Omar Abdallah

Adaptive Filtering by Non-Invasive Vital Signals Monitoring and Diseases Diagnosis

The reliability, reproducibility and accuracy of in-vivo measurements are of great importance and have to be thoroughly studied and to a great extend achieved. Reproducibility problems may result from the electronic components of the applied devices and the variability of measured variables as well as noise sources. The inaccuracy is caused by the approximation in the calculations or the used methods and by diverse sources of errors resulting from the subject under considerations and its surroundings. In sensible measurement like blood components, the positioning of the measuring sensor as well as the variation in the applied pressure and the characteristics of contact area between sensor and skin have a great effect on the accuracy and reproducibility of the measurements. The ambient noise like high frequency and line frequency (50 or 60 Hz) noise can be filtered by the detected biosignals like Photoplethysmogram (PPG) using the conventional analog or digital filters without a great effort. The motion artifact of the subject caused by him as well as by physical motion of body parts or by the surrounding has a varying frequency which may have the same range of the signal frequency. It is difficult to filter noise from these signals, and errors resulting from filtering can distort them. Usually physicians are misled by these noisy signals and the analysis can go wrong. An adaptive filter is essential by biosignal and bio-image processing for noise cancellation without destroying or manipulating the valuable detected information. Biomedical signals such as photoplethysmogram (PPG) (Figure 1), electrocardiogram (ECG), electroencephalogram (EEG), electromyogram (EMG) and impedance cardiogram (ICG) are very important in the diagnosis of different pathological variations. By the detection of these bio-signals as well as by the further derived parameters like oxygen saturation by pulse oximeter, the motion artifact is a great challenge, which may lead to erroneous results or even no results can be delivered [Lee]. The effectiveness of ECG monitors can be significantly impaired by motion artifact, which can cause misdiagnoses, lead to inappropriate treatment decisions or trigger false alarms. However, it is difficult to separate the noise from bio-signal due to its frequency spectrum overlapping that of the ECG. A portable ECG recorder using accelerometer based on motion artifact removal technique will be a great help for patients for tele-homecare or ambulatory ECG monitoring.

Signal Processing by Reflectance Pulse Oximetry for Monitoring the fractional Oxygen Saturation and the Detektion of Anemia

A hazardous pitfall among the deficiencies of currently used pulse oximeter is that carboxyhemoglobin (COHb) and methemoglobin (metHb) concentrations can not be detected. This leads to erroneous measurement of oxygen saturation in case of carbon monoxide poisoning and methemoglobinemia. Also the total hemoglobin concentration - which can only be measured in-vitro up to now - will not be considered. Another pitfall of transmission pulse oximetry is that it will not be able to give any result for low perfusion of tissue. To overcome these shortcomings a new non-invasive reflectance pulse hemometer is designed to measure the hemoglobin concentration and the actual oxygen saturation (SaO2) considering the concentrations of COHb and metHb. Light emitting sources with different wavelengths and a photodiode (PD) as a light detector are used. We will show in this article the signal processing of the reflected light detected by the photodiode using a modified Lambert-Beer law. A brief comparison with other possible methods like photon diffusion theory will also be given. The sensor has to be applied primarily at forehead or at other better perfused locations of the body. First measurements with this sensor have shown promising results for this non-invasive method to detect hypoxia “whatever its causes” and anemia even in case of low tissue perfusion.

New Estimation Approach for Total Hemoglobin Concentration Based on a Fuzzy Expert System

Indeed, special emphasis is put on the optical methods as an aid tool to measure the total hemoglobin (THb) concentration which is one of the most frequently ordered laboratory measurements. The estimation approach is considered the cornerstone of those methods. We propose a new intelligent approach based on a fuzzy expert system that depends on Wang-Mendel method to generate a fuzzy rule-base. Real input-output data pairs were accurately measured to build that rule-based system, where each pair represents a different expected case. The inputs were six values of the light intensity with different wavelengths that were measured by the optical stage of a new THb concentration measuring device and also the value of the oxygen saturation (SpO2). The output values are measurements of the total hemoglobin concentration of an accurate reference laboratory. The capabilities of the developed fuzzy expert system are tested for estimating the total hemoglobin concentration over a wide range of cases by means of the root mean square (RMS) error and the correlation values. The RMS error’s value was 1.24 g/dl and the correlation value was 0.977 which indicated that the estimated THb concentrations using the proposed approach were highly correlated to the reference laboratory measurements.

Photoplethysmogram Signal Conditioning by Monitoring of Oxygen Saturation and Diagnostic of Cardiovascular Diseases

High performance biosignal preparation for the noninvasive diagnosis of diseases or calculation of physiological parameters is a very important task. High resolution and high signal noise ratio have to be achieved by the hardware design using a high resolution ADC and a PGA with the desired filters. After the detection of the signals by the calculation units (MC, DSP and PC) the signal conditioning will be continued. When the signal is measured, it is subjected to noise of different sources that has to be canceled at the first step. The motion artifacts by photoplethysmogm (PPG) are very difficult to eliminate with conventional filters. The frequency of the resulting noise signal has the same range of that of the PPG signal. Therefore, we use an adaptive filter using least mean square method (LMS) for this purpose. The second stage is the extraction of the distinctive features or characteristics of the filtered signal. One of the parameters values is the detection of peaks and valleys of the PPG signal. These parameters are used for the calculation of the heart rate, oxygen saturation and the hemoglobin concentration. Also other features like notch, the rise time from valley to peak and form of PPG have to be classified for the diagnostic of cardiovascular diseases. This paper describes an adaptive filter and a reliable peak and valley detection method used by the multisensor developed for monitoring of vital parameters and diagnosis of cardiovascular diseases. The proposed algorithms were applied to different PPG signals as will be discussed in the results.

ROBUST ESTIMATION APPROACH FOR A COMPACT HEMOGLOBIN COMPONENTS ANALYZER BASED ON FUZZY EXPERT SYSTEMS

The current invasive methods to determine the total hemoglobin concentration (tHb) and the four hemoglobin components fractions dissipate time and blood. Using a few drops of blood, a compact haemoglobin components analyzer can measure these physiological variables. This paper introduces a fast robust estimation approach, which considered the essential ingredient of the analyzer. It does not depend directly on the optical equations such as Lambert Beers law. Because using these optical equations includes defining some of unknown parameters that is considered the most difficult task. As a new trend and according to the general concept of the optical equations without defining any of their unknown parameters, the proposed approach is based on a unification of two fuzzy expert systems. One provides high interpretability and the other provides high accuracy. Wang-Mendel method and a new proposed modified one were used to generate a fuzzy rule-base with the aid of more than three hundred real measurements by the compact analyzer as well as a reference laboratory. The experimental results confirmed the effectiveness and the robustness of the developed whole fuzzy expert system for analyzing the total hemoglobin concentration and it`s four components ratios over one hundred and sixty different cases. The accuracy of the proposed approach was tested by means of Root Mean Square error (RMS) and Correlation (R) values. The RMS error of the tHb concentration was 0.82 g/dl and the correlation value was 0.98, which indicates that estimated values were highly correlated to the measurements of the reference laboratory.

Towards Noninvasive Monitoring of Total Hemoglobin Concentration and Fractional Oxygen Saturation Based on Earlobe Pulse Oximetry

Till now, there is no available device which can measure the total hemoglobin (THb) concentration and the fractional oxygen saturation (SaO2) noninvasively. Finger, earlobe, nose bridge clamp and forehead sensors have been already used to monitor the functional oxygen saturation of the hemoglobin. Earlobe sensor has a lot of advantages that make it attractive for measuring the hemoglobin concentration and the SaO2. The structure of earlobe enables the application of the theoretical discipline with smaller errors. This may enable the calculation of other blood constituents like glucose. Less disturbance of the patient is achieved for monitoring. In cases of low perfusion, the pulse wave velocity will be affected and the time delay problem will be appeared. But the time delay for the earlobe sensor will be stay smaller than the finger sensor. For motion artifact effect in ambulance overcoming, an adaptive filter is used for reliable measurements. The effect of the motion artifact on the earlobe sensor will be also smaller than on the finger sensor. For long time monitoring and for home use the earlobe sensor consumes less power than the finger sensor. Available reformed light emitting diodes (LEDs) with different wavelengths and especially in the infrared region, where the light absorption of tissue is too high, can be applied by the earlobe clip. The noninvasive measurements are based on the Photoplethysmography (PPG) signal which will be studied for the earlobe and the finger sensors under various conditions using Lambert Beer Law (LBL). The difficulties related to the calculations will be also discussed. The study reported that the earlobe sensor can be a suitable sensor under various conditions to calculate the THb concentration and SaO2.