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njit-etd2003-081 - New Jersey Institute of Technology

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135<br />

BP power spectrum. This graph in addition to graphs <strong>of</strong> the heart rate power spectrum,<br />

the raw BP signal, and the BP IBI were displayed on the control panel. In addition to<br />

the graphical displays, the calculated values <strong>of</strong> the LF area, the HF area, and the length<br />

<strong>of</strong> the data file in minutes could be found on the control panel. Because <strong>of</strong> its interactive<br />

nature, the program allowed for adjustment <strong>of</strong> sampling frequency as well as the upper<br />

and lower bounds for the VLF, LF, and HF ranges.<br />

4.2.4 Coherence and Weighted Coherence Analysis <strong>of</strong> Heart Rate and Respiration<br />

The coherence and weighted coherence analysis between heart rate and respiration were<br />

performed using the coherenc.vi <strong>of</strong> LabVIEW. Again, the physiological signals were<br />

read from a spreadsheet file (Read From Spreadsheet File.vi) as consecutive, space<br />

delimited data columns, where one column consisted <strong>of</strong> the raw ECG signal and the<br />

other column consisted <strong>of</strong> the raw respiration signal. Each signal was independently<br />

analyzed and displayed on the control panel. The raw ECG signal was again passed<br />

through a high-pass filter (HP_FILT.vi) and successively into peak detection (Search<br />

(BP).vi) and correction (Correct.vi) blocks. The user then manually detected and<br />

corrected the bad or missing R peaks as before to generate the IIBI array. This IIBI<br />

array just obtained from the detection and correction <strong>of</strong> the raw ECG was then input<br />

together with the filtered raw respiration signal into the coherenc.vi where the power<br />

spectra and cross-power spectrum <strong>of</strong> the ECG IIBI and the raw respiration signal were<br />

calculated. From these power spectra a coherence plot between the derived heart rate<br />

and respiration was generated and the weighted coherence value was calculated. Two<br />

movable cursors on the coherence plot allow the user to selectively choose and obtain a

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