Methodology investigation of expirograms for enabling contact free breath XXXX analysis.

@entity1 @entity167 @entity515 @entity2507 @entity358 @entity544 @entity1068
The present techniques for breath @entity167 determination have usability limitations concerning practical use and the time and effort required for the test @entity1 . The rationale of the physiological assumptions in a recently demonstrated technique for breath analysis without a mouthpiece is investigated in this paper. Expirograms quantifying @entity1068 , @entity544 ( @entity515 ) and water ( @entity2507 ) from 30 test subjects were analysed, with respect to the influence of individual variations in end-expiratory @entity515 and @entity2507 concentrations, and possible benefits from simultaneous measurement of @entity515 or @entity2507 . Both healthy subjects and @entity1 suffering from @entity358 performed breath tests with small and maximum volume expiration. The breath tests were recorded basically with a standard evidential instrument using infrared absorption spectroscopy, and equipped with a mouthpiece. Average concentrations were significantly higher for the maximum than for the small expirations. For the maximum expirations, the healthy subjects had a significantly higher end-expired PCO(2) of 4.4    0.5 kPa (mean    standard deviation) than the @entity1 (3.9    0.7 kPa). The corresponding values for @entity2507 were 39    1 and 38    1 mg l(-1). The results indicate that the @entity515 variability is consistent with the requirements of accuracy for @entity167 ignition interlocks. In addition, @entity515 as tracer gas is preferable to @entity2507 due to its low concentration in ambient air. In instruments for evidential purposes @entity2507 may be required as tracer gas for increased accuracy. Furthermore, the study provides support for early determination of breath @entity167 concentration, indicating that determination after 2 s will introduce an additional random error of 0.02 mg l(-1) or less.
