Determination of the Effects of Exposure to Diesel Exhaust on Peak Expiratory Flow Rate
in Potsdam Schoolchildren
David Illig with Advisor Dr. S. Schuckers
Honors Program Thesis Proposal
March 14, 2008
1. Introduction
While Potsdam, like many rural environments, has relatively low levels of air pollutants,
exposures while riding in school buses may be a contributor to acute adverse respiratory
responses. This research focuses on the exposure and associated cardiopulmonary effects of
children attending Potsdam School District to diesel exhaust emissions released from school
buses. A unique feature of the research is the utilization of the wearable physiologic monitor,
called the LifeShirt™, which can measure heart activity, and respiration. The purpose of this
Honor’s project is to validate the LifeShirt respiratory measurements and study the impact of
diesel exhaust emissions on respiration in children.
The LifeShirt is a semi-elastic shirt which measures real-time continuous electrocardiography
(ECG), respiratory inductance plethysmography (RIP), and body posture and activity via
accelerometry (ACC). From these measurements, the VivoLogic software package can calculate
many additional respiratory and cardiac measurements, including peak flow. To validate the
measurements taken from the LifeShirt, we will compare them to simultaneous measures of peak
flow.
Peak expiratory flow rate (PEF) is a measurement of a patient’s maximum ability to exhale
which can be used to monitor airflow through the bronchi and determine restriction in the lungs’
airways. Peak flow readings are high when patients are well, but lower when the airways become
constricted. Doctors may determine lung functionality, asthma symptoms, and treatment for
other lung-related medical problems by analyzing changes in peak flow values over time. The
traditional procedure for measuring peak flow requires the patient to take a deep breath and
exhale into a sensor for as long as possible and as hard as they can.
Two studies at Clarkson University utilized both the LifeShirt and peak flow meters to obtain
lung-related measurements. One of these studies was performed in a controlled environment in a
lab, in which subjects had measurements taken before and after running on a treadmill. The other
study was carried out on children during a school day including their school bus ride to
determine if the exhaust from school busses impacts the breathing abilities of children riding the
busses.
A comparison of measurements from peak flow meters and the LifeShirt will be performed to
determine the accuracy of the LifeShirt’s measurements. If the LifeShirt’s measurements are
comparable to the peak flow meter’s measurements, MATLAB software and signal processing
techniques will be used to determine an automated means of extracting peak flow measurements
from the raw data recorded by the LifeShirt. These peak flow measurements will then be used to
aid in studying the impact of diesel exhaust emissions on respiration in children recorded in the
study mentioned previously.
2. Background
2.1 Respiratory Inductance Plethysmography
Plethysmography is a noninvasive lung volume measurement technique based on Boyle’s Law,
which states that the product of pressure and volume is a constant.1,2 In plethysmography,
changes in thoracic pressure and volume changes during respiratory efforts are used to calculate
lung volume.1,2 RIP measures changes in inductance of the body and produces a volume signal
from these measures.3 Utilizing a traditional plethysmograph, a patient is placed inside of a
sealed chamber containing a mouthpiece into which the patient is required to breath.1 This
method thus requires the patient to go to a hospital or other medical facility, as the equipment
required is not portable. With RIP however, small, easily portable devices such as the LifeShirt
can be used to measure lung volume. It has also been shown that the results of using a device
such as the LifeShirt to measure respiratory data outside of a laboratory environment possess
high agreement with measurement results from laboratory equipment.3,4 The LifeShirt system
incorporates rib cage and abdominal inductive plethysmographic sensors whose sum is equal to
total tidal volume.5 From the LifeShirt measurement of tidal volume, many additional respiratory
parameters can be derived.5
2.2 Peak Expiratory Flow Rate
PEF is defined as the rate at which tidal volume changes with respect to time. PEF measures a
patient’s maximum ability to exhale.6 PEF readings are used to indicate how narrow or open the
airways are.6 Thus, when PEF is high, a patient is well, and a lower PEF indicates that the
patient’s airways are constricted. From changes in recorded PEF values, over time patients and
doctors may determine lung functionality, the presence and severity of asthma symptoms, and
potential treatment options for respiratory problems. PEF is usually measured by requiring a
patient to take a deep breath and exhale into a sensor for as long and as hard as possible.
However, this requires that patients be able to comprehend instructions given to them by a
doctor, making this test unsuitable for young, unconscious, or sedated patients. This procedure
also would not be appropriate for patients who have medical limitations preventing them from
making vigorous respiratory efforts.
2.3 Lung Volume Measurements in Children
Assessment of respiratory function is important during early childhood as the lungs and airways
grow.7 Lung volume measurements have been used to assess the long-term effects of lung
trauma on young children, including bronchopulmonary dysplasia and bronchiolitis.1 Symptoms
of cystic fibrosis, pulmonary hypoplasia, pulmonary fibrosis, and musculoskeletal abnormalities
can also be detected using lung volume measurements.1 Tidal volume and its derived parameters
can also be used to detect the presence of asthma symptoms in children.1,3 Although there are
many different means of measuring lung volume, including gas dilution techniques,
plethysmography, radiological methods, and magnetic resonance imaging, most of these require
that the patient be tested with a large, nonportable piece of equipment.1,8 For very young children
or children who are uncooperative with doctor’s instructions, it may not be possible to use these
procedures to measure lung volume.8 RIP, however, has been shown to be relatively simple to
perform, require minimal patient cooperation, and apply to a broad range of age groups.7 This
makes a device such as the LifeShirt ideal for measuring lung volume parameters in young
children.
3. Research Methodology
In completing this research project, three major objectives will need to be accomplished. First, a
means of comparing the PEF measurement of the LifeShirt to the values recorded by the peak
flow meter must be created. The algorithm used to compare these results will then be translated
into a MATLAB program to be used to efficiently and consistently extract PEF values from the
LifeShirt data. Finally, once the MATLAB program has been used on all subjects, statistical tests
will be used to determine if the children’s respiration was affected by the diesel exhaust of the
school busses.
3.1 Comparison between Peak Expiratory Flow Rate Measurement
When the study on the impact of diesel exhaust emissions on respiration in children was
performed, peak flow meters were used to measure PEF independent of the LifeShirt. At that
time, it was not known if the VivoLogic software utilized to analyze LifeShirt data could be used
to directly calculate PEF. Difficulty in interpreting the PEF measurements recorded by
experimentalists and in synchronizing the LifeShirt’s internal clock recording with external
clocks provided motivation for a way to directly acquire PEF measurements from the LifeShirt
data.
With that in mind, an early objective of this project was to determine a means of calculating PEF
directly from tidal volume. It was soon determined that the software can in fact measure PEF;
however, the VivoLogic manual warns that the measure of PEF by the LifeShirt may be
significantly higher than that measured from peak flow meters.5 Currently efforts are being made
to calculate PEF using the tidal volume and time measurements made by the LifeShirt in a way
such that this recording correlates with the measurements made using the peak flow meters, with
particular focus on creating an appropriate algorithm for determining when a breath has been
completed.
3.2 Creation of MATLAB Program to Extract Peak Expiratory Flow Rate from Data
Once an algorithm for determining PEF from the LifeShirt measurements has been created that
correlates with the peak flow meter measurements, this algorithm will be translated into a
computer program. The MATLAB programming language was selected as it is already in use by
Dr. Schuckers and others analyzing the data from this study. Having been a teaching assistant for
ES100 for the last two years, I also have been using MATLAB extensively at Clarkson. The
choice of MATLAB also provides powerful built-in graphical and data importing capabilities
compared to other languages such as C++ or Java, which will be advantageous to the goals of
this project. This program will also eliminate confusion related to timing issues between the
LifeShirt clock and other clocks, making it easier to tell when data values were actually
recorded. Some challenges in creating this program will be how to tell when a breath starts and
stops and how to focus only on those breaths that were done to measure PEF, instead of
analyzing all breaths.
3.3 Impact of Diesel Exhaust Emissions on Peak Expiratory Flow Rate
Upon creation of the MATLAB program, reliable PEF measurements will be easily accessible
for each experimental subject by running the MATLAB program on the data set for that subject.
PEF was measured before and after each bus ride, as well as during other times of the day. From
the PEF measurements before bus rides and at other times of day, a baseline PEF value will be
determined for each subject. The PEF measurements after each bus ride will be compared to this
baseline value for each subject using an appropriate statistical test (to be determined at a later
date). If the test shows statistical significance between the PEF measurements after each bus ride
compared to PEF measurements at other times, this will indicate that the diesel exhaust
emissions are having an effect on respiration in children riding busses in the Potsdam School
District.
4. Expected Results
From my literature review, I expect to find that the diesel exhaust emissions of the school busses
are in fact having an effect on the PEF for the subjects involved in the study. Even though the
subjects were perhaps only briefly exposed to the diesel exhaust, the literature review indicates
that this should still affect their respiration.
5. Timetable
Date
Late March 2008
Description
Select appropriate algorithm to calculate PEF from raw
LifeShirt data and begin conceptualizing how to convert this
algorithm into programming terms
Early April 2008
Perform necessary revisions to Thesis Proposal
Late April 2008
Thesis Progress Report
May 2008 – August 2008 Summer research at Clarkson
 Complete MATLAB program
 Use MATLAB program to convert LifeShirt data into PEF
values
 Analysis of PEF data
o Qualitatively compare PEF data from after bus rides
to data during the rest of the day
o Determine appropriate baseline value for PEF
o Select appropriate statistical test to quantitatively
compare PEF data from after bus rides to data during
the rest of the day
 Continuously work on abstract and chapters 1-3
September 2008
 Begin work on chapters 4-6
 Meeting on thesis progress
Early October 2008
 Completion of draft versions of chapters 4-6
 Integration of abstract and chapters 1-6 into one document
 Revisions to integrated document
Mid-October 2008
Preliminary thesis due
Late October 2008
Implement revisions to thesis from thesis feedback
November 2008
 Work on oral presentation
 Continue revisions to thesis
December 2008*
 Thesis due
 Oral presentation
*Note that I currently plan on graduating in December 2008.
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