Remember the breathing thing you had to do for
Steady Breathing? You have to do it again now. Once the power goes out, you'll have to start the L1/R1 breathing again (remember not to just spam them; keep the meter in the middle as much as possible).
To exit the area and unlock the trophy: walk forward out of the cell, turn right and walk forward until an inmate walks near you. At this point, don't touch any buttons until Carla says it's safe to move again. Turn left and keep walking forwards – you'll see another inmate; again, don't touch any buttons – then keep walking forward. The lights will come back on. Now dash forward to leave the area, and the trophy will unlock once you've escaped.
Solution taken from PlayStation Trophies:
https://www.playstationtrophies.org/game/indigo-prophecy/tro...