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Sim One - The First Computer-Controlled Patient Simulator

April Barnes and Rosalyn P, Scott, MD, MSHA

As simulation becomes an essential component of education, training, assessment and maintenance of professional certification throughout healthcare, it is difficult to believe that the first computer-controlled patient simulator was built 44 years ago! In 1966 Dr. Stephen Abrahamson and Dr. Judson Denson developed Sim One at the University of Southern California to train anesthesiology residents in endotracheal intubation. Abrahamson, an engineer, and Denson, a physician, collaborated with Sierra Engineering and Aerojet General Corporation to form an interdisciplinary team of experts from medicine, engineering, education and computer science (Abrahamson 1974, Cooper & Taqueti 2004). The Sim One prototype was built with funds from a $272,000 grant from the U.S. Office of Education after being rejected by the National Institutes of Health and military funding sources (Cooper & Taqueti 2004).

The working prototype of Sim One included five components: computer, interface unit, instructor's console, anesthesia machine and mannequin. The mannequin replicated physiologic responses such as a chest that moved with breathing, blinking eyes, pupils that dilated and constricted and a jaw that opened and closed. Sim One also had a heartbeat, temporal and carotid pulse and blood pressure. In addition to the life-like appearance, Sim One was constructed to "behave" and "respond" as a real patient would. Abrahamson, Denson & Wolf (1969) were able to demonstrate that residents trained on Sim One achieved professional levels of performance in fewer elapsed days and in smaller number of trials in the operating room than residents without simulator training. Although the sample size was small, the results of this study were interpreted to indicate that training with simulators produced a significant time saving in training and a significant lower threat to patient safety in the long term.

Sim One simulator cost approximately $100,000 to construct and was not widely accepted at the time. It was considered too expensive for commercialization and there was a general resistance to any alternative to the conventional apprenticeship model of training. Some also speculate the narrow vision of applications for the simulator failed to create enough demand. (Cooper & Taqueti 2004). Unfortunately, only one Sim One was constructed and was not maintained.


  1. Abrahamson S. Human simulation for training in anesthesiology In: Ray CD, editor. Medical Engineering. Chicago: Yearbook; 1974; p. 370-4
  2. Abrahamson S, Denson JS, Wolf RM. Effectiveness of a simulator in training anesthesiology residents. The Journal of Medical Education. 1969; 44(6):515-9.
  3. Cooper JB, Taqueti VR. A brief history of the development of mannequin simulators for clinical education and training. Quality & Safety in Health Care. 2004; 13(Suppl 1):i11-8.