Device for increasing microcirculation

Abstract

A method and device for increasing microcirculation in the lower limb are described. The device includes a means for immobilizing the limb, for example a plaster cast, and an electrical stimulation device, which applies electrical stimulation to opposed leg muscles such that antagonistic and agonistic muscle groups contract near simultaneously, resulting in near isometric contraction. The combination of this contraction and the leg restraint have been found to markedly increase blood circulation and in particular microcirculation in the limb.

Claims

1. A kit for improving blood circulation in a lower limb of a patient, the kit comprising: a stimulation device comprising at least one electrode for administering an electrical stimulus to opposed leg muscles of a patient; a power supply connectable to the electrode; and a controller for activating the electrode to administer an electrical stimulus to the muscles sufficient to cause the muscles to contract isometrically; and a below knee immobilisation device configured to eliminate motion in an ankle of a patient; wherein the immobilisation device and the stimulation device are provided as separate devices such that the immobilisation device and the stimulation device are configured to couple to the patient independently of each other, and wherein the stimulation device is configured to position the at least one electrode at the popliteal fossa of the patient.

2. The kit of claim 1 wherein the stimulation device includes the electrode, controller, and power supply mounted on a flexible substrate.

3. The kit of claim 1, wherein the immobilisation device comprises an orthopedic cast, a brace, or a boot.

4. A device for improving blood circulation in a lower limb of a patient, the device comprising: a stimulation device comprising at least one electrode for administering an electrical stimulus to opposed leg muscles of a patient, a power supply connectable to the electrode, and a control means for activating the electrode to administer an electrical stimulus to the muscles sufficient to cause the muscles to contract isometrically, wherein the stimulation device is configured to position the at least one electrode at the popliteal fossa of the patient; and means for eliminating motion in an ankle of a patient; wherein said means for eliminating motion and said stimulation device are provided as separate devices such that the means for eliminating motion and the stimulation device are configured to couple to the patient independently of each other.

5. A method for improving blood circulation in a lower limb of a patient, the method comprising: applying an immobilisation device to an ankle of the patient; eliminating motion in the ankle of the patient using the immobilisation device; attaching a stimulation device to a lower limb of the patient independent of the immobilisation device, wherein said stimulation device and said immobilisation device are provided as separate devices; and providing an electrical stimulus from the stimulation device to opposed leg muscles at the lateral popliteal nerve of the patient sufficient to cause the muscles to contract isometrically.

6. The device of claim 4, wherein the stimulation device includes an electrode, a controller, and a power supply mounted on a flexible substrate.

7. The device of claim 4, wherein the means for eliminating motion comprises an orthopedic cast, a brace, or a boot.

8. The method of claim 5, wherein the stimulation device includes an electrode, a controller, and a power supply mounted on a flexible substrate.

9. The method of claim 5, wherein the immobilisation device comprises an orthopedic cast, or a brace, or a boot.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 depicts an electrical stimulation device;

(2) FIG. 2 depicts a human knee;

(3) FIG. 3 depicts an electrical stimulation device and an immobilisation device;

(4) FIG. 4 is a graph showing measure results for mean peak venous velocity in patients' legs when immobilised by a plaster cast, with the patients in different positions, using the electrical stimulation device in an active state or inactive state;

(5) FIG. 5 is a graph showing measured mean peak venous velocity in patients' legs when immobilised by a plaster cast, with the patients in all positions, using the electrical stimulation device in an active state or inactive state; and

(6) FIG. 6 is a graph showing measured mean microcirculatory velocity in the feet of patients, using the electrical stimulation device in an active state or inactive state, in different positions and under different experimental conditions.

DETAILED DESCRIPTION OF THE INVENTION

(7) Deep vein thrombosis, or DVT, refers to formation of a blood clot within the deep veins. DVT commonly affects the leg veins (femoral, popliteal) or deep veins of pelvis. The majority of thrombi originate in the soleal veins and venous valve pockets.

(8) Risk factors of DVT include the following: Age>40 years; Cancer (7 increased risk); Trauma; Previous DVT or PE; Recent surgeryespecially surgery of lower limb particularly hip or knee (40-84% risk); Obesity; Varicose veins; Oestrogen therapy (women); Immobility; Long Haul FlightsEconomy class Syndrome.

(9) The application of a plaster cast to limb fractures can increase DVT risk as a combination of factors. Trauma to lower limb; surgery of lower limb; and prolonged immobility, can all combine to increase the risk of DVT. There is a lack of evidence of the real risk, but it is estimated to be 20%. DVT can often be asymptomatic, and there is a high risk of developing PE following DVT in plaster cast. The UK's National Institute for Clinical Excellence (NICE) offers the guideline that a high level of clinical vigilance and an effective thromboprophylaxis should be considered even in simple cast treatment. DVT incidence rates are especially high in surgical patients.

(10) Current prophylaxis can be pharmacological or physical. Both of these have disadvantages. Pharmacological prophylaxis can be used in plaster casts, but the disadvantages include active bleeding; allergic reactions; risk of VTE persists for weeks or months after hospital discharge; drug interactions with several substances e.g. antibiotics, foods; and clinical supervision requires money and inconvenience. Current mechanical treatments (for example, intermittent pneumatic compression or graduated compression stockings) cannot be used in plaster casts, and where the treatment is possible, there are numerous disadvantages, including skin damage/pain/ulceration; uncomfortable to wear; the size may be impractical; weight; external power source necessity; poor compliance.

(11) Direct electrical stimulation of lower limb muscles has been shown to be effective in significantly improving blood flow. With this in mind, we investigated whether electrical stimulation in combination with a plaster cast would be effective in reducing the risk of DVT.

(12) An illustration of a geko devise is shown in FIG. 1. Use was made of an electrical stimulation device referred to as the geko device. This consists of a pair of electrodes 2 mounted on an elongate flexible strip 1, together with a power source 4 and a control device for actuating the electrodes 2. The device is a disposable neuromuscular stimulation device, which is applied externally to the lateral aspect of the knee in to the popliteal fossa. Prior to its application, the attachment area of the knee was exfoliated and wiped with the electrode preparation wipe. After 30 seconds, the device was secured slightly above the crease in the popliteal fossa. This enabled the device to stimulate the common peroneal nerve (also referred to as the lateral popliteal nerve) resulting in isometric contraction of lower limb musculature, as the nerve innervates both antagonistic and agonistic muscle groups.

(13) Objectives

(14) Primary objective: Examine the flow characteristics of deep venous flow in the leg veins using Doppler ultrasound imaging and how this flow is modified by the application of a plaster and with a geko device in healthy volunteers.

(15) Secondary Objective: Evaluate microcirculatory blood flow changes, using Laser Doppler fluxmetry associated with cast-immobilisation and with the use of geko device.

(16) Study Population: Healthy male and female Volunteers, aged 18-65 years. Sample Size: 10 volunteers.

(17) Exclusion criteria: previous leg fracture (within last 12 months); previous venous thrombosis; family history of venous thrombosis; history of musculoskeletal disorders e.g. osteoarthritis, rheumatoid arthritis; history of neurological disorders e.g. stroke, multiple sclerosis; Chronic obesity (BMI>34); Pregnancy.

(18) Application: Common Peroneal Nerve

(19) Superficial electrical stimulation (1 Hz) applied to the common peroneal nerve located in the popliteal fossa. The appropriate location is shown in FIGS. 2 and 3.

(20) Physiology: electrical stimulation proximal to bifurcation causes near-isometric compression of lower limb musculature, which activates venous muscle pump, leading to increased venous return, resulting in reduced stasis, which leads to a reduced risk of DVT.

(21) Outcome 1: Femoral Vein Ultrasound

(22) This was measured in four different leg positions: Supine; Leg Elevated at 20; Standing (weight bearing); and Standing (non-weight-bearing). Each of these was used with two variables: plaster cast or no plaster cast; and geko active or geko inactive.

(23) This gives 16 positions in total; with n=9 (data from one volunteer was excluded due to failure of ultrasound recordings). The positions are listed in Table 1 below:

(24) TABLE-US-00001 TABLE 1 POSITION NUMBER SETTING 1 NO PLASTER CAST/GEKO OFF/SUPINE 2 NO PLASTER CAST/GEKO OFF/LEG ELEVATED 3 NO PLASTER CAST/GEKO OFF/STANDING- WEIGHT BEARING 4 NO PLASTER CAST/GEKO OFF/STANDING- NONWEIGHT BEARING 5 NO PLASTER CAST/GEKO ON/SUPINE 6 NO PLASTER CAST/GEKO ON/LEG ELEVATED 7 NO PLASTER CAST/GEKO ON/STANDING-WEIGHT BEARING 8 NO PLASTER CAST/GEKO ON/STANDING- NONWEIGHT BEARING 9 PLASTER CAST/GEKO OFF/SUPINE 10 PLASTER CAST/GEKO OFF/LEG ELEVATED 11 PLASTER CAST/GEKO OFF/STANDING-WEIGHT BEARING 12 PLASTER CAST/GEKO OFF/STANDING-NONWEIGHT BEARING 13 PLASTER CAST/GEKO ON/SUPINE 14 PLASTER CAST/GEKO ON/LEG ELEVATED 15 PLASTER CAST/GEKO ON/STANDING-WEIGHT BEARING 16 PLASTER CAST/GEKO ON/STANDING-NONWEIGHT BEARING

(25) Measurements were taken after each volunteer spent 10 minutes in each position to allow for the blood flow changes and equilibrum. These measurements were taken with the geko device inactive and was then repeated after the geko had been active for 10 minutes.

(26) The device was set to visible twitch of the lower limb musculature as detailed in the Manufacturer's instructions for use. The setting for individual was noted and same level of electrical stimulation was applied to the volunteer throughout the study in order to avoid irregularities in the result.

(27) Following baseline measurements, a below knee orthopaedic cast was applied to immobilise one leg of the volunteer. The fibreglass-based material was used due to its ability to mould and dry quickly. On application of the cast, volunteer lay supine for 30 minutes to allow the cast to set and temperature beneath the cast to adjust, in order to avoid bias caused by initial OC induced-heat. The application and removal of the plaster cast followed routine clinical practice.

(28) Once an OC was applied, measurements were taken in above four positions with the geko device inactive. The measurements were then repeated after the geko had been active for 5 minutes.

(29) At the end of the assessment the OC was removed. Volunteer's leg was clinically assessed prior to discharge from the study.

(30) PEAK VENOUS VELOCITY (cm/s) has been demonstrated to have a proportional relationship with VENOUS RETURN, which is a measurement for reduced STASIS and a reduced DVT risk.

(31) The measured results for patients with a plaster cast are shown in FIG. 4.

(32) The results for the four leg positions are as follows.

(33) Supine:

(34) Mean PVV=15.5 cm/s (sd=2.9)

(35) Mean PVV=25.4 cm/s (sd=9.2)

(36) 1.8-fold increase in PVV when GEKO activated in supine position

(37) Independent sample t-test: statistically significant (P<0.05)

(38) Leg Elevated At 20:

(39) Mean PVV=19.5 cm/s (sd=6.2)

(40) Mean PVV=24.6 cm/s (sd=8.4)

(41) 0.8-fold increase in PVV when GEKO activated in supine position

(42) Independent sample t-test: statistically not significant (P>0.05)

(43) Standing (Weight Bearing):

(44) Mean PVV=9.9 cm/s (sd=4.9)

(45) Mean PVV=22.3 cm/s (sd=8.4)

(46) 2.2-fold increase in PVV when GEKO activated in standing (weight bearing) position

(47) Independent sample t-test: statistically significant (P<0.05)

(48) Standing (Non-Weight Bearing):

(49) Mean PVV=10.7 cm/s (sd=3.1)

(50) Mean PVV=29.3 cm/s (sd=8.5)

(51) 2.7-fold increase in PVV when GEKO activated in standing (weight bearing) position

(52) Independent sample t-test: statistically significant (P<0.05)

(53) FIG. 5 shows the combined results from all leg positions with a plaster cast.

(54) Mean PVV in Plaster Cast when GEKO is inactive=14.2 cm/s (sd=5.4)

(55) Mean PVV in Plaster Cast GEKO active=25.4 cm/s (sd=9.2)

(56) 1.8-fold increase in PVV in Plaster Cast across all 4 positions with GEKO active

(57) Independent sample t-test: statistically significant (P<0.05).

(58) Thus, use of the geko device in combination with a plaster cast causes a statistically significant increase in peak venous velocity.

(59) Outcome 2: Laser Doppler Fluxmetry

(60) 2 probes connect to the dorsal surface of the foot. n=10.

(61) FIG. 6 shows the mean microcirculatory velocity in the foot in all sixteen postural positions and experimental conditions.

(62) The figure shows that Mean Microcirculatory Velocity in all four positions without the application of geko in a plaster cast=21.7 Arbitary Units (AU). Whereas Mean Microcirculatory Velocity in all four positions with the application of geko in a plaster cast=67.5 AU.

(63) There is therefore a 3-fold increase in Mean Microcirculatory Velocity when geko activated in a plaster cast. ANOVA, Post-hoc test (Bonferroni): statistically significant (p<0.05)

CONCLUSION

(64) Primary Outcome: venous blood flow assessment: electrical stimulation to achieve isometric muscle contraction is effective in enhancing blood flow in the plaster cast, to a statistically significant degree (p<0.05). A potential clinical application may be mechanical DVT prophylaxis.

(65) Secondary Outcome: microcirculatory blood flow assessment: electrical stimulation to achieve isometric muscle contraction is effective in enhancing microcirculatory blood flow to the skin in the plaster cast, to a statistically significant degree (p<0.05). Potential clinical applications include wound care healing (increased microcirculatory blood flow will reduce inflammation, promote phagocytosis and fibroblast stimulation); ulcer management; and sports injuries.

(66) Stimulation of the common peroneal nerve proximal to bifurcation causes near-isometric compression of the lower limb musculature including peroneus longus muscle, a powerful foot everter. A cast confines the limb causing restricted foot eversion. As geko is activated in an immobilised limb, stimulation of the peroneus longus mucle combined with restricted eversion causes the plantar plexus to compress against the sole of the cast, emptying the venous plexus at a greater velocity. As increased lower limb PVV has been linked to improved venous return and reduce venous stasis, the risk of DVT reduces likewise.

(67) In a cast, electrical stimulation of the lower limb caused the mean vessel diameter to increase (greater venodilation due to enhanced pressure caused by increased PVV). Electrical stimulation of the limb without the cast although, causes increased venous return (as indicated by the increased PVV) but the mean vessel diameter reduces. However, this relationship between mean PVV and mean vessel diameter is reversed when geko is activated without the OC application. This indicates stimulation of geko in an OC maybe causing more efficient emptying of venous plexus due to compression generated by the OC itself.