Study design: Pilot study.Background: Dry needling has been an emerging treatment option for physical therapists over the last decade. Despite the fact that studies have demonstrated the overall benefit of dry needling, there is no clear understanding how long needles should be left in place (situ). This pilot study investigated the effects of needles remaining in situ based on autonomic responses over time.Methods: A convenience sample of 21 subjects were recruited for this study. Automated pupillometry was utilized to obtain a direct measure of autonomic nervous system activity. Directly following a baseline measurement, 8 type J Seirin Acupuncture needles were inserted paravertebral at the C7-T3 segments. A total of 8 post-needling 60 seconds pupil measurements were taken at 3 minutes intervals for 24 minutes post needling.Outcomes: A statistical significant difference in mean pupil diameter was found following the needle intervention (p < .01), which implies an increased sympathetic activity. This subject sample had a statistically significantly larger mean pupil diameter immediately after the needling, which lasted until measure point 7, at 18 minutes (P < .05). At measure point 8 there was no longer a statistical significant difference compared to the premeasurement measure.Discussion: The results of this study provide evidence that dry needling results in a significant increased activity of the sympathetic nervous system for up to 18 minutes. Between 18 and 21 minutes autonomic activity returned to a non-significant difference compared to baseline. The results of this study could assist clinicians in clinical decision making to determine needle placement time.
Keywords: Pupillometry; autonomic nervous system; dry needling; time effect.