Table 4. Effectiveness of the closed-loop control system.
| Closed-loop (n = 89) | Opened-loop (n = 86) | P | |
|---|---|---|---|
| BIS<40 (%) | 11.68±9.22 | 14.53±13.44 | 0.106 |
| 40<BIS<60 (%) | 84.11±9.50 | 79.92±13.17 | 0.016 |
| BIS>60 (%) | 4.21±4.43 | 5.55±7.36 | 0.147 |
| SR | 0 | 0 | 1.000 |
| Mean BIS | 47.55±2.61 | 47.57±3.99 | 0.966 |
| PE | -5.28±5.28 | -5.23±7.49 | 0.963 |
| MDPE | -5.28±5.44 | -4.47±8.78 | 0.467 |
| MDAPE | 10.14±3.05 | 11.68±4.11 | 0.006 |
| Wobble | 7.98±2.20 | 8.23±2.42 | 0.483 |
| GS | 22.21±8.50 | 27.19±15.26 | 0.009 |
Data are presented as mean ± SD.
Closed-loop = automated control of propofol infusion group guided by the bispectral index; Opened-loop = manual control infusion group guided by the bispectral index; BIS<40(%) = percentage of time in which the BIS value was less than a value of 40; 40<BIS<60(%) = percentage of time in which the BIS value was between 40 and 60 during the maintenance; BIS>60(%) = percentage of time in which the BIS value was greater than a value of 60; SR = burst suppression ratio was calculated as SR>10% lasting at least one minute; PE = Performance error was defined as the difference between the actual value and the set value of BIS; MDPE = Median performance error; MDAPE = Median absolute performance error; Wobble = the intraindividual variability in PE; GS = Global score of BIS.