The changes of central venous pressure by body posture and positive end-expiratory pressure

BACKGROUND: Central venous pressure (CVP) monitoring provides a useful estimate of the volume status of the systemic circulation. Both increase in the intrathoracic pressure by applying positive-end expiratory pressure (PEEP) and various patient positioning may commonly mislead the interpretation of CVP. We investigated the effect of body posture and different PEEPs on CVP in anesthetized patients. METHODS: Ninety-one patients (ASA I or II) scheduled for elective surgery with supine (50 patients), lateral decubitus (27 patients), or prone position (14 patients) were included. After induction of general anesthesia, CVP, mean arterial pressure (MAP), heart rate (HR), end-tidal CO2 (EtCO2) and peak inspiratory pressure (PIP) were measured under different PEEP conditions of 0, 5, 10, and 15 cmH2O in each body posture. RESULTS: CVP and PIP increased gradually by the increment of PEEP in patients with all positions. The magnitude of changes of CVP and PIP was significantly greater than other PEEP conditions when PEEP was 15 cmH2O, especially in prone position (P < 0.05). There were no differences in MAP, HR and EtCO2 during the increase of PEEP in all positions. CONCLUSIONS: These results suggest that PEEP as much as 15 cmH2O may alter reliability of CVP in estimating adequate circulatory volumes, especially in prone position.