Local cold exposure test with a new arterial photoplethysmographic sensor in healthy controls and patients with secondary Raynaud's phenomenon

Local cold exposure tests are used to diagnose cold-induced vasospastic dis orders and to evaluate therapeutic success. We investigated the pulsatile s ignal detected with a newly developed arterial photoplethysmography (APPG) method and the si,anal change induced by local cold exposure using a temper ature-controlled finger holder, comparing it with laser Doppler flux (red a nd green laser, rLDF and gLDF) and red blood cell velocity measured in nail fold capillaries (CBV). Ten healthy volunteers and 10 age- and sex-matched patients suffering from Raynaud's phenomenon due to systemic sclerosis were investigated using a moderate cooling temperature of 16 degrees C for 5 mi n. All signals were recorded simultaneously. The results show a significant reduction of CBV (P < 0.0001), rLDF (P < 0.0003), and gLDF (P = 0.0214) du ring cooling and characteristic changes in the APPG signal (for instance a decrease in pulse wave amplitude; P < 0.0001). Significant differences in t he APPG amplitude could be detected under resting conditions; at cooling te mperatures there were also significant differences in CBV and APPG. The tem perature-controlled finger holder with its built-in APPG probe appears to b e a useful tool for evaluating the effect of local cooling on finger skin p erfusion and differentiating between healthy controls and patients with sec ondary Raynaud's phenomenon due to systemic sclerosis. The gLDF signal was rather weak, limiting its value in cold stress tests. The differences betwe en controls and patients in CBV were somewhat smaller than in previous stud ies, suggesting the advantage of lower local cooling temperatures, e.g., 12 degrees C. (C) 1999 Academic Press.