Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 196-203).

Thesis (Ph. D.)--Northeastern University, 2008. / Title from title page (viewed April 28, 2009) Graduate School of Arts and Sciences, Dept. of Physics. Includes bibliographical references (p. 123-125).

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The research related to designing portable monitoring devices for physiological signals has been at its peak in the last decade or two. One of the main obstacles in building such devices is the effect of the subject's movements on the quality of the signal. There have been numerous studies addressing the problem of removing motion artifact from the electrocardiogram (ECG) and photoplethysmography (PPG) signals in the past few years. However, no such study exists for the Impedance Plethysmography (IP) signal. The IP signal can be used to monitor respiration in mobile devices. However, it is very susceptible to motion artifact. The main aim of this dissertation is to develop adaptive and non-adaptive filtering algorithms to address the problem of motion artifact reduction from the IP signal.

The pressure ulcer is a well-known clinical problem that has plagued many patients in acute-care hospitals and chronic-care facilities. The pressure ulcer has the potential to diminish the quality of a patient's life by hindering the person's physical and emotional well-being. In addition, pressure ulcers are a high-cost problem. Past studies have shown that costs related to the treatment of pressure ulcers have reached 1.335 billion dollars a year in the United States alone. A pressure ulcer is defined as a lesion created by unrelieved pressure, which causes tissue ischemia and subsequently damages the underlying tissue. This sequence of events is mainly centered on ischemia. Ischemia is a condition created by an insufficient flow of blood to an organ or part of an organ such as the skin. The outcome of ischemia is cell death at the tissue level, which is commonly termed necrosis. In the past, researchers employed several different non-invasive techniques in order to detect changes in the condition of human skin when blood flow was restricted. The two most commonly used practices were Laser Doppler Velocimetry and Continuous Wave Ultrasound. Laser Doppler Velocimeter is used to measure cutaneous blood flow in a study region. The moving red blood cells in blood vessels cause a Doppler shift of incident laser light, which correlates with the velocity of blood flow. Continuous Wave Ultrasound involves an ultrasound signal, which is transmitted into the skin. The change in frequency of the reflected signal with respect to the transmitted signal provides an indication of blow flow. The objective of this research was to examine a method for the detection of arterial blood flow, which utilized the 4-electrode sensor for the measurement of Tissue Impedance or the Bio-impedance method. The system developed, for the synchronous detection method, consisted of both analog hardware and software tools. The analog hardware utilized synchronous detection. The software monitored and performed mathematical operations on the retrieved data. The system developed during this research demonstrated the ability to measure the pulsatile impedance of the skin and present the results in a fashion useful to healthcare providers.

One countermeasure to cardiovascular spaceflight deconditioning being tested is the application of intermittent artificial gravity provided by centripetal acceleration of a human via centrifuge. However, artificial gravity protocols have not been optimized for the cardiovascular system, or any other physiological system for that matter. Before artificial gravity protocols can be optimized for the cardiovascular system, cardiovascular responses to the variables of artificial gravity need to be quantified. The research presented in this document is intended to determine how the artificial gravity variables, radius (gravity gradient) and lower limb exercise, affect cardiovascular responses during centrifugation. Net fluid (blood) shifts between body segments (thorax, abdomen, upper leg, lower leg) will be analyzed to assess the cardiovascular responses to these variables of artificial gravity, as well as to begin to understand potential mechanism(s) underlying the beneficial orthostatic tolerance response resulting from artificial gravity training. Methods: Twelve healthy males experienced the following centrifuge protocols. Protocol A: After 10 minutes of supine control, the subjects were exposed to rotational 1 Gz at radius of rotation 8.36 ft (2.54 m) for 2 minutes followed by 20 minutes alternating between 1 and 1.25 Gz. Protocol B: Same as A, but lower limb exercise (70% V02max) preceded ramps to 1.25 Gz. Protocol C: Same as A but radius of rotation 27.36 ft (8.33 m). Results: While long radius without exercise presented an increased challenge for the cardiovascular system compared to short radius without exercise, it is likely at the expense of more blood “pooling” in the abdominal region. Whereas short radius with exercise provided a significant response compared to short radius without exercise. More fluid loss occurred from the thorax and with the increased fluid loss from the thorax blood did not “pool” in the abdominal region but instead was essentially “mobilized” to the upper and lower leg. The exercise fluid shift profile presented in this document is applicable to not only artificial gravity protocol design but also proposes a mechanistic reason as to why certain artificial gravity protocols are more effective than others in increasing orthostatic tolerance.

Aptikus minimalius PAL simptomus, yra labai svarbūs diagnostiniai, greitai atliekami neinvaziniai tyrimo metodai (kulkšnies-žasto indeksas, nykščio indeksas, ėjimo testas, segmentinių slėgio gradientų matavimas ir kt.). Ambulatorinėje grandyje retai matuojamas kulkšnies-žasto indeksas riboja galimybę nustatyti PAL kiek galima anksčiau, numatyti galimas gyvybiškai svarbių organų kraujagyslines komplikacijas, laiku siųsti pacientą konsultuoti angiochirurgui. Mažai tyrinėtu alternatyvaus neinvazinio impedanso pletizmografijos tyrimu galima nustatyti ne tik periferinių arterijų ligos simptomus, bet vienu metu įvertinti eilę kitų parametrų. Darbo tikslas buvo nustatyti neinvazinio impedanso pletizmografijos metodo efektyvumą kojų arterinei kraujotakai įvertinti ir šį metodą palyginti su kitais neinvaziniais bei invaziniais diagnostikos metodais. Tyrimo metu nustatyta statistiškai reikšminga kulkšnies-žasto indekso bei impedanso pletizmografijos parametrų sąsaja pacientams, sergantiems lėtiniu prieširdžių virpėjimu, lyginant su pacientais neturinčiais šio ritmo sutrikimo, nustatyta impedanso pletizmografijos - bangos viršūnės laiko parametro sąsaja su angiografiškai aptikta kraujagyslės okliuzijos vieta. Pagrindinio impedanso pletizmografijos parametro (bangos viršūnės laiko) specifiškumas yra 96 proc., jautrumas – 73 proc. atsižvelgiant į KŽI pokyčius, o lyginant su angiografija – jautrumas 100 proc., specifiškumas – 50 proc. Taigi, neinvazinis impedanso pletizmografijos... [toliau žr. visą tekstą] / In cases of observing even the slightest PAD symptoms, rapid non-invasive diagnostic test methods become extremely important (the ankle-brachial index, thumb index, walking test, measurement of segmental pressure gradients, etc.). in an outpatient setting , the ankle-brachial index (ABI) is rarely measured, thus limiting the opportu¬nities for the earliest possible detection of PAD, prediction of vascular com¬plications of vital organs, and timely referral of the patient for a con¬sultation with an angiosurgeon. An alternative non-invasive test method of impedance plethysmo¬graphy, which has been little investigated so far, allows both detection of symptoms of peripheral arterial disease and concurrent assessment of a number of other parameters. The aim of the study is to assess the efficiency of a non-invasive method of impedance plethysmography in diagnosing arterial circulation disorders in the legs, and to compare this method with other non-invasive and invasive diagnostic methods of peripheral arterial disease. A significant correlation between the Ankle-Brachial Index and the im¬pedance plethysmography parameters was established in subjects with permanent atrial fibrillation, but not in subjects without this rhythm disorder. During the study, an obvious correlation between the Crest Time in¬ter¬val measured by the impedance plethysmography method and the vas¬¬cular occlusion site shown on angiography was established. Specificity of the impedance plethysmography... [to full text]

This Mater's thesis deals with the evaluation of pulse wave velocity using multi-channel whole-body impedance cardiography. Data were taken from the group of healthy volunteers whose impedance changes were measured during rest, respiratory maneuvers, tilt and stress exercise. The result of this measurement are values of peaks of pulse wave time shifts towards R-wave. The velocity values towards the thorax electrodes were recalculated on the basis of knowledge about the pulse wave time shifts and the distances from the heart to the scanned locations, which were measured using the arterial segment's lengths.