CO2 is a major determinant of the serum pH and works alongside sodium, potassium, and chloride to maintain electrical neutrality at a cellular level. The normal range is 4.7 – 6.0 kPa. Total carbon dioxide consists of CO2 in solution or bound to proteins, HCO3−, CO32−, and H2CO3. Most of the carbon dioxide (90%) is transported in blood as plasma bicarbonate.
CO2 is an acidic gas. Regulation of carbon dioxide in the blood is essential in the maintenance of the acid-base balance in respiratory and metabolic systems.
The bicarbonate content of serum or plasma is a significant indicator of electrolyte dispersion and anion deficit. Together with pH determination, bicarbonate measurements are used in the diagnosis and treatment of numerous potentially serious disorders associated with an acid-base imbalance in the respiratory and metabolic systems. Hypercapnia means excessive carbon dioxide in the blood.
Increased levels may be observed in compensated respiratory acidosis and metabolic alkalosis. Causes include:
- Severe vomiting
- Lung diseases / respiratory failure including COPD
- Cushing or Conn syndrome
- Metabolic alkalosis
Reduced levels may be observed in compensated respiratory alkalosis and metabolic acidosis. Causes include:
- Addison disease
- Chronic diarrhoea
- Diabetic ketoacidosis
- Metabolic acidosis
- Kidney disease – renal tubular acidosis
- Alcohol poisoning
- Salicylate overdose
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5mL venous serum or plasma
Enfer Medical offers enzymatic PEP technology for the quantitative assay for CO2. This test is CE-IVD certified.
For clients using the Enfer Medical Client Portal, the Enfer Medical Patient Request Form (PRF) will be generated when you have completed your “Test Request” within the portal linked below.
Please note that samples suspected of containing high risk pathogens such as Mycobacterium tuberculosis should be clearly identified on the form and packed separately from other samples.
Results are available next working day.
This assay is available seven days a week.
The packaging/preparation of samples for delivery to the laboratory are required to be in adherence to all national regulations for the safe transport of biological materials. HSE guidance can be reviewed HERE.
There are specific packaging instructions and labelling requirements requiring triple packaging including:
- Primary leak-proof container – tube or vial containing the sample.
- Secondary watertight container, with absorbent material, intended to protect the primary container.
- Outer container protects the secondary container.
- Patient Request forms must be placed between the secondary container and the outer shipping container.
Further information on the packaging/preparation of samples for delivery to the laboratory is contained within the Enfer Medical Laboratory User Manual which clients are provided with.
Storage & Stability
Specimens must be tested within 1 day of collection and stored at 2-8°C.
In addition to the packaging of samples, the transport/delivery of clinical samples to the laboratory is required to be in adherence to all national regulations for the safe transport of biological materials. Enfer Medical provides a fully compliant logistics service, aligned with clients’ testing requirements.
Prompt transport of specimens:
To ensure prompt testing of samples and release of results within the published test turnaround times, samples should arrive to the laboratory by 18:00. Test turnaround time is measured from receipt of the sample at the laboratory until the time the authorised results are reported to users.
In rare cases specimens may not be suitable for testing on arrival to the laboratory. In that case the sample will be rejected at the receipt stage and the service user will be notified immediately and an explanation as to why the sample could not be processed will be provided. Reasons why samples cannot be processed include but are not limited to:
- Samples received beyond the stability limits and/or not at the correct temperature indicated for each test.
- Incorrect sample type received.
- Leaking samples, sample not received or sample insufficient for analysis as stated below within sample requirements.
- Non-compliant samples or request forms i.e. those missing sample date information, missing sample test request and/or missing sample site/type information.
- Samples received without the necessary patient identifiers.
Quantitative results for CO2 are reported in numeric value in mmol/L. Please contact us for more information on the reference ranges used at Enfer Medical.
Critical results are communicated in accordance with the Communication of critical results for patients in the community- national laboratory handbook CSP041/2019
Following receipt at the Laboratory, results should be available on the next working day and will be reported to the referring clinician via the Enfer Medical Client Portal or in a format agreed with clients.
Established clients can login to the portal using the link above.