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njit-etd2003-081 - New Jersey Institute of Technology

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239<br />

providing higher resolution in time and frequency while suppressing interferences between<br />

the signal components.<br />

The respiration analysis validated the physiological states the COPD subjects were<br />

in. With shortness <strong>of</strong> breath, the breathing rate has to increase to supply the body with<br />

more oxygen and remove more carbon dioxide, thus shifting the frequency <strong>of</strong> respiration<br />

into higher ranges that could reach as high as 0.55 Hz (33 bpm). The HRV analysis <strong>of</strong><br />

normal subjects showed that with rest the average heart rate slows down while the<br />

variability in the heart rate increases. On the other hand, with exercise, the average heart<br />

rate speeds up while the variability in the heart rate decreases. Both the time-frequency<br />

and statistical analysis <strong>of</strong> the HRV signals showed that a stressful exercise level drastically<br />

changed the HRV signal and that there was a significant difference between the three<br />

states <strong>of</strong> rest, exercise, and recovery.<br />

In the second phase <strong>of</strong> this research, the cross spectral analyses (i.e. coherence,<br />

weighted coherence and partial coherence) were used to investigate the increase or<br />

decrease <strong>of</strong> the HRV, BPV or any <strong>of</strong> the combinations <strong>of</strong> HRV, BPV and respiration that<br />

changed the behavior in the autonomic nervous system. Examination <strong>of</strong> the results for the<br />

47 COPD and 8 normal subjects presented some real challenge because the peaks <strong>of</strong> the<br />

ECG R-waves, blood pressure peaks and even respiration signals <strong>of</strong> COPD patients were<br />

difficult to detect and analyze. However, the interrelationships between heart rate and<br />

respiration, heart rate and blood pressure, and blood pressure and respiration could be<br />

quantified and helped in understanding the various coupling effects between various<br />

systems inside the body.

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