With positive end-expiratory pressure (PEEP)-induced reduction in cardiac output, measurement of ventricular filling pressure assists in proper therapeutic decision-making. Because PEEP may increase pleural and juxtacardiac pressure, central venous pressure (CVP) and left atrial pressure (LAP) measurements during PEEP may not simply reflect ventricular filling, but rather reflect the sum of intracardiac and extracardiac forces. Monitoring devices placed within the central circulation use saline solution-filled lumens and transducer systems for pressure monitoring. Therefore, any device designed to estimate the extracardiac influence of PEEP on intraluminal monitoring devices would be expected to reflect such changes best when the device is also filled with saline solution. In the present study, esophageal pressure (Pes) was measured with a saline solution-filled balloon-equipped nasogastric tube to estimate the extracardiac influence of PEEP on CVP and LAP. Pes, CVP, LAP, and cardiac index (CI) were measured in 17 patients subjected to 0, 5, 10, 15, 20 cm H2O PEEP. Comparing 0 with 20 cm H2O PEEP, CVP (7 +/- 1.0 mm Hg to 13.4 +/- 1.3 mm Hg), LAP (6.3 +/- 1.1 mm Hg to 11.7 +/- 1.4 mm Hg), and Pes (6.1 +/- 1.4 mm Hg to 12.1 +/- 1.5 mm Hg) all increased significantly as CI fell (2.72 +/- 0.14 L/min/m2 to 2.20 +/- 0.15 L/min/m2).(ABSTRACT TRUNCATED AT 250 WORDS)