Clinical studies of the vibration syndrome using a cold stress test measuring finger temperature.

Since nine years multicentre, transversal and longitudinal clinical studies on hand-arm, vibration-exposed patients are being performed in cooperation with French occupational medicine centers and social security institutions. These studies are based upon current clinical assessment and standardized, temperature-measuring cooling tests. Data acquisition uses a portable, 10-channel, micro-processor-based temperature recorder and miniature thermal sensors. Temperature is monitored at the ten finger tips continuously, before, during and after a cold stress performed in strictly controlled conditions. Data from examinations performed at outlying sites are transferred through the telephonic network to a central processing unit. Data analysis uses a specific, expert-type software procedure based upon previous clinical studies on (i) 238 "normal" subjects, and (ii) 3,046 patients with vascular disturbances of the upper extremities of various etiologies. This procedure includes a staging process which assigns each finger a class representing the degree of severity of the abnormalities of response to cold ("dysthermia") related to vascular disorders. All data processing is fully automatic and results in a printed examination report. To date, over 1,623 vibration-exposed forestry, building and mechanical workers were examined. Sixty-three per cent of patients had received high dose of vibration (daily use of chain saws, air hammers, ballast tampers over many years). Typical white finger attacks or only neurological symptoms were found in 36% and 23% of patients respectively. The rate of sever dysthermia was much higher in patients with white finger attacks (83%) than in patients without (32%). In 90% of the vibration-exposed patients, the severity of dysthermia has differed greatly from one finger to another and between hands, while in non-exposed patients with primary Raynaud syndrome the dysthermia are generally similar for all fingers but the thumbs. Of 208 forestry workers who were asymptomatic but had dysthermia on a first examination, 31% have developed vascular or neural symptoms within subsequent follow-up. Of 223 symptomatic patients with more or less severe dysthermia at a first examination performed in winter, 17% had the same abnormalities in summer and microvascular lesions at capillaroscopy, while the other 83% had reversible dysthermia and only functional capillaroscopic abnormalities. These studies suggest that temperature-measuring cooling tests performed under well-defined, standard conditions provide significant data for grading the severity and assessing the reversibility of Raynaud phenomena, and for detecting subclinical vasomotor disorders in asymptomatic patients.