Local Cold Exposure Test with a New Arterial Photoplethysmographic Sensor in Healthy Controls and Patients with Secondary Raynaud's Phenomenon

Abstract

Local cold exposure tests are used to diagnose cold-induced vasospastic disorders and to evaluate therapeutic success. We investigated the pulsatile signal detected with a newly developed arterial photoplethysmography (APPG) method and the signal change induced by local cold exposure using a temperature-controlled finger holder, comparing it with laser Doppler flux (red and green laser, rLDF and gLDF) and red blood cell velocity measured in nailfold 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°C for 5 min. 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) during cooling and characteristic changes in the APPG signal (for instance a decrease in pulse wave amplitude;P< 0.0001). Significant differences in the APPG amplitude could be detected under resting conditions; at cooling temperatures there were also significant differences in CBV and APPG. The temperature-controlled finger holder with its built-in APPG probe appears to be a useful tool for evaluating the effect of local cooling on finger skin perfusion and differentiating between healthy controls and patients with secondary Raynaud's phenomenon due to systemic sclerosis. The gLDF signal was rather weak, limiting its value in cold stress tests. The differences between controls and patients in CBV were somewhat smaller than in previous studies, suggesting the advantage of lower local cooling temperatures, e.g., 12°C.