Table 4

SpO2 instability

SpO2 coefficient of variation (%)SpO2 <91% (episodes/hour)SpO2 <91% (episode duration, s)SpO2 >95% (episodes/hour)SpO2 >95% (episode duration, s)
Manual control (original recordings)4.2 (3.3–4.8)n.a.n.a.n.a.n.a.
Core PID1.8 (1.7–2.3)g16 (14–19)a,h7.9 (7.2–8.8)a,e17 (14–28)a,i11 (9.4–21)a,g
Core PID+SC2.9 (2.3–5.4)a24 (19–40)c9.1 (8.2–9.3)27 (18–30)c9.2 (8.6–20)c
Core PID+adaptive Kp1.7 (1.5–2.1)b10 (7.7–12)b,d9.2 (8.7–11)b13 (7.1–17)b,d16 (13–25)b,d
Core PID+TRA1.7 (1.6–2.2)b13 (9.6–14)d8.9 (8.2–9.6)b15 (9.5–24)d13 (11–25)d
Enhanced PID−SC1.7 (1.5–2.1)11 (8.0–13)e9.7 (9.0–11)d13 (7.3–18)g15 (13–26)e
Enhanced PID−adaptive Kp2.7 (1.8–3.8)c18 (15–25)f9.4 (8.9–10)17 (13–25)e9.7 (8.7–23)f
Enhanced PID−TRA1.8 (1.6–2.4)d13 (11–16)f9.2 (8.7–10)c11 (5.3–17)f9.3 (8.3–24)f
Enhanced PID1.7 (1.6–2.3)g13 (11–15)f,g9.7 (9.0–11)d,g12 (5.2–15)f,h,j9.7 (8.6–26)f,g
Enhanced PID 30 s lockout2.2 (2.0–2.8)h15 (12–17)13 (12–15)f,h13 (5.8–16)j14 (12–29)h
PD control4.5 (3.0–7.4)h27 (14–56)h21 (17–27)f,h15 (7.1–36)28 (11–42)h
  • Indices of SpO2 instability with different algorithms. Median (IQR). Within-column statistical comparisons (Friedman analysis of variance with Dunn's post hoc test): a differs from b, p<0.05; c differs from d; e differs from f; g differs from h; I differs from j.

  • Kp, proportional coefficient; PD, proportional–derivative; PID, proportional–integral–derivative; SC, Severinghaus compensation; TRA, target range attenuation.