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theses

The method of obtaining blood pressure with the use of a mercury sphygmomanometer, or the generic ‘cuff,’ is inaccurate, time-consuming, uncomfortable, lacks pulse waveform data and is not continuous. With these factors considered, the universal method for taking blood pressure yields unreliable measurements that put patients at a higher risk of misdiagnosis.

In this thesis, we introduce the Continuous Non-Invasive Blood Pressure Sensor (CNIBP), a cuffless blood pressure sensor. This new sensor incorporates the recent method of partial applanation tonometry as an alternative to CNIBP. Partial applanation tonometry is a method that determines blood pressure by means of converting arterial contact force, deflection and area to pressure. In this case, the radial artery is flattened using the CNIBP which provides the subject with a continuous arterial pressure waveform. Therefore, a thorough system to measure blood pressure is established.

In prior experiments, utilizing this method, failure to reproduce a computational method indirectly led to a downfall in the functionality of the sensor. In addition to this, a non-deflection corrected calibration method showed to have a higher percentage of error when compared to our deflection corrected method. In the addressed experiment presented in this thesis, the use of raw data through an algorithm built into Matlab achieves to establish a pressure-area-deflection relationship, which results in accurate blood pressure pulse waveforms. Using this innovative calibration, we are able to retrieve values of force, in units of volts, from the arterial tonometer which are then easily converted into the common unit of blood pressure, millimeter of mercury (mmHg). In this research, the partial applanation tonometer pressure readings were compared with those from an automatic cuff pressure monitor.

It was found that continuous pressures and pulse waveforms are retrieved in about one-fourth of the time of the generic cuff. In the comparison of systolic pressures, it was established that continuous systolic blood pressure values are not statistically different than the cuff blood pressure. As compared to the cuff, our errors were less than +/- 20 mmHg. These adjustments resulted in an overall, average blood pressure error of less than 5% when compared to the cuff and previous tonometer experiments expressing similar methods.

We can conclude that our partial deflection tonometer is capable of providing blood pressure accuracy comparable to the standard occlusive cuff monitor. At the same time, our device provides faster readings along with complete pulse waveform information in a continuous manner.

ETD_10843

M.S.

Includes bibliographical references

doi:10.7282/t3-v2a3-fh48

ETD graduate

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