Table 2. Univariate risk ratio and 95% CI of mortality, for the second, third, and fourth category in reference to the first category. The average risk for the three variables is presented on the last line.

Variables	1st Quartile	2nd Quartile	3rd Quartile	4th Quartile
Length of CPR (minutes)	Ref	1.0 (0.2–4.5)	4.6 (0.7–30.4)	7.1 (0.6–75.1)
Lactate (mmol/L)	Ref	1.4 (0.3–6.4)	1.9 (0.3–10.4)	No survivor
pH	Ref	4.1 (0.7–24.0)	3.6 (0.6–21.6)	No survivor
Average risk	1	2.2	3.4	7.1

Abbreviations: CI, confidence interval; CPR, cardiopulmonary resuscitation; Ref, reference.

Note: The different quartiles are < 40, 40–59, 60–104, and ≥ 105 for length of CPR; < 8.0, 8.0–13.9, 14.0–17.9, and ≥ 18.0 for lactates; and > 7.0, 6.85–7.0, 6.61–6.84, and ≤ 6.60 for pH, respectively.

For example, a patient with a lactate of 14.0 mmol/L (in the third quartile) has a 1.9-fold increase in the risk of mortality, as compared with a patient with a lactate of 7.0 mmol/L.