9 Analyzing Pain and Stress from PPG Perfusion Signal Patterns
155
Fig. 9.3 Example episode of surgical stress index (SSI)
with P PG A n as PPG amplitude and H B I n as heart beat interval.
To match a range between 0 and 100, the PPGA and HBI values must be normalized [7]. A histogram transformation based on thousands of PPG signals is used to
handle inter-patient variability.
The SSI is available in GE Healthcare patient monitors or as standalone device.
According to GE Healthcare, the SSI is only valid for narcotized patients. Hence,
it cannot be used for optimization of pain therapy in postoperative care. Figure 9.3
shows the differences between the ANI as analgesia related index and SSI as stress
related index.
9.4 Intraoperative Assessment of Pain
Intraoperative assessment of pain is difficult, because patients under narcosis cannot
be asked for their pain score (VAS score). Therefore, anesthesiologists must assess
the level of analgesia by observing patients’ vital signs and other conditions during
the surgery.
The following analysis has been performed on the data from the University
Hospital Aachen [7]. The ANI and the SSI have been computed and evaluated using
data from various surgeries.
9.4.1 Analgesia Nociception Index
Since the ANI based on ECG is available as a commercial product, it does not need a
validation [8]. To validate ANI computation from PPG, the PPG signal must be from
a valid source. Therefore, a self-developed implementation [7] was used to compute
155
Fig. 9.3 Example episode of surgical stress index (SSI)
with P PG A n as PPG amplitude and H B I n as heart beat interval.
To match a range between 0 and 100, the PPGA and HBI values must be normalized [7]. A histogram transformation based on thousands of PPG signals is used to
handle inter-patient variability.
The SSI is available in GE Healthcare patient monitors or as standalone device.
According to GE Healthcare, the SSI is only valid for narcotized patients. Hence,
it cannot be used for optimization of pain therapy in postoperative care. Figure 9.3
shows the differences between the ANI as analgesia related index and SSI as stress
related index.
9.4 Intraoperative Assessment of Pain
Intraoperative assessment of pain is difficult, because patients under narcosis cannot
be asked for their pain score (VAS score). Therefore, anesthesiologists must assess
the level of analgesia by observing patients’ vital signs and other conditions during
the surgery.
The following analysis has been performed on the data from the University
Hospital Aachen [7]. The ANI and the SSI have been computed and evaluated using
data from various surgeries.
9.4.1 Analgesia Nociception Index
Since the ANI based on ECG is available as a commercial product, it does not need a
validation [8]. To validate ANI computation from PPG, the PPG signal must be from
a valid source. Therefore, a self-developed implementation [7] was used to compute