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  • 1.
    Ghorbani, Ramin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Fitting of single-exhalation profiles using a pulmonary gas exchange model: application to carbon monoxide2019In: Journal of Breath Research, ISSN 1752-7155, E-ISSN 1752-7163, Vol. 13, no 2, article id 026001Article in journal (Refereed)
    Abstract [en]

    Real-time breath gas analysis coupled to gas exchange modeling is emerging as promising strategy to enhance the information gained from breath tests. It is shown for exhaled breath carbon monoxide (eCO), a potential biomarker for oxidative stress and respiratory diseases, that a weighted, nonlinear least-squares fit of simulated to measured expirograms can be used to extract physiological parameters, such as airway and alveolar concentrations and diffusing capacities. Experimental CO exhalation profiles are acquired with high time-resolution and precision using mid-infrared tunable diode laser absorption spectroscopy and online breath sampling. A trumpet model with axial diffusion is employed to generate eCO profiles based on measured exhalation flow rates and volumes. The concept is demonstrated on two healthy non-smokers exhaling at a flow rate of 250 ml s−1 during normal breathing and at 120 ml s−1 after 10 s of breath-holding. The obtained gas exchange parameters of the two subjects are in a similar range, but clearly distinguishable. Over a series of twenty consecutive expirograms, the intra-individual variation in the alveolar parameters is less than 6%. After a 2 h exposure to 10 ± 2 ppm CO, end-tidal and alveolar CO concentrations are significantly increased (by factors of 2.7 and 4.9 for the two subjects) and the airway CO concentration is slightly higher, while the alveolar diffusing capacity is unchanged compared to before exposure. Using model simulations, it is found that a three-fold increase in maximum airway CO flux and a reduction in alveolar diffusing capacity by 60% lead to clearly distinguishable changes in the exhalation profile shape. This suggests that extended breath CO analysis has clinical relevance in assessing airway inflammation and chronic obstructive pulmonary disease. Moreover, the novel methodology contributes to the standardization of real-time breath gas analysis.

  • 2. Metsälä, Markus
    et al.
    Schmidt, Florian M.
    University of Helsinki.
    Skytta, Mirva
    Vaittinen, Olavi
    Halonen, Lauri
    Acetylene in breath: background levels and real-time elimination kinetics after smoking2010In: Journal of Breath Research, ISSN 1752-7155, E-ISSN 1752-7163, Vol. 4, no 4, article id 046003Article in journal (Refereed)
    Abstract [en]

    We have measured the acetylene concentration in the exhaled breath of 40 volunteers (31 non-smokers, nine smokers) using near-infrared cavity ring-down spectroscopy. The acetylene levels were found to be the same as in ambient air for non-smokers, whereas elevated levels were observed for smokers. Real-time measurements with sub-second time resolution have been applied to measure the elimination kinetics of acetylene in breath after exposure to tobacco smoke. Three exponential time constants can be distinguished from the data and these can be used to define the residence times for different compartments, according to the multi-compartment model of the human body.

  • 3.
    Schmidt, Florian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Vaittinen, Olavi
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Metsälä, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lehto, Markku
    Forsblom, C.
    Groop, P-H
    Halonen, Lauri
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ammonia in breath and emitted from skin2013In: Journal of Breath Research, ISSN 1752-7155, E-ISSN 1752-7163, Vol. 7, no 1, article id 017109Article in journal (Refereed)
    Abstract [en]

    Ammonia concentrations in exhaled breath (eNH(3)) and skin gas of 20 healthy subjects were measured on-line with a commercial cavity ring-down spectrometer and compared to saliva pH and plasma ammonium ion (NH4+), urea and creatinine concentrations. Special attention was given to mouth, nose and skin sampling procedures and the accurate quantification of ammonia in humid gas samples. The obtained median concentrations were 688 parts per billion by volume (ppbv) for mouth-eNH(3), 34 ppbv for nose-eNH3, and 21 ppbv for both mouth-and nose-eNH(3) after an acidic mouth wash (MW). The median ammonia emission rate from the lower forearm was 0.3 ng cm(-2) min(-1). Statistically significant (p < 0.05) correlations between the breath, skin and plasma ammonia/ammonium concentrations were not found. However, mouth-eNH(3) strongly (p < 0.001) correlated with saliva pH. This dependence was also observed in detailed measurements of the diurnal variation and the response of eNH(3) to the acidic MW. It is concluded that eNH(3) as such does not reflect plasma but saliva and airway mucus NH4+ concentrations and is affected by saliva and airway mucus pH. After normalization with saliva pH using the Henderson-Hasselbalch equation, mouth-eNH(3) correlated with plasma NH4+, which points to saliva and plasma NH4+ being linked via hydrolysis of salivary urea.

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