Non-invasive assessment of fluid responsiveness by changes in partial end-tidal CO2 pressure during a passive leg-raising maneuver

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.PLR-induced increases in CO and PETCO2 were strongly correlated (R2 = 0.79; P < 0.0001). The areas under the receiver-operating characteristics (ROC) curve for a PLR-induced increase in CO and PETCO2 (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 PETCO2 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%).Induced changes in PETCO2 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 CO2 production.The passive leg-raising (PLR) maneuver provides a dynamic assessment of preload dependence inducing a transient and reversible increase in cardiac preload. The abrupt transfer of blood contained in the venous reservoir of the legs and splanchnic compartment while moving the patient from a semirecumbent to supine position with legs elevated increases cardiac preload as a 'self-volume challenge' and, when both ventricles are operating in the steep part of the Frank-Starling curve, also improves cardiac output (CO) [1]. This maneuver has been demonstrated to predict fluid responsiveness in many studies over a wide population, including clinical situations in which other parameters of fluid responsiveness have failed, such as patients with cardiac arrhythmias or with spontaneous breathing [1-3]. However, since the hemodynamic effects of PLR are usually sudden and transient, a fast-resp