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Oxygen Delivery

  • Eleonora Duscio
  • Francesco Vasques
  • Federica Romitti
  • Francesco Cipulli
  • Luciano Gattinoni
Chapter
Part of the Lessons from the ICU book series (LEICU)

Abstract

Oxygen plays an essential role in aerobic life, acting as final acceptor of electrons in mitochondria from which energy, as ATP, is supplied to the whole organism. We may recognize three primary essential steps for oxygen utilization: first, the transport of oxygen-rich gas mixture from the ambient to the lung by ventilation and then its transfer from alveoli to blood; second, the transport of oxygenated blood to tissues; and, third, oxygen reduction to water in mitochondria. Oxygen movement from inspired gas toward mitochondria is possible thanks to pressure gradients: oxygen partial pressure is indeed 150 mmHg in the inspired gas and between 4 and 25 mmHg in its final destination, the mitochondria. After the oxygen has been delivered to tissues, the mixed venous blood returns to alveoli, and another cycle of oxygen transport and utilization begins. Mixed venous blood contains an amount of oxygen that represents oxygen that has been delivered but not consumed and can be considered as a sort of reserve. Although the term oxygen transport, strictly speaking, should refer to all the processes through which oxygen is transferred from inhaled gas to the final place of utilization, in the intensive care literature, it usually refers only to the hemodynamic phase. In this chapter, we will analyze primarily the hemodynamic phase of oxygen transport, and we will give some hints about oxygen utilization. It should not be forgotten, indeed, that in several conditions which may be common in intensive care patients, primarily sepsis and septic shock, the real problem is not only in the hemodynamic phase of oxygen delivery but also the oxygen utilization. This step relates to all the processes occurring in mitochondria where oxygen, acting as final acceptor of the electron cascade, makes possible the high levels of aerobic energy production.

Keywords

Oxygen delivery Oxygen content Hemoglobin Oxygen partial pressure Oxygen hemoglobin saturation Oxyhemoglobin Reduced hemoglobin Methemoglobin Carboxyhemoglobin Pulse oximetry Cardiac output Oxygen extraction fraction Mixed venous saturation Energy crisis Early goal-directed therapy Supernormal Values Arterial underfilling hypothesis 

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Copyright information

© European Society of Intensive Care Medicine 2019

Authors and Affiliations

  • Eleonora Duscio
    • 1
  • Francesco Vasques
    • 1
  • Federica Romitti
    • 1
  • Francesco Cipulli
    • 1
  • Luciano Gattinoni
    • 1
  1. 1.Department of Anesthesiology, Emergency and Intensive Care MedicineUniversity of GöttingenGöttingenGermany

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