Users
engaged in very low carbohydrate ketogenic dieting should be aware of
the possibility of obtaining elevated BrAC results based on their diet.
Methanol
Methanol may be present in elevated concentrations on a person’s breath
after consuming large amounts of fruit \cite{Lindinger1997}, in alcoholics \cite{Wigmore2008,Jones1988}, or through accidental exposure due to the improper
production of distilled spirits \cite{Kane1968,Paasma2007,Aghababaeian_2019}. There are two unfortunate cases
reported in the literature where a breath alcohol analyzer mistook
methanol for ethanol, delaying medical treatment, resulting in the
subjects dying from methanol poisoning \cite{Jones1989}. Users should be
aware of the potential, but the unlikely possibility of elevated BrAC
results due to methanol.
Limitations
Vaporous ethanol reference material produced by breath simulators cannot
account for the complex physiologic gas exchange taking place in the
lungs and airways of live subjects \cite{Jones1990,Gullberg1990,Anderson2003,Lubkin1996,Wilson1986,Vosk2014}. The SD of measurements taken in vivo has been shown to be greater than the SD produced by breath
simulators \cite{Gullberg1989}. Further research is needed to determine the measurement uncertainty for in vivo results.
The calibration longevity of the
analyzers was not examined in this study. An important consideration for
those wishing to use these instruments is that the device must be
sent back to the manufacturer regularly for recalibration. Individuals or institutions using these instruments may need to keep several on hand while periodic
recalibrations are performed.
Users of these instruments should incorporate quality assurance practices to
ensure the accuracy meets the requirements of the
intended use \cite{Dubowski1994}. The use of compressed ethanol-gas reference standards would be a convenient way to perform accuracy checks \cite{Dubowski1996-dw,Silverman1997-zs}. Further investigation with these analyzers using compressed ethanol-gas standards is needed, as the efficacy was not assessed in this study.
Conclusions
The breath alcohol analyzers
examined in this study showed the ability to measure vaporous
ethanol with confidence in the results, especially at concentrations \(\le\) 0.080 g/210L. At the
0.080 g/210L ethanol vapor concentration, the combined expanded
measurement uncertainty was \(\le\) ± 0.013 g/210L at the 95% coverage
interval for all instruments. The likelihood of false readings from
potential interfering substances appears to be small but may be a
concern for those engaged in ketogenic diets with elevated levels of
isopropanol. More work needs to be conducted with these instruments in vivo to determine the measurement uncertainty for the results which include a biological component.