Objective The study of induced circulatory changes requires simultaneous assessment of multiple regional circulations because of interactions and compensatory mechanisms. Positive end expiratory pressure mechanical ventilation (PEEP) is known to cause marked, and potentially deleterious, cardiovascular changes. Our aim was to use a comprehensive approach to assess PEEP-induced circulatory changes in open vs closed abdomen animals. Material and methods In the anesthetized rabbit, we used implantable Doppler micro-probes to measure blood flow simultaneously in the ascending aorta, inferior vena cava, portal vein, hepatic artery, common carotid artery, and renal artery. We studied spontaneously breathing animals (Group A), and open (Group B) and closed abdomen (Group C) animals mechanically ventilated at 0 (ZEEP) and 12 cm H 2 O PEEP. Results In Group A, all biological and hemodynamic variables remained unchanged for three hours at the end of the surgical procedure. In Groups B and C, ZEEP produced no significant hemodynamic change. PEEP induced a decrease in carotid, hepatic, and renal artery blood flow in Groups B and C, a decrease in heart rate and mean arterial blood pressure in Group B, and a decrease in aorta blood flow in Group C. Conclusions These experimental results demonstrate the usefulness of the comprehensive approach of circulatory changes, and confirm that PEEP may have deleterious effects on regional blood flow, even without significant change in cardiac output, especially when the abdomen is open.

LEFRANT JEAN-YVES; BRUELLE, PASCAL; RIPART, JACQUES; IBANEZ, FABIEN; AYA, GUY; PERAY, PASCALE; SAISSI, GILBERT; LA COUSSAYE, JEAN-EMMANUEL DE; ELEDJAM, JEAN-JACQUES

The purpose of the study was to compare cardiac output (CO) measurement by continuous (CTD) with that by conventional thermodilution (TD) in critically ill patients. In 19 of 20 critically ill patients requiring a pulmonary artery catheterism, 105 paired CO measurements were performed by both CTD and TD. Regression analysis showed that: CTD CO = 1.18 TD CO − 0.47. Correlation coefficient was 0.96. Bias and limit of agreement were — 0.8 and 2.4 L · min−1, respectively. When a Bland and Altman diagram was constructed according to cardiac index ranges, biases were −0.2 and −0.3 and −0.8 L · min−1 · m−2 and limits of agreement were 0.3, 0.7 and 1.6 L · min−1 · m−2 for low (<2.5 L · min−1 · m−2), normal (between 2.5 and 4.5 L · min−1 · m−2) and high (> 4.5 L · min−1 · m−2) cardiac indexes, respectively. It is concluded that CTD, compared with TD, is a reliable method of measuring CO, especially when cardiac index is ≤4.5 L · min−1 · m−2.