Evaluation of multi-exponential curve fitting analysis of oxygen-quenched phosphorescence decay traces for recovering microvascular oxygen tension histograms

Although it is generally accepted that oxygen-quenched phosphorescence decay traces can be analyzed using the exponential series method (ESM), its application until now has been limited to a few (patho)physiological studies, probably because the reliability of the recovered oxygen tension (pO2) histograms has never been extensively evaluated and lacks documentation. The aim of this study was, therefore, to evaluate the use of the ESM to adequately determine pO2 histograms from phosphorescence decay traces. For this purpose we simulated decay traces corresponding to uni- and bimodal pO2 distributions and recovered the pO2 histograms at different signal-to-noise ratios (SNRs). Ultimately, we recovered microvascular pO2 histograms measured in the rat kidney in a model of endotoxemic shock and fluid resuscitation and showed that the mean microvascular oxygen tension, 〈pO2〉, decreased after induction of endotoxemia and that after 2 h of fluid resuscitation, 〈pO2〉 remained low, but the hypoxic peak that had arisen during endotoxemia was reduced. This finding illustrates the importance of recovering pO2 histograms under (patho)physiological conditions. In conclusion, this study has characterized how noise affects the recovery of pO2 histograms using the ESM and documented the reliability of the ESM for recovering both low- and high-pO2 distributions for SNRs typically found in experiments. This study might therefore serve as a frame of reference for investigations focused on oxygen (re)distribution during health and disease and encourage researchers to (re-)analyze data obtained in (earlier) studies possibly revealing new insights into complex disease states and treatment strategies

In Vivo Assessment of Mitochondrial Oxygen Consumption

The protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT) has been proposed by us as a potential clinical noninvasive tool for monitoring mitochondrial function. We have been working on the development of mitochondrial respirometry for monitoring mitochondrial oxygen tension (mitoPO2) and mitochondrial oxygen consumption (mitoVO2) in skin. In this work we describe the principles of the method in experimental animals.</p

Myocardial Microcirculation and Mitochondrial Energetics in the Isolated Rat Heart

Normal functioning of myocardium requires adequate oxygenation, which in turn is dependent on an adequate microcirculation. NADH-fluorimetry enables a direct evaluation of the adequacy of tissue oxygenation while the measurement of quenching of Pd-porphyrine (PpIX) phosphorescence enables quantitative measurement of microvascular pO2. Combination of these two techniques provides information about the relation between microvascular oxygen content and parenchymal oxygen availability in Langendorff hearts. In normal myocardium there is heterogeneity at the microcirculatory level resulting in the existence of microcirculatory weak units, originating at the capillary level, which reoxygenate the slowest upon reoxygenation after an episode of ischemia. Sepsis and myocardial hypertrophia alter the pattern of oxygen transport whereby the microcirculation is disturbed at the arteriolar/arterial level. NADH fluorimetry also reveals a disturbance of mitochondrial oxygen availability in sepsis. Furthermore it is shown that these techniques can also be applied to various organs and tissues in viv