Mark Wefers Bettink

Chapter 2 34 mitochondria is the goal in the blood-tissue oxygen distribution. Therefore, mitoPO 2 is the result of the balance between oxygen supply and the cells ability to consume it (as shown in figure 3). Figure 3. The oxygen balance. Mitochondrial oxygen tension (mitoPO 2 ) is a resultant of mitochondrial oxygen supply and demand. The respiratory chain occupies the demand side, and the biggest part of its oxygen consumption is coupled to synthesis of adenosine triphosphate (ATP). A small part is used for energy dissipation and heat generation by uncoupling via proton leak over the mitochondrial inner membrane (9). Oxygen supply is dependent on tissue blood flow (TBF), tissue blood volume (TBV), local hemoglobin saturation (HbO 2 ), microvascular oxygen tension (μPO 2 ), and factors influencing the oxygen gradient between microvessels and mitochondria (ΔPO 2 ). Reprinted with permission from: Mik (17) Conclusion Since a primary goal of caregivers is maintaining supply and demand, mitochondrial oxygen levels and oxygen consumption might be useful parameters for monitoring the effectiveness of therapies in optimizing oxygen supply. Achieving oxygen hemostasis, and thus maintaining cellular oxygen concentration and oxygen metabolism within a normal range may be an ultimate goal. COMET is able to provide insight in the oxygen balance at tissue level, and thus provides important information about aspects of mitochondrial function. Considering the complexity of the pathophysiology of a critically ill patient,