Value of the simultaneous determination of PCO2 in monitoring exposure to 1,1,1-trichloroethane by breath analysis.

Eight volunteers were exposed for eight hours to about 200 ppm of 1,1,1-trichloroethane. On the next morning five series of five alveolar samples were collected for the simultaneous determination of PCO2 and 1,1,1-trichloroethane concentration. Three different methods of sampling were used: voluntary hyperventilation, 10-s breathholding, and "standard." A linear relationship between the alveolar concentrations of both gases was observed in all subjects. Expired air was also collected in two subjects and an analogous relationship was observed. Also the Bohr dead space was found to be of similar size for CO2 and for 1,1,1-trichloroethane. In the monitoring of solvent exposure by breath analysis it is suggested that the results should be corrected for hyperventilation or hypoventilation and for dilution of alveolar air with dead space air by a proportional adjustment of the solvent concentration at the mean normal adveolar PCO2 or by disregarding the samples with a PCO2 outside normal range. The PCO2 determination in 40 unselected workers has shown that in more than a third of them, to monitor exposure by breath analysis would have been of little meaning without such an adjustment or rejection criteria.