US-12616381-B2 - System for management and prevention of venous pooling

US12616381B2US 12616381 B2US12616381 B2US 12616381B2US-12616381-B2

Abstract

A monitoring system comprises sensors adapted to be worn by a user, and, a processor linked with the sensor. The processor receives sensor data and processes this data to determine user posture data including data indicative of vertical distance between level of the user's heart and ankle. Based on the posture data together with a value for degree of user chronic venous insufficiency and/or blood density, generate an estimate of user static venous pressure while the user is static, without calf muscle pump activity. The processor also processes the sensor data to determine if there is calf muscle pump activity, and generates an estimate of user active venous pressure according to the static venous pressure estimate, rate of calf muscle activity, and a value for degree of user chronic venous insufficiency. The processor may generate the venous pressure estimate in real time, and may control an NMES device accordingly.

Inventors

Gavin Corley
Gearóid Ó'Laighin
Paul Breen
Barry Broderick
Pierce A. Grace
Derek O'Keeffe

Assignees

NATIONAL UNIVERSITY OF IRELAND, GALWAY
UNIVERSITY OF LIMERICK

Dates

Publication Date: 20260505
Application Date: 20240305
Priority Date: 20111111

Claims (20)

1 . A monitoring system comprising: a plurality of sensors adapted to be worn by a user; a processor linked with the plurality of sensors, wherein the processor is adapted to receive sensor data and process said data to: determine user posture data including data indicative of vertical distance between level of the user's heart and ankle; determine user step count to estimate user calf muscle activity and to determine whether the user is static or active; determine a user state, wherein the possible user states comprise: a user static state, a user active state, a pressure-increasing state, and a pressure-decreasing state; and estimate real-time venous pressure based on the user state, the estimated calf muscle activity, user posture, and a predetermined value of chronic venous insufficiency; and a neuromuscular electrical stimulation device, wherein the neuromuscular electrical stimulation device is configured to be activated by the processor according to estimated real-time venous pressure.
2 . A monitoring system as claimed in claim 1 , wherein the processor is adapted to estimate the rate of calf muscle activity from rapid changes in acceleration caused by impact forces during impact of the user's heel during calf muscle activity.
3 . A monitoring system as claimed in claim 1 , wherein the sensors are adapted to measure the tilt of the user's trunk, thigh, and shank.
4 . The monitoring system of claim 1 , wherein the processor is configured to receive specific values for the length of the user's trunk, thigh and shank.
5 . The monitoring system of claim 1 , wherein the processor is configured to receive the predetermined value of chronic venous insufficiency based on measurements by a clinician.
6 . A monitoring system as claimed in claim 1 , wherein the possible user states further comprise a state for checking for user activity.
7 . A monitoring system as claimed in claim 6 , wherein the processor is adapted to execute a state machine algorithm in which: if the state machine is in the user static state and an activity interrupt indicating a stepping motion is detected, the processor moves the user static state to a user activity check state, if the state machine is in the user static state, and no activity interrupt or no-change in vertical height is detected, the user static state remains and the processor updates the time associated with the current posture, if the state machine is in the user static state, and there is no activity interrupt but a decrease in vertical height is detected, the processor moves from the user static state to a pressure-decreasing state, and if the state machine is in the user static state and there is no activity interrupt but an increase in vertical height is detected, the processor moves from the user static state to a pressure-increasing state.
8 . A monitoring system as claimed in claim 1 , wherein the processor is adapted to control the NMES device in order to minimize venous pooling.
9 . A monitoring system as claimed in claim 8 , wherein the processor is adapted to determine or select NMES device parameters according to at least one of: the venous pressure estimate, a venous pressure-time integral, physical activity levels, leg elevation levels, and NMES device usage statistics.
10 . A monitoring system as claimed in claim 1 , wherein the processor is adapted to generate or select NMES device stimulation parameters including at least one of: stimulation amplitude; pulse width; frequency; stimulation envelope ramp-up, ramp-down, on and off times; number of channels and stimulation schedule.
11 . A monitoring system as claimed in claim 1 , wherein the NMES device is arranged to stimulate both the posterior and anterior muscle groups of the lower leg.
12 . A monitoring system as claimed in claim 1 , wherein the NMES device is arranged to apply stimulation to the peroneal nerve.
13 . A monitoring system as claimed in claim 1 , wherein the NMES device includes an output stage having a 3-way H-bridge circuit.
14 . A monitoring system as claimed in claim 1 , wherein the processor is configured to estimate real-time venous pressure using the equation: Pressue=ρgh, wherein ρ is blood density, g is acceleration due to gravity, and h is the height between the ankle and the heart of the user.
15 . A monitoring system as claimed in claim 1 , wherein the plurality of sensors comprise one or more selected from accelerometers, ultrasound range detectors, piezoelectric sensors, gyroscopes, flex sensors, magnetometers, foot switches, smart textiles incorporating electrical sensing elements.
16 . A monitoring system as claimed in claim 1 , wherein the plurality of sensors comprise one or more selected from a hip-worn sensor to detect step counts and postural transitions, a thigh-worn sensor to detect walking, lying, sitting and/or standing events, and a sensor arranged to be worn on the lower leg to measure step counts, distinguish between standing, sitting, and lying and to measure lower leg elevation.
17 . A monitoring system as claimed in claim 1 , wherein usage data from the neuromuscular electrical stimulation device and data from the sensors is recorded in a memory.
18 . A monitoring system as claimed in claim 17 , wherein the data recorded in the memory comprises at least one of: date and time of day applied stimulus, intensity of the stimulus, duration of stimulation, duration and time of user activity, posture, lower leg elevations, and estimate venous pressure-time integrals.
19 . A method for assessing the effectiveness of the monitoring system of claim 17 , comprising: downloading data stored in the memory; and using the data to assess: the effectiveness of the stimulation, the user's compliance to the stimulation, and/or to monitor patterns of the user's activity.
20 . A computer readable medium comprising software code adapted to be executed by a digital processor to perform the steps of a processor of a system of claim 1 , including the steps of: receiving sensor data and processing said sensor data to determine user posture data including data indicative of vertical distance between level of the user's heart and ankle; and based on said posture data together with a value for degree of user chronic venous insufficiency and/or blood density, generating an estimate of real time user venous pressure.

Description

INTRODUCTION Field of the Invention The invention relates to artificial stimulation of flow from the leg and foot and specifically to its application for the prevention and treatment of chronic venous insufficiency (“CVI”). Prior Art Discussion In the healthy lower leg, blood flow in the veins must typically work against gravity to return to the heart. This unidirectional flow is facilitated by the presence of two mechanisms: venous valves and the calf muscle pump. Venous valves are located throughout the veins and maintain unidirectional flow towards the heart. During contraction, the calf muscles eject blood through the veins and back towards the heart. Both correctly functioning valves and healthy calf muscle pump function are essential for maintaining healthy venous flow and avoiding venous pooling. Pooling of venous blood in the lower leg is a major contributory factor in the development of chronic venous insufficiency (CVI) which can result from breakdown of the venous valves and/or poor calf muscle pump function. It leads to blood pooling in the veins resulting in increased venous pressure. These pressures are highest during standing and lowest when lying due to the effect of gravity. This increased pressure results in: pain, swelling, oedema, skin changes, varicose veins, deep vein thrombosis and venous leg ulcers. Venous leg ulcers are the most severe and costly manifestation of CVI and are an enormous problem for both patients and healthcare providers. Circumstances that predispose a person to prolonged venous pooling and the resultant conditions of CVI are: Occupational—work posture that requires long periods of sitting or standing (shopkeepers, barmen, hairdressers, pilots, computer programmer).Patients—during surgery, during recovery, patients with leg casts.Older persons—inactivity, chronic disease and chronic vascular disorders.Muscle paralysis—wheelchair bound patients, stroke patients, multiple sclerosis. Currently, a common treatment for varicose veins and venous leg ulcers is graduated compression therapy. Compression stockings are the most common form of compression therapy and are typically prescribed for the prevention of varicose veins and deep vein thrombosis (“DVT”) and for the prevention of the recurrence of venous ulcers. Graduated compression stockings have been shown to reduce the incidence of DVT and are believed to alleviate some of the symptoms of varicose veins. However, compression hosiery is limited by poor compliance and has not been demonstrated to slow the progression of varicose veins. Graduated compression bandaging is typically used for the most severe symptoms of CVI such as oedema and venous leg ulceration. Graduated compression bandaging consists of several layers of tightly wrapped bandages which exert an inward force on the leg, helping to close venous valves and to counteract the harmful venous pressures in the leg. Despite being the current gold standard treatment for venous leg ulcer care, this treatment modality doesn't allow the clinician to fully address the underlying cause of venous leg ulcers-blood pooling. Individuals who are predisposed to prolonged venous pooling and CVI currently have very limited options to prevent the progression of symptoms of CVI. Furthermore, clinicians treating this condition are not able to closely monitor the status of venous pooling in these patients and the treatment regimen is based on changes in the severity of the symptoms of this pooling-swelling and ulceration. Consequently it is desirable to monitor and report the status of venous pooling in these patients and apply an intervention for reducing this pooling where possible so that the worsening of symptoms of CVI such as varicose veins and venous leg ulcers may be prevented. NMES Blood Flow Stimulation: If prolonged venous pooling is detected it would be desirable to intervene to reduce the pooling. The lower leg muscles act as a natural muscle pump which helps to eject venous blood from the lower leg. Voluntary activity such as walking naturally activates and conditions this muscle pump. However, CVI patients are typically unable to maintain healthy muscle pump function, due to a sedentary lifestyle and exercise is often painful. Therefore an alternative means for activating this muscle pump or rehabilitating it is desirable in these patients. Neuromuscular electrical stimulation (NMES) is the application of electrical stimuli to a muscle or nerve resulting in a stimulated muscle contraction. Application of NMES to the lower leg muscles has been shown to result in artificial activation of the calf muscle and has been shown to promote venous outflow from the leg and promote muscle strengthening. NMES can be applied via surface electrodes placed over a nerve or muscle on the user's leg (surface NMES) or using implanted micro-stimulators within the patient's leg (implanted NMES). Surface NMES devices exist today for the treatment of a range of conditions. Several invest