Transcutaneous pO2 measurements in Raynaud's phenomenon. Value and limitations

To determine whether measurements of transcutaneous pO2 (TcPO2) by Tacomette (Novametrix Medical Systems Inc., Connecticut, U.S.A.) could be a valuable method to evaluate nutritive skin perfusion, baseline TcPO2 was measured under standardized conditions in normals and in patients with several types of Raynaud's phenomenon (RP). The control group (n = 41; TcPO2 = 34.4 +/- 14.3 mm Hg) and the patients with primary RP (n = 81; TcPO2 = 25.0 +/- 9.7 mmm Hg) had a significantly higher baseline TcPO2 (p less than 0.05) in comparison to the secondary RP-patients with a connective tissue disease (n = 54; TcPO2 = 10.5 +/- 7.9 mm Hg). In RP patients the group with trophic skin lesions showed a significant lower TcPO2 (p less than 0.01). The reproducibility expressed as the standard error of a single observation was moderate (13-27%). After 20 minutes acclimatization it took 32 minutes before a stable baseline value was reached which makes the procedure a lengthy one. Its non-invasive nature is severely hampered by the skin injuries observed in 3 patients, while the abolition of vascular tone induced by the heating makes the interpretation of intervention studies difficult. In conclusion baseline TcPO2 measurements were found lower in patients with disturbances of nutritional skin blood flow. However, because of the overlap of values between groups the discriminative value of this method is limited. Comparative studies with other techniques that determine capillary perfusion like the 133Xenon wash out technique and dynamic capillary microscopy are necessary to validate this technique as a reliable alternative.