I had an epi after labouring for 24 hours (established labour for about 12 hours). Had to have a vacuum because DD was stuck and in distress and had to be brought out quicker. They had a hard time getting the vaccum to work but after 3 attempts it worked. If it hadn't, I was going to be rushed for an emergency c/s. I don't think the assitance was anything to do with the epi though. My waters broke 30mins before contractions started and things were progressing too slowly which is why intervention was needed.