Cultured human cells are used as the model for this assay.  Aliquots of cell suspensions are transferred to a heated respiration chamber and the basal rate of oxygen consumption is measured polargraphically via a calibrated Clark electrode.  Next, a small sample of the material to be tested is added to the respiration chamber and any changes to the rate of cellular oxygen consumption are then determined.  Oxygen uptake will be expressed with respect to the number of viable cells in the respiration chamber.  For cell lines that are too fragile to be placed into the respiration chamber, alternative methods to assess oxygen consumption using oxygen sensitive fluorescent dyes can be used.

The image above displays the output from the Clarke Electrode showing the change in oxygen concentration within the respiration chamber over time.  The first arrow marks the start of the baseline measurement while the second arrow indicates the addition of the test material.  Note the change in slope after the addition of the test material, indicating an increased rate of oxygen consumption.