Quantitative measurements of the alcohol concentration and the temperature of breath during a prolonged exhalation.

After healthy men drank a moderate dose of alcohol their breath-alcohol concentrations and breath-temperatures were quantitatively determined as a function of expired-volume. All test were made in the post-adsorptive phase of ethanol metabolism and breath samples were analysed by gas-liquid chromatography. The temperatures of breath rose steadily from start to end of exhalation with a mean of 34.48 degrees C after a forced vital capacity (FVC) maneuver. The standard deviation of a single measurement of breath-temperature in randomly selected subjects was +/- 0.402 degrees C. No statistically significant increases in the temperature of breath were noted after an expired volume of 70% FVC. At average expired-breath volumes of 13.5%, 26.2%, 52.2%, 71.7% and 94.2% FVC the breath-temperatures were 33.3 degrees C, 33.5 degrees C, 33.9 degrees C, 34.1 degrees C and 34.4 degrees C whereas breath-alcohol concentration were 79.7%, 85.9%, 90.5%, 95.9% and 98.8% of the 100% FVC alcohol levels. When I corrected for the lower temperatures of breath in the early stages of expiration, the concentrations of alcohol were 86.6%, 90.8%, 93.5%, 96.5% and 98.5% of the 100% FVC levels. These results show that at least 70% of a man's vital capacity must be discarded before a breath-concentration plateau for ethanol develops. But even after a discard breath-volume of 10% FVC the concentration of alcohol reaches 80% of the level in end-expiratory breath. I suspect that ethanol dissolves in the mucous-membranes of the upper respiratory tract and equilibrates with breath in the airway dead-space and in the mouth.