Appendix

AppendixThe Role of Professional Societies in Biomedical Engineering

Swamy Laxminarayan

New Jersey Institute of Technology

Joseph D. Bronzino

Trinity College/Biomedical Engineering Alliance for Connecticut (BEACON)

Jan E. W. Beneken

Eindhoven University of Technology

Shiro Usai

Toyohashi University of Technology

Richard D. Jones

Christchurch Hospital

A.1 Biomedical Engineering Societies in the World

American Institute for Medical and Biological Engineering (AIMBE) • IEEE Engineering in Medicine and Biology Society (EMBS) • Canadian Medical and Biological Engineering Society • European Society for Engineering in Medicine (ESEM) • French Groups for Medical and Biological Engineering • International Federation for Medical and Biological Engineering (IFMBE) • International Union for Physics and Engineering Sciences in Medicine (IUPESM) • International Council of Scientific Unions (ICSU) • Biomedical Engineering Societies in Japan • BME Activities in Australia and New Zealand • Bioengineering in Latin America

A.2 Summary

Professionals have been defined as an aggregate of people finding identity in sharing values and skills absorbed during a common course of intensive training. Parsons [1954] stated that one determines whether or not individuals are professionals by examining whether or not they have internalized certain given professional values. Friedson [1971] redefined Parson’s definition by noting that a professional is someone who has internalized professional values and is to be recruited and licensed on the basis of his or her technical competence. Furthermore, he pointed out that professionals generally accept scientific standards in their work, restrict their work activities to areas in which they are technically competent, avoid emotional involvement, cultivate objectivity in their work, and put their clients’ interests before their own.

The concept of a profession that manages technology encompasses three occupational models: science, business, and profession. Of particular interest in the contrast between science and profession. Science is seen as the pursuit of knowledge, its value hinging on providing evidence and communicating with colleagues. Profession, on the other hand, is viewed as providing a service to clients who have problems they cannot handle themselves. Science and profession have in common the exercise of some knowledge, skill, or expertise. However, while scientists practice their skills and report their results to knowledgeable colleagues, professionals—such as lawyers, physicians, and engineers—serve lay clients. To protect both the professional and the client from the consequences of the layperson’s lack of knowledge, the practice of the profession is regulated through such formal institutions as state licensing. Both professionals and scientists must persuade their clients to accept their findings. Professionals endorse and follow a specific
code of ethics to serve society. On the other hand, scientists move their colleagues to accept their findings through persuasion [Goodman, 1989].

Consider, for example, the medical profession. Its members are trained in caring for the sick, with the primary goal of healing them. These professionals not only have a responsibility of the creation, devel­opment, and implementation of that tradition, they also are expected to provide a service to the public, within limits, without regard of self-interest. To ensure proper service, the profession itself closely monitors licensing and certification. Thus medical professionals themselves may be regarded as a mech­anism of social control. However, this does not mean that other facets of society are not involved in exercising oversight and control over physicians in their practice of medicine.

Professional Development. One can determine the status of professionalization by noting the occur­rence of six crucial events: (1) the first training school, (2) the first university school, (3) the first local professional association, (4) the first national professional association, (5) the first state license law, and (6) the first formal code of ethics [Wilensky, 1964; Goodman, 1989; Bronzino, 1992].

The early appearances of training school and the university affiliation underscore the importance of the cultivation of a knowledge base. The strategic innovative role of the universities and early teachers lies in linking knowledge to practice and creating a rational for exclusive jurisdiction. Those practitioners pushing for prescribed training then form a professional association. The association defines the task of the profession: raising the quality of recruits, redefining their function to permit the use of less technically skilled people to perform the more routine, less involved tasks, and managing internal and external conflicts. In the process, internal conflict may arise between those committed to established procedures and newcomers committed to change and innovation. At this stage, some form of professional regulation, such as licensing or certification, surfaces because of a belief that it will ensure minimum standards for the profession, enhance status, and protect the layperson in the process.

The latest area of professional development is the establishment of a formal code of ethics, which usually includes rules to exclude the unqualified and unscrupulous practitioners, rules to reduce internal competition, and rules to protect clients and emphasize the ideal service to society. A code of ethics usually comes at the end of the professionalization process.

In biomedical engineering, all six critical steps mentioned above have been clearly taken. Therefore, biomedical engineering is definitely a profession. It is important here to note the professional associations across the globe that represent the interest of professionals in the field.

A.1 Biomedical Engineering Societies in the World

Globalization of biomedical engineering (BME) activities is underscored by the fact that there are several major professional BME societies currently operational throughout the world. The various countries and continents to have provided concerted “action” groups in biomedical engineering are Europe, the Amer­icas, Canada, and the Far East, including Japan and Australia. while all these organizations share in the common pursuit of promoting biomedical engineering, all national societies are geared to serving the needs of their “local” memberships. The activities of some of the major professional organizations are described below.

American Institute for Medical and Biological Engineering (AIMBE)

The United States has the largest biomedical engineering community in the world. Major professional organizations that address various cross sections of the field and serve over 20,000 biomedical engineers include (1) the American College of Clinical Engineering, (2) the American Institute of Chemical Engi­neers, (3) The American Medical Informatics Association, (4) the American Society of Agricultural Engineers, (5) the American Society for Artificial Internal Organs, (6) the American Society of Mechanical Engineers, (7) the Association for the Advancement of Medical Instrumentation, (8) the Biomedical Engineering Society, (9) the IEEE Engineering in Medicine and Biology Society, (10) an interdisciplinary

Association for the Advancement of Rehabilitation and Assistive Technologies, (11) the Society for Biomaterials, (12) Orthopedic Research Society, (13) American Society of Biomechanics, and (14) Amer­ican Association of Physicist in Medicine. In an effort to unify all the disparate components of the biomedical engineering community in the United States as represented by these various societies, the American Institute for Medical and Biological Engineers (AIMBE) was created in 1992. The AIMBE is the result of a 3-year effort funded by the National Science Foundation and led by a joint steering committee established by the Alliance of Engineering in Medicine and Biology and the U. S. National Committee on Biomechanics. The primary goal of AIMBE is to serve as an umbrella organization “for the purpose of unifying the bioengineering community, addressing public policy issues, identifying common themes of reflection and proposals for action, and promoting the engineering approach in society” s effort to enhance health and quality of life through the judicious use of technology” [Galletti, 1994].

AIMBE serves its role through four working divisions: (1) the Council of Societies, consisting of the 11 constituent organizations mentioned above, (2) the Academic Programs Council, currently consisting of 46 institutional charter members, (3) the Industry Council, and (4) the College Fellows. In addition to these councils, there are four commissions, Education, Public Awareness, Public Policy, and Liaisons. With its inception in 1992, AIMBE is a relatively young institution trying to establish its identity as an umbrella organization for medical and biologic engineering in the United States. As summarized by two of the founding officials of the AIMBE, Profs Nerem and Galletti:

What we are all doing, collectively, is defining a focus for biological and medical engineering. In a society often confused by technophobic tendencies, we will try to assert what engineering can do for biology, for medicine, for health care and for industrial development, We should be neither shy, nor arrogant, nor self-centered. The public has great expectations from engineering and technology in terms of their own health and welfare. They are also concerned about side effects, unpredictable consequences and the economic costs. Many object to science for the sake of science, resent exaggerated or empty promises of benefit to society, and are shocked by sluggish or misdirected flow from basic research to useful applications. These issues must be addressed by the engineering and medical com­munities. For more information, contact the Executive Office, AIMBE, 1901 Pennsylvania Avenue, N. W., Suite 401, Washington DC 20006-3405 (Tel: 202-496-9660; fax: 202-466-8489; email: AIMBE@aol. com).

IEEE Engineering in Medicine and Biology Society (EMBS)

The Institute of Electrical and Electronic Engineers (IEEE) is the largest international professional organi­zation in the world and accommodates 37 different societies under its umbrella structure. Of these 37, the Engineering in Medicine and Biology Society represents the foremost international organization serving the needs of nearly 8000 biomedical engineering members around the world. The field of interest of the EMB Society is application of the concepts and methods of the physical and engineering sciences in biology and medicine. Each year, the society sponsors a major international conference while cosponsoring a number of theme-oriented regional conferences throughout the world. A growing number of EMBS chapters and student clubs across the major cities of the world have provided the forum for enhancing local activities through special seminars, symposia, and summer schools on biomedical engineering topics. These are supplemented by EMBS’s special initiatives that provide faculty and financial subsidies to such programs through the society’s distinguished lecturer program as well as the society” s Regional Conference Committee. Other feature achievements of the society include its premier publications in the form of three monthly journals (Transactions on Biomedical Engineering, Transactions on Rehabilitation Engineering, and Transac­tions on Information Technology in Biomedicine) and a bi-monthly EMB Magazine (the IEEE Engineering in Medicine and Biology Magazine). EMBS is a transnational voting member society of the International Federation for Medical and Biological Engineering. For more information, contact the Secretariat, IEEE EMBS, National Research Council of Canada, Room 393, Building M-55, Ottawa, Ontario K1A OR8, Canada. (Tel: 613-993-4005; fax: 613-954-2216; email: Soc. emb@ieee. org).

Canadian Medical and Biological Engineering Society

The Canadian Medical and Biological Engineering Society (CMBES) is an association covering the fields of biomedical engineering, clinical engineering, rehabilitation engineering, and biomechanics and biom­aterials applications. CMBES is affiliated with the International Federation for Medical and Biological Engineering and currently has 272 full members. The society organizes national medical and biological engineering conferences annually in various cities across Canada. In addition, CMBES has sponsored seminars and symposia on specialized topics such as communication aids, computers, and the handi­capped, as well as instructional courses on topics of interest to the membership. To promote the professional development of its members, the society as drafted guidelines on education and certification for clinical engineers and biomedical engineering technologists and technicians. CMBES is committed to bringing together all individuals in Canada who are engaged in interdisciplinary work involving engineering, the life sciences, and medicine. The society communicates to its membership through the publication of a newsletter as well as recently launched academic series to help nonengineering hospital personnel to gain better understanding of biomedical technology. For more information, contact the Secretariat, The Cana­dian Medical and Biological Engineering Society, National Research Council of Canada, Room 393, Building M-55, Ottawa, Ontario K1A OR8, Canada (Tel: 613-993-1686; fax: 613-954-2216).

European Society for Engineering in Medicine (ESEM)

Most European countries are affiliated organizations of the International Federation for Medical and Biological Engineering (IFMBE). The IFMBE activities are described in another section of this chapter. In 1992, a separate organization called the European Society for Engineering in Medicine (ESEM) was created with the objective of providing opportunities for academic centers, research institutes, industry, hospitals and other health care organizations, and various national and international societies to interact and jointly explore BME issues of European significance. These include (1) research and development,

Education and training, (3) communication between and among industry, health care providers, and policymakers, (4) European policy on technology and health care, and (5) collaboration between eastern European countries in transition and the western European countries on health care technology, delivery, and management. To reflect this goal the ESEM membership constitutes representation of all relevant disciplines from all European countries while maintaining active relations with the Commission of the European Community and other supranational bodies and organizations.

The major promotional strategies of the ESEM’s scientific contributions include its quarterly journal Technology and Health Care, ESEM News, the Society’s Newsletter, a biennial European Conference on Engineering and Medicine, and various topic-oriented workshops and courses. ESEM offers two classes of membership: the regular individual (active or student) membership and an associate grade. The latter is granted to those scientific and industrial organizations which satisfy the society guidelines and subject to approval by the Membership and Industrial Committees. The society is administered by an Admin­istrative Council consisting of 13 members elected by the general membership. For more information, contact the Secretary General, European Society for Engineering in Medicine, Institut fьr Biomedizinische Technik, Seidenstrasse 36, D-70174 Stuttgart, Germany. (Fax: 711-121-2371

French Groups for Medical and Biological Engineering

The French National Federation of Bioengineering (Genie Biologique et Medical, GMB) is a multidisci­plinary body aimed at developing methods and processes and new biomedical materials in various fields covering prognosis, diagnosis, therapeutics, and rehabilitation. These goals are achieved through the creation of 10 regional centers of bioengineering, called the poles. The poles are directly involved at all levels, from applied research through the industrialization to the marketing of the product. Some of the actions pursued by these poles include providing financial seed support for innovative biomedical engi­neering projects, providing technological help, advice, and assistance, developing partnerships among universities and industries, and organizing special seminars and conferences. The information dissemi­nation of all scientific progress is done through the Journal of Innovation and Technology in Biology and Medicine. For more information, contact the French National Federation of Bioengineering, Coordinateur de la Federation Francaise des Poles GBM, Pole GBM Aquitaine-Site Bordeaux-Montesquieu, Centre de Resources, 33651 Martillac Cedex, France.

International Federation for Medical and Biological Engineering (IFMBE)

Established in 1959, the International Federation for Medical and Biological Engineering (IFMBE) is an organization made up from an affiliation of national societies including membership of transnational organizations. The current national affiliates are Argentina, Australia, Austria, Belgium, Brazil, Bulgaria, Canada, China, Cuba, Cyprus, Slovakia, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, Japan, Mexico, Netherlands, Norway, Poland, South Africa, South Korea, Spain, Sweden, Thailand, United Kingdom, and the United States. The first transnational organization to become a member of the federation is the IEEE Engineering in Medicine and Biology Society. At the present time, the federation has an estimated 25,000 members from all of its constituent societies.

The primary goal of the IFMBE is to recognize the interests and initiatives of its affiliated member organizations and to provide an international forum for the exchange of ideas and dissemination of information. The major IFMBE activities include the publication of the federation’s bimonthly journal, the Journal of Medical and Biological Engineering and Computing, the MBEC News, establishment of close liaisons with developing countries to encourage and promote BME activities, and the organization of a major world conference every 3 years in collaboration with the International Organization for Medical Physics and the International Union for Physical and Engineering Sciences in Medicine. The IFMBE also serves as a consultant to the United Nations Industrial Development Organization and has nongovern­mental organization status with the World Health Organization, the United Nations, and the Economic Commission for Europe. For more information, contact the Secretary General, International Federation for Medical and Biological Engineering, AMC, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, the Netherlands. (Tel: 20-566-5200, ext. 5179; fax 20-691-7233; email: Ifmbe@amc. uva. nl)

International Union for Physics and Engineering Sciences in Medicine (IUPESM)

The IUPESM resulted from the IFMBE’s collaboration with the International Organization of Medical Physics (IOMP), culminating into the joint organization of the triennial World Congress on Medical Physics and Biomedical Engineering. Traditionally, these two organizations held their conferences back to back from each other for a number of years. Since both organizations were involved in the research, development, and utilization of medical devices, they were combined to form IUPESM. Consequently, all members of the IFMBE’s national and transnational societies are also automatically members of the IUPESM. The statutes of the IUPESM have been recently changed to allow other organizations to become members in addition to the founding members, the IOMP and the IFMBE.

International Council of Scientific Unions (ICSU)

The International Council of Scientific Unions is nongovernmental organization created to promote inter­national scientific activity in the various scientific branches and their applications for the benefit of human­ity. ICSU has two categories of membership: scientific academies or research councils, which are national, multidisciplinary bodies, and scientific unions, which are international disciplinary organizations. Currently, there are 92 members in the first category and 23 in the second. ICSU maintains close working relations with a number of intergovernmental and nongovernmental organizations, in particular with UNESCO. In the past, a number of international programs have been launched and are being run in cooperation with UNESCO. ICSU is particularly involved in serving the interests of developing countries.

Membership in the ICSU implies recognition of the particular field of activity as a field of science. Although ICSU is heralded as a body of pure scientific unions to the exclusion of cross and multidisci­plinary organizations and those of an engineering nature, IUPESM, attained its associate membership in the ICSU in the mid-1980s. The various other international scientific unions that are members of the ICSU include the International Union of Biochemistry and Molecular Biology (IUBMB), the Interna­tional Union of Biological Sciences (IUBS), the International Brain Research Organization (IBRO), and the International Union of Pure and Applied Biophysics (IUPAB). The IEEE is an affiliated commission of the IUPAB and is represented through the Engineering in Medicine and Biology Society [ICSU Year Book, 1994]. For more information, contact the Secretariat, International Council of Scientific Unions, 51 Boulevard de Montmorency, 75016 Paris, France. (Tel: 1-4525-0329; fax: 1-4288-9431; email: Icsu@paris7.jussieu. fr)

Biomedical Engineering Societies in Japan

The biomedical engineering activities in Japan are promoted through several major organizations: (1) the Japan Society of Medical Electronics and Biological Engineering (JSMEBE), (2) the Institute of Electron­ics, Information and Communication Engineering (IEICE), (3) the Institute of Electrical Engineers of Japan (IEEJ), (4) the Society of Instrument and Control Engineers (SICE), (5) the Society of Biomech­anisms of Japan (SBJ), (6) the Japanese Neural network Society (JNNS), (7) Japan Ergonomics Research Society (JERS), and (8) the Japan Society of Ultrasonics in Medicine (JSUM). The various special sister societies that are affiliated under the auspicies of these organizations mainly focus on medical electronics, biocybernetics, neurocomputing, medical and biologic engineering, color media and vision system, and biologic and physiologic engineering. The JSMEBE has the most BME concentration, with two confer­ences held each year in biomedic engineering and three international journals that publish original peer- reviewed papers. The IEICE, which is now 77 years old, is one of the largest international societies, constituting about 40,000 members. The aim of the society is to provide a forum for the exchange of knowledge on the science and technology of electronics, information, and communications and the development of appropriate industry in these fields.

BME Activities in Australia and New Zealand

The BME activities in Australia and New Zealand are served by one transnational organization called the Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) covering Australia and New Zealand and a national organization called the College of Biomedical Engineers of the Institute of Engineers, (CBEIE) serving the Australian member segment.

The Australasian College of Physical Scientists and Engineers in Medicine was founded in 1977 and comprises 6 branches and 339 members. The membership is made up of 76% from Australia, 17% from New Zealand, and the rest from overseas. A majority of members are employed in pubic hospitals, with most of these in departments of medical physics and clinical engineering. The primary objectives of the college are (1) to promote and further the development of the physical sciences and engineering in medicine and to facilitate the exchange of information and ideas among members of the college and others concerned with medicine and related subjects and (2) to promote and encourage education and training in the physical sciences and engineering in medicine. Entry to ordinary membership of the college requires applicants to have an appropriate 4-year bachelor’s degree and at least 5 years of expe­rience as a physical scientist or engineer in a hospital or other approved institution.

Bioengineering in Latin America

Latin American countries have demonstrated in the past decade significant growth in their bioengineering activities. In terms of IEEE statistics, Latin America has the fastest growing membership rate. Currently, there are over 10,000 IEEE members alone in this region, of which about 300 are members of the Engineering in Medicine and Biology Society. In an effort to stimulate this growth and promote active International interactions, the presidents of the IEEE, EMBS, and the IFMBE met with representatives of biomedical engineering societies from Argentina, Brazil, Chile, Columbia, and Mexico in 1991 [Rob­inson, 1991]. This meeting resulted in the formation of an independent Latin American Regional Council of Biomedical Engineering, known by its spanish and portugese acronym as CORAL (Consejo Regional de Ingenieria Biomedica para Americana Latina). Both the EMBS and the IFMBE are the founding sponsoring members of the CORAL. The main objectives of CORAL are (1) to foster, promote and encourage the development of research, student programs, publications, professional activities, and joint efforts and (2) to act as a communication channel for national societies within Latin American region and to improve communication between societies, laboratories, hospitals, industries, universities, and other groups in Latin America and the Caribbean. Since its inception, CORAL has already provided the centerpiece for bioengineering activities in Latin America through special concerted scientific meetings and closer society interactions both in a national and international sense. For more information, contact the Secretary General, CORAL, Centro Investigacion y de Estudios, Avanzados Duel Ipn, Departamento Ingenieria Electrica, Seccion Bioelectronica, Av. Instituto Politecnico Nacional 2508, Esg. Av. Ticoman 07000, Mexico Apartado Postal 14-740, Mexico.

A.2 Summary

The field of biomedical engineering, which originated as a professional group on medical electronics in the late fifties, has grown from a few scattered individuals to very well-established organization. There are approximately 50 national societies throughout the world serving an increasingly growing community of biomedical engineers. The scope of biomedical engineering today is enormously diverse. Over the years, many new disciplines such as molecular biology, genetic engineering, computer-aided drug design, nanotechnology, and so on, which were once considered alien to the field, are now new challenges a biomedical engineer faces. Professional societies play a major role in bringing together members of this diverse community in pursuit of technology applications for improving the health and quality of life of human beings. Intersocietal cooperations and collaborations, both at national and international levels, are more actively fostered today through professional organizations such as the IFMBE, AIMBE, CORAL, and the IEEE. These developments are strategic to the advancement of the professional status of bio­medical engineers. Some of the self-imposed mandates the professional societies should continue to pursue include promoting public awareness, addressing public policy issues that impact research and development of biologic and medical products, establishing close liaisons with developing countries, encouraging educational programs for developing scientific and technical expertise in medical and biologic engineering, providing a management paradigm that ensures efficiency and economy of health care technology [Wald, 1993], and participating in the development of new job opportunities for bio­medical engineers.

References

Fard TB. 1994. International Council of Scientific Unions Year Book, Paris, ICSU.

Friedson E. 1971. Profession of Medicine. New York, Dodd, Mead.

Galletti PM, Nerem RM. 1994. The Role of Bioengineering in Biotechnology. AIMBE Third Annual Event. Goodman G. 1989. The profession of clinical engineering. J Clin Eng 14:27.

Parsons T. 1954. Essays in Sociological Theories. Glencoe, Ill, Free Press.

Robinson CR. 1991. Presidents column. IEEE Eng Med Bio Mag.

Wald A. 1993. Health care: Reform and technology (editors note). IEEE Eng Med Bio Mag 12:3.

The primary purpose of the respiratory system is gas exchange. In the gas-exchange process, gas must diffuse through the alveolar space, across tissue, and through plasma into the red blood cell, where it finally chemically joins to hemoglobin. A similar process occurs for carbon dioxide elimination.

As long as intermolecular interactions are small, most gases of physiologic significance can be consid­ered to obey the ideal gas law:

PV □ nRT

Where p = pressure, N/m2

Control of respiration occurs in many different cerebral structures [Johnson, 1991] and regulates many things [Hornbein, 1981]. Respiration must be controlled to produce the respiratory rhythm, ensure adequate gas exchange, protect against inhalation of poisonous substances, assist in maintenance of body pH, remove irritations, and minimize energy cost. Respiratory control is more complex than cardiac control for at least three reasons:

1. Airways airflow occurs in both directions.

3. Parts of the respiratory system are used for other functions, such as swallowing and speaking.

As a result, respiratory muscular action must be exquisitely coordinated; it must be prepared to protect itself against environmental onslaught, and breathing must be temporarily suspended on demand.

The purpose of a pulmonary function laboratory is to obtain clinically useful data from patients with respiratory dysfunction. The pulmonary function tests (PFTs) within this laboratory fulfill a variety of functions. They permit (1) quantification of a patient’s breathing deficiency, (2) diagnosis of different types of pulmonary diseases, (3) evaluation of a patient’s response to therapy, and (4) preoperative screening to determine whether the presence of lung disease increases the risk of surgery.

One of the most common problems in bioelectric theory is the calculation of the potential distribution,

O (V), throughout a volume conductor. The calculation of O is important in impedance imaging, cardiac pacing and defibrillation, electrocardiogram and electroencephalogram analysis, and functional electrical stimulation. In bioelectric problems, O often changes slowly enough so that we can assume it to be quasistatic [Plonsey, 1969]; that is, we ignore capacitive and inductive effects and the finite speed of electromagnetic radiation. (For bioelectric phenomena, this approximation is usually valid for frequencies roughly below 100 kHz.) Under the quasistatic approximation, the continuity equation states that the divergence, V% of the current density, J (A/m2), is equal to the applied or endogenous source of electrical current, S (A/m3):

V • J = S. (10.1)

In regions where there are no such sources, S is zero. In these cases, the divergenceless of J is equivalent to the law of conservation of current that is often invoked when analyzing electrical circuits. Another fundamental property of a volume conductor is that the current density and the electric field, E (V/m), are related linearly by Ohm’s Law,

J = g E, (10.2)

Where g is the electrical conductivity (S/m). Finally, the relationship between the electric field and the gradient, V, of the potential is

E = — V O. (10.3)

The purpose of this chapter is to characterize the electrical conductivity. This task is not easy, because g is generally a macroscopic parameter (an “effective conductivity”) that represents the electrical prop­erties of the tissue averaged in space over many cells. The effective conductivity can be anisotropic, complex (containing real and imaginary parts), and can depend on both the temporal and spatial frequencies.

I □ ^LA □ Vra

II □ VLL — VRA

HI □ VLL — VLA

Where RA = right arm, LA = left arm, and LL = left leg. Because the body is assumed to be purely resistive at ECG frequencies, the four limbs can be thought of as wires attached to the torso. Hence lead I could be recorded from the respective shoulders without a loss of cardiac information. Note that these are not independent, and the following relationship holds: II = I + III.

The evolution of the ECG proceeded for 30 years when F. N. Wilson added concepts of a “unipolar” recording [3]. He created a reference point by tying the three limbs together and averaging their potentials so that individual recording sites on the limbs or chest surface would be differentially recorded with the same reference point. Wilson extended the biophysical models to include the concept of the cardiac source enclosed within the volume conductor of the body. He erroneously thought that the central terminal was a true zero potential. However, from the mid-1930s until today, the 12 leads composed of the 3 limb

Observe that the Reuss laminate is identical to the Voigt laminate, except for a rotation with respect to the direction of load. Therefore, the stiffness of the laminate is anisotropic, that is, dependent on direction [Agarwal and Broutman, 1980; Nye, 1976; Lekhnitskii, 1963]. Anisotropy is characteristic of composite materials. The relationship between stress aij and strain ekl in anisotropic materials is given by the tensorial form of Hooke’s law as follows:

3 3

^□□□CkA. (40.3)

K=1 l =1

Here is the elastic modulus tensor. It has 34 = 81 elements, however since the stress and strain are represented by symmetric matrices with six independent elements each, the number of independent modulus tensor elements is reduced to 36. An additional reduction to 21 is achieved by considering elastic materials for which a strain energy function exists. Physically, C2323 represents a shear modulus

The Fick method employs oxygen as the indicator and the increase in oxygen content of venous blood as it passes through the lungs, along with the respiratory oxygen uptake, as the quantities that are needed to determine cardiac output, CO = O2 uptake/A — VO2 difference). Oxygen uptake (mL/min) is measured at the airway, usually with an oxygen-filled spirometer containing a CO2 absorber. The A — VO2 difference is determined from the oxygen content (mL/100 mL blood) from any arterial sample and the oxygen content (mL/100 mL) of pulmonary arterial blood. The oxygen content of blood used to be difficult to measure. However, the new blood-gas analyzers that measure, pH, pO2, pCO2, hematocrit, and hemo­globin provide a value for O2 content by computation using the oxygen-dissociation curve.

There is a slight technicality involved in determining the oxygen uptake because oxygen is consumed at body temperature but measured at room temperature in the spirometer. Consequently, the volume of

H = height in inches, A = age in years, L = liters, L/min = liters per minute,

SEE = standard error of estimate, SD = standard deviation *Kory, Callahan, Boren, Syner. 1961. Am J Med 30:243.

*Leiner, Abramowitz, Small, Stenby, Lewis. 1963. Amer Rev Resp Dis 88:644.

Although vaccinology and manufacturing methods have come a considerable distance over the past

40 years, much more development will occur. There will be challenges for biotechnologists to arrive at safer, more effective vaccines for an ever-increasing number of antigen targets. If government interference

114 Fluid Shear Stress Effects on Cellular Function Charles W. Patrick, Jr., Rangarajan Sampath, Larry V. McIntire

Devices and Methodology Used for in Vitro Experiments • Shear Stress-Mediated Cell — Endothelium Interactions • Shear Stress Effects on Cell Morphology and Cytoskeletal Rearrangement • Shear Stress Effects on Signal Transduction and Mass Transfer • Shear Stress Effects on Endothelial Cell Metabolite Secretion • Shear Stress Effects on Gene Regulation • Mechanisms of Shear Stress-Induced Gene Regulation • Gene Therapy and Tissue Engineering in Vascular Biology • Conclusions

In the natural lungs, the factors underlying exchange across the alveolo-capillary barrier and transport by the blood can be grouped into four classes:

1. The ventilation of the lungs (the volume flow rate of gas) and the composition of the gas mixture to which mixed venous (pulmonary artery) blood will be exposed

3. The pattern of pressure and flow through the airways and through the pulmonary vascular bed and the distribution of inspired air and circulating blood among the various zones of the exchange system

4. The gas carrying capacity of the blood as regards oxygen and carbon dioxide (and secondarily nitrogen and anesthetic gases)

In an artificial lung, replacing the gas transfer function of the natural organ implies that blood circulation can be sustained by mechanical pumps for extended periods of time to achieve a continuous, rather than a batch process, and that venous blood can be arterialized in that device by exposure to a gas mixture of appropriate composition. The external gas supply to an artificial lung does not pose particular problems, since pressurized gas mixtures are readily available. Similarly the components of blood which provide its gas-carrying capacity are well identified and can be adapted to the task at hand. In clinical practice, it is important to minimize the amount of donor blood needed to fill the extracor — poreal circuit, or priming volume. Therefore a heart-lung machine is generally filled with an electrolyte or plasma expander solution (with or without donor blood), resulting in hemodilution upon mixing of the contents of the extracorporeal and intracorporeal blood circuits. The critical aspects for the operation of an artificial lung are blood distribution to the exchanger, diffusion resistances in the blood mass transfer boundary layer, and stability of the gas exchange process.

Artificial lungs are expected to perform within acceptable limits of safety and effectiveness. The most common clinical situation in which an artificial lung is needed is typically of short duration, with resting or basal metabolism in anesthetized patients. Table 129.3 compares the structures and operating condi­tions of the natural lung and standard hollow fiber artificial membrane lungs with internal blood flow.

An artificial lung designed to replace the gas exchange function of the natural organ during cardiac surgery must meet specifications which are far less demanding than the range of capability of the mammalian lung would suggest. Nonetheless, these specifications must embrace a range of performance to cover all metabolic situations which a patient undergoing cardiopulmonary bypass might present. These conditions range in terms of metabolic rate from the slightly depressed resting metabolism char­acteristic of an anesthetized patient, lightly clad in a cool operating room, to moderate (25-28°C) and occasionally deep (below 20°C) hypothermia. Hypothermia and high blood flow are occasionally encoun­tered in patients with septic shock. In terms of body mass, patients range from 2-5-lb newborn with congenital cardiac malformations to the 250-lb obese, diabetic elderly patient suffering from coronary artery disease and scheduled for aortocoronary bypass surgery.

Whereas it is appropriate to match in advance the size and therefore the transfer capability of the gas exchange unit in the heart-lung machine to the size of the patient (largely out of concern for the volume of fluid needed to fill or “prime” the extracorporeal circuit), each gas exchange unit, once in use, must be capable of covering the patient’s requirement under any circumstances. This is the responsibility of the perfusionist, who controls the system in the light of what is happening to the patient in the operative field. In fact, the perfusionist substitutes his or her own judgment for the natural feedback mechanisms which normally control ventilation and circulation to the natural lungs. The following analysis indicates

‘The Advanced Research Projects Agency of the U. S. Department of Defense, chair of the Defense Technology Conversion Council which administers the Technology Reinvestment Project.

[2]Galen, in turn, based many of his beliefs on those of the hippocratic era scholars—Hippocrates, Aristotle, Polybus, and Diocles (4th century bc).

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