 200 prehospital ECGs acquired using Lifepak 12 monitors and transmitted by one of more than 20 emergency medical services (EMS) agencies to the emergency department (ED) of a Summa Akron City Hospital, a level 1 trauma center between January 1, 2007, and February 18, 2010. The ED sees more than 73,000 adult patients and treats 120 STEMIs annually. The laboratory performs 3,400 catheterisations annually. The first 100 patients with a diagnosis of STEMI and cardiac catheterisation laboratory activation from the ED were analysed  For comparison, a control group of 100 other ECGs from patients without a STEMI were randomly selected from our Medtronic database using a ra

© Gary Wilson/ Pre-hospital Research Forum

ndom-number generator. For patients with STEMI, an accurate computer interpretation was “acute MI suspected.” Other interpretations were counted as misses. Specificity and sensitivity were calculated with confidence intervals (CIs). The sample size was determined a priori for a 95% CI of ±10%.

Zero control patients were incorrectly labeled “acute MI suspected.” The specificity was 100% (100/100; 95% CI 0.96–1.0), whereas the sensitivity was 58% (58/100; 95% CI 0.48–0.67). This would have resulted in 42 missed cardiac catheterization laboratory activations, but zero inappropriate activations. The most common incorrect interpretation of STEMI ECGs by the computer was “data quality prohibits interpretation,” followed by “abnormal ECG unconfirmed.”

The authors found that prehospital computer interpretation is not sensitive for STEMI identification and should not be used as a single method for prehospital activation of the cardiac catheterising laboratory. Because of its high specificity, it may serve as an adjunct to interpretation. Other methods to identify STEMI include the use of telemetry or paramedic interpretation.


ECG use in neonatal resuscitation

Electrocardiogram Provides a Continuous Heart Rate Faster Than Oximetry During Neonatal Resuscitation

PEDIATRICS Vol. 130 No. 5 November 1, 2012

The aim of the research was to compare the time required to obtain a continuous audible heart rate signal from an electrocardiogram (ECG) monitor and pulse oximeter (PO) in infants requiring resuscitation.

Infants who had both ECG and PO placed during resuscitation were analysed using video and analog recordings. The median times from arrival until the ECG electrodes and PO sensor were placed, and the time to achieve audible tones from the devices, were compared.

© Gary Wilson/ Pre-hospital Research Forum

Forty-six infants had ECG and PO data. Thirty infants were very low birth weight (23–30 weeks). There was a difference in the median total time to place either device (26 vs 38 seconds), and a difference in the time to achieve an audible heart rate signal after ECG lead (2 seconds) versus PO probe (24 seconds) placement. In infants weighing >1500 g, the median time (interquartile range) to place the ECG was 20 seconds (14–43) whereas the time to place the PO was 36 seconds (28–56). The median times (interquartile range) to acquire a signal from the ECG and PO were 4 seconds (1–6) and 32 seconds (15–40, P = .001), respectively. During the first minutes of resuscitation, 93% of infants had an ECG heart rate compared with only 56% for PO.

The authors found that early application of ECG electrodes during infant resuscitation can provide the resuscitation team with a continuous audible heart rate, and its use may improve the timeliness of appropriate critical interventions.