Preface

There are many uses for computer technology within the practice of anesthesia. Usually, computers are used to automate practices which are already well-established. Using the computer to help teach difficult concepts is another matter, however, that goes far beyond the automation of procedure. Computer-aided learning is difficult to develop, but very rewarding in its effectiveness. This program, Gas Man^®, exploits this medium and helps learners understand anesthesia uptake and distribution.

The fundamental principles underlying anesthetic pharmacokinetics are simple. The two important rules are conservation of mass and physiologic maintenance of lung volume. Unfortunately, the dynamic implications of these principles are not easy to comprehend. Indeed, it is the need for explanation and demonstration of the dynamic changes in anesthetic tension equilibration which led me to design and implement this educational tool.

The Gas Man program is a powerful marriage of computer simulation and image production with the written word. In place of the instructor in a simulation laboratory, we have the instructor's voice (in print) and a laboratory, both inside a personal computer. By using the set of exercises in this Manual, and by learning how to use Gas Man as a tool for further exploration, users can study the simplicities and subtleties of the dynamic properties of anesthesia uptake and distribution regardless of where they are or what other resources are available to them.

I first began investigating the use of computers to help teach the concepts of anesthesia uptake and distribution in 1980, when I received a grant from the Apple Educational Foundation to explore the use of Apple II computers. In 1982 the first version of Gas Man for the Apple II was shown at the American Society of Anesthesiologists meeting and then the New York Society of Anesthesiologists Post Graduate Assembly (NYSA-PGA) where it won a Special Award. The program and a set of exercises similar to this Manual was published and distributed by Addison- Wesley in 1984. After many colleagues clamored for an updated version of the program suitable for microcomputers, we demonstrated in 1989 a version of Gas Man^® for the Macintosh. In 1994 we released Gas Man^® for Windows^®, and Version 2.1, with many new features, was released in conjunction with this manual in October 1995. As computer operating systems evolved, so did Gas Man, each time adopting the latest Graphical User Interface (GUI) features.

Gas Man's new features significantly broaden the base of users and uses. The ability to compare and contrast anesthetic techniques and agent choices should attract a solid following by hospital administrators, pharmacists, and anyone concerned with the cost of health care.

The ability of the Gas Man Overlay to normalize tensions to agent MAC and then explore the effects of blood/gas solubility provides drug and equipment manufacturers with insights not previously available. Vaporizers for new agents sevoflurane and desflurane have maximum dial settings that account for both MAC and solubility, allowing the same relative alveolar overpressure found with halothane and desflurane vaporizers. Gas Man insights played a role in designing new vaporizers. Meanwhile, clinicians can use the same displays to compare and contrast administrations with different drugs and different techniques. Gas Man's wide ideal- body weight range - from 50 g to 1500 Kg - animals of interest to veterinarians can now be simulated with ease.

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Gas Man has been reviewed favorably in numerous publications^{1, 2, 3, 4, 5, 10}. Several studies have demonstrated the effectiveness of Gas Man as an educational tool in centers other than where it was written^{6, 7} and when compared to lecture presentation⁸. Ongoing study of its efficacy as a simulation program has endorsed its accuracy⁹. More recently, others have demonstrated that Gas Man accurately predicts expired anesthetic concentrations during induction and upon emergence after anesthetics of short and long duration¹¹ . One recent study used Gas Man to explore context-sensitive decrement times across a wide spectrum of anesthetics, anesthetization periods, and decrement criteria¹². I am committed to the wide-ranging audience of Gas Man users to continue to refine and enhance the program and its applications.