TRANSCUTANEOUS OXYGEN AND CARBON-DIOXIDE MEASUREMENT IN PERIPHERAL VASCULAR-DISEASE

Combined transcutaneous oxygen tension (tcPO(2)) and transcutaneous ca rbon dioxide tension (tcPCO(2)) measurements were carried out at both the subclavicular and metatarsal level in 29 controls and 100 patients with peripheral arterial obstructive disease (PAOD) (intermittent cla udication: n=40, critical limb ischemia: n=60). Interindividual variat ion coefficients of arterial and subclavicular tcPCO(2) (n=94 subjects ) were superimposable, while tcPO(2) variability was twice the arteria l value. Furthermore, arterial tensions were better predicted by tcPCO (2) than by tcPO(2) measurement. In the 75 limbs with an ABI < 0.9 of patients with intermittent claudication, tcPCO(2) did not differ signi ficantly from controls (n=58 limbs), but it was elevated in those with critical limb ischemia (n=74 limbs), although control and pathologica l values overlapped widely even in this latter group. At variance with tcPCO(2), tcPO(2) was lower in intermittent claudication than in cont rols, and undetectable in most of the symptomatic limbs with critical ischemia, irrespective of concomitant diabetes. In the overall sample (n=255 limbs), tcPCO(2) did not show significant changes for tcPO(2) v alues ranging from 80 to 10 mmHg, and it increased markedly in several -but not all-patients whose tcPO(2) values were below that limit. To e valuate further the biological significance of an increase in tissue t cPCO(2), another sample of 24 subjects underwent acute forearm ischemi a for a period of thirteen minutes, a maneuver that increased tcPCO(2) markedly, indicating that this parameter is indeed a correlate of dra stic reductions in limb perfusion. Thus, tcPCO(2) is methodologically less variable than tcPO(2) and more predictive of arterial values. How ever, the wide overlap with control values restrains its use as an iso lated diagnostic tool to substantiate PAOD, even in the most advanced stages of disease. Marked elevations in tcPCO(2) can be found in patie nts with critical limb ischemia, although normal values may coexist wi th low or negligible tcPO(2) levels for reasons to be clarified. Furth er work is needed to establish the extent to which tcPCO(2) determinat ion may complement tcPO(2) to differentiate extreme from less severe d egrees of critical limb ischemia.