Endogenous CO monitoring in exhalation with tunable diode lasers: applications to clinical and biomedical diagnostics

Abstract

Middle infrared tunable diode lasers (TDL) were applied to studies of pulmonary excretion of endogenous carbon monoxide (CO). Variations of the CO content level in exhaled air of healthy nonsmokers were investigated for different environmental conditions with the applied laser technique. Correlation ofthe obtained data with atmospheric CO contamination and elevated oxygen content were studied as well as diurnal variations of the endogenous CO in exhalation was observed. Criteria for correct conditions ofthe endogenous CO detection in breath could be derived on this basis. Developed laser approach and methods were applied for the analysis ofthe excreted CO level in different diseases like bronchial asthma, cystic fibrosis, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, anemia and hepatitis. Laser based close-to-real-time monitoring ofthe endogenous CO elimination with breath in the course of different dynamic tests was demonstrated to be informative in studies of blood oxygen transport and pH variations in tissues for different challenge tests in human physiology.Keywords: endogenous carbon monoxide, tunable diode lasers, gas analysis, blood gases, blood pH. INTRODUCTIONAt present, notions of very important role of endogenous carbon monoxides in human physiology are developing intensively16. This metabolic molecule can act together with nitrogen oxide (NO) as mediator taking part in signal transfer in the course of various control processes in organism. The last studies of carbon monoxide activity in organism indicate a specific role not only in metabolic regulation of hem-containing protein structures like hemoglobin, myoglobin and cytochromes, but also in more complicated biochemical processes like transmission of nerve impulses, maintaining micro vessel muscle tone, inducing chemoreceptor activity, control of some hypothalamus hormone secretion etc. . Besides, CO elimination with breath is sensitive to blood pH variations7 and to extent of blood saturation with oxygen and thus could characterize gas transport properties of blood, its acid-base balance and biochemistry.Generation of CO in organism is known to be caused mainly by catabolism of hem-containing structures such as cytochrome, myoglobin, catalase, peroxidase, that normally takes place in cells of liver, spleen and red marrow8. Endogenous CO excreted due to this process is then bound by hemoglobin of blood erythrocyte to be transported from these organs to lung and then is excreted with exhaled airY. Incidentally a part of the CO could be captured and SPIE Vol. 3829 • 0277-786X1991$1O.OO 77 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/20/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspxaccumulated for some time by muscle fiber myoglobin and cell cytochromes that have a higher affinity for Co than hemoglobin Normally endogenous CO concentration in exhale air is constant because the rate of the CO production at normal conditions is stable. At the same time it could be affected by several reaso...