Table 1.

Patient, response, arrest and intervention characteristics included in analysis

	Patient Variables	Agency and Response Variables	Arrest Variables	Intervention Variables
Variables known during choice of airway management strategy	Age	Medical History	Time to EMS arrival	Presenting Rhythm
	Gender	Unique agency ID	Hour of the call	Etiology of Cardiac Arrest
	Race	Location	Arrest witness status	Bystander CPR
				Type of bystander CPR (compressions, ventilations)*
				Use of AED
Variables not known during choice of airway management strategy		Transport time	Death in the field	Hypothermia in the field
		Time on scene	Sustained ROSC in the field	Epinephrine administered
			When did sustained ROSC occur?*	Other drugs administered
			Emergency Department Outcome	Vascular access* (IV or IO)
			Hospital Outcome
			Neurologic Status at Discharge (PCPC)

^*indicates optional variables in CARES. ROSC — return of spontaneous circulation. PCPC — Pediatric Cerebral Performance Score. IV — intravenous line. IO — intraosseous line.