How do you set optimal PEEP? What do you look at the tells you you have optimal PEEP?

Steve,
What you need to do is a PEEP trial. What you will be looking at is the best PaO2, CO, and static compliance.
Slowly increase the PEEP levels and track the above mentioned values over time (say 30 min. to an hour each).
Optimal PEEP is where all 3 values are in a good range without comprising any of them.
Check Egans or Pilbeam for a good diagram and more explicit explanation.
Good Luck.

To determine optimal PEEP I prefer to take from the 'Open Lung Concept' as described by Burkhard Lachmann. The technique I use is as follows:

- PCV PC=15 cmH2O above PEEP RR=10 I:E=1:1
- increase PEEP 2-5 cmH2O every 2 mins from baseline until PEEP 25 cmH2O (if lung not recruited at 25 cmH20 continue increasing PEEP by 5 cmH2O up to a PEEP of 45 cmH20)
- then progressively decrease PEEP in steps of 2 cmH20 every 2mins, monitoring oxygenation to find derecruitment level
- then increase PEEP to previous recruitment level for 2mins and
then set PEEP at 2 cmH20 above alveolar collapsing PEEP

You will know when you hit the recruitment/derecruitment level because you should see a change in tidal volume, compliance, oxygenation and if you have the ability to monitor Volumetric CO2 you should see an increase in the amount of exhaled CO2. These changes should be quite noticeable.

This technique basically works by recruiting lung (opening the lung), finding the pressure at which the lung derecruits and then you recruit the lung at the recruitment pressure you have already determined (reopen the lung) and then set the PEEP above the pressure that the lung derecruits.

This technique allows to determine both the opening and closing pressures of the lung and lets you set the PEEP according to expiratory side of the pressure/volume curve.

I find this technique easy to use and I do sometimes modify it depending on the patient (I may choose a slightly different rate or I:E ratio) but the concept always remains the same.

Hope this provides you the info you were looking for.

JeffD