unusual breathing in toddler during sleep

since my daughter was born she has had an irregualr breathing pattern causing her to have pauses in her breathing during sleep. she often stirs in the night, then takes 3 breathes, pauses for 10-30seconds then takes another 3 breathes, pauses again....this pattern continutes for a large proportion of the night. she does have these pauses in the day and occur randomly with no known influence. however they are a rare occurance. doctors have tried caffiene medicine which failed to stimulate her CNS and oxygen caused the length of her apneas to increase, bipap ventilation has also fialed to stimulate her to breathe after puttin in a breathe during her pauses and we are now about to start using ASV. she is neurologically healthy and apart from hitting a few physical milestones late shes in perfect health and never had any problems. she does suffer from reoccurent secondary lactose intolerance but this is not connected to her breathing.