AbstractsMedical & Health Science

Non-invasive optical monitoring of free and bound oxygenin humans

by Svanberg Emilie Krite

Institution: University of Lund
Year: 2016
Keywords: oxygenation; Intensive care; free gas; near-infrared spectroscopy; absorption spectroscopy; scattering; Anesthesiology and Intensive Care
Posted: 02/05/2017
Record ID: 2072228
Full text PDF: http://lup.lub.lu.se/record/8777000


Background: Possibilities of detecting oxygen - both in its free form, as gas in the lungs, and in its bound form, as oxygenated hemoglobin - have been explored in this thesis. Perfusion and oxygenation of vital organs (e.g., heart, brain and kidneys) may be severely compromised in critical illness or major trauma, which is why blood is rapidly diverted to those organs to improve chances of survival. Blood vessels in less important organs (e.g., skin, skeletal muscles and intestines) are constricted, leading to reduced regional perfusion and oxygenation in these organs. Non-invasive measurements of changes in tissue perfusion and oxygenation, in e.g., the forearm, might give an early indication of clinical deterioration. Preterm infants are very vulnerable patients. Their organs, in particular the lungs, are not fully developed, and the respiratory distress syndrome (RDS) frequently occurs. The intestines may be affected by necrotizing enterocolitis (NEC). Complementary diagnostic and surveillance methods of RDS and NEC are desirable. Aims: The overall aim of this thesis, which includes Studies I-IV, was to develop and evaluate non-invasive optical techniques, based on light at different wavelengths, to complement future bedside surveillance in critically illness or severe injury, for adults as well as for infants. Methods: Changes in tissue oxygenation by near-infrared spectroscopy (I-II), blood perfusion by laser Doppler imaging (I) and blood volume by tissue viability imaging (I) in skeletal muscle and skin were studied, and continuous-wave and timeresolved near-infrared spectroscopy were compared (II) in healthy volunteers subjected to various defined regional physiological perturbations. For the first time, gas in scattering media absorption spectroscopy (GASMAS) was used to detect alveolar water vapor (III-IV) and oxygen gas (IV), as well as intestinal water vapor (III) in newborn infants. Main results: Near-infrared spectroscopy, laser Doppler imaging and tissue viability imaging provided valuable information on physiological changes in the microcirculation (I). Continuous-wave and time-resolved near-infrared spectroscopy techniques were both able to determine changes in tissue oxygenation, but the time-resolved technique provided more realistic values with smaller inter-individual differences (II). Alveolar (III-IV) and intestinal signals of water vapor (III), were readily detected, together with alveolar signals of oxygen gas (IV), non-invasively in newborn infants. Conclusions: Optical techniques, being non-invasive and providing data in real-time, are attractive as potential tools for surveillance in critical illness or severe injury, in particular concerning the oxygenation. As an overall conclusion, we believe, that fully developed time-resolved near-infrared techniques have the potential to become an additional monitoring method of choice for…