Breath ethyl alcohol concentration and analysis in the presence of chronic obstructive pulmonary disease.

We have made continuous measurements of exhaled ethanol concentration vs volume during slow expiration in subjects with plasma ethanol concentrations up to 700 mg/L. Subjects included individuals with normal pulmonary function and those with severe chronic obstructive pulmonary disease (COPD). In addition to the measurements of breath ethanol made using a flame ionization detector, paired measurements were also made of plasma ethanol and breath ethanol using a Model 900A Breathalyser. In normal subjects, the breath ethanol concentration was found to increase continuously during expiration until the very end of the expiration when a decline in concentration was noted. In the presence of COPD the ethanol concentration/volume tracing was essentially flat during the middle portion of expiration, but many subjects showed a decrease in concentration at the end of the expiration. One subject showed a sharp rise in breath concentration at the end of expiration. The results suggest that fluctuations in the ethanol concentration are caused by variation in the ventilation/perfusion ratio of regions of the lung supplying the expirate, and that breath with ethanol in equilibrium with the plasma is not routinely obtained, especially at the end of a maximal expiration. Thus, exhaled air at the end of maximal expiration does not always provide the best, or a close, indication of the plasma (or blood) ethanol concentration. The peak breath ethanol concentrations found were, as an equivalent plasma concentration, = -25 + 0.924 X plasma ethanol, mg/L. The Breathalyser readings = -45 + 0.898 X plasma ethanol, mg/L, with a mean difference of -81 mg/L.