Mark Wefers Bettink

Chapter 4 64 delivery) [3, 6]. Several methods have been developed over the years for measuring tissue oxygen consumption non-invasively. Most of these methods use hemoglobin- based measurement techniques, measuring a vascular or microvascular hemoglobin oxygen saturation in combination with a vascular occlusion test [9]. Typically, the mitoVO 2 measurements with COMET show much faster deoxygenation kinetics than those other approaches.[10] Therefore, the second aim of this study is to compare COMET variables to spectroscopic and transcutaneous techniques during vascular occlusion testing. In short, in this study we compare mitoPO 2 with an arterial blood gas to verify the validity of the COMET calibration for mitoPO 2 measurements in human skin and compared the dynamics of mitoPO 2 to several other techniques for assessing tissue oxygenation in a series of healthy volunteers. 2. Methods The study was approved by the local medical ethical committee and registered on www. toetstingonline.nl [NL61767.078.17]. The study complies with the Helsinki declaration on research ethics. Healthy volunteers were recruited at Erasmus Medical Center Rotterdam, the Netherlands. Informed consent was obtained prior to participant inclusion. Inclusion criteria were: subjects between 18 and 50 years of age and ASA-1-2. Exclusion criteria were: mental disability, presence of mitochondrial disease, diabetes, anemia, hemoglobinopathy, mild to severe COPD, porphyria and/or use of anti-coagulant medication. 2.1 Measuring mitochondrial oxygen tension The COMET (Photonics Healthcare BV, Utrecht, The Netherlands) was used for mitoPO 2 and mitoVO 2 measurements. COMET uses the protoporphyrin IX triplet state lifetime technique (PpIX-TSLT) to measure oxygen availability. It provides quantitative measures, does not affect the measured tissue, and does not need recalibration before use [1]. For the extensive description of COMET internal components and the implemented algorithm, we refer to previous work [4]. We have described the fundamental principles behind the technology and have provided a working implementation of the technique as well as a method for calculating mitoVO 2 from the mitoPO 2 kinetics [11]. Before mitoPO 2 measurements can be performed 5-Aminolevulinic acid (ALA) has to be applied to the skin to induce sufficient mitochondrial PpIX for detection of delayed