this is getting slightly off the original topic, but...

i was always brought up with the idea that you don't use mhi with patients on pcv. shane as you know, this doesn't always have to apply and there are times when we do it anyway. i've found more often in recent times that i will. what i always do first is examine why they're on pcv. then i switch the mode to volume-controlled simv and look at what their peak pressures are. if they're appropriately low enough, i'll use mhi if there's a good indication. it's multifactorial of course... what is their fio2, their peep etc etc.

to answer your last question - yes i think the peak of 40cmH2O should still apply for the same reasons of old. i don't think a limit of 30 would be beneficial.

recent case to ponder:

a 50yo man with a drug overdose and nasty aspiration pneumonia who collapsed both bases quite markedly within 24 hours of intubation. he wasn't being sedated but his gcs was quite low after 3-4 days.
his ventilatory pattern was a bit all over the place on simv and so he was put on pcv - peep was 10, ps +10 and pc needed to be 20 to keep his tidal volumes down! tidal volumes were 500-700. his pf ratio improved when just this was changed (and no physio done overnight).

however, when put on psv (not simv) his peak pressures were around 26-28, but his tidal volumes were about 1100-1400. his ventilatory pattern was almost cheyne-stokes like with significant apnoeic periods. you could argue this was a decent enough treatment in itself as he was getting great big tidal volumes, with nice breaks in between sets! combined with manual techniques and suction you could have a complete treatment.

would you use mhi with peep in this case? any other suggestions for changes to ventilation mode/settings? for the record, fio2 went from 0.5 to 0.75 over the first four days, with pao2 kept within normal limits with this increase.