PEEP and PAOP

Q: If patient has a Pulmonary Artery Catheter (PAC) in place and excessive Positive End Expiratory Pressure (PEEP) is applied on ventilator, what is the rule of thumb to calculate correct Pulmonary Artery Occlusion Pressure (PAOP/wedge Pressure)? 



Answer: PEEP usually does not effect PAOP/wedge pressure clinically but once the requirement of PEEP starts going above 8-10, PAOP should be adjusted by subtracting 

•  one-half of the PEEP level from the PAOP, if lung compliance is normal, or 
•  one-quarter of the PEEP level if lung compliance is reduced 

For example, if a patient with acute respiratory distress syndrome (ARDS) (decreased lung compliance) with an applied PEEP of 12 cm H2O and has a wedge pressure of 14 mm Hg, the recalculated wedge pressure would be 10 mm Hg. 

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Reference:

Teboul JL, Besbes M, Andrivet P, et al. A bedside index assessing the reliability of pulmonary artery occlusion pressure measurements during mechanical ventilation with positive end-expiratory pressure. J Crit Care 1992; 7:22.