Time delay of the qCON monitor and its performance during state transitions

We investigated the performance of the qCON index regarding its time delay for sudden changes in the anesthetic level as well as to separate responsiveness from unresponsiveness during loss and return of responsiveness (LO R and RO R ). For evaluation of the time delay, we replayed relevant EEG episodes to the qCON to simulate sudden changes between the states (i) awake/sedation , (ii) adequate anesthesia , or (iii) suppression. We also replayed EEG from 40 patients during LO R and RO R to evaluate the qCON’s ability to separate responsiveness from unresponsiveness. The time delays depended on the type of transition. The delays for the important transition between awake/sedation and adequate anesthesia were 21(5) s from awake/sedation to adequate anesthesia and 26(5) s in the other direction. The performance of the qCON to separate responsiveness from unresponsiveness depended on signal quality, the investigation window, i.e. ± 30 s or ± 60 s around LO R /RO R , and the specific transition being tested. AUC was 0.63–0.90 for LO R and 0.61–0.79 for RO R . Time delay and performance during state transitions of the qCON were similar to other monitoring systems such as bispectral index. The better performance of qCON during LO R than RO R probably reflects the sudden change in EEG activity during LO R and the more heterogeneous EEG during RO R .