The Sensitivity and Specificity of Pulmonary Carbon Dioxide Elimination for Noninvasive Assessment of Fluid Responsiveness.
BACKGROUND
We sought to determine whether the response of pulmonary elimination of CO2 (VCO2) to a sudden increase in positive end-expiratory pressure (PEEP) could predict fluid responsiveness and serve as a noninvasive surrogate for cardiac index (CI).


METHODS
Fifty-two patients undergoing cardiovascular surgery were included in this study. By using a constant-flow ventilation mode, we performed a PEEP challenge of 1-minute increase in PEEP from 5 to 10 cm H2O. At PEEP of 5 cm H2O, patients were preloaded with 500 mL IV saline solution after which a second PEEP challenge was performed. Patients in whom fluid administration increased CI by ≥15% from the individual baseline value were defined as volume responders. Beat-by-beat CI was derived from arterial pulse contour analysis, and breath-by-breath VCO2 data were collected during the protocol. The sensitivity and specificity of VCO2 for detecting the fluid responders according to CI was performed by the receiver operating characteristic curves.


RESULTS
Twenty-one of 52 patients were identified as fluid responders (40%). The PEEP maneuver before fluid administration decreased CI from 2.65 ± 0.34 to 2.21 ± 0.32 L/min/m (P = 0.0011) and VCO2 from 150 ± 23 to 123 ± 23 mL/min (P = 0.0036) in responders, whereas the changes in CI and VCO2 were not significant in nonresponders. The PEEP challenge after fluid administration induced no significant changes in CI and VCO2, in neither responders nor nonresponders. PEEP-induced decreases in CI and VCO2 before fluid administration were well correlated (r = 0.75, P < 0.0001) but not thereafter. The area under the receiver operating characteristic curves for a PEEP-induced decrease in ΔCI and ΔVCO2 was 0.99, with a 95% confidence interval from 0.96 to 0.99 for ΔCI and from 0.97 to 0.99 for ΔVCO2. During the PEEP challenge, a decrease in VCO2 by 11% predicted fluid responsiveness with a sensitivity of 0.90 (95% confidence interval, 0.87-0.93) and a specificity of 0.95 (95% confidence interval, 0.92-0.98).


CONCLUSIONS
PEEP-induced changes in VCO2 predicted fluid responsiveness with accuracy in patients undergoing cardiac surgery.
From the *Department of Anesthesia, Hospital Privado de Comunidad, Mar del Plata, Buenos Aires, Argentina; †Electronic Department, Bioengineering Laboratory, School of Engineering, Mar del Plata University, Mar del Plata, Argentina; ‡Swisstom AG, Landquart, Switzerland; §Department of Surgical Sciences Section of Anesthesiology and Critical Care, Hedenstierna Laboratory, University Hospital, Uppsala Sweden; and ‖CIBERES, CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain.
Gerardo
G
Tusman
Iván
I
Groisman
Gustavo A
GA
Maidana
Adriana
A
Scandurra
Jorge Martinez
JM
Arca
Stephan H
SH
Bohm
Fernando
F
Suarez-Sipmann
D000368:Aged; D019540:Area Under Curve; D015415:Biomarkers / Q000378:metabolism; D001944:Breath Tests / Q000379:methods*; D019296:Capnography; D002245:Carbon Dioxide / Q000378:metabolism*; D006348:Cardiac Surgical Procedures; D005260:Female; D005440:Fluid Therapy / Q000009:adverse effects / Q000379:methods*; D006439:Hemodynamics; D006801:Humans; D007262:Infusions, Intravenous; D008168:Lung / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D011175:Positive-Pressure Respiration; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D012965:Sodium Chloride / Q000008:administration & dosage* / Q000009:adverse effects; D013997:Time Factors
D015415:Biomarkers; D002245:Carbon Dioxide; D012965:Sodium Chloride