Thomas P. Engel, M.D.
Summary: This abstract describes the Computer Ethics Questions interactive tutorial computer program created by the author.
Introduction: The immediacy and remoteness of computer actions lead many people to think ethical issues associated with computers are different from other ethical situations. In addition, practical matters of copyright, etiquette, security and resource use are unfamiliar to many computer users. The Computer Ethics Questions interactive tutorial computer program was created to include computer ethics in the medical student curriculum with a minimum burden on students and faculty. The program was designed to inform, increase interest in this topic and encourage constructive behavior.
Methods: The tutorial consists of questions and discussion. Users respond to each question to go to the discussion. The discussion is different depending on the response. Users may go back to answer a question again and see other discussion. Users may also go directly to a specific question. The questions include: Has computer software ever killed anyone? Is personal electronic mail private? Is electronic mail anonymous? Is it appropriate to use strong language in computer discussion? Is it appropriate to encrypt electronic mail or other files? Is it appropriate to explore a computer network? Is it easy to select good computer passwords? Is it appropriate to read someone else's computer files without permission? Is it appropriate to call up records for a patient other than your own? Is it appropriate to access pornography on a network? Is it appropriate to copy computer programs or other files? Is the Internet free? Are ethical issues involving computers different from other ethical situations? The computer program was created with the Apple Media Tool cross-platform authoring environment.
Results: The tutorial contains seventeen questions, 34 areas of discussion, title, contents and recommended reading. The tutorial is part of computer competency training and is required of all medical students at Loma Linda University and may become part of the curriculum at other medical schools. The ethics discussion is concise; users can go through the tutorial in about half an hour. Individuals and responses are not tracked. The response from network administrators, finance administrators, faculty and students has been very positive.
Discussion: As with other ethical domains, computer ethics is not settled. The tutorial does not dictate absolute answers. The tutorial emphasizes similarities between computer ethics and other ethical situations where appropriate and offers practical information. The computer based tutorial program fulfills the goal to inform, increase interest in this topic and encourage constructive behavior. The computer program may be used by anyone at no cost. Both Apple Macintosh and Microsoft Windows versions of the program are available via anonymous FTP from the GASNet Anesthesiology Server at gasnet.med.yale.edu.
Thomas Engel, M.D.
Computer technology offers the opportunity to combine text, sounds, diagrams, pictures and digital video to create interactive educational materials. Creating these programs combines content expertise with writing, education, graphic arts and programming skills. There are many technical issues to consider. Basic decisions about the target computer platform, method of delivery of the software and development tool must be made early in the development effort.
The choice of target platform includes Microsoft Windows, Apple Macintosh or both. Although Windows accounts for more than half of the potential audience for multimedia software, many of these machines have limited capability. Macintosh computers have extensive support for multimedia software. With careful selection of file formats and development tools, it is possible to create one project that will run on both Windows and Macintosh. Other platforms such as OS/2 and Unix are much fewer in number and may be able to run Macintosh or Windows software.
CD-ROM is a natural choice for delivery of multimedia educational software due to very high capacity and very low cost. A CD-ROM can hold 650 MB. This can be the entire text of a small library or about 1000 color photographs or about 20 minutes of digitized video or some fractional combination of these. Compression or small size can increase the number of photographs or amount of digital video that may be included with reduced image quality. CD-ROMs are very inexpensive to produce. Final duplication is US$1-2 per copy. A single CD-ROM can be used with both Macintosh and Windows computers.
Apple QuickTime digital video offers the best cross-platform support and the best performance. QuickTime is also modular and easily extended for the future. Microsoft AVI is awkward cross-platform and lower performance. MPEG is an independent standard, but it requires very fast hardware. Careful construction of digital video clips can take advantage of specific compressor characteristics for best performance.
The choice of cross-platform multimedia authoring tools includes Macromedia Director, Authorware Professional, Apple Media Tool, HyperCard/ToolBook and HTML. Macromedia Director is the most popular authoring tool. Director projects are based on timelines, sets and animated cast members. Director has a steep learning curve. Director is well suited for animation. AuthorWare Professional projects are based on flow charts. Very large projects can be awkward in this environment. Authorware is well suited for making quiz oriented tutorials. The Apple Media Tool is based on screens and offers good cross-platform delivery and good organization of content. Apple Media Tool is well suited for kiosk applications. HyperCard/ToolBook has more programming flexibility but less built-in capability. Cross-platform support is awkward. New versions of HyperCard, SuperCard or Oracle Media Objects may improve cross-platform results. HTML is the language of the World Wide Web on the Internet. HTML is currently limited as a primary application but is excellent as a secondary application. HTML is based on network delivery and can be awkward on CD-ROM.
Thomas Engel, M.D., Keith Ruskin, M.D. and Jo E. Reed, M.A.
The volume and specificity of technical information in all fields is extremely large and rapidly growing. Paper based education and reference materials are growing inadequate. Review and publication of paper journals and books is time consuming and information may be out of date prior to publication. Access is impeded by the sheer volume of information, a phenomenon especially evident in the field of medicine.
The GASNet Anesthesiology Server is an example of the future direction and migration path toward ubiquitous computer based education and reference sources. The server supports platform-independent access via the Internet. Please visit the GASNet Anesthesiology Server at http://gasnet.med.nyu.edu/HomePage.html. The CERN virtual library points to the GASNet Anesthesiology Server.
The GASNet Anesthesiology Server combines existing paper resources with future information technology. The server prepublishes abstracts from the paper Journal of Neurosurgical Anesthesia and Journal of Clinical Monitoring. The server also publishes the full text of Educational Synopses in Anesthesiology and Critical Care, a peer review journal published primarily in electronic form. Citations from this journal are similar to paper journals and will be included in Index Medicus. The server also publishes the bibliographies of the Society of Neurosurgical Anesthesia and Critical Care and Malignant Hyperthermia Association of the United States of America.
The GASNet Anesthesiology Server also hosts an on-line textbook of anesthesiology. This World Wide Web based textbook supports text, figures and digital video. Updates to the textbook are instantly available to all users. The server also hosts a moderated E-mail list for discussion and comprehensive pointers to other Internet based anesthesiology resources.
The Server also hosts a clip media library that includes text, tables, pictures, diagrams, sounds, and digital video. The library is designed to reduce the burden of creating paper or electronic educational materials and is based on voluntary contributions. Materials are available from the library at no cost for use in other completed works. Users must maintain credit to the original authors.
Computer and networking technology promise to change technical education and offer the opportunity to improve access, timeliness and quality of technical education and reference materials. Current computer systems can combine existing paper based information with future computer based resources and can facilitate creation of education and reference materials.
Thomas Engel, M.D.
Summary: This abstract describes a concise, explicit and flexible fuzzy logic system for prioritizing surgical cases.
Introduction: Operating rooms, surgeons, anesthesiologists and nursing staff are finite resources. Sometimes the demand for these resources exceeds their availability. When this occurs, decisions on the priority of surgical cases must be made. These decisions frequently lead to disagreements. An explicit set of rules offers the possibility of prior agreement and consistent application. Such a set of rules must account for the incomplete, ambiguous and widely varying information present in many situations. Fuzzy logic offers a concise, explicit and flexible solution to this problem. Fuzzy logic values may be true (1.0), false (0.0) or any value in between. A fractional value indicates a degree of truth and is similar to a probability. Fuzzy logic calculations consist of three parts: fuzzification, application of rules and defuzzification. Fuzzification is the conversion of input observations into fuzzy logic values for categories. Where categories overlap, the sum of the value of each possibility may not exceed 1.0. Each fuzzy logic rule is evaluated to form a value for the rule. Defuzzification is the combination of the values of the rules to form an exact output result. Fuzzy logic algorithms and rules are independent of any computer or programming language.
Methods: This fuzzy logic system consists of six inputs, fourteen rules and one output, the priority of the case. Inputs include "the patient is available," "the surgeon is available," "surgery will change the outcome" and "delay will harm the patient." Fuzzification is accomplished by assigning one of the categories very low (0.0), low (0.25), medium (0.5), high (0.75) and very high (1.0) to each input for each case. Rules include "if surgery will change the outcome and delay will harm the patient then the case is an emergency" and "if the case is an emergency and the patient is available and the surgeon is available then the priority is very high." The value of each rule is calculated with "and" (least of the two values), "or" (greatest of the two values) and "not" (1.0 minus the value). Defuzzification is accomplished by calculating the weighted average of the values of the rules that assign priority. The output is expressed by a fraction and the closest category. This system is implemented with a computer spreadsheet program. Fuzzy logic values and formulas are stored in named cells. Named cells make rules easier to read.
Results: This system assigns a priority to each surgical case based upon input categories. It always produces the same priority given the same inputs. The algorithm is explicit and accounts for a wide variety of situations.
Discussion: Assignment of priority to surgical cases can be accomplished by standard (Boolean) logic rules or even neural networks. Fuzzy logic requires many fewer rules than standard logic and gracefully incorporates ambiguous information. Fuzzy logic yields an explanation of its reasoning in the calculated values of each of the rules. Neural networks are computationally expensive, do not give explanations as easily and require a large number of examples. Neural networks can perform very poorly with situations outside of their example set. This fuzzy logic system offers the possibility of prior agreement and consistent application of an explicit algorithm for prioritizing surgical cases. Prior agreement and consistent application may facilitate appropriate scheduling.
Thomas Engel, M.D., Richard Applegate II, M.D. and Patricia Applegate, M.D.
Transesophageal echocardiography is a valuable ultrasound technique for diagnosing heart wall motion abnormalities, valve function and overall performance in patients in inpatient, outpatient and intraoperative settings. Interpretation of transesophageal echocardiography images is very difficult to learn.
"Transesophageal Echocardiography Tutorial and Reference" is an interactive electronic book created at Loma Linda University School of Medicine. The tutorial is consists of 420 total pages in 20 chapters and contains 170 real-time digitized video images, 200 diagrams and extensive text. It has a table of contents and index as well as hypertext features. Chapters are organized by content and include introductory material, anatomy, image orientation, examples, comparisons, unknowns and selected references. Users may navigate rapidly through the tutorial with on-screen buttons and menus and with keyboard commands. Users may search throughout the tutorial by chapter name, page name, page number, index keywords, user entered text and user defined bookmarks.
The video images are encoded with the Apple Compact Video Compressor (QuickTime 1.5 and later) and are very highly compressed. The entire tutorial is 55 MB. The video images are quarter screen (320 by 240 pixels at 72 dpi) and play at 15 frames per second. Most video images play continuously and indefinitely in a seamless loop. The tutorial has very modest hardware requirements. The video images will play at full frame rate on any color Apple Macintosh computer system without additional hardware.
The tutorial is designed in the form of a book to aid user navigation. Locations, paths and branches within its material are obvious and immediately familiar to the user. The tutorial is based on template pages that allow rapid incorporation of new material. Addition of new pages and revision of existing ones do not require programming skills. New pages are automatically integrated into the chapter, table of contents and index. Page templates and the underlying computer program are independent of content and may be used for a wide variety of subjects.
The tutorial is designed to work in a network environment. The application and data files may be stored on a server and support multiple simultaneous users. The tutorial application stores individual user information on the user's machine. The tutorial suffers minimal loss of performance with low bandwidth networks.
Thomas Engel, M.D.
The dramatic increase in computational power of desktop computers greatly encourages the creation of mathematical models in anesthesiology, physiology, pharmacology and molecular biology. Simulation models offer explicit quantification and testing of ideas, increased access for understanding scientific problems and suggestions for further experiments. This abstract describes a computer simulation workshop for faculty and staff at Loma Linda University. The workshop is designed to increase participants' interest, knowledge and comfort with computer simulations of a wide variety of scientific problems. The workshop requires minimal math or computer skills.
The workshop topics include: overview; value of mathematical (computer) models; discrete vs. continuous models; simulation with particles; some famous models; analog vs. digital computers; types of differential equations; state variables, derived variables and constants; state space; naming conventions; analytical vs. numerical solutions; linearity, nonlinearity and chaos; numerical solution methods; constructing models; conservation in models; software for creating models; visualization of results; cross-platform issues; neural networks, cellular automata, meshes and other exotic methods;annotated bibliography. Famous models discussed include: Guyton, A. C., et. al., Circulation: overall regulation, Annual Review of Physiology, 34: 13-46, 1972 and Forrester, J. W., World dynamics, Wright-Allen Press, Inc., Cambridge, Massachusetts, 1971.
Participants build a model that answers the question: "What is the optimal hemoglobin concentration for oxygen delivery in surgical patients?" This model is based on viscosity vs. hemoglobin concentration, flow rate vs. viscosity and oxygen content vs. hemoglobin concentration. The model predicts oxygen delivery vs. hemoglobin concentration under different conditions.
Thomas Engel, M.D.
This abstract describes work in progress on a comprehensive computer based mathematical model for human cardiovascular physiology and pharmacology. The model is written in Object Pascal and runs on Apple Macintosh computers. The model is built in five layers: body composition, hemodynamics, mass transport, pharmacokinetics and pharmacodynamics. Each layer depends primarily on the layer beneath it. Body composition divides the human body into vascular spaces and tissue compartments. Hemodynamics describes heart contraction, pressures and flows. Mass transport describes concentrations of substances carried with the blood. Pharmacokinetics and pharmacodynamics describe the absorption, transformation, elimination and effects of these substances.
Thomas Engel, M.D.
Summary: This abstract describes the use of AppleSearch text indexing and retrieval software for anesthesia information management. This system allows rapid searching of a large number of documents based on content and retrieval of relevant information by resident physicians to aid them in preparing for patient care and examinations.
Introduction: AppleSearch from Apple Computer, Inc. is a multi-user, client-server system for indexing and retrieval of text information contained in documents. AppleSearch can index the text from documents in large variety word processing and presentation program formats. AppleSearch offers a number of advantages for speed, accuracy and ease of use over other text retrieval systems. AppleSearch searches occur on the server. AppleSearch builds an extensive index of the source documents. The server has fast access to its hard disk and only sends the results of the search to the client. Search speed is independent of the bandwidth of the network connection. AppleSearch clients use plain text queries such as "Is malignant hyperthermia related to pregnancy?" Boolean logic pattern matching is not required. The search uses many aspects of the query and source documents to find relevant documents. One of these is "stemming." AppleSearch automatically uses all forms of each word in the query when it searches the source documents, as in "pregnancy" and "pregnant." AppleSearch assigns a score to each document and presents the most relevant ones. AppleSearch can summarize the results of a search in a "newspaper" format, can show the full text of a document and can provide access to fully formatted information with the program that created the document. The AppleSearch server software runs on 68040 Macintosh computers. The client software runs on any networked Macintosh or Windows computer.
Methods: Many reference materials exist in computer format in our department. These include lists of drug doses for preoperative medication, induction, maintenance, regional anesthesia and chronic pain management; equipment lists; resuscitation procedures; memos; policy statements; lecture slides and notes for resident physician education; and selected abstracts of published papers. These resources were collected and placed on a Macintosh Quadra 950 computer. This computer runs the AppleSearch server software. Approximately 200 documents are indexed. Residents use several Macintosh computers with a variety of network connections to the server.
Results: Organization and collection of the documents consists of copying them to a directory on the server. AppleSearch indexes are created and maintained on the server automatically. New material is incorporated automatically. Residents are able to use the system effectively with minimal training. Searching from Ethernet (10 Mbit/sec), LocalTalk (230 Kbit/sec) and AppleTalk Remote Access (9.6 Kbit/sec) connections all occurs at approximately the same speed. Most searches are completed in a few seconds.
Discussion: A large quantity of information is available to resident physicians. This large quantity makes rapid access to specific information difficult. Sophisticated tools for indexing and retrieval, such as AppleSearch, can facilitate rapid access and encourage more queries.
Thomas Engel, M.D.
Summary: This abstract describes use of Apple Newton Message Pad personal digital assistants for anesthesiology. These devices allow the organization and rapid retrieval of lists and other notes for reference in the operating room.
Introduction: Apple Computer, Inc. manufactures the Newton Message Pad personal digital assistant. This is a small, battery powered, hand-held computer, height 18.5 cm (7.25 in.), width 11.4 cm (4.5 in.), depth 1.9 cm (0.75 in.), weight 0.4 kg (0.9 lb.). Users use a stylus to write on a pressure sensitive LCD screen. The device recognizes a wide variety of handwriting styles for data entry and commands. Handwriting recognition is computationally intensive; the Newton Message Pad incorporates a 20 MHz ARM 610 RISC microprocessor and provides approximately 5 MIPS processing power. This device has three main software programs: a notes file, calendar and address book. The notes file allows the user to organize and recall information by subject and content. The Message Pad supports network connection to Apple Macintosh computers for backup, recovery, synchronization and downloading software packages. A serial connection to Microsoft Windows computers is also available. This allows data entry on Macintosh or PC type computers. The Message Pad also supports printing to network (Postscript) printers and FAX machines. Newton devices can exchange information with each other via a built-in infrared link. The Newton software development system is hosted on Macintosh computers. This system is highly integrated and uses NewtonScript, an object oriented programming language.
Methods: Many reference materials exist in computer format in our department. These include lists of drug doses for preoperative medication, induction, maintenance, regional anesthesia and chronic pain management; equipment lists; resuscitation procedures; hand out materials for resident physician education and selected abstracts of published papers. These resources were collected and organized on a Macintosh computer and copied to the Newton Message Pad. Many additional notes were also created for this project. Department and personal name and address lists were created by individual users. Department and personal calendar entries were also created by individual users. The information is organized by category. An overview feature automatically creates an outline of the information on the Message Pad. A user can call up selected items directly from the outline. A find feature allows the user to search for information based on content. An assist feature automates many tasks.
Results: The Newton Message Pad personal digital assistant provides rapid retrieval of lists and other notes. The handwriting recognition feature performs reliably after a short training period. Use of existing information and entry of new information with the full sized keyboard on a Macintosh computer was rapid and convenient. The network connection to a Macintosh computer also provides robust storage of Message Pad information for back up security.
Discussion: The small size of personal digital assistants make them convenient for use in the operating room. Their great processing power makes them suitable for many tasks. Handwriting recognition provides an easy to use interface for devices that are too small for a keyboard. Our department is working to increase the amount of information that may be accessed with these devices.
Thomas Engel, M.D., Richard Applegate II, M.D. and Patricia Applegate, M.D.
Transesophageal echocardiography can provide valuable information on heart function during surgery. Interpretation of echocardiography images is a difficult skill to learn. This skill often takes months of practice under the supervision of a skilled physician teacher. This abstract describes an interactive computer based tutorial for teaching interpretation of transesophageal echocardiography images to resident anesthesiologists.
The tutorial uses video images and sounds and runs on color Apple Macintosh computers. The video and sound are digitized and played as QuickTime movies. QuickTime allows any color Macintosh computer to play real-time video images and synchronized sound without special hardware. The video images and sound are highly compressed. In most cases a single cardiac cycle is shown. The cycle is carefully constructed and played in a loop to yield a smooth, continuous motion. The use of individual loops rather than full length segments improves playback frame rate and reduces the tutorial disk space requirements. The tutorial was created with Claris HyperCard and requires both QuickTime and the HyperCard Player.
The tutorial emphasizes understanding and application of transesophageal echocardiography to anesthetic management and includes tutorial, reference and self test sections. The tutorial is organized into sections covering major topics. Each section has several pages illustrating specific points. Each section is followed by self test questions. Residents may move sequentially page by page through the tutorial or jump from section to section. Residents may also jump directly to a glossary to see the definition of a word. A table of contents and integrated help are also included. The tutorial is self contained. Residents can move through the tutorial at their own pace and without the supervision of an attending anesthesiologist.
The computer based tutorial can serve as an introduction to transesophageal echocardiography for resident anesthesiologists, and increase the value of time spent learning with attending anesthesiologists.
Thomas Engel, M.D.
Summary: Apple Macintosh client software provides access to the Hewlett-Packard Component Monitoring System to capture patient information for analysis and archival storage.
Introduction: The Hewlett-Packard Component Monitoring System (CMS) is popular in operating suites and intensive care units. The CMS can manage all common types of patient sensors and reports measurements on a central display. The CMS supports sensor devices from several manufacturers. Hewlett-Packard recently added the capability for other computers to access CMS information. This access is via the Hewlett-Packard MECIF protocol. (MECIF is an abbreviation of Medical Computer Interface.)
Methods: The MECIF protocol is client-server based. The Component Monitoring System is an information server. A single CMS can support connections with several serial devices and several software clients on each serial device. The MECIF uses a variant of the RS-232 protocol with mandatory hardware handshaking. MECIF clients send messages to the server requesting patient information. The server responds with messages containing the requested information. A client may request CMS configuration information such as the number of sensors in use, parsed numbers such as heart rate, or sampled wave forms such as the electrocardiogram. Messages consist of binary data with a synchronization byte followed by a header (containing the message type, source, destination and message length) and any message specific data.
The Macintosh computer operating system includes a device driver to manage serial communications. This driver configures the Macintosh hardware and manages interrupts and buffers for the serial data. The Macintosh operating system interface is defined with Pascal data structures and procedure calls.
The Macintosh client software is a stand alone application program written in Pascal with the THINK Pascal development system by Symantec Corporation. The program is organized in three layers. A low level layer makes device driver calls to send and receive messages. A middle layer composes outgoing messages, decodes incoming messages, checks for errors and dispatches messages to the high level procedures. The high level layer consists of procedures to record, analyze and display the patient information.
Results: The Macintosh client software includes a high level procedure to store CMS parsed numbers in a text file for archival storage. Other programs use this information for statistical analysis. Other high level procedures may be added to store or display waveforms. Additional high level procedures do not require modification of low or middle level layers. Many high level procedures may be used simultaneously.
Discussion: Patient monitoring information is valuable for a variety of projects including automated anesthesia records, statistics for research and quality assurance, real time wave form analysis, alternative human interface elements, closed loop drug administration and improved alarms. Macintosh client software for the Hewlett-Packard Component Monitoring System makes patient information available for these projects.
Thomas Engel, M.D. and Susan Wheeler
Anesthesiologists must use a large number of patient monitors. Each monitor has its own display, controls and alarms. Anesthesiologists must constantly watch and interpret a large number of analog waves and dials as well as digital displays to assess the patient's condition. Integration of information from patient monitors and consistent user interface features can improve this situation. Integration of information from patient monitors can allow more general communication of the patient's condition to the anesthesiologist. This high level communication requires new user interface elements. A drawn human face may form an appropriate high level user interface element for anesthesia patient monitors.
Drawn faces have been used to represent data for many years. Herman Chernoff used faces to graphically represent points in k-dimensional space in 1973. Chernoff faces map each coordinate of the point to a facial feature such as eye size or mouth shape. Each parameter is independent and mapped to only one feature. The resulting faces may be easier to interpret than other more arbitrary geometric figures since faces form expressions which communicate emotional content. This technique is especially useful for qualitatively dividing several data point faces into groups. In Chernoff's faces, parameter to facial feature mapping is arbitrary and the significance of a data point may not be consistent with its representation. For example, data points which represent hypoxia might be mapped to a smiling face. Drawn faces which consistently communicate the significance of data points in relationship to patient condition may be more appropriate for anesthesia patient monitors.
The proposed face uses coordinated facial features to make expressions. Expressions are interpolated to provide smooth combination and transition. The proposed face uses two parameters: one mapped to the expressions asleep, awake and surprised, and the other to the expressions sad, neutral and happy. The values of the two parameters are combined to form one facial expression to communicate the patient's current state. The central values for each parameter should indicate an acceptable state. Asleep can indicate no action necessary; surprised can indicate immediate action required. Happy can indicate optimal patient condition; sad can indicate abnormality. A computer program is supplied to draw the faces on an Apple Macintosh computer screen. Actual digitized photographs may be used; computer technology for motion pictures can generate photo-realistic interpolated faces which may maximize the desired communicative effects.
Interpolated faces may be used to communicate high level information on the patient's condition to the anesthesiologist. A face may represent an organ system, anesthesia machine or the whole patient and facilitate rapid qualitative assessment of the patient's condition.
Thomas Engel, M.D.
Computer simulation models are useful today to increase understanding of patient physiology and to teach anesthesiologists. In the future, sophisticated models may be used in the operating room to administer anesthesia. Physiologic simulation is particularly interesting in anesthesiology because anesthetic agents produce rapid changes and the patient's state is usually far from equilibrium. This abstract describes work in progress on a computer based anesthesia patient simulator for Apple Macintosh computers.
The program simulates a patient, anesthesia machine, monitors and anesthetic record. The program can also draw many different graphs of physiologic parameters. The patient model is built in five layers: body composition, hemodynamics, mass transport, pharmacokinetics and pharmacodynamics. Body composition is the most basic layer; other layers are built on top of it. The simulated patient has a beating heart with four separately contracting chambers, and eight tissue compartments for anesthetic uptake, distribution and effects. Pressures, flows and concentrations are simulated in real time and feedback in the model acts to maintain hemostasis.
The simulation program is written in Pascal and runs on Apple Macintosh computers. The Macintosh offers several advantages for computer simulation, including large capacity and high speed for numerical computation. The Macintosh operating system provides device independent services for networks, printers and displays. The Macintosh is also accessible to computer novices.
In addition to providing realistic visible patient behavior, the simulation model has accurate and consistent values for internal quantities. Most of these internal values are available to the user as graphs or tables. The simulation program is tightly integrated with the Macintosh environment; it can run concurrently with other programs, and it can share data with them for further analysis or presentation.
The simulation program is not tied to a specific simulated patient. A user may select general patient characteristics such as age, sex and body weight, as well as modify specific physiologic parameters. The program adjusts other parameters to maintain consistency. The program can simulate more than one patient at a time, and a user may compare the responses of different patients side by side on a display.
The simulation program provides a window for monitors, including the electrocardiogram and arterial, pulmonary artery and central venous pressure wave forms. It also provides an automated anesthesia record for the simulation. A user can apply techniques from dynamic systems analysis to further understand the model. The program can plot trajectories in many two dimensional projections of the complex multidimensional phase space. The program can also draw Poincaré sections for periodic functions such as the cardiac cycle. Comparative drug concentrations may be plotted in each compartment, or an effect may be plotted against the drug concentration in a compartment.
This anesthesia simulation program for Macintosh computers addresses several difficult simulation problems, including realistic internal values as well as realistic visible behavior, complex interactions and accurate feedback, and scaling patient parameters while maintaining consistency. In addition to duplicating a clinical situation, the simulation program provides analysis tools from nonlinear dynamics to study its complex model.