Finger sudorometry and assessment of the sudomotor drive

Sudorometry of the finger was carried out using the ventilated capsule method, the aim being to use the level of relative humidity within the sudorometer as an indirect measure of the sudomotor drive. Subjects inserted a finger through a diaphragm of a finger-shaped, temperature-controlled chamber which also contained the humidity sensor. Manoeuvres known to alter the sudomotor drive produced changes in chamber humidity. The relative humidity within the sudorometer became constant after local anaesthesia of the digital nerves and after upper limb sympathectomy, suggesting that fluctuations in the sudorometer output were dependent upon an intact autonomic nervous system. In an environment in which temperature was controlled and arousal effects from the process of measurement were minimised, chamber humidity always increased during a Stroop test, providing a rapid means of indirectly assessing sudomotor drive mechanisms.