A static handgrip method for distal quantitative sweat measurements

The quantitative sudomotor axon reflex test (QSART) measures sympathetic C fibre function when iontophoresed acetylcholine (Ach) evokes a measurable reliable sweat response. This study tests a novel, simplified method of sweat stimulation which accompanies hand dynamometry. In 34 healthy subjects we compared the standard sudomotor axon reflex test with a simplified method using static handgrip as sweat stimulus and recorded from the distal forearm, thumb and little finger tips. The standard method failed on technical grounds beyond the forearm. At the distal forearm, sweat rates were 313 ± 140 nl/min, representing a four-fold increase from baseline. Static handgrip induced sweat rates of 339 ± 156 (thumb) and 296 ± 139 (little finger) nl/min, representing a 1.7 and 1.6 fold increase from baseline. Static handgrip did not significantly alter distal forearm sweat secretion, and in females handgrip induced significantly less sweating over the thumb than in males. After dynamometry or Ach stimulation, over the three sites (thumb, little finger and forearm), the stimulated sweat secretion volumes were measured at 0.0278 ± 0.021 μl/cm2/min (thumb), 0.0204 ± 0.020 μl/cm2/min (little finger), and 0.0503 ± 0.0283 μl/cm2/min (forearm) after correction. Our study suggests the static handgrip method can be used to stimulate distal sweat production and may be of particular significance in investigating length-dependant neuropathies and assessing distal C fiber function.