Transcutaneous oximetry is a noninvasive test. It directly measures the oxygen level of tissue beneath the skin. As oxygen is carried to tissues by blood flow in the arteries, TcpO2 is an indirect measure of blood flow. It measures the amount of oxygen that reaches the skin through blood circulation. 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.