Programmable Biofeedback Chest ExerciserEileen Bock, Lauren Cassell, Margaret Gipson, Laurie McAlexander

Department of Biomedical Engineering, Vanderbilt University, Nashville, TN

Circuit Design (shown in Figure 1 below):Circuit Design (shown in Figure 1 below):• 2” stretch sensor used rather than bend sensor2” stretch sensor used rather than bend sensor• 6 V operational amplifier (low power) used6 V operational amplifier (low power) used• Four 3V batteries used for powerFour 3V batteries used for power• Two-stage inverting amplifier used – 1Two-stage inverting amplifier used – 1stst stage with gain of two, stage with gain of two, 22ndnd stage with gain of 10 stage with gain of 10• Wire-wrapped to achieve a compact, portable circuitWire-wrapped to achieve a compact, portable circuit

• Obtain IRB approval of the clinical testing protocol proposed• Send output voltage to PDA so patient will be able to view breathing rate and depth portably• Incorporate vibrating biofeedback system to act as patient warning

• Create a one-size-fits all design to ensure that patients with different chest circumferences will be able to wear the same device with minimal adjustment• Save breathing data on a removable data storage device for physician use• Modify threshold values for breathing depth and rate so that device can be used for aerobic exercise applications• Redefine threshold values for possible use in clinical environment for patients with breathing disorders

METHODS

BACKGROUND

FUTURE DIRECTIONS

RESULTS

Figures 2 and 3. The graphs illustrate the correlation between exhaled air and chest expansion in two different test subjects. The purpose of the tidal volume experiments was twofold, to investigate the relationship between chest expansion and breath volume and to calibrate our device to measure voltage versus tidal volume for an accurate depth of breath determination. This information was used to determine that the 2” stretch sensor purchased was ideal for this application.

CONCLUSIONS

ABSTRACT

y = 1.1539x + 0.3692

R2 = 0.8503

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1.5

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3.5

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Chest Expansion (cm)

Exha

led

Air (

L)

y = 0.8493x + 0.6736

R2 = 0.842

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0.5

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1.5

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Chest Expansion

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Heart failure occurs when the heart can no longer develop the Heart failure occurs when the heart can no longer develop the pressure needed to eject the desired stroke volume from the heart, pressure needed to eject the desired stroke volume from the heart, and therefore tissues cannot get the nutrients they need. Patients and therefore tissues cannot get the nutrients they need. Patients with heart disease benefit from deep breathing to exercise the with heart disease benefit from deep breathing to exercise the muscles surrounding the lungs. Since it is often difficult for a patient muscles surrounding the lungs. Since it is often difficult for a patient with heart failure to exercise by traditional methods, deep breathing with heart failure to exercise by traditional methods, deep breathing is preferred as a method of exercise to alleviate and even improve is preferred as a method of exercise to alleviate and even improve the effects of the disease. The device has been constructed so that the effects of the disease. The device has been constructed so that a patient wears it around the upper torso to monitor the depth and a patient wears it around the upper torso to monitor the depth and rate of respiration. If the patient does not take a certain number of rate of respiration. If the patient does not take a certain number of sufficiently deep breaths in a predetermined amount of time, the sufficiently deep breaths in a predetermined amount of time, the device will alert the patient. This alert will indicate to the patient that device will alert the patient. This alert will indicate to the patient that the breaths he or she is taking are not sufficient to provide the breaths he or she is taking are not sufficient to provide adequate exercise to the target muscles.  The patient's physician adequate exercise to the target muscles.  The patient's physician will determine the appropriate breathing exercise schedule for the will determine the appropriate breathing exercise schedule for the patient.  The device will record the patient's compliance with the patient.  The device will record the patient's compliance with the regimen prescribed by the physician and will store the record on a regimen prescribed by the physician and will store the record on a data storage system that can be read by the patient’s physician. data storage system that can be read by the patient’s physician. 

Figures 6 and 7. The graph on the left shows the relationship between output voltage and tidal volume at an initial stretch sensor length of 5.5 cm. The right shows a bar graph of R2 values for different stretch sensor resting length, and at 5.5 cm, the most linear relationship is obtained.

The purpose of the project is to design, build, and implement a The purpose of the project is to design, build, and implement a programmable biofeedback chest exerciser for patients with heart programmable biofeedback chest exerciser for patients with heart and lung disease. Deep breathing has been found to be an effective and lung disease. Deep breathing has been found to be an effective form of exercise for heart failure patients. A biofeedback chest form of exercise for heart failure patients. A biofeedback chest exerciser will monitor depth and rate of breathing and communicate exerciser will monitor depth and rate of breathing and communicate with the subject so that he or she follows a physician’s protocol. The with the subject so that he or she follows a physician’s protocol. The change in a subject’s thoracic circumference as breathes in and out change in a subject’s thoracic circumference as breathes in and out is measured, and a variable resistor is incorporated into a strap to is measured, and a variable resistor is incorporated into a strap to be worn around the subject’s chest.  A two stage inverting amplifier be worn around the subject’s chest.  A two stage inverting amplifier circuit amplifies the voltage change that occurs as a result of the circuit amplifies the voltage change that occurs as a result of the change in resistance. This output voltage is connected to LabVIEW change in resistance. This output voltage is connected to LabVIEW which detects when depth and rate thresholds are not met in which detects when depth and rate thresholds are not met in accordance with a physician’s prescribed protocol. A biofeedback accordance with a physician’s prescribed protocol. A biofeedback system will be incorporated into a wireless data acquisition device system will be incorporated into a wireless data acquisition device to notify the patient when an adequate breathing rate or depth is not to notify the patient when an adequate breathing rate or depth is not accomplished.  accomplished. 

 Circuit Experiments/Analysis:

Preliminary experiment to investigate relationship between chest circumference and tidal volume to determine ideal stretch sensor length Tidal volume vs. output voltage measurements taken to determine ideal resting length of stretch sensor to get the most linear range Interfaces created to display single and multiple breaths to determine which method is most applicable Breathing exercises to determine deep breath threshold Alarm system implemented on interface that will alert subject when breathing depth is not adequate

ACKNOWLEDGEMENTS

The design team would like to thank Dr. Douglas Sawyer, Dr. John Newman, Dr. Paul King, Dr. Stacy Klein, and Dr. Bob Galloway for their help in this project.

• Linear relationship between tidal volume and chest expansion was established• Chest expansion is an effective tool to measure respiration• 2” stretch sensor is ideal for this measurement type• Single and multiple breaths can be recorded using LabVIEW software• A starting length of 5.5 cm for the stretch sensor yields the most linear relationship between output voltage and tidal volume• A deep breath in the average subject is 3 liters• A deep breath will reset the alarm on the LabVIEW equipment, and failure to reach threshold will result in a flashing light as a user warning

Figures 4 and 5. These LabVIEW screen shots depict multiple breaths on the left, and a single breath on the right. Additionally, the screen shot on the right shows the light that will flash when a deep breath is not taken (a voltage threshold is not reached) in a specified period of time.

5.5 cm

y = 362.46x - 225.4

R2 = 0.8216

00.5

11.5

22.5

33.5

0.624 0.625 0.626 0.627 0.628 0.629 0.63 0.631

Output Voltage (V)

Tida

l Vol

ume

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 IRB Protocol:

Part 1Part 1: 10 subjects, wear device for one : 10 subjects, wear device for one hour each, perform breathing exercises hour each, perform breathing exercises and common activities (e.g., walking,and common activities (e.g., walking, conversing), subject survey to determine conversing), subject survey to determine compliance and comfortcompliance and comfort Part 2Part 2: 10 new subjects, wear device for: 10 new subjects, wear device for 3 hours, perform same tasks as Part 1, 3 hours, perform same tasks as Part 1, subject survey to determine compliance subject survey to determine compliance and comfortand comfort Part 3Part 3 (clinical testing) (clinical testing): one experimental : one experimental and two control groups, wear device withand two control groups, wear device with prescribed regimen for a period of 6 prescribed regimen for a period of 6 weeks, measure improvement of weeks, measure improvement of inspiratory force with incentive inspiratory force with incentive spirometer spirometer

R^2 Values

00.10.20.30.40.50.60.70.80.9

5.5 cm 6.0 cm 6.5 cm