Oxygen inhalation--induced transcutaneous PO2 changes as a predictor of amputation level

Noninvasive transcutaneous PO2 (TcpO2) determinations have been developed to study peripheral arterial occlusive disease. To evaluate this technique as a predictor of amputation outcome, a blind, prospective study of 101 patients undergoing 119 amputations (23 above-knee [AK], 57 below-knee [BK], and 39 forefoot) was performed. TcpO2 measurements were obtained from the dorsum of the foot and 10 cm distal to the patella, both prior to and 10 minutes after inhalation of 100% oxygen. On the basis of preliminary results, initial TcpO2 values greater than 10 mm Hg or an increase greater than 10 mm Hg after oxygen inhalation were considered to predict a successful outcome, whereas failure was predicted when the initial TcpO2 value was less than 10 mm Hg and the increase after oxygen inhalation did not exceed the 10 mm Hg level. In the BK amputation group the test was 95% sensitive, 100% specific, and 95% accurate. Retrospective utilization of the above criteria in patients who had undergone both oxygen inhalation testing and AK amputation suggested that 9 of 17 limbs (53%) might have undergone a more distal BK amputation successfully. These results document the effectiveness of an initial TcpO2 determination coupled with the response to 100% oxygen inhalation as an excellent predictor of the outcome of lower extremity amputations.