PARTIAL PRESSURE OF CARBON DIOXIDE, BLOOD
(pCO2)

Sample type

Serum (preferred) or plasma (lithium heparin)

Uses

Evaluate the total carbonate buffering system in the body, acid-base balance. High results may represent respiratory acidosis with CO2 retention, or metabolic alkalosis (eg, prolonged vomiting).

Low value may indicate respiratory alkalosis as in hyperventilation or metabolic acidosis (eg, diabetes with ketoacidosis).

Precautions

Maintain specimen in a tightly-stoppered tube.

Do not use oxalate, EDTA, or citrate plasma.

Separate serum or plasma from cells within 45 minutes of collection.

Interfering factors

Respiratory conditions will primarily affect pCO2, whereas metabolic disturbances are first reflected in the HCO3.

Values are slightly lower in supine position. Difference between arterial blood and venous blood varies considerably, depending on the skin temperature, length of stasis, and muscular activity.

Pre-analytical errors

If you receive a hemolyzed sample or unlabeled sample or you receive EDTA or citrate or oxalate plasma tubes

The corrective action

You should reject it and request for another sample

Post-analytical errors

I. reports were sent to the incorrect patient

The corrective action

communication with patient, apologizing for the error, and providing him with the correct report

II. write the wrong name in the report or the wrong results.

The corrective action

If the report is not delivered to the patient and this error is discovered, the correct result or the correct name must be written, but if the report is delivered to the patient, you must communicate with him, apologies to him, and tell him that an error has occurred and replace it with the correct report.

Reference range

Arterial: 35-45 mm Hg

Venous: 41-51 mm Hg