Transcutaneous Oxygen Tension (TcPO2) Measurement as a Diagnostic Tool in Patients with Peripheral Vascular Disease

Transcutaneous oxygen tension (TcPO2) was measured through Clark's elec trode at the dorsum of the foot in 52 healthy controls whose ages ranged from twenty to sixty-five years (mean 45.05 ±14.09) and 36 nondiabetic patients with peripheral vascular disease (PVD) (5 stage I, 16 stage II, 4 stage III, 11 stage IV), under standardized conditions at rest and during recovery from limb ische mia obtained with pneumatic cuff compression for 3 minutes. At rest the TcPO2 averaged 71.20±14.26 mm Hg (range 46-92) in the con trols and 51.56±26.38 in the PVD patients (p < .01). A wide overlap was ob served between the two groups and among the different stages of the disease, and consequently, the diagnostic value of TcPO2 at rest was limited (sensitivity equal to 32%). During the recovery from ischemia the time constant (recovery half-time, T½) averaged 38.01±7.23 sec in the controls and 55.84 ± 19.82 in the PVD patients (p < .01). The T½ added to the diagnostic value of the method, making it more sensitive (55%), especially for stage II patients. The TcPO2 at rest was lower with increasing severity of the disease; both the TcPO2 at rest and the T½ correlated with the ankle-arm pressure index in the diseased limbs (r = .48 and - .41 respectively, p < .001). The method showed a limited degree of reproducibility in the controls when the right and the left lower extremity were compared in each subject; in fact, the intrasubject variance of TcPO2 and T½ was of the same magnitude as the intersubject variance (F=1.73 and 1.26 respectively), and the standard devia tions of the difference between lower extremities was elevated (13.32 mm Hg for TcPO2 and 7.80 sec for T½). Moreover, the T½ decreased with increasing age in the controls (r = - .47, p < .001). The authors conclude that, although it is a good indicator of the severity of PVD, the TcPO2 has a limited diagnostic value in this kind of patients, owing to the wide range of normalcy, to the low degree of reproducibility in a single individual, and to the influence of the age factor.