Partial pressure of oxygen in the human body: a general review

Abstract

The human body is a highly aerobic organism, in which it is necessary to match oxygen supply at tissue levels to the metabolic demands. Along metazoan evolution, an exquisite control developed because although oxygen is required as the final acceptor of electron respiratory chain, an excessive level could be potentially harmful. Understanding the role of the main factors affecting oxygen availability, such as the gradient of pressure of oxygen during normal conditions, and during hypoxia is an important point. Several factors such as anaesthesia, hypoxia, and stress affect the regulation of the atmospheric, alveolar, arterial, capillary and tissue partial pressure of oxygen (PO₂). Our objective is to offer to the reader a summarized and practical appraisal of the mechanisms related to the oxygen's supply within the human body, including a facilitated description of the gradient of pressure from the atmosphere to the cells. This review also included the most relevant measuring methods of PO₂ as well as a practical overview of its reference values in several tissues.

Keywords: Hypoxia; altitude acclimation; barometric pressure; gradient of pressure; pressure of oxygen.

Figure 1

Relationship between elevation and Barometric Pressure (filled circles) and Atmospheric Partial Pressure of Oxygen (hollow circles). *Calculations were based on the standard atmosphere and were done by the authors.

Figure 2

Arterial oxygen tension (PaO₂) at different altitudes in humans according to the values given in several reports [3,4,12,17].