Biomechanical System Prototype with Advanced Biofeedback for

Rehabilitation of Bedridden Patients

Frederico Santos

1 a

, Luis Roseiro

1 b

, C

andida Malc¸a

1,2 c

, Alexandra Andr

3 d

, Ruben Dur

aes

4 e

William Xavier

5 f

, Arm

enio Cruz

6 g

and Marco Silva

1 h

Polytechnic of Coimbra, ISEC, Rua Pedro Nunes, 3030 -199 Coimbra, Portugal

Centre for Rapid and Sustainable Product Development, IPL, Rua de Portugal, 2430-028 Marinha Grande, Portugal

Polytechnic of Coimbra, ESTeSC, Rua 5 de Outubro, 3045-043 Coimbra, Portugal

ORTHOS XXI, Rua Santa Leoc

adia 2735, 4809-012 Guimar

aes, Portugal

WISEWARE, Zona Industrial da Mota, Rua 12, Lote 51, Frac¸

ao E, 3830-527 Gafanha da Encarnac¸

ao, Portugal

Nursing School of Coimbra, Avenida Bissaya Barreto 143, 3004-011 Coimbra, Portugal

Keywords:

Prolonged Immobility Syndrome, Rehabilitation Therapy Equipment, Lower and Upper Limbs Rehabilitation,

Biomechanical System, Advanced Biofeedback.

Abstract:

Citizens with physical limitations, namely bedridden patients, are often unable to perform physical activity

alone, which can translate into long periods of immobilization, with serious consequences for their health.

This type of patient usually stays in bed for long periods, leading to getting several motor problems due to their

immobility. Thus, it is important to develop biomechanical systems that can be used in the implementation of

physical rehabilitation activities for this type of patient. This work presents a prototype, speciﬁcally developed

for bedridden patients, aiming to contribute to the prevention of complications associated with their immobility

for long periods of time. The developed equipment is based on a modular structure allowing a linear module

with active/passive operation and alternatively an active/passive rotary module, to perform different types of

physical movements on upper and lower limbs. This work describes the developed management and control

system with emphasis on the use of biofeedback sensors and real-time data analysis. The ﬁrst tests carried

out on the prototype clearly identiﬁed the beneﬁts of the system when used in physical-motor rehabilitation

procedures for long-term bedridden patients.

1 INTRODUCTION

The World Health Organization has set clear guide-

lines concerning sedentary behaviour, recommending

that all citizens must have regular physical activity.

However, in citizens with physical limitations, partic-

ularly in the case of bedridden patients, the capability

of performing a physical activity is limited, which can

translate into long periods of immobilization, with se-

https://orcid.org/0000-0002-4061-9786

https://orcid.org/0000-0001-6043-6007

https://orcid.org/0000-0003-0012-4380

https://orcid.org/0000-0002-9425-6482

https://orcid.org/0000-0002-4643-7035

https://orcid.org/0000-0002-0864-0809

https://orcid.org/0000-0003-3254-3176

https://orcid.org/0000-0003-3142-1679

rious consequences for their health. This type of pa-

tient usually stays in bed for long periods, leading to

getting several motor problems due to their immobil-

ity. Reductions in muscle mass, bone mineral density

and physical impairment are the ﬁrst evidence, asso-

ciated with others that can appear, like muscular at-

rophy, muscular weakness, respiratory complications,

blood circulation complications and bone demineral-

ization (Parry and Puthucheary, 2015), (Parola et al.,

2021) and (Campos et al., 2021).

The absence of muscular stimulation will affect

the skeletal system (Eimori et al., 2016) and early mo-

bilization is a key to increasing functional capacity

and muscle strength in this type of patient, leading

to signiﬁcant outcomes (Miranda Rocha et al., 2017)

and (Arias-Fern

andez et al., 2018). Thus, it is im-

portant to develop biomechanical systems that can be

198

Santos, F., Roseiro, L., Malça, C., André, A., Durães, R., Xavier, W., Cruz, A. and Silva, M.

Biomechanical System Prototype with Advanced Biofeedback for Rehabilitation of Bedridden Patients.

DOI: 10.5220/0011799500003414

In Proceedings of the 16th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2023) - Volume 1: BIODEVICES, pages 198-205

ISBN: 978-989-758-631-6; ISSN: 2184-4305

 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)

used in the implementation of physical rehabilitation

activities, speciﬁcally for this type of patient. To de-

velop and implement correctly this kind of device is

necessary to have a properly deﬁned physical rehabil-

itation program. Several programs have been deﬁned

by some authors, speciﬁcally for bedridden patients,

like the works of (Akar et al., 2017) and (Maimaiti

et al., 2019).

According to (Barandas et al., 2015) and (Condino

et al., 2019) the implementation of real-time biofeed-

back systems is important for the effectiveness of

rehabilitation plans, since there are a progressive

growth in people’s motivation and emotional involve-

ment. (Barandas et al., 2015) even mentions that one

of the reasons for the lack of adherence to the pre-

scribed exercise program is precisely the lack of mo-

tivation.

During rehabilitation exercises sessions, it is im-

portant to monitor the patient’s evolution and the pa-

tient’s physical state. To do it, is required to have

one or more equipment capable of monitoring the pa-

tient’s vital signs and the forces that the patient can

produce autonomously. The monitoring of vital signs

can be performed through common medical equip-

ment/devices. However, given the technological evo-

lution, there are already commercialized devices that

allow monitoring some of the most important vital

signs, in a practical and fast way. Moreover, the mea-

surement of forces produced by the patient during the

exercises, allows the clinics to better judge the patient

rehabilitation. In addition, measurement history al-

lows for better evaluation and ﬁne-tuning of rehabil-

itation exercises. Another important aspect of mea-

suring the forces applied/suffered by the patient is the

possibility of automatically adjust the exercises and

limiting the amplitude of movements to the patient’s

condition.

The work presented has its context in the project

ABLEFIT, which aims to contribute to the develop-

ment of methodologies and systems that ensure phys-

ical activity for this type of patient. This project

focuses on the development of physical rehabilita-

tion equipment for bedridden patients, that can con-

tribute to the prevention of complications associated

with their immobility for long periods. The developed

equipment involves a structural support and position-

ing unit, a set of actuators with biofeedback sensors,

and a control, monitoring and gamiﬁcation unit, with

user interface. In the following chapters, the design

and development of this mechatronic physical reha-

bilitation system and its user interface are addressed.

2 THE ABLEFIT PROJECT

The ABLEFIT project comprises the research and de-

velopment of an advanced physical rehabilitation sys-

tem for bedridden patients with prolonged immobil-

ity, capable of:

• Prevent complications associated with immobility

in bed;

• Increase the functional capacity of the muscu-

loskeletal, cardiac and respiratory systems;

• Promote the integration of physical exercise pro-

grams suited to the clinical condition of each pa-

tient;

• Improve the patient’s quality of life.

The equipment should have an advanced control

system to monitor several parameters related to both

the patient and the performed exercise, especially tak-

ing into account the speed and strength performed by

the patient, or imposed by the equipment. This will

allow to record and evaluate the patient’s progress

and performance. This registration, together with the

implementation of a future gamiﬁcation solution, are

two extremely important factors when it comes to pa-

tient motivation. Gamiﬁcation serves as a stimulus

for the user to practice certain exercises. The exis-

tence of a record that allows users to understand their

evolution throughout the rehabilitation period encour-

ages them not to give up on the process, which can

be an important factor in the efﬁciency/effectiveness

of the exercises. Real-time biofeedback systems are

extremely important for the effectiveness of rehabili-

tation plans, as there is a progressive increase in peo-

ple’s motivation and emotional involvement.

Regarding the physical-motor rehabilitation com-

ponent, the equipment must have the ability to per-

form a set of exercises that guarantee results for pa-

tients. The base system was thus deﬁned for mobi-

lization requirements with ﬂexion, extension, abduc-

tion and adduction of both upper and lower limbs.

2.1 The Prototype

Some of the most common exercise equipment fo-

cuses on one type of movement. This is the case

of stationary bicycles where circular movements are

performed or rowing simulation machines with linear

movements. The prototype concept brings together

both types of movement, and is based on two comple-

mentary modules:

• Linear module for the implementation of linear

movements with a curvilinear trajectory of the up-

per and lower limbs;

Biomechanical System Prototype with Advanced Biofeedback for Rehabilitation of Bedridden Patients

199

• Rotating module for the implementation of circu-

lar movements of the upper and lower limbs.

For the intended modularity, a support structure

was developed, with a ﬁtting system for replacing

the modules and vertical tuning, which allows adjust-

ment to the adequate and safe interface with the pa-

tient. The C-shaped system allows adjustment to the

bed where the patient is. Figure 1 shows a view of

the system and its interface that ﬁts to a hospital bed.

The support structure, in addition to guaranteeing the

stability of the modules/interfaces, allows adjustment

and ﬁtting in any bed where a patient lies.

Figure 1: ABLEFIT prototype 3D system visualization next

to an hospital bed.

Figure 2 presents a 3D representation of the sys-

tem with the integrated tablet for visualization / mon-

itorization and the rotary and linear modules, that are

interchangeable, according to the pretended exercises.

This 3D visualization allows an understanding of the

concept developed and presented in the prototype.

2.1.1 Linear Module

The linear module is based on a linear guide unit that

presents a maximum speed of 420 mm/s, a push force

of 400 N and a stroke of 800 mm, which guarantees

the required levels of force, speed and range of mo-

tion for usage in rehabilitation. This linear guide also

includes an absolute encoder enabling a precise and

safe positioning/motion even at startup. This type of

actuator allows its control both in terms of velocity

and position, guaranteeing the implementation of the

system both in an active system line and as a passive

system. The user interface handle is ﬁxed to the slid-

Figure 2: 3D system visualization of the prototype with the

interchangeable rotary and linear components.

ing base of the linear guide. This interface (Figure 3)

includes the motor carriage connection base, a per-

pendicular recessed load cell to the carriage for force

measurement, which allows quantifying the force ap-

plied in both directions of the linear movement, and

an ergonomic external structure for gripping the pa-

tient hand (handle). At the top of the load cell beam,

with a snap-on/disengage system, there is a clip-on

pedal ﬁtting system, which allows the coupling of a

safety hinged boot (walker), thus ensuring the use of

the linear system with the lower limbs, providing leg

support.

Figure 3: Linear module connection to an adapted hinged

walking boot.

BIODEVICES 2023 - 16th International Conference on Biomedical Electronics and Devices

200

2.1.2 Rotary Module

The rotary module involves the use of a DC motor

with reduction gearbox, ﬁxed to a mechanical frame

support connector component, which is attached to

the vertical adjustable, interchangeable end of the

structure. The rotary motor system also guarantees

the use of the system in both an active and passive sys-

tem line, providing enough force and speed. This en-

gine together with the selected gearbox allows a max-

imum speed of 223 rpm, and allows the execution of

a nominal torque of 297.1 Ncm.

The hand handler interface is shown in Figure 4,

and it allows rotation around the shaft. This grip can

be replaced by another one with a pedal strap, as de-

scribed for the linear system, where the boot and strap

are ﬁtted for use with the lower limbs.

Left Embedded

Load Cell

Rotary Motor

Hand Interface

Frame Support Connector

Right Cell Bluetooth

interface

Right Embedded

Load Cell

Left Cell Bluetooth

interface

Figure 4: Rotary module constitution.

2.2 Management and Control System

Figure 5 presents the complete system, that is com-

posed of:

• Sensors to provide the biofeedback, including

the measurement of the applied forces, velocity

and/or cadence and vital signals;

• Tablet/monitor to be used as interface with the

clinic for parameterization or to be used as gami-

ﬁcation visualizer, to encourage the patient;

• The actuators for the linear or rotary movements,

as previously described;

• Database to keep all the patients exercises plans

and relevant data information. The exercises data

include the measured forces, vital signals and du-

ration of exercise, allowing to create automatic re-

ports that can be locally or remotely accessed or

automatically sent to the clinics;

• Microcontroller that acts as the brain of the all the

system, interconnecting all the previous compo-

nents.

This section pretends to better describe each of the

enumerated components. The database is in develop-

ment and will be better explained in future works.

2.2.1 Sensors

To provide a complete biofeedback to the clinics and

to allow the system to better adjust to the limits of the

patient, multiple sensors are required.

The main quantity to measure on rehabilitation

movements is the applied force on the contact point

between the patient and the system. Also, the vital

signs should be evaluated previously, during and by

the end of the exercises.

Sensors on Linear Module

Since the linear module actuator already provides the

position information of the carriage allowing the cal-

culation of the velocity of the movement, the only ex-

tra required quantiﬁcation is the force applied by the

system to the patient (the system is forcing the move-

ment) or by the patient to the interface (system acts

as load). To measure this force, two distinct versions

were developed:

1. The ﬁrst experimental sensor setup designed for

this task consisted on a matrix of 4 load cells

(FX29 Compact Compression Load Cell, from TE

Connectivity), shown in Figure 6. The used cells

had a range of 250 N with an ampliﬁed output

that can be directly interfaced to the system mi-

crocontroller ADC. This handle conﬁguration ap-

proach enables to measure if the patient is twist-

ing the handle while pooling or pushing it. The

four cells setup could also be used to measure the

handgrip strength with a handle designed for this

effect. This prototype setup, in mechanical terms,

turned out to be complex to adjust and calibrate.

2. The second sensor setup uses only one ﬂexural

load cell, as shown in Figure 7. This sensor is

able to measure only the forces on the direction

of the movement of the linear system, allowing to

evaluate the direction of the applied force. The

used sensor was an AnyLoad load cell, model

108BA, with an analog mV output, that must be

connected to the main microcontroller through a

speciﬁc electronic load cell ampliﬁer module. The

main disadvantage of the usage of this cell is the

noise interference susceptibility, that could result

in erroneous measurements.

At the end, the chosen force measurement version

was the ﬂexural load cell, mainly because it allows a

simpler and more robust assembly and ﬁxation. Also,

with this load cell is easier to adapt the clip-on pedal

ﬁtting system to be used with the lower limbs (see

Figure 3).

Biomechanical System Prototype with Advanced Biofeedback for Rehabilitation of Bedridden Patients

201

Linear Motor

Power Driver

USER

Caregiver/User

Graphic Interface

Vital Signals

Motor

Power Driver

Linear Motor System

13 8

14 7

15 6

16 5

Microcontroller

System

Rotary Motor

System

Figure 5: ABLEFIT Functional Diagram.

Figure 6: Force feedback acquisition with 4 load cells.

Figure 7: Force feedback acquisition with a ﬂexural load

cell.

Sensors on Rotary Module

For rotary movements, its required to quantify the

forces applied on left and right hand/foot interfaces

and the cadence. The characteristic of the movement

on this module, requires the measuring device to be

cable free, i.e., it is impossible to have cables attach-

ing the measuring device to the main microcontroller.

This resulted on the development of a self-powered

device with Bluetooth wireless communication, that

is replicated in each side.

The measure of the force is carried throw an S-

type load cell that is attached to the lateral rotation

shaft, allowing the quantiﬁcation of the force exerted

by the arm or feet (see Figure 4. This load cell inter-

faces with a low-power microcontroller in a similar

way as described for the ﬂexural load cell applied to

the linear module.

For the cadence quantiﬁcation, an Inertial Mea-

surement Unit (IMU) can be used, tacking advance of

the embedded gyroscope.

Regarding this device is battery powered, special

attention was carried on power consumption. A low

consumption microcontroller from Nordic Semi-

conductor was chosen, providing a Bluetooth Low

Energy (BLE) interface for the communication with

the main microcontroller.

Sensors for Vital Signals

A survey of all vital signs that would be important

to measure during rehabilitation sessions was carried

out. The vital signs considered to be most relevant and

that can be evaluated using COTS wearable devices

are the following:

• Heart Rate;

• Blood Pressure;

• Peripheral Oxygen Saturation;

• Respiratory Frequency;

• Body Temperature.

BIODEVICES 2023 - 16th International Conference on Biomedical Electronics and Devices

202

A preliminary analysis of available devices, with

open SDK and Bluetooth interface, was already car-

ried and will be integrated in the nearby future.

2.2.2 Actuators

As mentioned before, the described system allows the

patient to make exercises using a linear module for

curvilinear movements and a rotary module for circu-

lar movements, both providing the coupling of upper

or lower limbs. These actuators are exchangeable and

only one is connected at a time.

The chosen linear guide was the EZS6-D080-

AZAKD from OrientalMotor company. This actuator

have a speciﬁc controller unit that can be interfaced

with the main microcontroller using ModBus RTU

Protocol. This actuator controller enables to set the

maximum acting force when used in active/passive

modes.

For the rotary movement, a permanent magnet DC

motor with reduction gearbox from Dunkermotoren

company was chosen. The speed and force control for

this motor is carried through a common motor power

driver interfaced with the main microcontroller.

The supply voltage for both actuators is 24V, hell

suited to be directly supplied by a regulated battery

module, allowing safe standalone off-grid operation.

2.2.3 Tablet/Monitor

Fixed to the main structure of the prototype (see Fig-

ure 2) is an Android based tablet used for interaction

with both the patient and the clinic professionals.

For the clinic, the tablet is used to conﬁgure all

the system so that it respects the physical limits of

the patient. The developed application has access to

the patient personal data and the respective list of pre-

scribed exercises. It also allows to access the history

of exercises which includes the data from biofeedback

sensors. This feature permits to obtain an historical

assessment of the patient condition over time.

Figure 8 shows a work in progress application.

Left picture is a screen capture of the parameteriza-

tion of the exercise. The right picture shows and real-

time graph of the measured force.

Another usage of the tablet is the gamiﬁcation and

encouragement of the patient. This feature is under

development at the moment, and the idea is to encour-

age and motivate the patient to realize the exercise.

For example, if the exercise is a rotational movement

with lower limbs, similar to cycling, then the tablet

could show a road with moving scenario to give the

idea of movement. Additionally, to motivate the pa-

tient to apply more force, some virtual cyclists could

Figure 8: ABLEFIT Android APP.

be added, running at the similar speed, so that the pa-

tient try to overtaken them.

2.2.4 Main Microcontroller

The main element of the electronic control system is

the microcontroller, that receives the set-point deﬁni-

tions for the exercise, the information from the all the

sensors, and controls the actuation of the connected

module, either the linear or the rotary actuators.

The microcontroller chosen was an ESP32 that al-

ready integrates a BLE and Wi-Fi interfaces, provid-

ing all the required wired and wireless communica-

tion with the previously present components.

The retrieved information from the attached actua-

tor, is forwarded to the tablet and also internally used

in a classic closed loop fashion control, taking care

that the patient never exceed it’s own physical limita-

tion, as initially conﬁgured by the clinic professional,

for the sake of security.

3 EXPERIMENTAL TESTS

The prototype ﬁrst tests were implemented to identify

possible exercises functionalities, having been carried

out under supervision of health professionals.

Figure 9 shows examples of performing exercises

with the rotary module and Figure 10 shows examples

of performing exercises with the linear module.

The preliminary tests showed that extension and

ﬂexion movements were full performed in active and

passive modes. This special feature allows the proto-

type to be used for rehabilitation of patients that can

Biomechanical System Prototype with Advanced Biofeedback for Rehabilitation of Bedridden Patients

203

Figure 9: Examples of experimental tests with the rotary

module.

produce movement, and also the rehabilitation of pa-

tients that have loosed all the muscular activity.

4 CONCLUSIONS

This work present the design of a biomechanical pro-

totype equipment for the accomplishment of physical

rehabilitation exercise by bedridden patients. The de-

veloped system allows the realization of a speciﬁc set

of exercises, considered relevant for this type of pa-

tient. The system incorporates a linear module and a

rotation module, that are interchangeable. Both mod-

ules can be used in active or passive modes, fully con-

ﬁgurable and customized, safeguarding the physical

limitations of the patient.

The developed management and control system

is able to collect information from biofeedback sen-

sors and correctly control the actuators movement ac-

cording to the prescribed exercise. An Android based

tablet is used to motivate the patient through gamiﬁ-

cation, and is also used by the clinic to conﬁgure the

exercises, to visualize real-time data or to access his-

torical patient information.

Preliminary tests performed by health profession-

als showed the mechatronics prototype robustness,

evidencing an excellent adjustment and positioning

Figure 10: Examples of experimental tests with the linear

module.

capability, fulﬁlling the function of interfacing with

the patient in hospital beds, enhancing the realization

of upper and lower limb exercises.

BIODEVICES 2023 - 16th International Conference on Biomedical Electronics and Devices

204

ACKNOWLEDGEMENTS

This research was co-ﬁnanced by the European Re-

gional Development Fund (ERDF) through the part-

nership agreement Portugal 2020 - Operational Pro-

gramme for Competitiveness and Internationalization

(COMPETE2020) under the project POCI-01-0247-

FEDER-047087 ABLE-FIT: Desenvolvimento de um

Sistema avanc¸ado para Reabilitac¸

ao.

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