Highlights:
The Scenario
The Review
What It Means for You
The Scenario
Engine 23 arrives on the scene of a 56 -year-old male who suffered a cardiac arrest while mowing the grass. Bystanders witnessed the arrest, immediately called 911, and began cardiopulmonary resuscitation. Two firefighters take over CPR from the bystanders; one EMT begins placing the automated external defibrillator on the patient while a second EMT quickly inserts an esophageal-tracheal combitube. The AED recommends a countershock, which the EMTs deliver, and CPR resumes.
As the medic unit arrives, one of the firefighters detects a pulse after a “no shock indicated” announcement from the AED. One of the arriving paramedics prepares to replace the ETC with an endotracheal tube. After removing the ETC, the medic has difficulty inserting the ETT. At the start of the second attempt, the patient redevelops ventricular fibrillation and the team delivers an additional countershock. CPR resumes, the medic secures the ETT, and the team completes preparation for transport. The patient never regains a pulse and the emergency department terminates the resuscitation attempt on arrival.
The EMT-B believes that the paramedic should not have attempted to replace the ETC, arguing that the difficult intubation may have contributed to the re-fibrillation. The paramedic points out that the ETT is considered the “gold standard” of airway control. He considers the ETC a secondary airway device that provides substandard ventilation during a resuscitation effort, which may have contributed to the patient’s demise.
If the paramedic is right, cardiac arrest victims receiving the ETC should have lower survival rates compared to those who receive endotracheal intubation.
The Review
Cady, Weaver, Pirrallo, and Wang (2009) conducted a retrospective study in the Milwaukee-County fire-based EMS system. In a retrospective study, the event occurred before the research project began. One limitation of these types of studies is that researchers cannot control any variables. Therefore, retrospective reviews cannot establish cause and effect relationships, only associations.
In this system, after identifying a possible cardiac arrest, emergency medical dispatchers sent the closest basic life support first responders along with the closest advanced life support responders. Each BLS first response vehicle had at least two EMTs and an AED.
The EMTs were also equipped with an ETC. ETC training consisted of a six-hour course that included both a didactic and psychomotor component. In practice, when the EMTs arrived on scene of the cardiac arrest, they either inserted the ETC or ventilated with a bag-valve-mask while awaiting paramedic arrival.
At least two paramedics capable of providing endotracheal intubation staff each of the ALS units. Paramedic training for ETT insertion in this system exceeds the recommendations of the National Standard Curriculum. Once on scene of the cardiac arrest, the paramedics often insert an ETT, unless the EMTs have already secured the airway with an ETC.
The purpose of the study was to examine the effect of ETC or ETT insertion on three outcome measures; return of spontaneous circulation (ROSC), survival to hospital admission, and survival to hospital discharge. The study included all adult victims (> 21 y/o) of cardiac arrest with presumed cardiac etiology. Researchers excluded patients from the trial if:
- The cardiac arrest was the result of trauma;
- Paramedics made no resuscitation attempt;
- Paramedics terminated resuscitation efforts in the field;
- ETC insertion failed after multiple attempts;
- Paramedics replaced the ETC with an ETT in the field;
- Paramedics inserted an ETC after they could not successfully insert an ETT.
Researchers used logistic regression models to evaluate the confounding influence of several variables on each of the three study outcome measures. These variables included response time, whether anyone witnessed the arrest, whether bystanders performed CPR or used an AED, and whether ventricular fibrillation was the presenting rhythm.
During the nine-year period, 5,822 patients met the study criteria. Twenty-six percent (n = 1,487) had ETC insertion for the resuscitation effort. The remaining patients (74 percent, n = 4335) had ETT insertion. The ETT success rate on first or second attempt was 96.3 percent (95 percent confidence interval [95.9 percent, 96.7 percent]).
The researchers set the criteria for statistical significance at 0.05, which is represented by the p value. When p values are less than or equal to 0.05, differences between the two groups are considered statistically significant and therefore, were not likely to have been caused by chance. If the p value is greater than 0.05, the differences are not statistically significant and could be the result of chance alone.
Table 1 presents some of the study results. The patients receiving the ETT were slightly older (67 years vs. 64 years, p < 0.01), more likely to have their arrest witnessed (51 percent vs. 44 percent, p < 0.01), more likely to receive bystander defibrillation (0.3 percent vs. 0.0 percent, p = 0.04), and had shorter response times (median 5 minutes, interquartile range [IQ] 3-6) compared to those receiving the ETC (median 5 minutes, interquartile range [IQ] 4-7). Regression analysis determined that none of these potential confounders influenced any of the outcome measures.
Based on the results of the data, the researchers concluded that ETC insertion by EMTs did not influence ROSC, survival to hospital admission, or survival to hospital discharge compared to ETT insertion by paramedics.
| TABLE 1 | ETT | ETC | p value |
| Age (mean years) | 67 | 64 | < 0.01 |
| Witnessed arrest | 51% | 44% | < 0.01 |
| Received bystander defibrillation | 0.3% | 0.0% | 0.04 |
| Response time | 5 min ([IQ] 3-6) | 5 min ([IQ] 4-7 |
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| ROSC | 35.9% | 34.2% | 0.22 |
| Survival to admission | 25.7% | 25.4% | 0.84 |
| Survival to discharge | 6.4% | 6.5% | 0.90 |
What It Means for You
Researchers have not identified a single device that provides optimal airway control under all conceivable field conditions (American Heart Association, 2005).
In this study, insertion of an ETC by EMTs neither improved nor worsened outcomes for adult, non-traumatic cardiac arrest patients when compared to ETT placement by paramedics. Based on the results of this study, the paramedic could have continued to ventilate through the ETC for the remainder of the transport as there appears to be no difference in outcomes between patients treated with ETC versus those treated with ETT.
References
American Heart Association. (2005). Advanced cardiac life support guidelines, part 4: Advanced life support. Circulation, 112, III-25 - III-54.
Cady, C. E., Weaver, M. D., Pirrallo, R. G., Wang, H. E. (2009). Effect of emergency medical technician - placed Combitubes on outcomes after out-of-hospital cardiopulmonary arrest. Prehospital Emergency Care, 13, 495-499.
The author has no financial interest, arrangement, or direct affiliation with any corporation that has a direct interest in the subject matter of this presentation, including manufacturer(s) of any products or provider(s) of services mentioned.
