Optimization of measurement geometry for GASMAS lung function monitoring of infants

Sammanfattning: A technique for measuring oxygen concentration in the lungs of preterm infants is one of the latest advancements in neonatal care. It is called GAs in Scattering Media Absorption Spectroscopy (GASMAS) and enables non-invasive, bed-side monitoring of the lung function of our most fragile patients, preterm newborns. The technique is promising and its potential is now evaluated in preparation for clinical studies. This thesis work contains simulations performed on two newly developed 3D-printed models. One model is of the lungs with surrounding tissue and the other model is of the full chest region of a preterm infant. The lung model measurements concluded the GASMAS technique to measure oxygen concentration within 4 % for absorption pathlengths longer than 2 cm. The absorption pathlength was determined to be 20 % longer for the laser wavelength of 761 nm in comparison to 820 nm due to more scattering in the liquid tissue phantom. The measurements of the infant model concluded the most preferable laser and detector positions to be a geometry from the armpit to the chest where oxygen concentration could be determined within 2 percentage points for an absorption pathlength of 10 cm. An opportunity of measuring in-vivo on a three week old baby was also made possible where oxygen could be detected for the earlier mentioned geometry of armpit to chest. Even though the detected signal for the in-vivo tests was weak and the detected absorption pathlength too short for reliable oxygen concentration estimation to be made at this time, the results of this thesis further heightening the anticipation of GASMAS for lung monitoring to advance from laboratory proven to being verified in a clinical study.