Transcript 48x36 poster template - Research

Programmable Biofeedback Chest Exerciser
Eileen Bock, Lauren Cassell, Margaret Gipson, Laurie McAlexander
Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
BACKGROUND
Heart failure occurs when the heart can no longer develop the
pressure needed to eject the desired stroke volume from the heart,
and therefore tissues cannot get the nutrients they need. Patients
with heart disease benefit from deep breathing to exercise the
muscles surrounding the lungs. Since it is often difficult for a patient
with heart failure to exercise by traditional methods, deep breathing
is preferred as a method of exercise to alleviate and even improve
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
rate of respiration. If the patient does not take a certain number of
sufficiently deep breaths in a predetermined amount of time, the
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
adequate exercise to the target muscles. The patient's physician
will determine the appropriate breathing exercise schedule for the
patient. The device will record the patient's compliance with the
regimen prescribed by the physician and will store the record on a
data storage system that can be read by the patient’s physician.
Circuit Experiments/Analysis:
 Part 1: 10 subjects, wear device for one
hour each, perform breathing exercises
and common activities (e.g., walking,
conversing), subject survey to determine
compliance and comfort
 Part 2: 10 new subjects, wear device for
3 hours, perform same tasks as Part 1,
subject survey to determine compliance
and comfort
 Part 3 (clinical testing): one experimental
and two control groups, wear device with
prescribed regimen for a period of 6
weeks, measure improvement of
inspiratory force with incentive
spirometer
 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
RESULTS
4
3.5
y = 1.1539x + 0.3692
R2 = 0.8503
3
2
1.5
1
0.5
0
0.5
y = 0.8493x + 0.6736
R2 = 0.842
3.5
2.5
0
Tidal Volume (L)
5.5 cm
3.5
3
2.5
2
1.5
1
0.5
0
0.624
R^2 Values
y = 362.46x - 225.4
R2 = 0.8216
0.625
0.626
0.627
0.628
0.629
0.63
0.631
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Output Voltage (V)
5.5 cm
6.0 cm
6.5 cm
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.
CONCLUSIONS
Exhaled Air (L)
The purpose of the project is to design, build, and implement a
programmable biofeedback chest exerciser for patients with heart
and lung disease. Deep breathing has been found to be an effective
form of exercise for heart failure patients. A biofeedback chest
exerciser will monitor depth and rate of breathing and communicate
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
is measured, and a variable resistor is incorporated into a strap to
be worn around the subject’s chest. A two stage inverting amplifier
circuit amplifies the voltage change that occurs as a result of the
change in resistance. This output voltage is connected to LabVIEW
which detects when depth and rate thresholds are not met in
accordance with a physician’s prescribed protocol. A biofeedback
system will be incorporated into a wireless data acquisition device
to notify the patient when an adequate breathing rate or depth is not
accomplished.
IRB Protocol:
Exhaled Air (L)
ABSTRACT
1
Chest Expansion (cm)
1.5
2
3
2.5
2
1.5
1
0.5
0
0
0.5
1
1.5
2
2.5
3
3.5
4
Chest Expansion
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.
METHODS
Circuit Design (shown in Figure 1 below):
• 2” stretch sensor used rather than bend sensor
• 6 V operational amplifier (low power) used
• Four 3V batteries used for power
• Two-stage inverting amplifier used – 1st stage with gain of two,
2nd stage with gain of 10
• Wire-wrapped to achieve a compact, portable circuit
• 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
FUTURE DIRECTIONS
• 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
ACKNOWLEDGEMENTS
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.
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.