Oxygen transport—1. Basic principles

Physiology of oxygen transport

Although oxygen is the substrate that cells use in the greatest quantity and on which aerobic metabolism and cell integrity depend, the tissues have no storage system for oxygen. They rely on a continuous supply at a rate that precisely matches changing metabolic requirements. If this supply fails, even for a few minutes, tissue hypoxaemia may develop resulting in anaerobic metabolism and production of lactate.

Oxygen transport from environmental air to the mitochondria of individual cells occurs as a series of steps. The heart, lungs, and circulation extract oxygen from the atmosphere and generate a flow of oxygenated blood to the tissues to maintain aerobic metabolism. The system must be energy efficient (avoiding unnecessary cardiorespiratory work), match oxygen distribution with metabolic demand, and allow efficient oxygen transport across the extravascular tissue matrix. At the tissue level, cells must extract oxygen from the extracellular environment and use it efficiently in cellular metabolic processes.

Oxygen uptake in the lungs

Arterial oxygen tension (PaO_{2 …}