Date of Award

Spring 1999

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering - (M.S.)

Department

Biomedical Engineering Committee

First Advisor

Stanley S. Reisman

Second Advisor

Peter Engler

Third Advisor

John J. LaManca

Abstract

Time-frequency signal representations characterize signals over a joint time-frequency plane. They combine time-domain and frequency-domain analysis to yield a potentially more revealing picture of the temporal localization of a signal spectrum. Time-frequency distributions (TFDS) of signals map a one-dimensional function of time, x (t), into a two-dimensional function of time and frequency, p(t, f). Most TFDs are "time-varying representations' which are similar conceptually to a musical score with time running along one axis and frequency along the other axis.

Many Gulf War Veterans complained of symptoms like unexplainable tiredness. This condition is known as the Gulf War Syndrome. The purpose of the research was to determine the changes occurring in the autonomic nervous system of these veterans under stress. Time frequency analysis of heart rate variability was used as a tool to compare the condition of Gulf War Veterans with Gulf War Syndrome with healthy Veterans.

A total of 27 Gulf War Veterans, 12 healthy and 15 sick, were subjected to a 45 minute tilt test at VA Medical Center, East Orange. Their age group is from 25 to 50 years. The EGG, blood pressure and the respiration of each subject was measured continuously during these 45 minutes.

From the raw ECG data, the interbeat beat intervals were extracted. From this data the power spectrum of heart rate variability, low frequency (LF) and high frequency (parasympathetic) activity (HF) with respect to change in time were obtained. The results were statistically analyzed and comparisons were performed on the data obtained from healthy and sick subjects before and during the tilt. The data were compared based on parameters like the age, low frequency activity (LF), high frequency activity (HF) and the ratio LF/HF.

The results indicated that for the same age group all veterans suffering from gulf war syndrome have lower autonomic activity (i.e. parasympathetic and sympathetic activity) than their healthy counterparts. Also a higher rate of drop in activity level with age of veterans suffering from gulf war syndrome is observed as compared to their healthy counterparts.

All the above indicators lead to the conclusion that veterans suffering from gulf war syndrome show lower autonomic activity in general as compared to healthy veterans, thus indicating a difference in functioning in their autonomic nervous system. This could be attributed to the gulf war syndrome. Our findings suggest that heart rate variability might be one of the indicators to evaluate gulf war syndrome.

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