Transcutaneous oximetry (TCPO2) is a noninvasive test that directly measures the oxygen level of tissue beneath the skin. Because oxygen is carried to tissues by blood flow in the arteries, TCPO2 is an indirect measure of blood flow.
This test is often used to evaluate advanced peripheral arterial disease, a condition in which blood flow to an extremity (usually the leg) is greatly reduced.
Results of this test help physicians determine how severely tissues are deprived of blood flow. The test is often especially useful in predicting wound healing or amputation healing.
Transcutaneous oximetry (TcpO2) measures the amount of oxygen that reaches the skin through blood circulation. Physicians primarily use it to assess the severity of artery disease in the legs or, much less commonly, in the arms or hands.
Severe atherosclerosis (hardening of the arteries) in the extremities can block blood and oxygen flow and cause walking discomfort, gangrene, and limb loss. Measuring oxygen at the skin surface is a valuable indicator of how much oxygen gets to underlying tissues. Transcutaneous oximetry is useful when other noninvasive testing is not possible and is especially useful in predicting wound healing or amputation healing.
However, the value of the test is sometimes limited because only small areas can be measured. Because there are errors associated with this test, it requires physician interpretation for useful results.
No special preparation is required for the test.
Transcutaneous oximetry has no known side effects or complications and is essentially risk free.
WHAT TO EXPECT
The test is performed in a vascular diagnostic laboratory and causes no discomfort. The area to be tested is first cleaned with alcohol and cleared of any wound dressings. If necessary, the site is also shaved. A gel that conducts electrical impulses is applied, and then the physician places adhesive sensors containing a platinum electrode that can sense oxygen on the affected limb.
Electrodes in the sensors heat the area underneath the skin to dilate (widen) the capillaries so oxygen can flow freely to the skin, providing an optimal reading. This takes about 15 minutes. The readings are converted to an electrical current and the signal is displayed on a monitor and recorded. Once the test is completed, the sensors are removed, the testing sites are cleaned, and any dressings are reapplied.
A physician in the vascular diagnostic laboratory reviews the result.
The patient can resume normal activities immediately after the test.