154
M. Koeny
Fig. 9.2 Comparison of RRhf between non-stress episode (top) and stress episode (bottom)
The parasympathetic tone is computed by calculating the AUC over four time
periods of 16 s (A1–A4). The minimum of the four AUC episodes (AUCmin) is
selected and used for ANI index computation using Eq. 9.1.
AN I =
100 · (α · AU C min + β)
12.8
with : α = 5.1, β = 1.2
(9.1)
Figure 9.4 shows a sequence of ANI associated with painful surgical events.
The ANI is designed to be computed using standard ECG derived from the patient
monitor with no need for additional monitoring.
ANI can be computed using PPG and invasive blood pressure recordings too
[6]. Computation of ANI using many sources improves the reliability, especially
in situations where a signal is influenced by artifacts. In postoperative care, the ANI
can be acquired without disturbing the patient with cables.
9.3.3 Surgical Stress Index
The surgical stress index (SSI) was developed by Huiku et al. [7]. During evaluation,
different parameters were used such as heart beat interval (HBI), amplitude of PPG
signal (PPGA), blood pressure and pulse transition time. Analgesic drug concentration was used a reference to assess the stress level. Best correlation results between
analgesic drug concentration and SSI were found using the combination of PPGA
and HBI. Therefore, SSI is computed using Eq. 9.2.
SS I = 100 − (0.7 · P PG A n + 0.3 · H B I n )
(9.2)
M. Koeny
Fig. 9.2 Comparison of RRhf between non-stress episode (top) and stress episode (bottom)
The parasympathetic tone is computed by calculating the AUC over four time
periods of 16 s (A1–A4). The minimum of the four AUC episodes (AUCmin) is
selected and used for ANI index computation using Eq. 9.1.
AN I =
100 · (α · AU C min + β)
12.8
with : α = 5.1, β = 1.2
(9.1)
Figure 9.4 shows a sequence of ANI associated with painful surgical events.
The ANI is designed to be computed using standard ECG derived from the patient
monitor with no need for additional monitoring.
ANI can be computed using PPG and invasive blood pressure recordings too
[6]. Computation of ANI using many sources improves the reliability, especially
in situations where a signal is influenced by artifacts. In postoperative care, the ANI
can be acquired without disturbing the patient with cables.
9.3.3 Surgical Stress Index
The surgical stress index (SSI) was developed by Huiku et al. [7]. During evaluation,
different parameters were used such as heart beat interval (HBI), amplitude of PPG
signal (PPGA), blood pressure and pulse transition time. Analgesic drug concentration was used a reference to assess the stress level. Best correlation results between
analgesic drug concentration and SSI were found using the combination of PPGA
and HBI. Therefore, SSI is computed using Eq. 9.2.
SS I = 100 − (0.7 · P PG A n + 0.3 · H B I n )
(9.2)