Biomedical Engineering

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BIOMEDICAL ENGINEERING

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Since the early 1960s biomedical engineering has transformed healthcare in industrialized countries, confronting healthcare professionals and the lay public with new problems, decisions, and possibilities. The need to understand those problems, decisions, and possibilities has contributed to the importance of bioethics in healthcare.

Biomedical Engineers and Biomedical Engineering

Biomedical engineers develop sophisticated quantitative methods of measurement and analysis for the diagnosis and treatment of health problems. Those methods typically draw on an understanding of various biomedical sciences, including normal and pathological physiology. For example, biomedical engineers use engineering methods to study the stresses and pressures in human joints so that they can develop replacements and study the mechanisms of cellular excitation and electrical propagation in tissue so that they can improve cardiac pacemakers. Their work includes the design, development, testing, and refinement of medical devices and procedures to prevent, diagnose, and treat trauma and disease. For example, biomedical engineers developed magnetic resonance imaging (MRI) not only as a new technique for noninvasive diagnosis but also to guide the treatment of tumors. Other biomedical engineers develop and oversee the manufacture, marketing, and maintenance of high-technology medical products.

In doing this work biomedical engineers collaborate with medical research investigators, healthcare providers, and other mechanical, electrical, chemical, aero/astro, and nuclear engineers. The collaborators often lack a biomedical background but may address special technical problems that arise in the design and development of medical products.

The devices that biomedical engineering makes possible vary from "smart" thermometers for home use to multi-million-dollar MRI equipment. Some biomedical devices come into direct contact with patients, becoming "the machine at the bedside" (Reiser and Anbar); other machines become part of the patient's body, such as cardiac defibrillators; these are new elements in the public's experience of healthcare.

Current Practices and Approaches

There are more than 3 million engineers in the United States, but engineering work is not well understood by the public, which often confuses the engineer who designs or develops a device with the technician who operates it or the skilled worker who assembles it. The most common, and mistaken, view of engineering in general and biomedical engineering in particular is that it entails only the application of science. This "applied science" model disregards the central place of design and synthetic or creative thinking.

Engineers invent, design, develop, and adapt devices, constructions, materials, and processes in response to human needs and wants. Their concern is the actual behavior of the objects and systems they study; that behavior results from many simultaneous influences, only some of which are the object of study in the natural sciences. Biomedical engineers, like other engineers, often enhance and extend the distinct body of knowledge known as engineering science.

In the early twenty-first century the dominant fields of engineering—mechanical, civil, electrical, computer, chemical, and materials—are based on the physical and mathematicalcomputer sciences. Biomedical engineering may draw on engineering knowledge from any of those fields to help solve health problems by using state-of-art technology. In being defined by an area of human concern—medicine—biomedical engineering is similar to another new field or area of engineering: environmental engineering.

Biomedical engineering has a somewhat different character within each of the established engineering fields. Electrical engineering informs the biomedical investigation of the bioelectric phenomena involved in nerve and muscle function and the designs of devices, such as pain-blocking stimulators and implanted electrodes, to aid hearing. Mechanical engineering illuminates problems in biomechanics, the large-scale and small-scale solid and fluid mechanics of the living body. Biomechanics leads to the production of devices such as artificial joints and has many of its applications in orthopedic surgery, physical therapy, rehabilitative medicine, and other empirical areas of healthcare. Advances in biomechanics include the investigation of cartilage at the cellular and subcellular levels and even at the molecular level.

Since the 1990s bioengineering as practiced by chemical engineers has been transformed by advances in molecular biology that have provided the theoretical and experimental basis for predicting how the human body will interact with nonhuman materials. It has produced major new tools, such as monoclonal antibodies. Therefore, molecular biology informs the design of devices in which there is dynamic exchange between human and nonhuman systems, for example, dialysis machines, heart-lung machines, artificial organs, and implants for the sustained delivery of medications. It also informs nondevice research areas such as therapeutic protein research and lends important techniques to tissue engineering: the use of engineering theory and methods to develop cell-based artificial organs. New skin for burn patients is the first of many therapies expected from tissue engineering.

Most biomedical engineers are employed outside healthcare facilities. However, a small percentage of biomedical engineers are "clinical engineers" who work in healthcare facilities and oversee the use, adaptation, integration, maintenance, and repair of an increasingly sophisticated array of devices. In rehabilitation technology, for example, "rehabilitation engineers" often collaborate in prescribing appropriate devices and designing unique devices for individuals.

Because cutting-edge technology often finds ready application in the development of military and medical devices, engineers who are attracted to such work may choose biomedical engineering as an alternative to military work. The desire to avoid military work may explain in part why the proportion of biomedical engineers in the United States who are women is high in comparison to the proportion in other engineering fields. The high proportion of women also may be due to women's interest in the helping professions, the relative openness of new fields to women, and the high rate of representation of women in the life sciences.

Collaborations between engineers and physicians in the United States highlight the cultural differences between those professions in this country. Although corporate management or "the market" may constrain engineering work, engineers thoroughly discuss and "brainstorm" how best to deal with all existing constraints. In contrast, physicians, especially surgeons and others who must make critical decisions quickly, are accustomed to unilateral decision making. Engineers often find the hierarchical organization and authoritarian practices of medicine perplexing and even counterproductive.

The naming of devices illustrates the dominance of medicine over engineering in collaborations on medical devices. Medical devices that are named for individuals (e.g., in orthopedic surgery the Harris hip and the Galante hip) bear the names of the physicians who collaborated on them or brought them into clinical use even when the design is largely the work of a single biomedical engineer. The influence of physicians on biomedical engineering in the United States is demonstrated further by the fact that theU.S. market for medical technologies, especially technologies used in healthcare facilities, is driven by physicians and the administrators of healthcare facilities. Even when U.S. physicians do not collaborate in design and development, their demands as major customers have a much greater effect on the design of biomedical engineering devices than do those of other health professionals. In contrast, in Sweden, where the healthcare system is government-sponsored, all the healthcare workers who are expected to use a device are involved in setting the requirements for the device to be designed or purchased.

Biomedical Engineering, Medical Technology, and Issues in Bioethics

One reason for the growing public interest in bioethics is the rapid change in healthcare practice that has resulted from biomedical innovation. The resulting technology has both desirable and undesirable effects as well as many effects that, although not clearly negative or positive, alter the responsibilities of professionals and laypersons in regard to birth and death, illness, and injury. As people confront new information and new possibilities, they are faced with difficult decisions that were unknown to previous generations. New biomedical technology forces people to become "moral pioneers" (Rapp).

There are several major categories of medical technology that have important implications for the definition of decisions and responsibilities. Medical information systems are computer-based systems that store patient information and assist in clinical problem solving. Rehabilitation devices are designed to give patients greater independence, comfort, and dignity. Drug delivery systems often alter patient participation in administering medications as well as affecting the safety, reliability, and efficacy with which medications are administered. Teaching devices enable students to learn and practice clinical skills, often reducing patient suffering and lessening guilt and stress among student-practitioners during clinical training. Finally, some technologies improve the use of healthcare technology. For example, assessment systems help clinicians match rehabilitation technology to an individual patient's needs and abilities.

New technologies also change responsibilities by altering the healthcare labor force. Devices that require special skills to operate or for the interpretation of their output have created new healthcare occupations with new responsibilities. Other devices have reduced or eliminated the need for other kinds of work. Some devices, such as imaging technologies and therapeutic X rays, have tended to centralize care in large university or urban centers because of the expense or massiveness of the equipment or the requirements for its installation and maintenance (Reiser). For example, the powerful magnets used in magnetic resonance imaging require extensive shielding so that they do not affect metal objects in the vicinity. Other kinds of technology, such as information technology, have fostered decentralization by giving practitioners in less populated areas ready access to both specialized medical knowledge and patient information (Reiser).

New medical technology often makes healthcare more effective. However, some devices have become deeply entrenched in practice before their clinical value or lack of diagnostic clinical value has been established. This is illustrated by the electronic fetal heart monitor used during childbirth. After its introduction, this monitor was adopted quickly in hospital obstetrics units, but it was shown later not to improve birth outcome even for high-risk births (see Luthy et al.).

Medical technology has had a variety of profound effects on family-care as well as healthcare practice. For example, some people have criticized the intrusiveness of intensive-care technology in light of the relatively high frequency with which people die in intensive-care units. The unit isolates a critically ill patient from family members, making it impossible for them to care for and comfort the patient in his or her final hours and disrupting the grieving process.

Engineering innovations often change "standards of care" when the use of a particular device becomes required for care to qualify as competent. For example, a physician who does not order a diagnostic X ray in certain cases may be liable to charges of negligence.

Lasers, fiber-optic and endoscopic technology, and ultrasound irradiation have made some surgeries less invasive. Other areas of surgery, especially invasive neonatal surgery, have grown dramatically as new devices for surgery and new intensive-care technology for postsurgical recovery have been introduced. The outcome of these surgeries is sometimes problematic. The U.S. Congress, Office of Technology Assessment, reported that largely as a result of such heroic interventions, there were 17, 000 "technologically dependent" children chronically dependent on respirators, intravenous nutrition, and other medical devices for life support.

Bioethics has devoted much attention to effective but sometimes harrowing new therapies and means of life support. Diagnostic and monitoring devices have received less discussion. Diagnostic and monitoring technology often changes the character of medical decisions, along with their basis and the parties to them. For example, when a pregnancy can be terminated if prenatal testing shows an abnormality, a test, such as amniocentesis, which is done halfway through pregnancy, transforms the pregnancy into a "tentative pregnancy" even if the test results are normal (Rothman).

Some of the effects of technological devices and improvements are at least in part the responsibility of the engineers who design them. The engineering profession recognizes that engineers are responsible for both the safety and the performance of their products. The issue of safety in diagnostic, monitoring, and life-critical devices is especially prominent because a failure is often life-threatening. The scope of the biomedical engineer's responsibility for how devices are used has begun to be discussed widely among biomedical engineers only recently. That discussion has considered whether engineers bear some guilt for the suffering caused by the use of respirators in patients who have no hope of recovery (Lewis). This suggestion proposes a particularly stringent standard of professional responsibility for engineers because respirators perform their intended function very well and often enable people to resume active lives. However, when they are used on terminally ill patients, respirators may only prolong suffering for patients and families and use precious healthcare resources. This kind of misuse must be distinguished from, for example, the use of a device in a wet environment. Devices in the home or in a hospital frequently are used in areas that become wet, thus presenting the risk of electrocution. That risk is eliminated through the installation of groundfault-interrupt circuit breakers. There are no similar engineering measures to ensure that respirators are used only in patients who have some hope of recovery.

Because the basis of professional responsibility is the special knowledge that a professional possesses, professional responsibility must originate in the knowledge that enables a professional to recognize or remedy a particular class of ill effects and promote good ones. In recent years state and national legislation has strengthened the legal standing of patients' advance directives, such as living wills and healthcare proxy statements, about their care. Those measures have had some success in addressing problematic use of life-support technology. The engineers who design and develop medical technology have some responsibility to ensure that it furthers human welfare, but in a democracy all citizens bear some responsibility for government policies governing its use.

caroline whitbeck (1995)

revised by author

BIBLIOGRAPHY

Cravalho, Ernest G., and McNeil, Barbara J., eds. 1982. Critical Issues in Medical Technology. Boston: Auburn House.

Lewis, Steven M. 1988. "A Sense of Sin." Biomedical Engineering Society Bulletin 12(1): 1–2.

Luthy, David A.; Syn, Kirkwood K.; van Belle, Gerald; et al. 1987. "A Randomized Trial of Electronic Fetal Monitoring in Preterm Labor." Obstetrics and Gynecology 69(5): 687–695.

Mann, Robert W. 1985. "Biomedical Engineering: A Cornucopia of Challenging Engineering Tasks—All of Direct Human Significance." IEEE Engineering in Medicine and Biology Magazine 4(3): 43–45.

Rapp, Rayna. 1987. "Moral Pioneers: Women, Men, and Fetuses on a Frontier of Reproductive Technology." Women and Health 13(1 and 2): 101–117.

Reiser, Stanley. 1978. Medicine and the Reign of Technology. Cambridge, Eng.: Cambridge University Press.

Reiser, Stanley J., and Anbar, Michael, eds. 1984. Machine at the Bedside: Strategies for Using Technology in Patient Care. Cambridge, Eng.: Cambridge University Press.

Rothman, Barbara Katz. 1986. The Tentative Pregnancy: Prenatal Diagnosis and the Future of Motherhood. New York: Viking.

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U. S. Congress, Office of Technology Assessment. 1987. New Developments in Biotechnology, 5 vols. Washington, D.C.: U.S. Congress, Office of Technology Assessment.

Whitbeck, Caroline. 1991. "Ethical Issues Raised by New Medical Technologies." In The New Reproductive Technologies: Medical, Psychosocial, Legal, and Ethical Dilemmas, ed. Judith Rodin and Aila Collins. Hillsdale, NJ: Lawrence Erlbaum.

Whitbeck, Caroline. 1998. Ethics in Engineering Practice and Research. Cambridge, Eng.: Cambridge University Press.

Encyclopedia of Bioethics