The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts

COMPARISON OF MEAN EXPIRED CO2 AND VD/VT MEASUREMENTS CALCULATED USING THE DRAGER XL VENTILATOR VOLUMETRIC CAPNOGRAPHY VERSES THE RESPIRONICS NICO2 MONITOR.

Mark S. Siobal, Josephine C. Valdes; Anesthesia, SFGH/UCSF, San Francisco, CA

Background: Calculation of VD/VT requires a measurement of mean expired CO2 (PeCO2). The Drager XL Ventilator is equipped with integrated volumetric CO2 monitoring and calculates VCO2. This enables calculation of PeCO2 using ventilator measurements of VCO2 and VE, which is corrected for circuit compression volume. We calculated PeCO2 from the Drager XL Ventilator measurements and compared it to PeCO2 and VD/VT measurements from the Respironics NICO2 Monitor in intubated patients diagnosed with ALI/ARDS. Method: The ventilator flow sensor and mainstream CO2 sensor, and the NICO2 monitor combined CO2 / flow sensor were calibrated and attached between the ventilator circuit and the patient. Following stabilization, VCO2 and VE measurements from the ventilator were recorded and average over a 5 minute period. The averaged VCO2 and VE were used to calculate the fraction of exhaled CO2 (FeCO2) where FeCO2 = VCO2 / VE. PeCO2 was calculated by multiplying FeCO2 and the barometric pressure minus water vapor pressure (PeCO2 = FeCO2 (760 – 47). The PeCO2 calculated from ventilator measurements and the NICO2 monitor, and PaCO2 from the most recent ABG was used to determine VD/VT using the Enghoff modification of the Bohr equation: (VD/VT = (PaCO2-PeCO2) / PaCO2). The proximal and distal position of the ventilator CO2 sensor, and the NICO2 combined CO2 / flow sensor were then reversed and the measurements were repeated. A total of 31 measurements of PeCO2 and VD/VT in 9 patients were recorded and compared. The study was approved by the UCSF Committee on Human Research. Results: There was a strong correlation between Drager XL Ventilator and NICO2 monitor measurements of PeCO2 (r = 0.95, r squared = 0.90, p < 0.0001) and VD/VT (r = 0.97, r squared = 0.95, p < 0.0001) Conclusion: PeCO2 and VD/VT calculated directly from the Drager XL Ventilator measurements are in strong agreement with measurements from the NICO2 monitor. Sponsored Research - None