Ethanol metabolism in humans : a thesis presented in partial fulfilment of the requirements for the degree of Doctor in Philosophy at Massey University, New Zealand

Abstract

This thesis outlines the development breath alcohol measurement and investigations of the rate of absorption, equilibration and elimination of alcohol from the body using breath analysis. After a historical outline, the methods of alcohol detection are reviewed a comparitive study of some modern breath alcohol testing instruments detailed. The results show that the gas chromatograph Intoximeter was the most reproducible and accurate instrument. Of the fuel cell instruments, the Alcolimiter gave reproducible readings but with a higher frequency of mechanical breakdowns and the Alcometers failed to hold a calibrated value on repeated testing. The chemical analysis of the Borkenstein Breathalyzer offered portability and freedom from calibration but with a lowering of accuracy. No instrument offered the degree of flexibility required for laboratory investigation of factors affeecting breath alcohol concentrations. Consequently a gas chromatograph was modified for breath sampling at 30 second intervals. The partition coefficients for alcohol between air and blood were found to be related to the water content of the blood sample. Breath alcohol concentrations increased with expiration volume and were related to a rise in breath temperature. After correcting to a standard temperature of 34°, a linear increase in alcohol concentration remained which was greater with higher blood alcohol levels. Equations for estimating the distribution volume of alcohol in the body were derived and the Widmark factor 'r' was found to be related to the ratio, body water over blood water. The blood alcohol time curves resulting from a fixed dose of alcohol given to semi-fasted subjects were analysed to determine the apparent distribution volumes in the body. Volumes exceeding physiological limits were found in some subjects and ascribed to either a faster rate of metabolism during the absorptive phase or to anomalies in equilibration. A markedly non-linear alcohol elimination curve was seen in one alcoholic. Faster rates of alcohol oxidation were discussed in relation to the Michaelis-Menten kinetics of enzymatic catabolism and it is suggested that some subjects have a second enzyme for alcohol metabolism which operates at a higher Km than normal. The fluctuations of blood alcohol level during the absorptive phase were examined by measuring the abundance of a tracer dose of deuterated alcohol given orally after a loading dose of unlabelled alcohol. The fluctuations were ascribed to contractions of the pyloric sphincter releasing alcohol into the duodenum in an irregular fashion. The studies were extended to subjects drinking in a private bar. The rate of alcohol absorption appeared to keep pace with the rate of drinking which was spread over at least a three hour period. The rates of alcohol elimination from the blood were faster than in a previous study with a lower dose of alcohol. This is explained by lower blood alcohol levels from a smaller dose and is consistent with the enzyme kinetics of alcohol catabolism. An equation was derived to enable the estimation of blood alcohol levels from amount consumed which compared favourably with traditional methods for this calculation. The accuracy, rapidity and ease with which breath alcohol analyses could be made to determine alcohol concentrations in the body enabled its use with large groups of people consuming alcohol at party situations or in hotel bars and two examples of such studies are presented in the appendix.