Non-invasive assessment of fluid responsiveness by changes in partial end-tidal CO(2 )pressure during a passive leg-raising maneuver

BACKGROUND: The passive leg-raising (PLR) maneuver provides a dynamic assessment of fluid responsiveness inducing a reversible increase in cardiac preload. Since its effects are sudden and transitory, a continuous cardiac output (CO) monitoring is required to appropriately assess the hemodynamic response of PLR. On the other hand, changes in partial end-tidal CO(2 )pressure (PETCO(2)) have been demonstrated to be tightly correlated with changes in CO during constant ventilation and stable tissue CO(2 )production (VCO(2)). In this study we tested the hypothesis that, assuming a constant VCO(2 )and under fixed ventilation, PETCO(2 )can track changes in CO induced by PLR and can be used to predict fluid responsiveness. METHODS: Thirty-seven mechanically ventilated patients with acute circulatory failure were monitored with the CardioQ-ODM esophageal Doppler. A 2-minutes PLR maneuver was performed. Fluid responsiveness was defined according to CO increase (responders ≥ 15%) after volume expansion. RESULTS: PLR-induced increases in CO and PETCO(2 )were strongly correlated (R(2 )= 0.79; P < 0.0001). The areas under the receiver-operating characteristics (ROC) curve for a PLR-induced increase in CO and PETCO(2 )(0.97 ± 0.03 SE; CI 95%: 0.85 to 0.99 and 0.94 ± 0.04 SE; CI 95%: 0.82 to 0.99; respectively) were not significantly different. An increase ≥ 5% in PETCO(2 )or ≥ 12% in CO during PLR predicted fluid responsiveness with a sensitivity of 90.5% (95% CI: 69.9 to 98.8%) and 95.2% (95% CI: 76.2 to 99.9%), respectively, and a specificity of 93.7% (95% CI: 69.8 to 99.8%). CONCLUSION: Induced changes in PETCO(2 )during a PLR maneuver could be used to track changes in CO for prediction of fluid responsiveness in mechanically ventilated patients with acute circulatory failure, under fixed minute ventilation and assuming a constant tissue CO(2 )production.