<p>Cardiac catheterization has for a long time been a valuable way to evaluate the hemodynamics of a patient. One of the benefits is that the entire blood pressure waveform can be recorded and visualized to the cardiologist. These measurements are however disturbed by different phenomenon, such as respiration and the dynamics of the fluid filled catheter, which introduces artifacts in the blood pressure waveform. If these disturbances could be removed, the measurement would be more accurate. This report focuses on the effects of respiratory artifacts in blood pressure signals during cardiac catheterization. </p><p>Four methods, a standard bandpass filter, two adaptive filters and one wavelet based method are considered. The difference between respiratory artifacts in systolic and diastolic pressure is studied and dealt with during compensation. All investigated methods are implemented in Matlab and validated against blood pressure signals from catheterized patients. </p><p>The results are algorithms that try to correct for respiratory artifacts. The rate of success is hard to determine since only a few measured blood pressure signals have been available and since the size and appearance of the actual artifacts are unknown.</p>

Cardiac catheterization has for a long time been a valuable way to evaluate the hemodynamics of a patient. One of the benefits is that the entire blood pressure waveform can be recorded and visualized to the cardiologist. These measurements are however disturbed by different phenomenon, such as respiration and the dynamics of the fluid filled catheter, which introduces artifacts in the blood pressure waveform. If these disturbances could be removed, the measurement would be more accurate. This report focuses on the effects of respiratory artifacts in blood pressure signals during cardiac catheterization. Four methods, a standard bandpass filter, two adaptive filters and one wavelet based method are considered. The difference between respiratory artifacts in systolic and diastolic pressure is studied and dealt with during compensation. All investigated methods are implemented in Matlab and validated against blood pressure signals from catheterized patients. The results are algorithms that try to correct for respiratory artifacts. The rate of success is hard to determine since only a few measured blood pressure signals have been available and since the size and appearance of the actual artifacts are unknown.

The use of Electroencephalograms (EEG) are essential to the analysis of sleep disorders in patients. With the use of electroencephalograms, electro-oculograms (EOG), and electromyograms (EMG), doctors and EEG technician can make conclusions about the sleep patterns of patients. In particular, the classification of the sleep data into various stages, such as NREM I-IV, REM, Awake, is extremely important. The EEG signal itself is highly sensitive to physiological and non-physiological artifacts. Trained human experts can accommodate for these artifacts while they are analyzing the EEG signal. <br /><br /> However, if some of these artifacts are removed prior to analysis, their job will be become easier. Furthermore, one of the biggest motivations, of our team's research is the construction of a portable device that can analyze the sleep data as they are being collected. For this task, the sleep data must be analyzed completely automatically in order to make the classifications. <br /><br /> The research presented in this thesis concerns itself with the <em>denoising</em> and the <em>feature selection</em> aspects of the teams' goals. Since humans are able to process artifacts and ignore them prior to classification, an automated system should have the same capabilities or close to them. As such, the denoising step is performed to condition the data prior to any other stages of the sleep stage neoclassicisms. As mentioned before, the denoising step, by itself, is useful to human EEG technicians as well. <br /><br /> The denoising step in this research mainly looks at EOG artifacts and artifacts isolated to a single EEG channel, such as electrode pop artifacts. The first two algorithms uses Wavelets exclusively (BWDA and WDA), while the third algorithm is a mixture of Wavelets and In- dependent Component Analysis (IDA). With the BWDA algorithm, determining <em>consistent</em> thresholds proved to be a difficult task. With the WDA algorithm, the performance was better, since the selection of the thresholds was more straight-forward and since there was more control over defining the duration of the artifacts. The IDA algorithm performed inferior to the WDA algorithm. This could have been due to the small number of measurement channels or the automated sub-classifier used to select the <em>denoised EEG signal</em> from the set of ICA <em>demixed</em> signals. <br /><br /> The feature selection stage is extremely important as it selects the most pertinent features to make a particular classification. Without such a step, the classifier will have to process useless data, which might result in a poorer classification. Furthermore, unnecessary features will take up valuable computer cycles as well. In a portable device, due to battery consumption, wasting computer cycles is not an option. The research presented in this thesis shows the importance of a systematic feature selection step in EEG classification. The feature selection step produced excellent results with a maximum use of just 5 features. During automated classification, this is extremely important as the automated classifier will only have to calculate 5 features for each given epoch.

The use of Electroencephalograms (EEG) are essential to the analysis of sleep disorders in patients. With the use of electroencephalograms, electro-oculograms (EOG), and electromyograms (EMG), doctors and EEG technician can make conclusions about the sleep patterns of patients. In particular, the classification of the sleep data into various stages, such as NREM I-IV, REM, Awake, is extremely important. The EEG signal itself is highly sensitive to physiological and non-physiological artifacts. Trained human experts can accommodate for these artifacts while they are analyzing the EEG signal. <br /><br /> However, if some of these artifacts are removed prior to analysis, their job will be become easier. Furthermore, one of the biggest motivations, of our team's research is the construction of a portable device that can analyze the sleep data as they are being collected. For this task, the sleep data must be analyzed completely automatically in order to make the classifications. <br /><br /> The research presented in this thesis concerns itself with the <em>denoising</em> and the <em>feature selection</em> aspects of the teams' goals. Since humans are able to process artifacts and ignore them prior to classification, an automated system should have the same capabilities or close to them. As such, the denoising step is performed to condition the data prior to any other stages of the sleep stage neoclassicisms. As mentioned before, the denoising step, by itself, is useful to human EEG technicians as well. <br /><br /> The denoising step in this research mainly looks at EOG artifacts and artifacts isolated to a single EEG channel, such as electrode pop artifacts. The first two algorithms uses Wavelets exclusively (BWDA and WDA), while the third algorithm is a mixture of Wavelets and In- dependent Component Analysis (IDA). With the BWDA algorithm, determining <em>consistent</em> thresholds proved to be a difficult task. With the WDA algorithm, the performance was better, since the selection of the thresholds was more straight-forward and since there was more control over defining the duration of the artifacts. The IDA algorithm performed inferior to the WDA algorithm. This could have been due to the small number of measurement channels or the automated sub-classifier used to select the <em>denoised EEG signal</em> from the set of ICA <em>demixed</em> signals. <br /><br /> The feature selection stage is extremely important as it selects the most pertinent features to make a particular classification. Without such a step, the classifier will have to process useless data, which might result in a poorer classification. Furthermore, unnecessary features will take up valuable computer cycles as well. In a portable device, due to battery consumption, wasting computer cycles is not an option. The research presented in this thesis shows the importance of a systematic feature selection step in EEG classification. The feature selection step produced excellent results with a maximum use of just 5 features. During automated classification, this is extremely important as the automated classifier will only have to calculate 5 features for each given epoch.

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