Table 1 Comparison of patient characteristics and HRV-related variables between good and poor outcomes

Age (years)

61 (46–76)

58 (49–72)

61 (45–77)

Gender (F/M) (n)

26/50

7/15

19/35

APACHE II score

28 (26–31)

27 (26–29)

28 (27–32)

SOFA score, day 1

11 (8–13)

10 (7–11)

11 (8–14)

DC

1.83 (0.92–3.34)

2.69 (1.23–5.32)

1.64 (0.78–2.77)

AVNN (ms)

699 (605–827)

804 (698–842)

677 (574–788)

SDNN (ms)

40.9 (25.3–57.8)

47.6 (34.7–71.5)

35.5 (23.8–55.4)

rMSSD (ms)

10.4 (4.9–19.8)

15.3 (6.4–24.4)

9.1 (4.2–17.0)

pNN50(%)

0.88 (0.16–3.76)

1.17 (0.16–3.76)

0.77 (0.16–3.47)

Triangular index

7.3 (5.1–11.1)

9.8 (6.7–15.3)

6.6 (4.9–10.3)

Poincaré plot, SD1 (ms)

7.5 (3.5–14.8)

11.5 (4.5–19.7)

7.2 (3.1–12.9)

Poincaré plot, SD2 (ms)

17.4 (10.0–29.9)

31.0 (21.1–43.0)

13.3 (7.4–22.6)

ln total power (ms²)

8.06 (7.15–8.80)

8.48 (7.77–9.46)

7.84 (7.03–8.70)

ln ULF power (ms²)

7.83 (6.90–8.63)

8.06 (7.39–8.81)

7.72 (6.80–8.59)

ln VLF power (ms²)

4.83 (3.73–5.98)

6.06 (5.49–7.12)

4.41 (3.14–5.22)

ln LF power (ms²)

3.65 (1.72–4.59)

4.38 (3.54–5.30)

3.10 (1.36–4.33)

ln HF power (ms²)

3.53 (2.39–4.72)

3.96 (2.71–5.08)

3.11 (1.99–4.67)

LF/HF

0.98 (0.52–2.04)

2.23 (1.10–3.72)

0.73 (0.40–1.42)

Power law (β)

− 1.45 (− 1.74 to − 1.20)

− 1.36 (− 1.48 to − 1.05)

− 1.56 (− 1.80 to − 1.31)

DFA (α₁)

0.79 (0.64–0.98)

0.98 (0.87–1.22)

0.71 (0.60–0.86)

DFA (α₂)

0.92 (0.77–1.12)

1.10 (0.88–1.29)

0.88 (0.71–1.01)

ApEn

0.55 (0.27–0.84)

0.59 (0.30–0.95)

0.51 (0.26–0.81)

SampEn

0.37 (0.17–0.60)

0.38 (0.23–0.79)

0.36 (0.16–0.55)

MSE index

10.8 (3.5–19.4)

19.0 (14.8–22.6)

8.3 (2.9–13.6)