title: Non-invasive assessment of fluid responsiveness by changes in partial end-tidal CO2 pressure during a passive leg-raising maneuver.
abstract: 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 CO2 pressure (PETCO2) have been demonstrated to be tightly correlated with changes in CO during constant ventilation and stable tissue CO2 production (VCO2). In this study we tested the hypothesis that, assuming a constant VCO2 and under fixed ventilation, PETCO2 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 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%).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Unidad de Investigación Experimental, Servicio de Cuidados Críticos y Urgencias, Hospital SAS de Jerez, Jerez de la Frontera, C/Circunvalación s/n, 11407 Jerez de la Frontera, Spain. ignaciomonge@gmail.com.
authors.forename: Manuel Ignacio
authors.initials: MI
authors.lastname: Monge García
authors.forename: Anselmo
authors.initials: A
authors.lastname: Gil Cano
authors.forename: Manuel
authors.initials: M
authors.lastname: Gracia Romero
authors.forename: Rocío
authors.initials: R
authors.lastname: Monterroso Pintado
authors.forename: Virginia
authors.initials: V
authors.lastname: Pérez Madueño
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Díaz Monrové