A potential method of correcting intracavitary left ventricular filling pressures for the effects of positive end-expiratory airway pressure.

Based on the observation that positive end-expiratory airway pressure (PEEP) causes comparable increments in intrapericardial and right-sided intracardiac pressures, we hypothesized that intracavitary left ventricular filling pressures measured in the presence of PEEP can be corrected for increased intrathoracic pressure by subtracting the effects of PEEP on intracavitary right ventricular filling pressures. Ventricular function curves (aortic blood flow vs intracavitary left ventricular end-diastolic pressure [LVEDP]) were generated with and without 15 cm of water of PEEP in eight dogs. All curves were shifted to the right by PEEP (i.e., intracavitary LVEDP was higher for any submaximal level of aortic blood flow). However, when pressures measured in the presence of PEEP were "corrected" by subtracting the corresponding increment in intracavitary right ventricular end-diastolic pressure caused by PEEP at each level of ventricular filling, control and corrected PEEP data points appeared to fall on the same curve in five dogs, and differed only slightly in three dogs. Mean control and corrected PEEP curves derived by averaging polynomial regression coefficients for each condition differed significantly from uncorrected PEEP curves (p less than .05), but not from each other. Analogous curves based on mean left atrial pressure were corrected equally well by subtracting the effects of PEEP on mean right atrial pressure. We conclude that the increments in intracavitary right heart filling pressures caused by PEEP can be used to correct intracavitary left heart filling pressures for the effects of PEEP on intrathoracic pressure.