Aspiration of a homogenous whole blood sample into the blood-gas analyzer requires that the sample be artificially anticoagulated to prevent in vitro clotting. Heparin is the only anticoagulant suitable for blood-gas testing. Blood gas capillary tubes contain heparin.
After puncturing the ear lobe the blood must flow freely. Where this does not happen either:
Should blood not flow freely, reheat, re-puncture and retake the blood sample. Avoid squeezing or milking (excessive repetitive pressure) of the ear lobe as this will cause haemolysis and sample contamination with tissue fluid. In fact, in most cases, the need to facilitate blood flow by milking is usually a consequence of the issues above and the result will invariably show low oxygen and will need to be repeated.