Parametric studies of human thermal mechanisms and measurements

Raynaud's phenomenon: Infrared functional imaging applied to diagnosis and drug effects

A non-invasive, innovative approach to the study of Raynaud's Phenomenon is proposed. A group of patients, with respect of a control group, underwent a simultaneous assessment of thermal properties of all ten fingers using infrared functional imaging (IRFI). The assessment highlighted a quite different behaviour between patients with Primary- (PRP) and those with scleroderma - Raynaud's Phenomenon (SSc) and, compared with other existing techniques, seems to be an objective and effective tool to discriminate between PRP and RP secondary to SSc. 18 healthy volunteers (Norm), 20 Primary Raynaud's Phenomenon (PRP) and 20 Secondary Scleroderma (SSc) patients were studied subsequently to clinical evaluation and nail fold capillaroscopy. High-resolution infrared imaging of finger re-warming processes, immediately after a 2 min cold stress, allowed to identify objective parameters. Temperature integral Q (the temperature evaluation of the area under the time-temperature curve along the re-warming period) provided particularly effective figures in describing thermal properties of the fingers. Grand average Q values were (383.4 ∓ 12.5) °C×min, (502.9 ± 88.1) °C×min and (1022.0 ± 110.2) °C×min for the PRP, SSc and Normal groups, respectively. Separate evaluation of the temperature integral for each finger leads to very similar results for the fingers of all the PRP patients; a different thermoregulatory response was observed in SSc patients. The sensitivity of the method in order to distinguish healthy from ill fingers was 100%. The specificity in distinguishing SSc from PRP was 95%. In addition, IRFI parameters provided a better understanding of the impaired control of the finger's temperature in PRP and SSc with respect to the Normal group. This pilot study also applied IRFI for the measurement of drug effects in patients with Raynaud's Phenomenon. Sixteen out of twenty SSc patients were tested in a single 1-hour session of N-acetylcysteine infusion. IRFI clearly documented a significant increase of face and hands temperature during the drug administration. The grand average value of the finger's temperature after the 1 hour NAC administration was (29.6 ± 3.7) °C, while its value before was (27.9 ± 3.7) °C (p<0.001). N-acetylcysteine seems to act as a vasodilator in patients with Raynaud's phenomenon secondary to systemic sclerosis (scleroderma).