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ABSTRACT: A measurement technique for evaluation of processes occurring in the myocardium during blood flow arrest is presented. The system is devoted to monitoring the myocardium state during off-pump coronary artery by-pass grafting, i.e. during a surgical operation performed on a beating heart. A substantial part of the system is a probe whose construction is similar to a mechanical stabilizer. Such a stabilizer is used for preventing the myocardium from moving, thus it enables stitching of the graft and artery. In comparison to the commercially available stabilizer the developed probe is enhanced with a set of electrodes. These electrodes enable simultaneous measurements of impedance and electrograms. Examples of recordings made during in vivo studies are also presented. Thus, the proposed method is applicable and potentially very useful in clinical practice.
Physiological Measurement 07/2008; 29(6):S393-405. · 1.68 Impact Factor
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ABSTRACT: Originally, tissue stabilizer has been developed by Medtronic, Inc. It is used to prevent a certain part of myocardium from moving. For example, such an approach is utilized during Coronary Artery Bypass Grafting (CABG). Moreover, medical procedures during such operations involve blood arrest, thus, potentially may involve ischemia of myocardium. A construction of the modified tissue stabilizer used during surgery on a beating heart is presented in the paper. We have developed a stabilizer that aside preventing part of myocardium from moving enables recording of epicardial electrograms. Four electrograms are recorded simultaneously together with one lead of standard ECG as a reference signal. Time relations between electrograms, recorded at four different points surrounding potentially ischemic area, are strongly modified by processes triggered by myocardium ischemia. Aside a construction of the stabilizer the associated measurement system is also presented. Measurement properties of the developed stabilizer and measurement system have been examined during tank studies. Finally, the waveforms obtained during in vivo study are also presented.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:2936-9.
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ABSTRACT: This paper presents the construction of a six-ring probe for monitoring immittance changes. The spatial sensitivity of the probe is defined. This is used to examine the uniqueness of the probe in terms of its application to monitoring conductivity changes. A spatial distribution of the sensitivity is presented for isotropic and anisotropic cases. The latter case is restricted only to anisotropy met when measuring muscles, i.e. diagonal anisotropy. Theoretical calculations performed using the finite element method were verified experimentally using a specially developed measuring system. An example of in vivo measurements is included.
Physiological Measurement 05/2005; 26(2):S69-79. · 1.68 Impact Factor
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ABSTRACT: The paper considers the contribution of conductivity changes undergone in an anisotropical medium to measured resistance. This was achieved by extending the relationship proposed by Geselowitz to anisotropical materials described, therefore, by a conductivity tensor. It was found that each element of a conductivity change tensor contributed to the measured resistance only if a corresponding component of the electrical field was nonzero. Numerical calculations were performed for blood-flow-associated conductivity changes. A special experiment stand was developed which allowed experiments to be performed proving the theoretical results. It was found that the absolute value of resistance change measured in the direction perpendicular to the vessel axis was much smaller than that measured along the vessel axis. The results obtained may explain the fact that the actual change of measured resistance created by changes of conductivity induced by aortic blood flow is lower than expected from simplified models.
IEEE Transactions on Biomedical Engineering 02/2005; 52(1):41-9. · 2.28 Impact Factor
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ABSTRACT: This paper considers the applicability of effective conductivity measurements for monitoring physiological and/or pathological phenomena induced by ischemia in the myocardium. The sensitivity of a probe, calculated by means of the finite element method, to changes in the conductivity of the tissue examined is defined for this purpose. Probes developed by Schafer and collaborators (1995) and in our own departments have been examined on the basis of this sensitivity. Theoretical results were verified experimentally using a tank, enlarged models of the probes, and a specially developed electronic circuit. It follows from this study that the probe developed by Schafer et al. is characterized by positive and negative sensitivity. This can lead to misinterpretation of the measurements obtained. In contrast, the sensitivity of our probe is dominantly positive. An example of the in vivo result obtained during experimentally induced ischemia in a swine heart is included.
IEEE Transactions on Biomedical Engineering 04/2002; 49(3):240-6. · 2.28 Impact Factor
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ABSTRACT: The paper introduces a project conducted to create a complex human computer interface based on restricted head movements, eye blinks and the wrist rotation.
