Hemodynamic effects of habituation to a week-long program of neuromuscular electrical stimulation.

OBJECTIVES: Neuromuscular electrical stimulation (NMES) of the calf muscles has been shown to cause instantaneous increases in venous outflow from the lower leg and could be used as an adjunct to current gold-standard compression therapies for the prevention of venous stasis and its related pathologies. However, little is known about the effects of NMES in combination with compression therapies on subject comfort, compliance and popliteal venous blood flow over the course of a week-long NMES protocol. This study aimed to assess the effects of a NMES and compression protocol for the prevention of venous stasis on the compliance, comfort and venous blood flow of healthy volunteers over the course of seven days. DESIGN: Twenty-four healthy subjects were assigned to either a stimulation or control group. The stimulation group received 1.5 h of NMES daily while the control group received none. Daily measures of popliteal venous blood flow, subject compliance and comfort were recorded over 7 days. RESULTS: Ejected blood flow volumes and peak velocities in the popliteal vein during NMES were sustained over a 30-min stimulation session and increased by approximately 100% over the course of seven days. Mean stimulation intensities increased progressively throughout the week, while perceived pain during NMES decreased significantly. Mean compliance to the 7-day protocol was 100%. CONCLUSION: User habituation to a combined NMES and compression protocol resulted in significant increases in ejected venous volume and peak velocity over the course of 7 days. This resulted in the highest ejected venous volume reported from a single NMES induced contraction of the calf muscles to date which was twice the magnitude of values previously reported in the literature. These findings suggest that NMES based protocols applied over an extended period of days, weeks or months may provide greater hemodynamic effect for the prevention of venous stasis than previously observed during NMES sessions lasting less than a few hours.

Popliteal blood flow and plantar flexion force due to neuromuscular electrical stimulation (NMES) of the calf muscle pump are strongly associated with NMES intensity.

In spite of significant gains in venous flow using Neuromuscular Electrical Stimulation (NMES) of the calf muscles, little is known about the relationship between the applied electrical stimulus and the resulting venous blood flow in the deep veins of the leg. This retrospective study of repeated measures of blood flow, muscle force and NMES signals of 14 healthy subjects undergoing a week long NMES protocol aimed to determine the relationship between the applied NMES signals and the resulting muscle force and blood flow measures. Statistical analyses revealed strong correlations between NMES blood flow, NMES plantar flexion force and the applied NMES intensity.

Detecting electroporation by assessing the time constants in the exponential response of human skin to voltage controlled impulse electrical stimulation.

We propose a new method for extracting the electrical properties of human skin based on the time constant analysis of its exponential response to impulse stimulation. As a result of this analysis an adjacent finding has arisen. We have found that stratum corneum electroporation can be detected using this analysis method. We have observed that a one time-constant model is appropriate for describing the electrical properties of human skin at low amplitude applied voltages (<30V), and a two time-constant model best describes skin electrical properties at higher amplitude applied voltages (>30V). Higher voltage amplitudes (>30V) have been proven to create pores in the skin's stratum corneum which offer a new, lower resistance, pathway for the passage of current through the skin. Our data shows that when pores are formed in the stratum corneum they can be detected, in-vivo, due to the fact that a second time constant describes current flow through them.

Identifying changes in human skin electrical properties due to long-term NeuroMuscular Electrical Stimulation.

The skin electrical properties are identified using a standard NeuroMuscular Electrical Stimulation (NMES) voltage pulse. The three component series equivalent electrical model was chosen to account for the skin electrical properties. The values of each of these three electrical components of the equivalent electrical model were identified and compared throughout 40 minute daily NMES sessions and over 5 days. Current measurements were performed during the NMES sessions in a non-invasive way, in order to assess changes occuring during each stimulation session and due to long-term NMES.