شبیه سازی کامپیوتری برای بهبودهای ارگونومیک در عمل جراحی لاپاروسکوپی

It is the aim of this study to reduce the stress and strain of the medical staff during laparoscopic operations, and, simultaneously, to increase the safety and efficiency of an integrated operation room (OR) by an ergonomic redesign. This was attempted by a computer simulation approach using free modelling of the OR and 3D human models (manikins). After defining ergonomically “ideal” postures, optimal solutions for key elements of an ergonomic design of the OR (position and height of the image displays, height of the OR table and the Mayo stand) could be evaluated with special regard to the different individual body size of each member of the team. These data should be useful for the development of team adapted, user friendly integrated OR suites of the future.

In laparoscopic or minor access surgery, large incisions through the abdominal wall for intraabdominal operations are avoided. This is achieved by inserting three or more trocars (ports) into the abdominal cavity. Via these ports, a videotelescope and specially designed instruments are brought into the abdomen, enabling the surgeon to perform the operation in a similar manner as in open surgery but in a by far less invasive way. In comparison to open surgery, however, this new approach requires an additional spectrum of sophisticated devices and comprehensive technical support (light sources, camera control units, videoscreens etc.). Usually, the operative team comprehends three or four person: the surgeon, the scrub nurse and one or two assistants. The assistant has to align the videotelescope to visualize the site of the operation, while the surgeon performs the operation. The scrub nurse has the task to deliver the instruments required at the different steps of the operation and to support the surgeon's activities in all regards. As compared to conventional, open interventions, the working conditions in minimally invasive surgery are by far worse due to specific constraints of the technical environment (Berguer et al., 1999; Nguyen et al., 2001; Vereczkei et al., 2003). The positioning of the monitors is one of the essential items (Hanna et al., 1998). Real time video transmission of the intraabdominal view is a decisive precondition for a safe and efficient performance of the entire operation room (OR) team. Accordingly, each member of the team must have continuous and reliable visual access to the videoscreen. In most standard ORs, however, the screen(s) are positioned atop of the so-called laparoscopy trolleys containing the dedicated laparoscopic equipment as needed for the operation. These trolleys are bulky, and more often than not it is impossible to find an optimal position because no appropriate space is left at the table. A compromise between the “ideal” position and the available space is inevitable (Herron et al., 2001). Since continuous observation of the screens is mandatory for each member of the team, they have to accept unergonomic working postures for long-lasting periods of time. Together with static holding and a variety of additional physical and mental stress factors this augments considerably the strain of the OR team and can, potentially, even lead to a reduction of the safety level (Berguer et al., 2001). Accordingly, it has to be assumed that, if the problem of an optimal monitor positioning could be solved, this would not only improve the working conditions of the team but also increase the efficiency and safety of an operation. Leading manufacturers of OR suites are now offering new concepts of boom-mounted monitors which can be moved independent of bulky trolleys, allowing for a free spatial positioning of the screen(s) at the table. This offers the chance to realize an optimal observation of the operation to all members of the OR team. However, little is known about where, at which height and at which distance a screen should be ideally placed for the individual observer. In order to obtain valid data we attempted to identify the optimal positioning of the screen(s) using a computer simulation system. Another very important issue influencing the ergonomic situation at the OR table is an appropriate adjustment of the elevation of the screen(s) and of the OR table with the Mayo stand (Berguer et al., 2002). The differences in the individual body height of each member of the team make it difficult to find a position which is acceptable for each of them. Scientific data to solve this problem are scarce. Therefore, the computer simulation of the intraoperative setting was also used to identify an ergonomically reasonable compromise for the height of these objects.

In laparoscopic surgery, the position and the height of the surgical image displays is essential for the working conditions of the OR team. Up to now, ergonomical considerations did not play a major role when it had to be decided upon the place of the screen. The placement was more or less a question of the available space. Currently, new OR designs allow for a more flexible positioning of the screens consecutive to boom-mounted constructions (Feussner, 2003; Herron et al., 2001). A systematic approach to identify the “optimal” position of the screen seemed to be warranted. The position of the screen, however, is just one—though most important—variable influencing the ergonomic conditions of all members of the OR team. Two additional, major factors—among a large variety of others—are the height of the OR table and of the Mayo stand, in particular due to the fact that the body heights of the individual members of the team may vary considerably. To identify the “ideal” constellation is difficult since the positioning of the team and of the equipment, and of the patient varies according to the different types of operations. To evaluate the broad spectrum of options within a real OR would be extremely time consuming and expensive. Alternatively, real models and minikins could be built, but the flexibility of real models is low. Therefore, an integrated approach to identify an “optimal” constellation using a computer simulation program was attempted. A few reports have been published upon posture sampling and evaluation during laparoscopic surgery (Person et al., 2001; Radermacher et al., 1996), but to the best of our knowledge, a dedicated tool for the ergonomic evaluation of the OR environment using free modelling of a 3D human manikin does not yet exist. Therefore, the RAMSIS system was selected and adapted. RAMSIS is, originally, designed for ergonomical studies in automobile construction and is able to define the deviation of various postures from a predefined “comfort posture”. The “comfort posture” during a surgical operation was defined in this study by asking two well-experienced surgeons to demonstrate their subjectively most relaxed and comfortable working postures. These “ideal” postures served as the “golden standard”. It has to be clearly emphasized that this methodical approach is critical, and a systematic validation is still required. Nevertheless, it offered, for the first time, the opportunity to quantify the ergonomic situation in a surgical OR and to describe the working conditions of the individual member of the team with numerical data. This analysis revealed some facts of major importance: The operative team for standard laparoscopic interventions should have at least two separate image displays. Using only one image display exerts significant additional strain to all members of the team. This observation is not entirely new. It has been addressed repeatedly in surgical literature, but using the RAMSIS system makes it possible to explain the ergonomic background in objective terms. For laparoscopic surgery of the upper gastrointestinal tract and if the surgeon is positioned on the right-hand side of the patient his image display should be placed diagonally to him close to the patient's neck/left shoulder. The computer simulation demonstrates clearly that the use of adequate tools to compensate the different body heights of the team members is inevitable in many cases. Again, it could be argued that the use of steps of adequate height is already quite common in all OR's all over the world, but the RAMSIS evaluation offers precise data upon the difference in height which has to be compensated. Using steps is dangerous and less than ideal from the ergonomic point of view. Therefore, in the OR of the future, elevatable platforms will be integrated into the floor that can be lifted up according to the individual need which has been determined by this evaluation. Based upon a comprehensive computer simulation, an “ideal” ergonomic positioning of the team, the patient and the equipment could be preselected automatically prior to the operation. Furthermore, reliable simulation tools of an OR will certainly facilitate the design and the construction of new devices and entirely new OR's. It is admitted, however, that this preliminary study is just a first attempt to assess the ergonomical situation within the OR by the use of an objective modelling tool. Reliability and accuracy have still to be confirmed by a more comprehensive evaluation. However, it could be demonstrated that a simulation program which was originally designed for the automotive industry can be successfully applied for the evaluation of the OR environment. Further studies seem to be warranted.