TcPO2

Transcutaneous partial pressure of oxygen (TcPO2) is a noninvasive measure of the oxygen tension in the skin’s capillary bed, used as a proxy for tissue oxygenation. It is obtained with a small sensor placed on intact skin, which is heated to about 40 to 44 degrees Celsius to increase local blood flow and drive arterial oxygen to the sensor through a permeable membrane. The sensor uses a Clark-type electrode to measure the partial pressure of oxygen, yielding a TcPO2 value in millimeters of mercury (mmHg). Readings stabilize over several minutes and can be recorded at multiple sites to map tissue oxygenation.

The procedure involves selecting a clinically relevant site, typically the chest, arm, thigh, or foot, depending on the question. The area is prepared, a calibration is performed, and the electrode is left in place for several minutes for a stable reading. Measurements can be continuous or intermittent and may be repeated to assess changes over time or in response to therapy.

TcPO2 is used to assess tissue perfusion and oxygen delivery in several contexts. In surgery, it helps predict the viability of random skin flaps and grafts. In wound care, higher TcPO2 values generally correlate with better healing, while persistently low values suggest impaired perfusion. In vascular disease, TcPO2 aids evaluation of limb ischemia and guides management. In critical care, it can monitor tissue perfusion during shock, sepsis, or after resuscitation.

Interpretation should consider factors that affect skin oxygen tension, including local temperature, edema, skin thickness, perfusion at the measurement site, ambient conditions, smoking, vasopressor use, fever, and movement. TcPO2 reflects superficial tissue oxygenation and is not a direct measure of arterial oxygen content or whole-body oxygenation. Normal values vary by site and device.