Andy,
Interfacing to modern montiors in real time is a huge problem these days, I have spent a lot of time looking in to this and found no real solution. The only real time output from digital monitors tends to be the sync interface for defibs for cardioversion. All ther outputs even in analogue format tend to have been converted to digital, processed and converted back whcih causes a delay.
I would look around for some onld analogue monitors and then finding one with a respiratory as oposed to ECG output might be very hard.
Have you tried a sideways look at this? A neonatal apnoea monitor such as the Graseby MR10 might give you the sych pulse you might need.
Good luck in your search.
RoJo
