The primary objective of this study is to explore the application of the Firefly® device for delivering NMES to anatomically defined regions of the upper limb and to observe associated physiological changes. Specifically, the study will assess alterations in arterial and venous blood flow, as well as local muscle oxygen saturation, as potential indicators of muscle perfusion during NMES.
Participants will undergo NMES using the Firefly® device, applied to two predefined regions of the upper limb: one targeting the anterior arm nerve bundle (a collective term referring to motor and sensory nerves within the anterior and medial compartments of the upper arm, including the musculocutaneous and adjacent (median, medial cutaneous, ulnar and radial) nerves, and the other targeting the median nerve in the proximal forearm. Vascular responses will be assessed at two sites, the brachial artery and axillary vein, using Doppler ultrasound. For each nerve-vascular site pairing, NMES will alternate between stimulation OFF and ON conditions (10 OFF and 10 ON cycles), comprising one stimulation block of approximately 20 minutes. Each participant will complete four stimulation blocks in total. During both ON and OFF phases, blood flow volume and haemodynamic parameters, including peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI), will be recorded. Additionally, local muscle oxygen saturation (SmO₂) will be continuously monitored using functional near-infrared spectroscopy (fNIRS) to assess tissue-level physiological changes. The total study participation time per individual is approximately 2 hours.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
10
Firefly NMES device applied to the upper limb during a single-visit exploratory pysiological study
Firstkind
High Wycombe, Buckinghamshire, United Kingdom
Change in upper-limb blood flow volume during NMES (ON vs OFF)
Within-subject change in upper-limb blood flow volume (mL/min) measured using Doppler ultrasound during neuromuscular electrical stimulation (NMES) delivered via the Firefly device, comparing stimulation ON versus OFF conditions. Measurements will be collected across repeated stimulation cycles at predefined upper-limb stimulation zones and vascular assessment sites.
Time frame: During single study visit (approximately 2 hours), across repeated stimulation ON/OFF cycles
Change in upper-limb peak systolic velocity during NMES (ON vs OFF)
Within-subject change in upper-limb peak systolic velocity (PSV; cm/s) measured using Doppler ultrasound during NMES delivered via the Firefly device, comparing stimulation ON versus OFF conditions across repeated stimulation cycles at predefined upper-limb stimulation zones and vascular assessment sites.
Time frame: During a single study visit (approximately 2 hours), across repeated stimulation ON/OFF cycles.
Change in upper-limb end-diastolic velocity during NMES (ON vs OFF)
Within-subject change in upper-limb end-diastolic velocity (EDV; cm/s) measured using Doppler ultrasound during NMES delivered via the Firefly device, comparing stimulation ON versus OFF conditions across repeated stimulation cycles at predefined upper-limb stimulation zones and vascular assessment sites.
Time frame: During a single study visit (approximately 2 hours), across repeated stimulation ON/OFF cycles.
Change in upper-limb resistive index during NMES (ON vs OFF)
Within-subject change in upper-limb resistive index (RI; unitless ratio) derived from Doppler ultrasound measurements during NMES delivered via the Firefly device, comparing stimulation ON versus OFF conditions across repeated stimulation cycles at predefined upper-limb stimulation zones and vascular assessment sites.
Time frame: During a single study visit (approximately 2 hours), across repeated stimulation ON/OFF cycles.
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Change in upper-limb muscle oxygen saturation during NMES (ON vs OFF)
Within-subject change in upper-limb muscle oxygen saturation (SmO₂; %) measured continuously using functional near-infrared spectroscopy (fNIRS) during NMES delivered via the Firefly device, comparing stimulation ON versus OFF conditions across repeated stimulation cycles at predefined upper-limb stimulation zones and assessment sites.
Time frame: During a single study visit (approximately 2 hours), across repeated stimulation ON/OFF cycles.
Incidence of adverse events and device-related effects
Number and type of adverse events (AEs), serious adverse events (SAEs), adverse device effects (ADEs), serious adverse device effects (SADEs), and device deficiencies observed during study participation.
Time frame: During single study visit (approximately 2 hours)