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3 Journal of Medical Informatics & Technologies

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Measurements of blood saturation inside a ventricular assist device

Mocha J., Czerw M., Sobotnicki A.

Journal of Medical Informatics & Technologies

2012

Vol. 19

93--99

Information about the level how well arterial blood is saturated with oxygen, i.e. the overall patient saturation, in particular a patient with a ventricular assist device (VAD) inoculated, is very important for efficient and dependable course of blood circulation support. The paper presents the method for measurement of blood saturation with oxygen that is carried out with use of a commercially available pulse oximetric sensor upon necessary modifications and installed directly on a outflow connector of the VAD. Operability of the presented solution has been verified by experiments on a flow control test bench with use of animal blood. The final validation of the measuring circuit was carried out during experiments with an animal. The completed experiments demonstrated that both the blood saturation with oxygen as well as artificial pulse rate can be measured with accuracy. Unfortunately, similar measurements for venous blood proved infeasible.

Evaluation of volumetric parameters of the ventricular assist device using bioimpedance method

Sobotnicki A., Pałko T., Mocha J., Czerw M.

Journal of Medical Informatics & Technologies

2012

Vol. 19

117--123

Volumetric parameters of operation of the pulsatile ventricular assist device (VAD) are the key clinical indicators for the evaluation of adequacy of the process of mechanical heart assistance and ensuring the patient's safety. The bioimpedance method has been proposed to evaluate blood volume changes of the VAD. The method is based on volume electric conductivity of the blood. A change in VAD volume involves changes in impedance. Periodic changes in VAD volume during its operation result in a pulsatile impedance wave; its amplitude in the subperiod of filling and ejection correlates with the volume of blood in the VAD. The paper presents the way of acquisition of the bioimpedance signal. It also presents the results of experimental studies, that were carried out with the use of the flow test stand, and an approach to analysing the bioimpedance signal to evaluate the stroke volume.

Measurements of blood pressure inside a ventricular assist device

Mocha J., Sobotnicki A., Czerw M.

Journal of Medical Informatics & Technologies

2011

Vol. 17

287--293

Information about blood pressure at the inflow and outflow connectors as well as inside a Ventricular Assist Device (VAD) supplemented with information about pressures inside the pneumatic part enables to adjust operational parameters of the VAD in the optimum manner. Practical implementation of a method that makes it possible to measure blood pressure at plurality of points is a really sophisticated task in terms of technical and technological issues. On one hand it is mandatory to assure appropriate metrological properties of the entire measurement path, on the other hand the measuring transducers must be reliably separated from blood. Internal surfaces of these VAD parts that come in direct contact with blood must be smooth and uniform; it is extremely essential due to a risk of blood coagulation on any unevenness of surfaces. The paper presets the solution for measurements of blood pressure inside the VAD, where the suggested solution meets the assumed metrological criteria as well as very stringent safety requirements.