Partial pressure of oxygen, mixed sample (pO2)

This test measures the partial pressure of oxygen in a blood gas sample, which reflects how much oxygen is dissolved in your blood and available to move into tissues. It directly assesses gas exchange in the lungs and complements other measures such as oxygen saturation and carbon dioxide.

When the sample type is reported as mixed, it means the blood is not strictly arterial or standard venous. It may represent blood returning from the body via a catheter, or a specimen that blends sources. The reported source helps your care team interpret the result in the right clinical context.

pO2 helps your team understand how well your lungs are moving oxygen into your bloodstream. It is commonly ordered when you have breathing difficulties, suspected lung or heart problems, during anesthesia, or in intensive care to guide oxygen therapy and ventilator settings. It can also be used to monitor response to treatments.

Results can inform urgent decisions, such as adjusting supplemental oxygen, evaluating the need for further respiratory support, or investigating conditions like pneumonia, pulmonary embolism, or heart failure. In newborns, children, and people with chronic lung disease, it is an important part of ongoing assessment.

Your pO2 is interpreted together with the sample source, your level of supplemental oxygen, altitude, and other blood gas values. A result that is higher or lower than expected does not always mean a serious problem on its own, because collection conditions, recent breathing pattern, and underlying health can affect the value.

If a result does not match how you feel or the clinical picture, your clinician may repeat the test, check related measurements, review how the sample was taken, or adjust oxygen and medications. Ask your care team how the result fits with your symptoms and treatment plan.