Effect of Vitamin E on Exhaled Ethane in Cigarette Smokers: Discussion
Measurement of exhaled alkanes has been used by us and others as a noninvasive marker of lipid peroxidation. We favor ethane over pentane as a measure of lipid peroxidation because of the more rapid metabolism of pentane by animals and man. In addition, mass spectroscopic analysis of human exhalate demonstrates the presence of significant amounts of isoprene, which may be mistaken for n-pentane during gas chromatographic analysis rendering pentane quantification complex.
We have found that ethane is affected by cigarette smoke and diet, although others have not found the latter. A 3-h abstinence from cigarettes and an 8-h fast have yielded the most consistent results in the past in our laboratory. Since patients with obstructive lung disease may trap gas, ambient air, which contains significant amounts of ethane, may contaminate the collected sample and the more severe the obstruction, the greater the risk that ambient trapped air will contaminate the sample after the washout period. To circumvent this, we have used a particularly long washout period with hydrocarbon-free air and have employed vital capacity breaths at multiple times during the 8-min washout. We have found that hydrocarbon-free air is required since ambient air contains significant amounts of ethane, and the ambient air ethane content may change very quickly from moment to moment, particularly if the air intake vent is near a parking lot or other such source of pollution. purchase antibiotics online
The values for exhaled ethane we report in this article are higher than what has been reported in the literature for healthy nonsmoking subjects. A review by Kneepkens et al indicates that the range for ethane exhalation in nonsmoking adults is between 1.4 to 3.4 pm/kg/min. These values are lower than our results in smokers but in keeping with our previous reports about ethane exhalation in never smokers. The higher values for exhaled ethane found in this study may be representative of the fact that smokers have altered oxidant/antioxidant ratios, and hence, increased lipid peroxidative activity.