Arterial Carbon Dioxide Partial Pressure (PaCO₂) during Exhaled Respiratory Volume
This test measures the amount of carbon dioxide in your exhaled breath, reflecting how efficiently your lungs remove waste gases from your blood. It helps assess lung function and blood chemistry, particularly in conditions affecting breathing or acid-base balance.
["This test helps doctors check how well your lungs are working and whether your blood chemistry is balanced during breathing efforts."]
Key facts at a glance
- LOINC
- 60809-1
- Short code
- CO2 during expir VFr/PPres Away adap
- Synonyms
- CO2 during expir VFr/PPres Away adap
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 22
- Ref high
- 28
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82374
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What This Test Measures
Your exhaled breath contains carbon dioxide, which your body naturally produces as a byproduct of metabolism. This test measures the partial pressure of carbon dioxide in the air you exhale, often linked to how your lungs are functioning and how much carbon dioxide is being removed from your bloodstream.
Why It Matters in Your Health
Measuring exhaled carbon dioxide can help identify issues like chronic obstructive pulmonary disease (COPD), sleep apnea, or other lung conditions. It may also be used in monitoring during procedures that require precise respiratory control, such as anesthesia.
When You Might Need This Test
Your healthcare provider may recommend this test if you have symptoms like shortness of breath, frequent respiratory infections, or if you’re undergoing a procedure that requires careful monitoring of breathing patterns. It’s sometimes used in research or specialized clinical settings to study lung function.
What to Expect Before the Test
There are no special preparations needed for this test. You’ll likely be asked to exhale into a specialized device that collects and analyzes your breath over a set period. It’s a quick, painless process with no downtime.
Reference range
Adult: 22-28 mmol/LN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Abnormal levels of exhaled carbon dioxide can indicate underlying lung diseases, metabolic disorders, or other conditions affecting gas exchange. For example, elevated levels may suggest poor lung function or conditions like obesity hypoventilation syndrome, while lower levels might point to overbreathing or certain neurological issues.
Short name
PaCO₂ (exhaled)
Frequently asked questions
How does exhaled carbon dioxide differ from blood carbon dioxide tests?
Is this test painful or uncomfortable?
Can I eat or drink before this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy