Measurement of end-tidal PCO2 and PO2

This article describes the basic principles of the measurement of end-tidal carbon dioxide (CO2) and oxygen (O2) in humans. The description includes definitions of the major parameters of breathing (e.g., the composition of atmospheric air, arterial and venous blood; metabolism; lung capacity; volumetric measures of tidal volume, minute volume, and respiration frequency; pH regulation and cerebral acidity; barometric pressure and the partial pressures of CO2 and O2), the basic anatomical features of breathing, the means by which gases are exchanged between the lungs and blood, the techniques used in the measurement of respiratory variables, and the interpretation of these measurements.