Physiology and measurement of tissue perfusion

Sufficient tissue perfusion and oxygenation are vital for all metabolic processes in cells and the major influencing factor of tissue repair and resistance to infectious organisms. The concept of tissue perfusion has been aliked with blood flow, oxygen delivery or a combination of flow and nutritional supply including that of oxygen. A concept covering both oxygen delivery, tissue oxygen transport and oxygen consumption of the cells could be named tissue oxygen perfusion. This concept could be useful for clinicians describing tissue perfusion and oxygenation of the patient. Tissue perfusion must be evaluated on local tissue level. A single tissue that would represent the situation in all tissues of the body and be easily available for measurements, would be ideal. Subcutis and mucosa of the gastrointestinal tract are such types of tissue. Many monitoring systems are available for measuring tissue perfusion and oxygenation. However, only measurement of tissue oxygen tension and pH the gastrointestinal mucosa fulfil the criteria of tissue oxygen perfusion. Future evaluation of tissue perfusion will be of fundamental importance for the outcome of medical treatment. Presently measurements of tissue oxygen tension, and in intensive care units also gastrointestinal mucosal pH, seem to be the best monitoring systems clinically available for this purpose.