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K Hoeland

Publications and source records attributed to K Hoeland.

3 recordsLinked to original sources
PubMed2004

Mechanical and optical characteristics of a new fiber optical system used for cardiac contraction measurement.

In order to obtain a better physiological performance and a closer restoration of the regular rhythm of failing hearts, a new fiber optical sensor system for the measurement of cardiac contraction has been developed. It consists of an opto-electrical unit and a sensing fiber which has to be positioned in the heart. The objective of this new fiber optic sensor system is to use the inotropic information to adjust a stimulation algorithm in single or multichamber pacing or to detect arrhythmia in insufficient heart function. In this study, the mechanical and optical characteristics of different fibers are investigated. The relationship between the attenuation (with an achieved numerical maximum of 0.3 dB), the bending diameter and the angle of bending is determined in a range of 20-160 mm. The most suitable fiber for the application in cardiological problems is determined (WT8 fiber), for which the sensitivity is analyzed. Additionally, power spectra are calculated from WT8 fiber signals obtained from pig hearts, working under physiological conditions. The maximal frequency response was 23 Hz. It is concluded that the fiber optical measurement of cardiac contraction is not only feasible and reproducible, but the WT8 fiber also shows optimal behavior in the range of parameters occurring in the heart chambers. Nevertheless, in order to restrict the measured signal reliably to bending processes within the chambers only, it is concluded that a special combined fiber has to be constructed with a high sensitivity only at its terminal section within the heart.

Algorithms↗
PubMed2002

New sensor based on fibre optics for measurement of heart movement.

Innovative fibre-optic sensor technology for measuring the movement of the myocardial walls, and from this the heart chamber volumes, was developed. An optical fibre, with a mirror at its end, is inserted into a catheter located in the heart. An opto-electrical control unit positioned outside the heart contains both the light source and the signal receiver. It generates and couples the light into the fibre and transforms and analyses the reflected signal. With such a system, the movement of the cardiac wall can be continuously measured during each cycle, because the fibre moves synchronously with the heart, and this movement bends the fibre, changing the optical attenuation. Experiments where the fibres were wound around metal cylinders of different diameters revealed a maximum sensitivity of 4% mm(-1), diameter. The noise signal corresponded to about 1% of the diameter. First tests in a working pig heart showed a high correspondence of the fibre signal with cardiac parameters. Although these tests are promising, further long-term, extensive experiments in preclinical test devices, and later in clinical tests, must be carried out before the new sensor is used in clinical practice. The fibre-optic technique could be used in monitoring devices, assist devices, pacemaker systems or cardioverter defibrillators.

Animals↗