Which of the following is/are true with respect to transcutaneous PO2 (TcPO2) measurements?

a. TcPO2 levels provide an index of the adequacy of tissue perfusion and depends on the quantity of oxygen delivered and that extracted to meet metabolic demands

b. Extremity TcPO2levels are typically normalized to a well perfused area, such as the infraclavicular skin

c. TcPO2levels average about 60 mmHg in normal limbs

d. Patients with limb threatening ischemia usually have values less than 20 mmHg and may approach 0

Transcutaneous PO2 levels provide an index of the adequacy of tissue perfusion. They depend on the quantity of oxygen delivered by the blood and that extracted to meet metabolic demands. Because oxygen supply is a function of the arterial PO2, cardiac output and age peripheral measurements must be compared with levels from a well perfused central area, such as the infraclavicular skin. In normal limbs transcutaneous oxygen levels average 60 mmHg or 90% of the infraclavicular value. Many claudicants have resting values in the normal range, whereas in patients with limb threatened ischemia the values are usually less than 20 mmHg and many be zero.