Development of spectroscopic method for measuring in-vivo tissue oxygen saturation and using it in postoperative flap surgery for assessment of tissue perfusion

Objective: Tissue oxygen saturation (StO2) is known quite useful parameter for medical applications. For viability of free flaps, tissue oxygenation is important. Some diseases cause local microvascular modification results in tissue oxygenation changes. Therefore, in vivo StO2 measurements enable us to acquire information regarding the physiology and pathology of the tissue. The aim of this study is to develop a spectroscopic method running non-invasive in real time to measure StO2 in vivo and to investigate the sensitivity and specificity of the system in postoperative flap viability monitoring. Method: The experimental set up for the spectroscopic measurements was consists of a miniature spectrometer, a fiber optical probe and, a halogen-tungsten light source. In the study, human blood samples with different level of oxygen saturations have been prepared and spectra were acquired using a fiber optical probe in order to investigate correlation between the spectroscopic measurements and standart measurements of oxygenation saturation. Then, the method was used to determine tissue viability in postoperative flap cases. Results: A linear correlation obtained between the oxygen saturation of the blood samples and the ratio of the spectroscopic measurements at wavelengths of 660 nm to 790 nm. Then, oxygen saturations of the blood samples were estimated from the spectroscopic measurements within an error of 2.9%. In the clinical trial, spectroscopic measurements acquired on twenty patients and lower tissue oxygenation defined from the 4 flaps before the clinical observation. It has been shown that the spectroscopic measurements is able to define lower tissue oxygenation before the clinical observation with %100 sensitivity and specifity. Conclusion: The results suggested that fiber optical spectroscopy is a sensitive method to estimate the StO2 levels in vivo. The technique developed to measure tissue StO2 has potential to improve bedside monitoring device for assess tissue perfusion and follow up prognosis of flap.