PH
pH is the acidity or basicity of the patient's arterial blood. It is an element of the Arterial Blood Gas tests.
Collection instructions
There are special collection instructions for Arterial Blood Gas tests, refer there for further info.
Also, see APACHE Scoring table
see also
History
There have been different collection practices used when selecting the PH value, the original APACHE II user manual (version 1.0) is as above and that is how it should be collected.