A brief history of simulation mannequin for clinical training

While still in a relatively nascent stage of development, simulation for healthcare applications has already evolved through its initial historical phases. Recounting stories of some key simulation technologies could be useful for informing future simulation advocates. In this brief history of medical simulation we focus primarily on the origin of mannequin simulators, especially those employing computer control, and we examine some of the pedagogy and evaluations of effectiveness that aided dissemination. A listing of part-task trainers for surgical and medical procedures (which we refer to as “procedural” simulators) and more limited discussion of their origins are also given to indicate the extent of activity in that area.

ORIGINS OF THE MODERN ERA OF SIMULATION

We begin with the earliest published accounts of some part task trainers that are precursors to computer based simulators. Gaba has produced a detailed history of the development of mannequins and some screen simulators, particularly as they were first used in anesthesia, and he and his colleagues also reported on a 10 year experience in using simulation for crisis resource management training. Issenberg et al presented an overview of simulators and trainers in several domains.

Resusci®-Anne to SimMan®

While not computer driven and having relatively limited functionality, Resusci-Anne marks a beginning for discussion because it is widely used for medical training and is a progenitor of one of the two current commercial mannequin simulators. Created in the early 1960s, this mannequin for training in mouth to mouth ventilation was designed by Asmund Laerdal, a successful Norwegian manufacturer of plastic toys. He was encouraged to do so by Dr. Bjorn Lind and other Norwegian anesthesiologists, following Dr. Peter Safar’s revelations about the superiority of mouth to mouth resuscitation. The airway could be obstructed, and it was necessary to use hyperextension of the neck and forward thrust of the chin to open the airway before initiating insufflation of air into the mannequin by the mouth to mouth technique that Safar had described. Based on evidence of the efficacy of closed chest massage, Safar later advised Laerdal to include an internal spring attached to the chest wall, which permitted simulation of cardiac compression. The possibility of training for the ABC (airway, breathing, circulation) of cardiopulmonary resuscitation (CPR) on the simulator was thus born. This early simulator of a dying victim, not breathing and lacking a heart beat, became known as Resusci-Anne and has been widely used for CPR training.

The Laerdal company did not develop a higher fidelity mannequin until the mid-1990s when encouraged to do so by many, including Dr. Ake Grenvik, a Safar colleague at the University of Pittsburgh. Drs. Rene Gonzales and John Schaefer, also of the University of Pittsburgh, developed a more anatomically correct airway and simulator, which was manufactured by Medical Plastics Corporation (MPL) of Texas. Laerdal acquired MPL and developed the simulator, then called SimMan, which was substantially cheaper than other available higher fidelity mannequin simulators, thus altering the market in a fashion described by the disruptive innovation model of Christensen.

Sim One

Sim One is a starting point for true computer controlled, mannequin simulators, particularly for simulation of the entire patient Conceived by Dr. Stephen Abrahamson, an engineer, and Dr. Judson Denson, a physician, at the University of Southern California in the mid-1960s, it was built in collaboration with Sierra Engineering and Aerojet General Corporation. Abrahamson, in a video acceptance of an award from the Society for Technology in Anesthesia, described the idea as originating from Aerojet’s need to develop peacetime applications of its capabilities in the face of diminishing military funding, before the escalation of the Vietnam conflict. The initial concept of replicating anesthesia machine functions quickly evolved to the objective of recreating more of the entire patient. After meeting with rejection from the National Institutes of Health and military funding sources, the project to build a prototype was supported by a three year, $272 000 grant from the US Office of Education.

The simulator was a remarkably lifelike mannequin, controlled by a hybrid digital (with “4096 words of memory”) and analogue computer. It had many high fidelity features: the chest was anatomically shaped and moved with breathing, the eyes blinked, the pupils dilated and constricted and the jaw opened and closed. To a limited extent, it was used for training and to conduct some primitive experiments about efficacy. While not rigorously justified by the methods, the authors claimed that the simulator had a “twofold” advantage in training anesthesia residents in the skill of endotracheal intubation while “posing significantly less threat to patient safety.”

Sim One did not achieve acceptance. Only one was constructed; sadly, nothing remains of it. The computer technology was too expensive for commercialization. But, equally importantly, the market for training in other than an apprenticeship model was non-existent. Gaba speculates that the vision for the use of Sim One was too narrow to create sufficient demand. These pioneers were too far ahead of the technology and the demand for its application.

Harvey Cardiology Mannequin

Harvey is a full sized mannequin that simulates 27 cardiac conditions. It is the earliest example of the modern concept of a part-task trainer for medical skills training. It was first demonstrated in 1968 at the American Heart Association Scientific Sessions by Dr. Michael Gordon of the University of Miami Medical School under the title of a Cardiology Patient Simulator .The motivation behind Harvey can be traced to Gordon’s days as a cardiac fellow under his mentor, Dr. W Proctor Harvey of Georgetown University, after whom the mannequin was named. Inspired by Dr. Harvey’s use of audiovisuals in his teaching, Gordon built a comprehensive cardiology patient simulator in collaboration with the Center for Research in Medical Education (CRME).

The simulator displays various physical findings, including blood pressure by auscultation, bilateral jugular venous pulse wave forms and arterial pulses, precordial impulses, and auscultatory events in the four classic areas; these are synchronized with the pulse and vary with respiration. Harvey is capable of simulating a spectrum of cardiac disease by varying blood pressure, breathing, pulses, normal heart sounds, and murmurs.

Harvey has undergone fairly rigorous testing for educational efficacy, perhaps more than any other simulation technology. Pilot studies documenting Harvey’s effectiveness in teaching bedside cardiological examination skills were first reported in 1980. In 1987, a study of the use of Harvey among 208 senior medical students in five medical schools was sponsored by the National Heart, Lung, and Blood Institute. Fourth year medical students who trained with Harvey during their cardiology elective performed significantly better than their peers who interacted only with patients. This was assessed through skills post-tests using the simulator as well as patients. There were no reported differences in the way patients perceived the professional behavior of Harvey trained versus non-Harvey trained students. Rather, students who were better able to interpret findings on Harvey showed enhanced confidence and ability to interpret those same findings on patients at the bedside.

Harvey has been used for training medical and nursing students, interns, and residents, and for continuing education of family physicians. It has also been applied to testing bedside cardiovascular examination skills of medical students, residents, and attending physicians in internal medicine, paediatrics, and emergency settings. By providing a platform for standardized testing, Harvey was early in allowing for more comprehensive sampling of different skills.

As it matured, Harvey was equipped with a curriculum of cardiovascular conditions, with associated learning goals and data-rich slide programmes developed by a national consortium of physicians and educators. It is frequently used in conjunction with the UMedic multimedia computer curriculum, comprising 10 patient centered, cased based programmes, which provides a comprehensive generalist curriculum in cardiology.

Around the time in which testing with Harvey was gaining momentum, a separate heart sound simulator was shown to improve cardiac auscultation skills of nurses. Harvey also inspired the development of smaller, more portable cardiology patient simulators, for example, Simulator K.

Physiological models for realistic simulation

An important contribution to the history of realistic mannequin simulators was the development of mathematical models of the physiology and pharmacology of drugs in anesthesia. These served a dual function: they evolved into screen based simulators for different applications and also provided the underlying concepts in modelling physiology that were needed to support hands-on simulators with automatic control. Several computer based simulations of various aspects of anesthesia have been developed. Philip created a program for teaching uptake and distribution of anesthetic agents, which he called GasMan®.Sikorski et al described a computer based simulation for instructing anesthesia residents in managing intraoperative events.

More complete models of human physiology have enabled higher fidelity, more realistic simulations. Building on the work of others in physiological modelling, Dr. N T Smith and colleagues at the University of California San Diego (UCSD) conceived a multicompartment model of human physiology and pharmacology that formed the basis for SLEEPER, a screen based simulator. Intended primarily to teach physiology and pharmacology, it was a fairly complex system requiring more computing power than was then available in desktop computers. SLEEPER evolved into a broader application, BODY™, which was marketed first by Marquette Medical Systems and currently by Advanced Simulation Corporation.

Dr.Howard Schwid, a former fellow in the UCSD labs, further developed the concept of screen based simulation by simplifying the models to run on a desktop computer and thus reach a wider audience. Schwid and O’Donnell also expanded the application to include critical event management, for which there was a greater market; this was commercialised in a product called the Anesthesia Simulator Recorder, marketed in 1989. These workers built an expert system around the anesthesia simulator to provide learning objectives, management advice, and an automated debriefer. The new program was named Anesthesia Simulator Consultant (ASC). The basic product has further evolved into a family of screen based simulators marketed by Anesoft Corporation. Schwid and others conducted numerous experiments to assess the utility of ASC, including studies of efficacy of learning advanced cardiac life support skills, and comparison of screen based and mannequin simulation learning.

Realistic Mannequin Simulators

Independently, and for different objectives, two mannequin simulators were developed at approximately the same time at opposite ends of the USA. Both were partly inspired by efforts to improve patient safety under anesthesia—a movement that had been inspired by research into error and human factors in anesthesia and by the formation of the Anesthesia Patient Safety Foundation, which funded simulation research and development in the late 1980s. The pedagogies for employing these simulators have evolved into widely used tools for skills and behavior training in many domains.

At the Stanford Medical School affiliated Veterans’ Affairs Palo Alto Health Care System, Dr. David Gaba and colleagues fabricated what is probably the first prototype of a mannequin simulator developed for investigating human performance in anesthesia. A pre-prototype is shown in fig 4. The original version, used for experiments and training in early 1987, was numbered CASE 1.2 (Comprehensive Anesthesia Simulation Environment).It combined commercially available waveform generators and virtual instruments—for example, a non-invasive blood pressure monitor—on a Macintosh Plus computer, with a commercially available mannequin to create a “patient” whose vital signs could be manipulated to simulate critical events. Placed in a real operating room and surrounded by actual equipment, this was the beginning of the high realism, physical simulation environment. The next version, CASE 2.0, contained a model of cardiovascular physiology running on a Transputer (a microprocessor chip designed for parallel processing with other such chips), making it partially model driven (as opposed to CASE 1.2) and also an example of parallel processing.

The CASE system and its progeny were used by its developers at Stanford and subsequently by others to investigate various aspects of human performance in anesthesia and related domains. From those experiments, in which critical events were created and the response of subjects observed and measured, emerged a division of performance assessment into technical and behavioral skills. A training curriculum, Anesthesia Crisis Resource Management (ACRM), based on the then relatively new aviation model of crew resource management (CRM) was also developed, evaluated, and propagated. ACRM teaches generic responses to critical events and incorporates debriefings that use videotapes of simulation scenarios. Course evaluations suggested that the realism was sufficient to elicit realistic behaviors. In 1992, the CASE 2.0 system was transported to Boston, where a series of sessions was conducted to test the feasibility of transferring the educational model. Anesthesia faculty, residents, and nurse anesthetists in the hospitals affiliated with Harvard Medical School were engaged in a 10 week trial. Success there led to the establishment of a collaborative educational center dedicated to simulation based training—the Boston Anesthesia Simulation Center (later renamed to the Center for Medical Simulation)—which was probably the first adopter of the technology for education applications outside the centers that developed the different technologies.

The CASE system and ASC software models were licensed to CAE-Link (a descendent of the original Link Aeronautical Corporation that produced the pioneering “Link Trainer”, the first significant simulator in aviation)” for commercialisation. The CAE patient simulator used modified physiological models from the ASC models, with large sets of patient characteristics, including cardiovascular and respiratory function, acid-base balance, and pharmacokinetics and pharmacodynamics representing numerous disease states. The mannequin had many features, including airway anatomy that could be altered to mimic degrees of difficulty of intubation, palpable carotid and radial pulses, lungs that simulated behavior during spontaneous and controlled ventilation, heart and breath sounds, eyes that opened and closed, and a thumb twitch, as used for monitoring neuromuscular blockade during anesthesia. The system was driven by a Sun SPARC 1 computer, which allowed for automatic responses to drug interventions entered by the operator and for manual manipulation of physiological variables.

The company transmuted several times (from CAE-Link to CAE Medical Electronics, to Eagle of Binghamton, New York), and the product was eventually sold to Medsim Ltd, headquartered in Israel. Medsim, which previously had developed and marketed a part-task trainer for ultrasound training (UltraSim™) eventually abandoned patient simulation, in part because its marketing strategy to create training centers did not fit the demand of the times.

At around the same time that CASE 1.2 was being born, a multidisciplinary team at the University of Florida, Gainesville, led by Dr. Michael Good and mentored by Dr. J S Gravenstein, developed the Gainesville Anesthesia Simulator (GAS).⁶¹ It arose from an interest in training anesthesia residents in basic clinical skills. The project began with the capability for diagnosis of faults in anesthesia machines, in which controllable mechanical failure modes were embedded. Attaching a lung simulator to the machine extended the training challenge. This was developed into a complete mannequin, aimed primarily toward diagnosis of single source critical events in anesthesia. The mannequin had a sophisticated lung model, which mimicked uptake and distribution of anesthetic gases. Later versions incorporated a system for automatically recognizing drugs as they were injected. In contrast to the more instructor driven manual operation of CASE 1.2, this software enabled sequences of physiological changes both predefined and in response to actions of the trainer and trainee.

GAS was subjected to an important early test of efficacy, reported only in an abstract. Sixteen anaesthesia residents were randomized into two cohorts: with and without simulation instruction. Clinical evaluations—in which evaluators were blinded to the subject cohort status—indicated a more rapid learning curve for the simulation trained group, although both groups achieved the same level of proficiency at the end of the three month trial. The trial was ended primarily because of resident demand to participate in simulation training.

GAS was licensed to Loral Data Systems Inc, which later spun off the simulator product to a new company, Medical Education Technologies Inc (Sarasota, Florida). The METI product was dubbed the Human Patient Simulator™ (HPS). A pediatric version, Pediasim™, and a simpler and more portable model, the ECS™, were introduced in the late 1990s and early 2000s, respectively.

Other Mannequin Simulators

Several other mannequin simulators were constructed and used in the assessment of training processes but without becoming commercial products. Chopra et al developed the Leiden Anesthesia Simulator as a tool for teaching critical event management in anesthesia. It appears to have been modelled on CASE 1.2 and was used in an experiment to assess the efficacy of simulation based training to improve skills in critical event management. The Sophus Anesthesia Simulator was developed in 1991 by a team from the Department of Anesthesiology at Herlev Hospital, Roskilde University and Risø National Laboratory in Denmark. Schaefer and colleagues in Basel employed a combination of the Sophus simulator and part-task surgical skills trainer using a perfused pig liver to teach Team Oriented Management Skills (TOMS), developed independently from, but in a similar way to, crisis resource management. The combined simulator system was called Wilhelm Tell. ACCESS (Anesthesia Computer Controlled Emergency Situation Simulator) was developed in the United Kingdom as a part-task trainer for anesthesia skills.