RT Journal Article SR Electronic T1 Effect of Heliox on End-tidal CO2 Measurement in Healthy Adults JF Respiratory Care FD American Association for Respiratory Care SP respcare.02183 DO 10.4187/respcare.02183 A1 Jonathan B. Waugh A1 Donna D. Gardner A1 David L. Vines YR 2013 UL http://rc.rcjournal.com/content/early/2013/04/30/respcare.02183.abstract AB Purpose: Therapeutic gases and other modalities delivered by inhalation may affect the accuracy of capnographic measurements in two ways. First is the specificity of the measurement of CO2 within the device and second is the dilution effect of supplemental gases in the ambient air during CO2 sampling by the device. Our goal was to determine if variables such as inhaled gas composition, variable gas flow rates delivered via non-rebreather mask, and mouth position affect this technology’s capnographic measurements of end-tidal CO2 pressure (PetCO2). Methods: We measured PetCO2 and RR by capnography in 20 adult normal volunteers with coaching to maintain their respiratory frequency between 10-20 bpm. Arterial oxygen saturation was monitored to detect hypoxemia. A six minute washout period occurred between each six minute level of testing. Results: A mixed models analysis revealed that the average PetCO2 for all subjects and flow rates while breathing heliox, 36.9 +/-4.5 mm Hg (mean+/-SD), was not different (p = 0.501) from the value while breathing room air, 36.0+/-4.5 mm Hg. Repeated measurements on each of the same subjects over 6 minute periods of breathing spontaneously 0 L/min, with 10 L/min flow rate, and with 15 L/min flow rate of either air or heliox showed no difference in PetCO2 related to flow (0 L/min vs. 10 L/min, p = 0.759; 0 L/min vs. 15 L/min, p=0.642; 10 L/min vs. 15 L/min, p=0.865). Conclusions: It appears that PetCO2 measurements in normal subjects are not affected by heliox or gas flow at 10 or 15 L/min through a non-rebreathing mask with this device.