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

Abstract

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.