Evaluation Framework of Ergonomic Requirements for Iterative Design Develpment of Computer Systems and their User Interfaces for Minimally Invasive Therapy

T. Studeli(1), A.Freudenthal(1), H De Ridder(1)

Faculty of Industrial Design Engineering Delft University of Technology, Landbergstraat 15, 2628 CE Delft, The Netherlands

Interventional Centre, University od Oslo, Norway & Bringham and Women's Hospital, Harvard University, USA

e-mail: T.P.Studeli@tudelft.nl

Web:htpp://www.io.tudelft.nl and http://www.ariser.info

Abstract

This work describes novel characteristics of future computer systems for minimally invasive cardiag therapy by example of mitral valve repair or replacement. "Super vision" and "super sensing" are provided to the operation theatre by augmented reality technology and robotic applications. By specifying an evaluation framework, chalanges for ergonomics in the future are discussed. The study focuses on user-centered design, information presentation, surgeons's workload and safety, and security aspects. Although references on applicable ergonomics standards and well established literature are given, the aim of the study is to look ahead and analyze specific gaps in ergonomics knowledge for future systems: the design methodology better takes into account the multi-disciplinarity of the user and the developers. Presentation of information will be case-sensitive to user and task and information can be reduced or augmented if needed. The system manages user's workload dynamically, it shifts functions between users or between users and system. The security system can handle human errors and ensures patients safety.

Keywords: minimally invasive therapy (MIT); augmented reality (AR); ergonomic requirements; context awareness; time critical tasks; decision support; workload; information; safety and security

Background

Minimally invasive surgery is performed through one or several small incisions, using specialized surgical instruments. It has specialized fields for abdomen (laparoscopy), orthopedics (arthroscopy) and lung and heart (thoracoscopy). There is a trend to use an increasing amount of minimally invasive therapies (MITs) and they are widely seen as being the future in surgery. The patient profits in most cases from these therapies using smaller incisions ans scars reducing risk of infection, less bleeding and less pain and trauma. The effect is a shorter length of stay in the hospital and a reduced recovery time. As beneficiary for the patient ans MITs are being seen, as challenging the procedures themselves can be for the surgeon. MITs need more training and normally only experienced surgeons are able to conduct them. Compared to the classical approaches there are more strict selections of the patients, the procedure must be planned more in detail. During the operation there is less space to work (fine motor skills), less insight in the body (indirect and unnatural vision through camera), less information and less control. Surgeons also experience a higher risk potential in case of surgical errors.

In the last years a range of new materials and technologis led to new developments in the domain of computer-guided surgery and computer-enhanced surgical robotic systems. Unfortunately the design of those systems is technology driven in most cases and until now only few and only very specific research on human factors (HF) aspects has been done. The European research training network 'Augmented Reality in Surgery' (ARIS*ER) aims to fill this gap. HF specialists are equal partners in the ARIS*ER consortium; research in the core technologies goes parallel with research in ergonomics. The ARIS*ER project covers three MITs: percutaneous radio-frequency ablation of liver tumors, laparoscopic liver resection and thoracoscopic mitral valve repair replacement.

The aim is to improve minimally invasive therapies and face the lack of sensory feedback ans information support for the surgical team. This is effectuated by combining new technologies in image processing (segmentation and registration), robotics, 3D visualisation and tracking in one augmented reality (AR) system. The user centered design methodology involves all eight partners, engineers, surgeons and HF specialists (Freudenthal et al. 2005). The development of the system is done through several design iterations. The amount of iterations depends on the progress of the research in the different fields.

The role of the HF specialists is to guide the design process as well as to set up an evaluation framework that covers the most important ergonomics (incl. safety), medical and technical aspects. The overall evaluation framework is following the methodology in ARIS*ER. Eith each design iteration the design process is following the task chronology: investigate user requirements, match technology opportunities, and select and evaluate solutions. On all tasks in the design process industrial designers, engineers and surgeons work in close collaboration in focus groups, e.g. on work flow analysis or on prototypes and demonstrators. The evaluation is therefore iterative and follows the development of the core technology and the evaluation of running prototypes and systems.

Aim

This paper aims to describe the first results of the investigations that will lead to an evaluation framework tailored to the design and future MIT computer systems. It addresses aspects of user-centered design, information presentation, surgeons´s workload and safety, and security. Up til now the focus was on one of the clinical cases of ARIS*ER, the Port_Access variant for the thorascopic mitral valve repair or replacement procedure.

Methods

The methodology that was used up til now is following the stepwise approach of the ARIS*ER methodology:

• A task analysis (ISO 13407), assigning tasks to roles, ISO 6385, was performed in a co-research setting with technologists (n=10), experienced cardiac surgeons (n=2) and a HF specialist who moderate the session. A big sheet (A0) with grid was hung on the workshop wall, depicting the occuring main tasks of the surgical procedure in columns (inspired by Jalote-Parmar et al. 20006) and roles of the team and the actual equipment of the system in rows. First different tasks and subtasks during the procedure had to be identified and described. Secondly descriptions of the subtasks for the different roles were placed in the appropriate cells (roles as defined by van der Veer et al 2002).
• next in the workshop, an adapted critical incidents analysis (ISO/TR 16982) was conducted. The surgical procedure was presented and explained by two surgeons, following the procedure on the grid (above). Next the participants (n=12) were asked to select critical subtasks and to mark the corresponding cell on the grid with colour coded stickers. Safety critical subtasks were marked red, subtasks with critical lack of information blue and subtasks with critical workload yellow. The HF moderator asked the participants to explain their choice. This was later analyzed and formed the questions for the following parallele steps, the interviewes on the selected key reguirements in ergonomics.
• Interviews (ISO/TR 16982) with experienced medical doctors (MD) in MIT: the subjects (n=4) were questioned individually to deepen the understanding of the outcome from the critical incidents analysis in order to identify the tasks with especially high demands on information, especialy high workload situation, and especially high risk for the patients'safety.
• In three different workshops future technical possibilities for selected key tasks were discussed with focus on visualisation (n=12), medical aspects (n=4) and robotics (n=6).
• Results from all previous workshops and interviews were analyzed and combined to generate hypotheses on the design of future MIT computer systems
• Finally, a first step was made in the process of designing an evaluation framework by comparing the functions and tasks of future sustems with ergonomic, medical and safety standards.

Results

The task analysis (ISO 13407) shows the following characteristics of the thoracoscopic mitral valve repair or replacement by the example existing Port-Access procedure:

• Structure- the procedure can be divided into characteristic self-contained steps: 1. Preparation of the patient, 2. Thoracotamy (openings in chest), 3. Installation of cardio-pulmonary bypass (CPB), 4. Stopping the heart, 5. Operation at he heart, 6. Going from CPB and starting the heart, 7. Closing the wounds.
• Control- the head surgeon is in charge for the patient safety during the procedure. Although he is responsible for the outcome, he has limited control over some parts of the procedure. In the critical parts of the procedure, the work is mainly controlled by the conditions and the homeostasis of the patient.
• Team work- most tasks are shared ones in functional teams, e.g. anesthesiologist and assistant, head surgeon and assistant, scrub nurse and assitant.
• Safety and Timing- time matters, there is a constant time pressure, and most of the tasks have specific increased time critical aspects.