Automated Cardiopulmonary Resuscitation

Device Mita Bhowmick, Meryl Rodrigues, Rishabh Shetty, Ashish Vaswani

Department of Biomedical Engineering, Thadomal Shahani Engineering College, Bandra, Mumbai

mitabhowmick@gmail.com

merylrodrigues26@gmail.com

rishabh.shetty1@gmail.com

vaswaniashish@gmail.com

Abstract- In India, general awareness of

Cardiopulmonary Resuscitation (CPR) techniques

is limited to physicians and paramedics. There

exists a shocking lack of awareness about

resuscitation techniques in common public circles.

When administered precisely, CPR can save

thousands of lives each year that are lost due to

causes ranging from physiological shocks such as

asphyxiation due to drowning; to even sudden

myocardial infarction/ cardiac arrest (SCA).It is

proposed that designing a device which can

administer the technique with minimal human

intervention can help reduce failure rates

drastically. This is because manual CPR, when

performed even by qualified professionals does

have enough room for error. Automated CPR

aims to eliminate these errors, thereby reducing

failure rates. The objective is to make the

technique available in rural areas where there is

acute shortage of basic healthcare facilities. To

achieve this goal, it is intended to design an easy-

to-use device that can even be operated by a lay

man.

Keywords- Cardiopulmonary Resuscitation,

Automated CPR

I. INTRODUCTION

Manual CPR when performed even by qualified

professionals does have enough room for error.

Automated CPR aims to eliminate these errors,

thereby reducing failure rates. The objective is to

make the technique available in rural areas where

there is acute shortage of basic healthcare facilities.

To achieve this goal, it is intended to design an easy-

to-use device that can even be operated by a lay man.

When done manually, it is difficult to abide by WHO

standards since it is a life-saving technique and will

need to be carried out with the required specifications

for as long as needed. This is very difficult to achieve

manually. Hence, the objective is to study the

principle of administering cardiopulmonary

resuscitation manually, thereby extending the

technique mechanically by use of an automated

apparatus that uses inexpensive mechanisms to

achieve the same.

This involves calculating the displacement, force and

frequency of chest compressions prescribed as per

WHO standards. To identify target areas that such

equipment can cater to. For example, beaches,

swimming pools, aircraft, ambulances, etc. The final

objective of the project is to study the practical

viability of implementing microcontroller-based

timing devices to drive the mechanism for predefined

periods of time as required.

II. REVIEW OF LITERATURE

Before conceiving a new and efficient design, it was

important to review the existing products in the

market. Here is a comparison between the three

available products currently in use in the US market:

The Zoll Autopulse uses an inflatable belt that

autonomously surrounds the chest. This belt

compresses the entire thoracic area. Due to this, cases

of rib fracture have been reported in patients who

have been administered automated chest

compressions using this device.

Michigan Instruments’ Lifestat is a device that

administers localized compression only on the

desired region. However, the piston-like action of the

Lifestat is triggered using a pneumatic cylinder which

is heavy. Due to this, it scores low on the portability

count.

Another competing product is the Lucas, which is

similar in principle to the Lifestat. Oral resuscitation

is also taken care of in this model. The common

shortcoming associated with all the three devices is

their high cost. Average cost of existing models is

around Rs. 12 lakh.

III. SYSTEM DESIGN

The block diagram below illustrates the flow of the

project with the various Electronic and Mechanical

components used and their functional description

A. Power Supply

In the current prototype, an AC to DC alternator is

being used to get power from mains and drive the DC

motor. In the final product, a DC battery can be used.

This battery could be lithium ion or lead acid type,

depending on feasibility and cost considerations.

B. Electronic control

Currently, IC 555 is being used as a timer to adhere

to the compression criteria mentioned by the World

Health Organization. In the future, more specialized

microcontrollers and timing devices can be used to

replace it.

C. Mechanical elements

The base plate, disc, rod and the L-arm form the

basic building blocks of the device.

Before zeroing in on any one design for the project,

we analyzed various options before short listing one

that fulfilled all requirements satisfactorily, while

also being practically feasible.

DESIGN 1:

This design involves the use of a lower unit that is

slid under the patient. An upper unit is fit with a

toothed gear motor and two gear tracks- surrounding

the gear from above and below respectively. These

two tracks are secured to the lower unit with the help

of hooks. When the gear moves anticlockwise, the

tracks advance in opposite directions linearly.

Because of this, the upper unit compresses the

patient’s chest. When the motor rotates in the

clockwise direction, it returns to its original elevated

position. This process is repeated continually to

achieve sustained compressions. A major drawback

of this design is the point of application is not

localized to the heart. It is bulky and involves the

implementation of a gear that moves electronically in

one direction, as well as mechanically in the other.

This forced us to look for other designs to implement

our idea.

DESIGN 2:

Our second design consideration consisted of a motor

around whose axle, a high tension cord is wound.

This cord passes through a tensile spring and an

applicator cushion is attached at its end. A narrow

opening in the base on which the motor rests, restricts

the compression of the spring beyond a particular

limit. When the motor rotates in the anticlockwise

direction, the spring compresses by about 2 inches.

This raises the applicator cushion just above the

patient’s chest. When the motor is switched off, the

spring expands freely in the absence of a puling force

from the motor, which causes the applicator cushion

to compress the patient’s chest. Finding a suitable

spring that matches the requirements of stipulated

Young’s modulus and rigidity was a major hurdle in

this design and was more of a trial and error exercise

than a calculated inference. Wear and tear of the

spring could reduce the life of the spring and in

course of time, the response of the spring to the load

would considerably vary than what is expected.

DESIGN 3:

The third design involves the use of a cam which has

a groove of a suitable depth to facilitate a

displacement of 2 inches as previously mentioned. A

rod suspended vertically at the apex of the spring (or

any mechanically compressible element) would move

about its fulcrum to give us the required linear

motion. At the other end of the rod, the applicator

cushion would be attached. According to the position

of the fulcrum, the displacement could be magnified.

The number of grooves could be increased to provide

us with an increased number of compressions. Again,

the use of a spring poses a hurdle to the life span of

the apparatus

DESIGN 4:

A few design options using magnets surrounded by

intermittent magnetic fields that drive the

compression rod were also considered. One of the

ideas involved the use of two magnetic fields that are

two inches apart from each other. These two fields

are switched on alternately. When the upper field is

switched on, the rod is pulled up and when it is

switched off, the lower magnetic field pulls it down.

The upper magnetic field could be replaced by a

spring to pull the rod up. A motor rotating in the

anticlockwise direction could also be used for the

same.

Another design makes use of two ferromagnetic

elements, one forming the core of an induced

magnetic field formed by a conducting wire wound

around it. By using Faraday’s Law of

Electromagnetic Induction, an AC supply when

passed through the conducting wire would magnetize

the core and this would attract the other

ferromagnetic block whose other end would be

connected to the applicator cushion i.e. when the

field is produced the cushion is pulled up and when it

is switched off, the cushion compresses the chest.

A major disadvantage of this system is the fall of the

rod that is controlled only by the lower magnetic

field. To produce an effective weight 11 kg, a very

heavy rod would have to be used which could harm

the patient. Switching magnetic fields on and off is

easier said than done. The magnetic core takes a

considerable amount of time to get magnetized after

current is supplied to the coil. This design was

theoretically appealing but practically challenging.

DESIGN 5:

The final design that could be implemented is using

two rotating discs driven by two motors. These two

discs could either be cams or could 0have projections

on them. There would be a rod in between the two

discs which would have projections on it. The two

motors should move in opposite directions. The

distance between the projections/grooves should be

such that the required displacement is achieved.

When one motor propels the rod in the forward

direction, after the maximum displacement, the other

motor will pull it back to its original position. As a

result of this, by suspending this apparatus vertically,

using an element to prevent free fall of the rod, the

required compressions can be obtained.

The drawback of this design is that two motors are

used and that would increase expenses and

mechanical liability

FINAL DESIGN:

After analyzing the pros and cons of each of the

above ideas, we came across the works of an

American scientist, William Clark who has

developed various mechanical assemblies that

convert rotational motion to rectilinear motion. One

of these completely suited our needs of achieving

vertical displacement driven by a motor that is

controlled electronically.

A rod is provided with a projection at one end and a

restrictor block at the other. A disc is fit with two

diametrically opposite projections which drive the

vertical rod. An L-arm is placed on a pivot that

moves in tandem with the projections on the disc.

This motion can be better

explained with the diagram below:

RESULT:

Circular Disc- Since this was the most important

component of the device which would be driven by

the motor and would consequently drive the

applicator rod, we took extra care to provide it with

the right kind of support, without friction. For this,

we drilled a hole at the center of the disc, on the base

plate, welded a rod onto a small circular disc

(smaller than our circular disc) through a shaft on the

front side and the same way on the back side. This

meant that we had stability and at the same time,

freedom of movement for the disc.

Using nuts and bolts with washers we mounted our

main circular disc onto this assembly. We also made

two readymade Teflon projections on the disc for

contact with the L-arm and Applicator rod during the

actual working. The instruments used for this purpose

were the Welding Machine, Drilling Machine,

Tapping screws and the Lathe Machine.

The patient plate was again fabricated using an

aluminium plate which was sawed and filed to get

blunt edges and then it was bent at an angle of 16

degrees to accommodate the feet of the stand which

would be shifted into it while setting up the device

for use.

The Stand was made by using two hollow tubes

which were welded onto bases which resembled the

front ends of shoes. A handle was also welded at the

end of the tube for easy handling. Springs were used

to make easy adjustments when the base plate was

mounted onto the stands.

The Base plate with all its components safely

mounted on it was now ready to be mounted on the

stand to make the device fully functional. This was

achieved by screwing to it two wing-like projections

from either side. The unscrewed ends of these

projections were welded to hollow tubes which were

slightly larger in diameter than the tubes of the stand.

This meant that the tubes could easily slide and then

be tightened wherever necessary on the stand, which

lent the all-important feature of height adjustment

to our device. Again, free fall was prevented by the

springs on the stands.

By simply placing the base plate under the patient’s

chest, placing the base plate on the stands, locking in

the base of the stands on the under-side of the patient

plate and tightening the base plate to maintain its

position, the system would become one piece and

function as a single unit by providing the motor with

power supply.

Timing the compressions:

For the purpose of abiding by the standards set by the

WHO regarding the time for which the compressions

must be given and then paused while the paramedic

checks for the patient’s pulse, we used a simple IC

555 timer in the astable mode so that we could

control the On and Off times of the multivibrator.

The IC 555 is not capable of sourcing enough current

to drive the motor. We needed a current source in

order to drive the motor. This current source should

be able to take in logic command from the IC, then

boost current and drive the motor accordingly. We

had to select the IC for motor driving as per the

requirement of current of motor.

The L293D is a monolithic integrated high voltage,

high current four-channel driver designed to accept

standard DTL or TTL logic levels. It is designed to

drive inductive loads such as relay solenoids,

DC/stepper motors and switching power transistors.

The L293D’s ability to handle the load of my DC

motor makes it an ideal IC for driving our main

motor.

FUTURE SCOPE:

Using more versatile materials such as titanium, hard

PVC and other plastic in place of aluminium may be

beneficial to add rigidity and stability to the design.

Materials that can make the product light-weight

should be probed into.

Research could be initiated in this direction to look

for alternate materials that could be used to design

the skeleton of the device. With the help of

paramedical staff, an efficient mouth-to-mouth

resuscitator can be added as an accessory to make the

product a suitable replacement for manual CPR.

The stand can be calibrated so that it becomes easier

for the attendant paramedical staff to adjust the stand

to suit the patient’s physical characteristics.

Another area that can be worked on is the software

part, wherein, a microcontroller can be used to drive

the motor instead of the IC 555 which is being

employed currently. This would have the advantage

of making the system dynamic by interfacing the

microcontroller to an LCD interface and allowing the

paramedical staff to tweak the number of

compressions being given.

CONCLUSION: The objective of the project was

to achieve a product which would be economically

viable so that the general population could use it;

at the same time an important consideration to be

kept in mind was to achieve a displacement and

timing of compressions as close to WHO

standards as possible.

The approach selected to achieve automated chest

compressions was fabricated using aluminium,

stainless steel and inexpensive hardware. The project

was successfully implemented so that it could

circumvent the problems faced while administering

Manual CPR and also be easy to use with a minimal

amount of training. Any mechanical changes that

need to be made are easily achievable owing to the

fact that the mounting of all the components on the

base plate is done keeping that very idea in mind.

With access to better hardware and raw materials, a

marketable product can be designed in the future. The

mouth-to-mouth resuscitation part of CPR can be

looked into to make this design robust and worthy of

competing with the Michigan Instruments’ LifeStat.