Calibration of respiratory gas exchange measurements in inhalation toxicology studies.
The use of simplifying assumptions for determining respiratory gas exchange is associated with substantial errors in the estimates of oxygen consumption (VO2) and carbon dioxide production (VCO2). Studies were done to estimate the magnitude of these errors under common exposure conditions, and a simple procedure that reveals these errors is described for calibrating an open flow respirometer. The errors associated with various simplifying assumptions ranged from -1 to -21% for VO2, 0.1 to 15% for VCO2, and 4 to 45% for the respiratory exchange ratio (R). The calibration was performed with a standard calibration gas elevated in CO2 and depressed in O2 relative to air and bled into the respirometer at a measured flow rate. Dilution of the gas into the respirometer airstream simulates the effect of respiratory gas exchange, and expected values of VO2, VCO2, and R compared to measured values provide a check of accuracy of flow and gas fraction measurements, a test for system leaks, and a test for the effects of any simplifying assumptions on the calculation of respiratory gas exchange.
Mautz
W J
WJ
Department of Community and Environmental Medicine, University of California, Irvine 92717.
D000280:Administration, Inhalation; D000818:Animals; D001273:Atmosphere Exposure Chambers; D002245:Carbon Dioxide / Q000097:blood; D010100:Oxygen / Q000097:blood; D011659:Pulmonary Gas Exchange / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D014116:Toxicology / Q000379:methods*
D002245:Carbon Dioxide; D010100:Oxygen