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The Role of the Biomedical Engineer in the Clinic

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Friedrich Kaufmann
German Heart Institute
Berlin, Germany

Hospitals employ a wide variety of engineers to guarantee the smooth day-to-day running of patient care, diagnostics and treatment - from building services engineers to electrical engineers, IT engineers, medical technology engineers, and so on.

Of course, physicians too are skilled in the use of their specialist equipment: the echocardiography specialist is familiar with the features and the technology of his Doppler device. Company technicians are there to provide any additional tool, knowledge or help required. The unique role of the biomedical engineer is to form an interdisciplinary link between the physician and his respective technical environment. Ventricular assist device (VAD) implanting centers have a particular need for biomedical engineers. During implantation of the device, the VAD companies' clinical support specialists provide help in setting up the system and offer in-service training and troubleshooting courses. Engineers and field support technicians are also available for special diagnostics and repair procedures. So what exactly is the role of the biomedical engineer in the clinic?

The following commonly used diagram published by the American Heart Association displays the structure of a VAD team. It places the patient at the center, surrounded by clinical specialists - heart surgeons, cardiologists, physical therapists, psychiatrists and also nutritionists and social workers.

links imageA key position is assigned to the VAD coordinator, who frequently has a nursing background. In this diagram "other specialists as needed" support the VAD coordinator's team. The biomedical engineer is one of these specialists, although he should really be seen as part of the VAD coordinator's team. The VAD coordinator's tasks can be described as interdisciplinary, because the treatment of a VAD patient touches on and includes several disciplines ranging from administration to nursing (wound care) to the technical monitoring of both the patient and the device, and also research activities.

The key tasks of the biomedical engineer within the VAD team are: the diagnosis of VAD-related problems, the development of mitigation strategies and the analysis of the course and outcome of these problems. The results of these analyses must be communicated to the state authorities and should be discussed with the VAD manufacturers so that any weak points of the particular system used can be identified and addressed.

The work of the VAD coordinator is guided by a general principle: the aim to improve the quality of life of VAD patients, both today and in the future, by recognizing any non-optimal situation and developing strategies to improve it. This requires a deep understanding of the functionality of a VAD system and the interdependencies between the device and the patient (hemodynamics, circulatory regulation, coagulation system etc.) which may have an impact on its operation. Only then can strategies be developed which are likely to help in the particular case at hand and in future similar situations.

If an irregular function of the VAD system occurs, the bioengineer has to think ahead, learning from this acute situation how he can improve his response to future occurrences of the same type, and always keeping in mind how they might be avoided by recognizing telltale signs.

Even performing routine work such as the daily check-up on a VAD patient and their VAD system or teaching the patient how to react in emergency situations may lead to new knowledge which has to be thought over, discussed and communicated.

This "modus operandi" facilitates continuous advancement through the accumulation of experience and knowledge gained in daily practice—from the diagnosis and treatment of problems to the recognition and response to alarm situations.

So, do all VAD-implanting centers need a biomedical engineer in their VAD team? The routine work is, of course, done by the VAD coordinators who generally do not come from an engineering background but are highly experienced in their own professional field. Recognition of the direct results of any change in therapy, treatment, or parameter settings is the most valuable source of information to which only the clinical researcher has access. This extends to investigating pathology findings following complicated or catastrophic courses but successful clinical courses with no adverse events, e.g. post-transplantation or explantation of the device after weaning, are also examined. But the biomedical engineer is in a unique position to suggest how the technical features of existing VAD systems can be improved based on the clinical experience collected from the day-to-day lives of VAD patients which can neither be anticipated nor investigated in studies or trials of test bench setups.

The biomedical engineer is also an important partner for VAD manufacturing companies. VAD manufacturers can develop new devices by refining today's systems and drawing on past experience with earlier generations of devices but, unlike the clinician, they are not in a position to make a direct comparison with competing companies' products, which can provide insights that lead to the best technical solution.

From the perspective of patient support, the biomedical engineer is an asset to any VAD team, even in small VAD implanting centers. However, not least for financial reasons, engineers are mostly found in high volume centers, usually where the hospital cooperates closely with the life sciences faculties of the affiliated university.

The following example from my clinical practice may help to illustrate the biomedical engineer's field of activity: After the introduction of the HeartWare HVAD—currently the most frequently implanted device—we were confronted with several thrombosed pumps that had to be exchanged. In some instances, when the patients were readmitted to the hospital with severe signs of pump thrombosis such as high levels of hemolysis and increased power consumption, the sound of the running pump was perceived as having an additional rumbling noise. This alone, of course, cannot qualify as a new parameter indicating the need for pump exchange. But it shows that the analysis of the sound emitted by the pump can be useful to determine the state of the pump.

This is where the engineer enters the scene: merely recording the sound would not serve the purpose of finding markers indicating some abnormal operation of the pump. We needed equipment that would not only record the sound but also provide a means of signal processing, such as fast Fourier transformation (FFT), for spectral analysis.

Once in possession of the right equipment, we were able to compare a large amount of data from smoothly running pumps with data from pumps in which ingested particles had led to the well-known signs of thrombosis, mainly elevated power consumption and increased hemolysis. The bioengineer's interdisciplinary skills were required not only to detect peculiar patterns or significant changes in the acoustic spectrum, but also to understand the mechanism behind these observations in order to develop a standardized method.

To be specific: in case of an ingested particle, a sound peak is excited with the exact threefold frequency of the rotational speed of the pump. This is produced by eccentric rotation of the impeller caused by the imbalance of the added mass of the thrombotic particle on it. Every time the deflected part of the impeller sweeps over one of the electromagnetic coils driving the pump it will be pulled to the center by its electromagnetic force. This produces a kind of wobbling of the rotor with the threefold rotational frequency, because the pump is driven by three sets of magnetic coils.

Not only is the acoustic method useful for confirming pump thrombosis when other clinical signs are inconclusive, it is also a reliable indicator of the absence of thrombi inside the pump. Furthermore, it is a quick method for validating the success of lysis therapy and can be used to support decision-making on whether administration of the lytic agent should be prolonged.

Today, acoustic analysis is used in our outpatient department as a routine surveillance method. If pump thrombosis is suspected, the decision on pump exchange or lysis therapy will be made by VAD physicians and surgeons depending on the engineer's analysis of the state of the pump.

From our point of view, engineers should be actively involved in the clinical management of VAD patients and employed in centers performing regular LVAD implantation leading to a cumulative number of more than 50 patients.

Disclosure Statement: The author has no conflicts of interest to report.

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