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njit-etd2003-081 - New Jersey Institute of Technology

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171<br />

5.2.3 Time-Frequency Analysis (Wavelet) <strong>of</strong> COPD HRV data<br />

In order to analyze COPD HRV signals, it was necessary to use digitized HRV data sets.<br />

One example <strong>of</strong> the digitized HRV signals is from a COPD subject resting and pacedbreathing<br />

at 16 breaths per minute. Figure 5.11 illustrates the HR IIBI and its power<br />

spectrum plots for the case <strong>of</strong> a file from a COPD subject paced breathing at 16 bpm<br />

during a 5 minutes rest period. The HRV analysis was performed using the five different<br />

wavelet distributions (Morlet, Meyer, Daubechies 4, Mexican Hat and Haar) with the<br />

same specifications (length <strong>of</strong> analysis window equal to 200 and the length <strong>of</strong> the FFT<br />

analysis <strong>of</strong> 256).<br />

Figure 5.11 HR IIBI and power spectrum <strong>of</strong> a COPD subject at rest breathing at 16 bpm.<br />

There are an infinite number <strong>of</strong> possible functions that satisfy the criteria for a<br />

wavelet. For a function to be a wavelet, it must integrate to zero and must be localized in<br />

time. These requirements are shown in equation form below:

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