lungs compliance meter

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Lungs Compliance Meter A simple automated device to demonstrate the measure of volume/pressure change in lungs using compliance curve.

Submitted in Undergraduate Research and Initiative Program (UGRI) 2016

by

Vishal Aditya

Under the Guidance of

Dr. Chiranjoy Chattopadhyay

INDIAN INSTITUTE OF TECHNOLOGY JODHPUR

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Declaration

I do hereby declare that my project is an authentic work developed by me under the

guidance of Dr. Sabyasachi Sircar. Department of Physiology, All India Institute

of Medical Sciences, Jodhpur, India and Dr. Chiranjoy Chattopadhyay.

Department of Computer Science and Engineering, Indian Institute of

Technology Jodhpur during summer internship for the degree of B. Tech-CS&E

after 6th SEM at Amity School of Engineering and Technology, Amity University

Rajasthan, Jaipur.

I also declare that any or all contents incorporated in this report have not been

submitted in any form for the award of degree or diploma of any other institution or

university.

(Signature)

Vishal Aditya

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Acknowledgments

First of all, I would like to sincerely thank my supervisor, Dr. Chiranjoy

Chattopadhyay for his persistent support, guidance, help and encouragement

during the whole process of my internship and preparation for my project “Lungs

Compliance Meter”. I would also like to thank my faculty and all the members of

IIT Jodhpur for their support. “Lungs Compliance Meter” is a simple automated

device to demonstrate the measure of volume/pressure change in lungs using

compliance curve.

Date: Vishal Aditya

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ABSTRACT

Lungs Compliance Meter is a simple automated device to demonstrate the measure of

volume/pressure change in lungs using compliance curve. It is working model for teaching

Dynamic Airway Compression. The concept of lung compliance is generally considered to be

difficult by students and therefore, over the years, medical educators have attempted to explain it

in novel ways. However, all the methods published till now pertain to “static lung compliance”.

We have constructed a simple device for demonstrating “dynamic lung compliance” and

generating the flow-volume loop on any screen. The device comprises a 1500 mL plastic bottle

filled with water and fitted with a balloon with a long neck, an ultrasonic sensor, and a syringe for

sucking water, so that it can create negative pressure inside and air through tube inflates the

balloon. Ultrasonic Sensor fitted in the cap of bottle measures the water level, further volume &

pressure is calculated to plot the graph. Digitized data from the pressure and volume gauges are

fed to the screen, enabling students to observe and record how dynamic compliance varies with

the rate of increase in pressure inside the bottle. The recorded data enabled students in

understanding the mechanism and significance of dynamic airway compression that occurs in

chronic obstructive pulmonary diseases.

FIG 01: Lungs Compliance Meter Overview

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Contents

Acknowledgement -------------------------------------------------------------------------------------3

Abstract ----------------------------------------------------------------------------------------------------4

1 Introduction- What is Lungs Compliance Meter? ----------------------------------------6

2 Objectives- What it can do? ---------------------------------------------------------------------9

3 Procedures and Methodologies --------------------------------------------------------------10

4 Results and Discussion -------------------------------------------------------------------------18

5 Conclusions and Future Works --------------------------------------------------------------21

6 Bibliography---------------------------------------------------------------------------------------23

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1 INTRODUCTION

Lungs Compliance is the change in lung volume for each unit change in trans pulmonary

pressure. Compliance is seen at low volumes (because of difficulty with initial lung

inflation) and at high volumes (because of the limit of chest wall expansion). The total

work of breathing of the cycle is the area contained in the loop. Compliance of lungs

occurs due to elastic forces.

Two Types of Compliance: Static & Dynamic which can be generated by Inspiratory &

Expiratory compliance curves. Lungs Compliance Meter can be used to plot static &

dynamic compliances which can be used to study the mechanism and significance of

dynamic airway compression that occurs in chronic obstructive pulmonary diseases.

FIG 02: Compliance Curves

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Trans pulmonary pressure is the difference in pressure between alveolar pressure and

pleural pressure. The lung is an elastic structure with an anatomical organization that

promotes its collapse to essentially zero volume, much like an inflated balloon. The term

elastic means a material deformed by a force tends to return to its initial shape or

configuration when the force is removed. While the elastic properties of the lung are

important to bring about expiration, they also oppose lung inflation. As a result, lung

inflation depends upon contraction of the inspiratory muscles. How easily a lung inflates

will relate to the compliance of the lung. Recall that the resistance to deformation

(inflation) is termed elastane. However, compliance is the preferred term to describe the

elastic properties of the lung. Compliance, as the reciprocal of elastane, is a measure of

the ease of deformation (inflation).

Low compliance indicates a stiff lung (one with high elastic recoil) and can be thought of

as a thick balloon - this is the case often seen in fibrosis. High compliance indicates a

pliable lung (one with low elastic recoil) and can be thought of as a grocery bag - this is

the case often seen in emphysema. Compliance is highest at moderate lung volumes, and

much lower at volumes which are very low or very high. The compliance of the lungs

demonstrates hysteresis; that is, the compliance is different on inspiration and expiration

for identical volumes. Pulmonary compliance is calculated using the following equation,

where ΔV is the change in volume, and ΔP is the change in pleural pressure.

Compliance = ΔV/ ΔP

Pulmonary surfactant increases compliance by decreasing the surface tension of water.

The internal surface of the alveolus is covered with a thin coat of fluid. The water in this

fluid has a high surface tension, and provides a force that could collapse the alveolus. The

presence of surfactant in this fluid breaks up the surface tension of water, making it less

likely that the alveolus can collapse inward. If the alveolus were to collapse, a great force

would be required to open it, meaning that compliance would decrease drastically.

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FIG 03: Working of Lungs Compliance Meter

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2 Objectives- What it can do?

Generates plot for static & dynamic compliances.

GUI & Views for each plot to study in detail.

FIG 04: Compliance Curve

FIG 05: Inspiration Compliance FIG 06: Expiration Compliance

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3 PROCEDURES AND METHODOLOGIES

Hardware Requirements: -

Name Specification Price View

Plastic Bottle

Volume= (1500mL) approx. Rs.5

Balloon Big Size & more elastic Rs.8

Syringe 200-300mL big syringe

Raspberry Pi 3

1.2GHz 64-bit quad-core ARMv8 CPU

WLAN, Bluetooth

1GB RAM, 4USB Ports

Ethernet Port, MicroSD

Rs.3052

Ultrasonic Sensor

HC-SR04 Model

5V DC Supply

Range: 2cm- 4m

Measuring Angle: 15degrees

Rs.119

Resistors 1k ohm & 2k ohm

Jumper Wires

Male-Male, Male-Female, Female-Female

Rs.130

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Hardware Development: -

1. Make isolated system for bottle so that there’s no leakage.

2. Make a hole in the bottom of bottle to connect syringe for pulling/pushing H2O.

3. Fit Ultrasonic Senor in the cap/lid of bottle to measure water levels.

4. Fix a balloon inside bottle using thin tube with opening outside the cap for air

in/out.

5. Fill the bottle completely with water.

Software Development: -

1. Boot Raspbian/Noobs in Raspberry Pi.

FIG 07: Raspbian/Noobs

2. Install XRDP to enable remote desktop connection.

FIG 08: XRDP Remote Desktop Connection

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3. Install Dependencies: Python, Numpy, GPIO, PyQt4, PyqtGraph.

4. Design GUI in PyQt4 Designer.

FIG 09: Lungs Compliance Meter GUI

5. Create desktop launcher and add to start menu for easy access.

Connecting Sensor: -

Powering the module is easy. Just connect the +5V and Ground pins to Pin 2 and Pin 6 on the Pi’s GPIO header. The input pin on the module is called the “trigger” as it is used to trigger the sending of the ultrasonic pulse. Ideally it wants a 5V signal but it works just fine with a 3.3V signal from the GPIO. So I connected the trigger directly to Pin 16 (GPIO23) on my GPIO header. The module’s output is called the “echo” and needs a bit more thought. The output pin is low (0V) until the module has taken its distance measurement. It then sets this pin high (+5V) for the same amount of time that it took the pulse to return. So our script needs to measure the time this pin stays high.

The module uses a +5V level for a “high” but this is too high for the inputs on the GPIO header which only like 3.3V. In order to ensure the Pi only gets hit with 3.3V we can use a basic voltage divider. This is formed with two resistors. If R1 and R2 are the same then the voltage is split in half. This would give us 2.5V. If R2 is twice the value of R1 then we get 3.33V which is fine. So ideally you want R2 to be between R1 and R1 x 2. In my example circuit I used 1k ohm and 2.2k ohm resistors.

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Here is a diagram of my final circuit. I choose GPIO23 and GPIO24 but you can use any of the 17 available GPIO pins on the GPIO header.

FIG 10: Ultrasonic Sensor Connection

FIG 11: Wiring of Sensor

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Calculation of Volume & Pressure of Balloon: -

1. Measure total distance from sensor to bottom of bottle = H

2. Measure total volume of the bottle = Vi

3. Sense distance of water level from sensor each time it changes d (in cm)

4. Calculate water level h = Total distance H - Current Distance d

5. Calculate final volume Vf = π. R2 .h (R = radius of bottle)

6. Calculate volume of balloon V = Vi - Vf (in mL)

7. Calculate radius of balloon r = {(3/4). (1/π). V}1/3

8. Calculate pressure using Laplace Law P = (2. Surface Tension)/r (in cmH2O)

Functional significance of abnormally high or low compliance

Low compliance indicates a stiff lung and means extra work is required to bring in a

normal volume of air. This occurs as the lungs in this case become fibrotic, lose their

dispensability and become stiffer.

In a highly compliant lung, as in emphysema, the elastic tissue is damaged by enzymes.

These enzymes are secreted by leukocytes (white blood cells) in response to a variety of

inhaled irritants, such as cigarette smoke. Patients with emphysema have a very high

lung compliance due to the poor elastic recoil. They have extreme difficulty exhaling air.

In this condition extra work is required to get air out of the lungs. In addition, patients

often have difficulties inhaling air as well. This is due to the fact that a high compliant

lung results in many collapsed alveoli which makes inflation difficult. Compliance also

increases with increasing age.

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FIG 12: Subject Using the Compliance Meter

Compliance decreases in the following cases: -

Supine position

Laparoscopic surgical interventions

Severe restrictive pathologies

Chronic restrictive pathologies

Hydrothorax

Pneumothorax

High standing of a diaphragm

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Factors Affecting Pulmonary Ventilation: Compliance of the Lungs: -

Compliance is the ability of lungs and pleural cavity to expand and contract based on

changes in pressure. Lung compliance is defined as the volume change per unit of

pressure change across the lung, and is an important indicator of lung health and

function. Measurements of lung volumes differ at the same pressure between inhalation

and exhalation, meaning that lung compliance differs between inhalation and exhalation.

Lung compliance can either be measured as static or dynamic based on whether only

volume and pressure (static) is measured or if their changes over time are measured as

well (dynamic).

Key Points: -

o A low lung compliance would mean that the lungs would need a greater-

than-average change in intra-pleural pressure to change the volume of the

lungs.

o A high lung compliance would indicate that little pressure difference in

intra-pleural pressure is needed to change the volume of the lungs.

o Persons with low lung compliance due to obstructive lung diseases tend to

take rapid shallow breaths and sit hunched over to make exhalation less

difficult.

o Persons with high lung compliance due to restrictive lung diseases tend to

have difficulty expanding and deflating the lungs.

o Two factors determine lung compliance: elasticity of the lung tissue and

surface tensions at air water interfaces.

o Two factors determine lung compliance - elasticity of the lung tissue and

surface tensions at air water interfaces.

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Compliance and Elastic Recoil of the Lung: -

Compliance depends on the elasticity and surface tension of the lungs. Compliance is

inversely related to the elastic recoil of the lungs, so thickening of lung tissue will

decrease lung compliance. The lungs must also be able to overcome the force of surface

tension from water on lung tissue during inflation in order to be compliant, and greater

surface tension causes lower lung compliance. Therefore, surfactant secreted by type II

epithelial cells increases lung compliance by reducing the force of surface tension.

A low lung compliance means that the lungs are "stiff" and have a higher than normal

level of elastic recoil. A stiff lung would need a greater-than-average change in pleural

pressure to change the volume of the lungs, and breathing becomes more difficult as a

result. Low lung compliance is commonly seen in people with restrictive lung diseases,

such as pulmonary fibrosis, in which scar tissue deposits in the lung making it much

more difficult for the lungs to expand and deflate, and gas exchange is impaired.

Pulmonary Fibrosis: -

Pulmonary fibrosis stiffens the lungs through deposits of scar tissue, decreasing low

compliance and making it more difficult for the lungs to inflate and deflate.

A high lung compliance means that the lungs are too pliable and have a lower than

normal level of elastic recoil. This indicates that little pressure difference in pleural

pressure is needed to change the volume of the lungs. Exhalation of air also becomes

much more difficult because the loss of elastic recoil reduces the passive ability of the

lungs to deflate during exhalation. High lung compliance is commonly seen in those with

obstructive diseases, such of emphysema, in which destruction of the elastic tissue of the

lungs from cigarette smoke exposure causes a loss of elastic recoil of the lung. Those with

emphysema have considerable difficulty with exhaling breaths and tend to take fast

shallow breaths and tend to sit in a hunched-over position in order to make exhalation

easier.

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4 RESULTS AND DISCUSSION

Static & Dynamic Compliance was plot for inspiration & expiration in real-time.

Data Acquired each time sensor senses for user sucking/pushing water from syringe.

-----------------------------------

SENSING...

Distance: 3.32425832748 cm

Current volume of H2O: 1161.262 mL

V of balloon: 38.738 mL

P of balloon: 0.049 cmH2O

-----------------------------------

SENSING...

Distance: 3.75767946243 cm




-----------------------------------

SENSING...

Distance: 4.13385629654 cm




-----------------------------------

SENSING...

Distance: 4.2197227478 cm




-----------------------------------

SENSING...

Distance: 4.3751001358 cm



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-----------------------------------

SENSING...

Distance: 4.40781116486 cm




-----------------------------------

SENSING...

Distance: 5.04567623138 cm




-----------------------------------

SENSING...

Distance: 4.76763248444 cm




-----------------------------------

SENSING...

Distance: 4.86985445023 cm




-----------------------------------

SENSING...

Distance: 5.41776418686 cm




-----------------------------------

SENSING...

Distance: 5.19696474075 cm


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-----------------------------------

SENSING...

Distance: 5.38505315781 cm




-----------------------------------

SENSING...

Distance: 5.60994148254 cm




-----------------------------------

SENSING...

Distance: 5.65900802612 cm




-----------------------------------

SENSING...

Distance: 6.29278421402 cm




START GRAPH

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5 CONCLUSIONS AND FUTURE WORKS

Lungs Compliance Meter was successfully developed to

demonstrate the compliances of lungs in our respiratory

system. It will be helpful for all the medical researchers,

faculty & students for detailed analysis of various types of

compliances that can occur in the lungs of a human body.

FIG 13: Human Lungs Digitized data from the pressure and volume gauges are fed

to the screen, enabling students to observe and record how dynamic compliance varies

with the rate of increase in pressure inside the bottle. The recorded data enabled students

in understanding the mechanism and significance of dynamic airway compression that

occurs in chronic obstructive pulmonary diseases.

FIG 14: LCM Future Scope

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If compliance is decreased (decreased expansion of the lungs) large transmural pressure

gradient will be required to produce normal lung expansion. By greater expansion of

thorax by more forceful contraction of inspiratory muscles. If lung is less compliant, it is

called ‘Stiff Lung’ (as it lacks normal stretch ability).

Clinical Application of lung compliance is decreased in pulmonary fibrosis, when

normal lung tissue is replaced by fibrous connective tissue. As occurs in due to

chronically breathing of irritants like Asbestos Fibers.

Future Scope of Lungs Compliance Meter is to measure compliances of real human lungs

directly with only contact. Further, the data can be utilized to generate static & dynamic

compliances. This can be helpful in curing various lung diseases instantly.

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6 BIBLIOGRAPHIES

References

https://en.wikipedia.org/wiki/Pulmonary_compliance

http://physiology.lf2.cuni.cz/teaching/lung%20compliance_mital.ppt

https://www.boundless.com/physiology/textbooks/boundless-anatomy-and-

physiology-textbook/respiratory-system-22/factors-affecting-pulmonary-

ventilation-1375/factors-affecting-pulmonary-ventilation-compliance-of-the-

lungs-1026-6375/

Hyperlinks

Lungs Compliance Meter: http://www.vslcreations.in/lcm/

IIT Jodhpur: http://www.iitj.ac.in/

AIIMS Jodhpur: http://www.aiimsjodhpur.edu.in/

https://en.wikipedia.org/wiki/Pulmonary_compliance

http://physiology.lf2.cuni.cz/teaching/lung%20compliance_mital.ppt

https://www.boundless.com/physiology/textbooks/boundless-anatomy-and-physiology-textbook/respiratory-system-22/factors-affecting-pulmonary-ventilation-1375/factors-affecting-pulmonary-ventilation-compliance-of-the-lungs-1026-6375/




http://www.vslcreations.in/lcm/

http://www.iitj.ac.in/

http://www.aiimsjodhpur.edu.in/