PT - JOURNAL ARTICLE AU - Mark S. Siobal AU - Hannah Ong AU - Josephine Valdes AU - Julin Tang TI - Calculation of Physiologic Deadspace: Comparison of Ventilator Volumetric Capnography to Measurements by Metabolic Analyzer and Volumetric CO<sub>2</sub> Monitor. AID - 10.4187/respcare.02116 DP - 2012 Dec 04 TA - Respiratory Care PG - respcare.02116 4099 - http://rc.rcjournal.com/content/early/2012/12/04/respcare.02116.short 4100 - http://rc.rcjournal.com/content/early/2012/12/04/respcare.02116.full AB - Background: Calculation of physiologic deadspace (VD/VT) using the Enghoff modification of the Bohr equation requires measurement of the partial pressure of mean expired CO2 (PeCO2) by exhaled gas collection and analysis, use of a metabolic analyzer, or use of a volumetric CO2 monitor. The Drager XL ventilator is equipped with integrated volumetric CO2 monitoring and calculates minute CO2 production (VCO2). We calculated PeCO2 and VD/VT from ventilator derived volumetric CO2 measurements of VCO2 and compared it to metabolic analyzer and volumetric CO2 monitor measurements. Methods: A total of 67 measurements in 36 in patients recovering from acute lung injury or acute respiratory distress syndrome were compared. Thirty0one ventilator derived measurements were compared to measurements using 3 different metabolic analyzers and 36 ventilator derived measurements were compared to measurements from a volumetric CO2 monitor. Results: There was a strong agreement between ventilator derived measurements and metabolic analyzer or volumetric CO2 monitor measurements of PeCO2 and VD/VT. Correlation, bias, and precision between ventilator and metabolic analyzer measurements for PeCO2 were r = 0.97, r2 = 0.93 (p &lt; 0.0001), bias –1.04 and precision ± 1.47 mm Hg and for VD/VT r = 0.95, r2 = 0.91 (p &lt; 0.0001), bias 0.024 and precision ± 0.034. Correlation between ventilator and volumetric CO2 monitor for PeCO2 were r = 0.96, r2 = 0.92 (p &lt; 0.0001), bias –0.19 and precision ± 1.58 mm Hg and for VD/VT r = 0.97, r2 = 0.95 (p &lt; 0.0001), bias 0.006 and precision ± 0.033. Conclusion: PeCO2 and therefore VD/VT can be accurately calculated directly from the Drager XL ventilator volumetric capnography measurements without use of a metabolic analyzer or volumetric CO2 monitor.