Definition
Qx is the factor by which the cardiac output has to increase to maintain a mixed venous tension of 38 mmHg (5.1 kPa) at an arteriovenous difference of 2.3 mmol oxygen/L blood. The systematic symbol for the arterial oxygen compensation factor is Qx. The analyzer symbol may be Qx.
What does Qx tell you?
A high oxygen compensation factor indicates that the arterial blood is inadequate for proper O2 supply to the tissues.
Reference ranges
Qx reference range (adult):~ 1
disclaimer
Clinical interpretation
Qx is the factor by which the cardiac output must be increased to maintain a normal mixed venous oxygen tension at a normal arteriovenous difference of oxygen content.
High Qx indicates a subnormal capacity of the arterial blood for oxygen transport and release, and that cardiac output must be increased and/or mixed venous oxygen tension decreased to maintain an adequate oxygen supply to the tissues.
Considerations
Qx is a theoretical and calculated parameter based on the determination of the ODC. ODC is quite sensitive to the quality of the measurements, especially if the ODC is based upon high sO2 values, close to 97 %. Calculation of Qx is unreliable when sO2 > 97 %. The information provided by Qx must be interpreted with this in mind. Qx, like px, is very sensitive to the quality of the measurements.
