Biomedical subjects

C Nix

Publications and source records attributed to C Nix.

6 recordsLinked to original sources

PubMed2002

[Heart assist systems with integrated microsensors (HIM 2)].

The use of intracardiac pump systems is leading to more physiological support for coronary surgery patients. But the currently available micro blood pump with an integrated micro pressure sensor and an outer diameter of 6.5 mm is not suitable for a transfemoral placement of the device. Therefore a significantly smaller pump with an outer diameter of 4 mm (12F) is been developed and tested. To transfer the sensor technology in this, for the first time the MID (moulded interconnected device) technology is applied in a medical device. In a first step MID is used to integrate a smaller pressure sensor on the existing blood pump. The result should help to find a new packaging and connecting solution for integration of the miniaturized sensor on the 4 mm pump.

Assisted Circulation↗

PubMed2001

From a lab type to a product: a retrospective view on Impella's assist technology.

A lab type is best described by its value as a result of its handcrafted uniqueness in small numbers. Logically, there is not one lab type like another, and the fact that it has been realized does not mean that this special effort can be easily reproduced. Furthermore, most lab types have undergone stand alone test runs revealing fingerprints rather than universal results at a 20% effort to 80% effect ratio. A product development, on the other hand, is best described by an 80% effort to 20% effect ratio in terms of measurable results. Products are producible and cost effective goods which are well documented and have undergone numerous test runs and test procedures assuring safety and quality, a basic requirement for market approval and cost effective marking. Based on the intravascular pump technology, comprising a sensorized axial flow pump with an integrated micromotor, the iterative dependence of the product development on lab types is demonstrated showing in particular the importance of having highly developed lab types before initiating the product development. By example, we demonstrated that high product quality has a greater impact on the reduction of blood damage than numerous redesigns. Reengineering issues are addressed, which are part of the product development process. Furthermore, the previously mentioned technology serves as a platform leading directly from the perioperative biventricular system to a 7 day pump as well as a miniaturized 12 Fr version.

Animals↗

PubMed1997

The implantable fuzzy controlled Helmholtz-left ventricular assist device: first in vitro testing.

To perform first experimental tests for validation of a new left ventricular assist device (LVAD) with a high efficiency energy converter, a new pump design and a novel type of perfusion control, a functional labtype, were manufactured. With a stroke volume of 65 ml, a total pump housing volume of 450 ml (including valves and connectors), and a weight of 430 g, it is one of the smallest and lightest implantable pulsatile electromechanical LVADs. Pulsatile operation is generated by a special reduction and displacement gear which transforms a uniform rotational movement of a sensorless, electronically commutated DC motor into a translatory pusher plate movement. A prolonged duration for filling (60% of the cycle time) supports full-empty pumping and consequently a high overall pump efficiency. Active adaptation of output flow to organ perfusion demand is achieved by changing the rotational speed of the motor by means of a sensorless fuzzy controller, which detects preload and afterload induced effects at the motor current input. First in vitro test results obtained within a circulatory mock loop that simulates physiological preloads and afterloads are presented. They comprise preload sensitivity and the function of the novel perfusion controller as well as preload and afterload related flow data. The results prove the feasability of the energy conversion with the novel gear and control concept for an implantable electromechanical pulsatile LVAD.

Animals↗

PubMed1995

Fuzzy control concept for a total artificial heart.

The development of an electromechanically driven total artificial heart (Helmholtz-TAH) was initiated in 1990. Anatomical fitting, biocompatibility, and automatic physiologic adaptation of pump output are the basic requirements that characterize the overall TAH concept. For evaluation of these features, a TAH labtype was developed. It provides most features of the conceptual artificial heart and supports in vitro testing of energy conversion, pump behavior, structural parts, sensors, and control concepts. A fuzzy controller has been implemented for adaptation of the pump rate to body perfusion demand by left pump chamber filling detection. This controller will be an important element of a future extensive TAH control system. The implementation is supported by a professional fuzzy control development tool that allows on-line and real time optimization of control strategies for dynamic processes. The first experiments proved the feasibility and the advantages of this fuzzy control concept. The first in vitro test results are presented.

Fuzzy Logic↗

PubMed1983

"Own view" versus "good view" in a perspective-taking task.

Children who fail spatial perspective-taking tasks of the "3 mountains" variety apparently preferentially select pictures showing their own view. It has been suggested that this might arise, at least in part, because children in such tasks have been given particularly good views of the arrays. To test this, an experiment was conducted with 40 4-6-year-olds in which children were tested from both "good" and "poor" viewing positions. As hypothesized, children did not show any bias toward their own view when it was a poor one. However, when they themselves had a good view of the objects, they chose their own rather than another equally good view. Thus, 2 selection principles appear to operate hierarchically, selection of good view having priority over selection of own view.

Child↗

PubMedDate not supplied

A novel implantable electromechanical ventricular assist device. First acute animal testing.

A novel ventricular assist device (HIA-EMLVAD-AT1, Helmholtz Institute Aachen-Electromechanical Left Ventricular Assist Device-Animal Test Version 1), driven by a uniformly and unidirectionally rotating actuator and a patented hypocycloidic pusherplate displacement gear unit, was developed and tested in an acute animal experiment. The excellent free filling behavior of the pump chamber with a stroke volume of 65 ml is obtained by a 2:3 ejection-filling time relationship. The uniform motor rotation facilitates simple sensorless pre and afterload detection by motor current analysis. In contrast to common apical cannulation, the inlet cannula was placed via the left atrium through the mitral valve into the left ventricle. This connection mode is preferable for left ventricular recovery and preservation. Left atrial, left ventricular, and aortic pressure curves, as well as pulmonary artery flow data, were obtained. The data show very effective unloading of the natural ventricle and demonstrate the feasibility of this novel assist device. Directions for further improvement of technical features were also identified.

Animals↗