Respiratory gas analysis

Breathing gas analysis is the scientific examination of the human breath . The aim is, on the one hand, to identify marker substances that allow conclusions to be drawn about the clinical condition of a patient and, on the other hand, to develop mathematical models that allow the conversion of respiratory gas concentrations to the corresponding blood concentrations. The knowledge gained can then be implemented in breathing gas tests for medical diagnostics.

In contrast to blood samples, taking breathing gas samples is non-invasive for the patient and can be repeated as often as required. Breathing gas samples can be evaluated in real time and therefore enable continuous monitoring of changes in body substances, for example on the ergometer, in the sleep laboratory or in intensive care medicine.

In the past, only substances in high concentrations such as If, for example, carbon dioxide and alcohol are identified, the advances in analysis technology ( GC-MS , PTR-MS , SIFT-MS , IMS , chemical sensors ) have made it possible to convert a single molecule into a trillion molecules ( ppt ) discover.

history

The modern era of respiratory gas analysis was initiated by the Nobel Prize winner Linus Pauling , who proved that the human breath contains over 200 volatile organic compounds (VOCs) in picomolar concentrations.

Relationship between breathing gas and blood concentrations

A simple model for the relationship between respiratory gas and blood concentrations was given by Farhi:

${\displaystyle C_{A}={\frac {C_{\bar {v}}}{\lambda _{\text{b:air}}+{\dot {V}}_{A}/{\dot {Q}}_{c}}}.}$

Here, the alveolar concentration (it is assumed that it corresponds to the measured one), the mixed venous concentration, and the blood: air partition coefficient, and the ventilation-perfusion ratio (approx. 1 at rest). ${\displaystyle C_{A}}$ ${\displaystyle C_{\bar {v}}}$ ${\displaystyle \lambda _{\text{b:air}}}$ ${\displaystyle {\dot {V}}_{A}/{\dot {Q}}_{c}}$

If, for example, the average acetone concentration of in the end-tidal breath is multiplied by the partition coefficient according to this equation , then the result is values ​​that differ by a factor of 3 from the actually measured arterial blood values, which are in the range of . For isoprene with a partition coefficient , the ventilation-perfusion ratio can no longer be neglected in this equation. ${\displaystyle 1\,\mathrm {\mu g/l} }$ ${\displaystyle \lambda _{\text{b:air}}=340}$ ${\displaystyle \mathrm {1\,mg/l} }$ ${\displaystyle \lambda _{\text{b:air}}=0{,}95}$

Further developments of this model are therefore a current research area.

See also

• Hydrogen breath test

Individual evidence

1. ↑ Linus Pauling, Arthur B. Robinson, Roy Teranish, Paul Cary: Quantitative Analysis of Urine Vapor and Breath by Gas-Liquid Partition Chromatography . In: Proc Natl Acad Sci USA . tape 68 , no. 10 , 1971, p. 2374-2376 , doi : 10.1073 / pnas.68.10.2374 .
2. ↑ Anil S. Modak: single time point diagnostic breath tests: a review . In: Journal of Breath Research . tape 4 , no. 1 , 2010, p. 017002 , doi : 10.1088 / 1752-7155 / 4/1/017002 .
3. ^ Leon E. Farhi: Elimination of inert gas by the lung . In: Respiration Physiology . tape 3 , no. 1 , July 1967, p. 1-11 , doi : 10.1016 / 0034-5687 (67) 90018-7 .
4. ↑ Julian King, Helin Koc, Karl Unterkofler , Pawel Mochalski, Alexander Kupferthaler, Gerald Teschl , Susanne Teschl , Hartmann Hinterhuber, Anton Amann : Physiological modeling of isoprene dynamics in exhaled breath . In: Journal of Theoretical Biology . tape 267 , no. 4 , November 21, 2010, p. 626–637 , doi : 10.1016 / j.jtbi.2010.09.028 .
5. ↑ Julian King, Karl Unterkofler, Gerald Teschl, Susanne Teschl, Helin Koc, Hartmann Hinterhuber, Anton Amann: A mathematical model for breath gas analysis of volatile organic compounds with special emphasis on acetone . In: Journal of Mathematical Biology . tape 63 , 2011, p. 959-999 , doi : 10.1007 / s00285-010-0398-9 .

Web links

• Breathing gas analysis at the Institute for Breathing Gas Analysis of the Austrian Academy of Sciences
• Breathing gas analysis: Illnesses can be diagnosed using the air you breathe on Gesundheit.de
• Breath gas analysis: breath instead of blood on CliniCum.at
• Breath-Analysis Data Mining Project