study
 

Augmentation of venous, arterial, and microvascular blood supply in the leg by isometric neuromuscular stimulation via the peroneal nerve

Dr. AT Tucker1, 2, Dr. A Maass1, 2, Dr. DS Bain2, L-H Chen2, Dr. M Azzam1, H Dawson1, Prof. Dr. Atholl Johnston1

1The Ernest Cooke Vascular & Microvascular Unit, St. Bartholomew's Hospital, London, UK

2Centre of Clinical Pharmacology, William Harvey Research Institute, St Bartholomew's Hospital & The London School of Medicine and Dentistry, Queen Mary University of London, London, UK


A study to determine efficacy of the OnPulse™ technology to deliver increased venous blood flow via the electrical nerve stimulation and the activation of the calf muscles.

Summary of the study and its results

  • Up to a 25 fold increase in the speed of blood flow (LDF) compared to baseline
  • Blood volume flow increases up to 4 fold and velocity up to 3.5 fold
  • Skin temperature and oxygen levels better maintained in the foot when the device is used

 

Study design

The study involved 30 healthy volunteers with 2 visits per volunteer. Each volunteer was tested with 15x different stimulations applied - from low amplitude/low frequency to high amplitude/high frequency. The stimulation programmes were applied to a randomly selected leg in a sitting position for 5 minutes, 5 further minutes of response recording followed by a 5-minute recovery.

 

G-programme

 

Effect on blood flow

Photoplethysmography (PPG) measures the change in the signal relating to dorsal foot venous emptying. All PPG values were at least 50% compared to the mean of 10 foot flexions (theoretical maximum physiological response) for each volunteer. This indicates the potential to produce prolonged improved venous return from lower limbs.

 

1259Effect on blood flow

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Fig. 1 PPG measurements showing venous emptying response versus stimulation current, by frequency, compared to 10 dorsiflexions (theoretical maximum physiological response that can be obtained in the sitting position)

 

Microcirculatory blood flow

Laser Doppler Fluxmetry (LDF) (measured on the dorsum of foot) shows at 1Hz, at least a two-fold increase in the speed of skin blood flow in the stimulated leg compared to the control (contralateral resting leg). A significant increase in the temperature of the skin surface compared to the unstimulated leg was also recorded (data not shown).

 

1262Microcirculatory blood flow

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Fig. 2 Laser Doppler Fluxmetry (LDF) measurements of microcirculatory flux (speed of skin blood flow) bilaterally on dorsum of foot, for each stimulation setting as a percentage of baseline

 

Heart rate and tissue oxygen

During the tests pulse oxymetry monitored a stable heart rate and oxygen saturation above 97% (Fig. 3 a). Tissue oxygen as measured by a transcutaneous monitor (TCM4) showed a slight increase of 6% to 7% at stimulation levels 5 to 15 compared to the control (contralateral resting leg) (Fig. 3 b).

 

1264Heart rate and tissue oxygen

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Fig. 3a / Fig. 3b Heart rate & O2 saturated values as measured by pulse oxymetry and tissue oxygen values as measured by transcutenous monitor (TCM4)

 

Femoral vein velocity

Measured using ultrasound, venous blood velocity increased significantly (up to 3.5 fold) in the stimulated leg at all stimulations compared to baseline with all responses within normal physiological responses of dorsiflexion.

 

1266Femoral vein velocity

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Fig. 4 Venous blood velocity % change compared to baseline as measured by Ultrasound

 

Femoral vein volume flow

Using ultrasound and measured in the superficial femoral vein, venous blood volume flow increased significantly (up to 3 fold) in the stimulated leg at all stimulations compared to baseline and there was no significant change in mean vessel diameter throughout the study (data not shown).

 

1268Femoral vein volume flow

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Fig. 5 Venous blood volume flow % change compared to baseline as measured by Ultrasound

 

Comfort and tolerability

The device was well tolerated with verbal (VRS) rating scores at 'minimal sensation' for most settings (Fig.6 below).

 

1491Discomfort graph (large)

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Fig. 6 Tolerance scores as measured by discomfort questionnaires utilising VRS

 

Vascular ultrasound assessment

The Ultrasound example shows normal blood flow (74.3 cc/min) in the femoral vein at rest whilst breathing normally (A) and a 4 fold enhanced blood flow (328 cc/min) with the device applied (B). It also show the blood velocity increase from 13.6cm/s at rest (A) to 32.9 cm/s with the device active (B) (2.5 fold)

 

1361G-slide14-15_dia_L

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Fig. 7 Ultrasound comparison showing the superficial femoral vein at rest and with the device active at 1Hz.

 

Summary of results

  • PPG values (blood volume change) were equivalent to at least 50% of foot flexions** - evidence of dorsal foot vein emptying
  • Up to 25 fold increase in LDF (speed of blood flow) in stimulated leg compared to baseline*
  • Heart rate & Oxygen saturation are stable throughout the study duration
  • Skin temperature was preserved and tissue oxygen slightly increased in the stimulated leg compared to the unstimulated leg indicating increased blood flow even in the superficial layers of the skin
  • Blood volume flow and velocity increased up to 4 fold compared to baseline
  • The device has been well tolerated (rated as mainly minimal sensation = no pain)

 

 

* Blood flow and velocity at rest (unstimulated leg)

** 10 dorsiflexions (10 toe lifting movements)
- the maximum venous emptying that can be obtained by foot and calf pump activation