The Resuscitation Outcomes Consortium (ROC) is a North American clinical trials research network focussing on out-of-hospital cardiac arrest (OHCA) and traumatic injury. In this study, Wang and colleagues performed a secondary analysis of clinical data collected prospectively as part of an earlier trial (ROC PRIMED, 2011).
The authors sought to determine survival to discharge with satisfactory functional status in adult (≥ 18 years) cases of non-traumatic cardiac arrest managed with endotracheal intubation (ETI) vs insertion of a supraglottic airway (SGA). Secondary outcomes included 24-hour survival, return of spontaneous circulation (ROSC) and presence of airway and pulmonary complications (pulmonary oedema, internal thoracic or abdominal injuries, acute lung injury, sepsis and pneumonia).
Patients who did not require advanced airway insertion or in whom these efforts failed were excluded from the analysis. In addition, data from King County and Seattle emergency medical services (EMS) were excluded as these agencies were not using SGA devices at the time of the initial study. Patients receiving both ETI and SGA insertion were classified as SGA cases.
During the original trial period, 10 455 cases received advanced airway management, of whom 8 487 (81.2%) received successful ETI and 1,968 (18.8%) received successful SGA insertion. Data on the type of SGA used were available for 1 444 cases and included King LT (63%), Combitube (20.5%), and laryngeal mask airway (16.6%).
The researchers employed multivariable logistic regression to investigate the effect of the airway management device on survival to discharge and other secondary outcome measures, controlling for ROC centre, PRIMED trial arm and factors known to influence survival, such as age, gender, bystander or EMS witnessed arrest, bystander CPR, and initial ECG rhythm.
Patients undergoing out-of-hospital advanced airway management tended to be older and male. More than half of the OHCAs were bystander or EMS witnessed, and the presenting rhythm was shockable in approximately 25% of cases. Survival to discharge with satisfactory functional status was 4.7% for ETI and 3.9% for SGA. In comparison with successful SGA insertion, ETI was associated with increased survival to discharge with satisfactory functional status (odds ratio (OR) 1.40; 95% confidence ratio (CR) 1.04–1.89), 24-hour survival (OR 1.74; 95% CI 1.49–2.04), and ROSC (OR 1.78; 95% CI 1.54–2.04). ETI was not associated with secondary airway or pulmonary complications (OR 0.84; 95% CI 0.61–1.16). The survival improvement associated with ETI persisted when sites with less than 10% SGA use were excluded and if cases receiving both ETI and SGA insertion were reclassified as ETI rather than SGA patients. However, further analysis revealed the absence of successful ETI or SGA insertion demonstrated an increased odds of survival (OR 1.79; 95% CI 1.33–2.40) when compared with cases of successful placement.
The finding that no use of an advanced airway was associated with improved survival is noteworthy. Possible explanations include undesirable haemodynamic effects of advanced airway ventilation, or interruptions in chest compressions. Equally this group may simply represent patients in whom early ROSC was achieved and advanced airway attempts abandoned. These results must be interpreted with some caution, given that the original dataset was not designed to investigate advanced airway management attempts. The investigators did not follow up patients in whom no attempt was made to insert an advanced airway, and relied upon EMS reports of successful insertion.
Nonetheless, these results challenge assumptions that paramedic ETI confers no survival benefit in cardiac arrest, and that SGAs are universally acceptable as an alternative.
Future airway management policies must take account of these findings in determining the optimum airway management approach for the paramedic profession.