Early cardiovascular sympathetic reflex activation is independent of occlusion time during reactive hyperemia

Abstract

Purpose: The aim of the present study was to investigate the role of occlusion time in dynamic changes of autonomic activation during reactive hyperemia.
 Methods: Healthy subjects (n = 30) in the age range of 18–25 years participated in this study. Vascular reactivity was assessed by measuring the dynamic changes in finger pulse volume amplitude (PVA) and pulse transit time relative to the RR intervals in the test (occluded arm) and control arm (contralateral non-occluded arm) during 1, 3 and 5 minute of occlusion using two separate Photoplethysmographic sensors. Heart Rate Variability was computed from a simultaneously acquired ECG signal to monitor the dynamic changes in cardiac autonomic nervous activity. Time-varying analysis of all signals were shown every 1 second in average response graphs.
 Results: Time-varying analysis of vascular and autonomic response during reactive hyperemia demonstrated the presence of a characteristic response pattern with an increase in the Sympathetic index and a decrease in Parasympathetic index at 8 to 10 seconds, an increase in heart rate at 20 seconds and a progressive increase in PVA during the first 60 seconds after occlusion regardless of the time spent in the procedure. Moreover, a decrease in pulse transits time relative to RR intervals, followed by an increase regardless of the occlusion time was evidenced. 
 Conclusions: Early cardiovascular sympathetic activation is independent of occlusion time during reactive hyperemia, which suggests this is a vascular autonomic reflex response involved in the generation of the physiological phenomenon of reactive hyperemia.

Autonomic and Vascular Responses during Reactive Hyperemia in Healthy Individuals and Patients with Sickle Cell Anemia

“…A quick sympathetic nervous system response, reflected in increments in the LF and the LF/HF ratio, was observed in healthy subjects after occlusion in this study. This has been interpreted as an early cardiovascular sympathetic reflex (10 s after occlusion) in response to RH caused by the metaboreflex [33]. The accumulation of metabolites during exercise has been shown to activate the metaboreflex [34,35].…”