Noninvasive pulmonary blood flow for optimal PEEP.

Recent data in the literature suggest that effective pulmonary blood flow (Qp) measured invasively as cardiac output minus shunt flow, assumes its largest value at a PEEP level that is optimal in the sense that it also provides close to maximal oxygen delivery. Qp obtained noninvasively from simultaneous measurements of mixed expired and end-tidal CO2-concentrations is therefore proposed as a simple clinical indicator of the effects of PEEP on the cardio-pulmonary system. It is shown that modern respiratory equipment can be easily adapted to implement such a noninvasive evaluation of PEEP therapy. If the method is proven useful an automatic search for optimal PEEP becomes a future possibility.