Table 4.

Risk Ratio of Getting ECPR for Arrest Characteristics/Management

Variable	Risk Ratio (95% CI)a	P Value	Risk Ratio (95% CI)b	P Value	Risk Ratio (95% CI)c	P Value
Hospital resuscitation activated	0.3 (0.3–0.4)	<0.001	0.5 (0.4–0.6)	<0.001	0.5 (0.4–0.6)	<0.001
Presenting rhythm status
Asystole	Reference	···	Reference	···	Reference	···
PEA	1.0 (0.8–1.2)	0.83	0.9 (0.8–1.1)	0.43	0.9 (0.8–1.1)	0.45
Pulseless VT	1.4 (1.1–1.7)	0.012	1.2 (1.0–1.6)	0.11	1.2 (0.9–1.5)	0.15
VF	2.0 (1.6–2.4)	<0.001	1.6 (1.3–1.9)	<0.001	1.5 (1.2–1.8)	<0.001
Palpable pulse initially	1.4 (1.1–1.8)	0.005	1.2 (0.9–1.5)	0.14	1.2 (0.9–1.5)	0.23
Any VF/VT	2.1 (1.9–2.4)	<0.001	2.0 (1.7–2.2)	<0.001	1.9 (1.7–2.2)	<0.001
Compression method
Manual	0.073 (0.054–0.098)d	<0.001	0.139 (0.101–0.191)d	<0.001	0.137 (0.099–0.189)d	<0.001
Mechanical	1.3 (1.0–1.5)	0.023	1.3 (1.0–1.6)	0.017	1.5 (1.1–2.1)	0.006
Open cardiac massage	20.1 (17.1–23.8)	<0.001	18.349 (14.718–22.876)d	<0.001	18.026 (14.399–22.566)d	<0.001
Any ROSC	1.6 (1.4–1.9)	<0.001	1.5 (1.3–1.7)	<0.001	1.5 (1.3–1.8)	<0.001
Total duration before durable ROSC	1.024 (1.023–1.026)d	<0.001	1.024 (1.023–1.026)d	<0.001	1.024 (1.023–1.026)d	<0.001
Induced hypothermia	3.5 (2.9–4.3)	<0.001	3.2 (2.7–3.9)	<0.001	3.2 (2.7–3.9)	<0.001

ECPR indicates extracorporeal cardiopulmonary resuscitation; PEA, pulseless electrical activity; ROSC, return of spontaneous circulation; VF, ventricular fibrillation; and VT, ventricular tachycardia.

^aUnadjusted risk ratio.

^bRisk ratio adjusting for patient variables.

^cRisk ratio adjusting for patient and hospital variables.

^dA mixed effects logistic model was used because of convergence issues, and the reported odds ratio is an approximation to the risk ratio.