VENTRICULAR PERFORMANCE A potential method of correcting intracavitary left ventricular filling pressures for the elfects of positive end - expiratory airway pressure

نویسنده

  • RoY V. DITCHEY
چکیده

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 enddiastolic pressure [LVEDPI) 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 < .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. Circulation 72, No. 3, 660-667, 1985. POSITIVE end-expiratory airway pressure (PEEP) complicates hemodynamic monitoring in critically ill patients by increasing intrathoracic pressure. This effect alters the usual relationship between intravascular filling pressures and cardiac output, and invalidates standard guidelines' 2 for optimizing left ventricular preload in patients in low-output states. This is because left ventricular filling and stroke volume are functions of transmural, rather than intracavitary left ventricular end-diastolic pressure (LVEDP).3 As a result, the increment in pressure around the left ventricle caused by PEEP effectively shifts ventricular function curves based on intracavitary pressures to the right (i.e., ventricular volume and cardiac output are lower for any measured pressure).' To remain useful as indexes of From the Cardiology Division, University of Colorado Health Sciences Center, Denver. Supported in part by the Ravin-Goodstein Fund. Address for correspondence: Roy V. Ditchey, M.D., Cardiology Division, Box 130, University of Colorado Health Sciences Center, 4200 East Ninth Ave., Denver, CO 80262. Received March 27, 1984; revision accepted May 30, 1985. 660 left ventricular preload in this setting, intracavitary filling pressures must be corrected for the effects of PEEP on intrathoracic pressure. We recently found that PEEP causes changes in intracavitary right ventricular end-diastolic pressure (RVEDP) that are similar to changes in mean intrapericardial pressure over a wide range of ventricular filling conditions.5 Based on this observation, and the knowledge that right ventricular pressure constitutes part of the effective pressure around the left ventricle,3 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 right-sided intracardiac pressures. To test this hypothesis, we generated ventricular function curves with and without 15 cm of water of PEEP in anesthetized dogs. Curves based on intracavitary LVEDP and mean left atrial pressure were "corrected" by subtracting the effects of PEEP on intracavitary RVEDP and mean right atrial pressure, respectively, at each level of ventricular filling. CIRCULATION by gest on M ay 3, 2017 http://ciajournals.org/ D ow nladed from LABORATORY INVESTIGATION-VENTRICULAR PERFORMANCE

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تاریخ انتشار 2005