Anna-Lisa Osvalder

Application of usability testing to the development of medical equipment. Usability testing of a frequently used infusion pump and a new user interface for an infusion pump developed with a Human Factors approach

Abstract In medical care, the infusion pump is one of the most common pieces of technical equipment often involved in incidents due to handling. In order to improve usability and reduce errors, a new user interface for an infusion pump has been designed based on an analysis of observations, interviews, heuristic evaluation, reported incidents and theory about mental capacity and human error. The purpose of this study was to determine whether or not the new interface would reduce the number of handling-errors and problems, and how it could be further improved. For this purpose usability tests were performed by 18 nurses from three different hospital wards. The results showed that the number of handling problems were reduced for the new interface compared to the existing interface, but the number of errors was still high. The tests indicated a need to further improve the new interface in terms of spring-loaded modes where the users are only in the desired mode as long as they actively hold down a button. In identifying user requirements for medical equipment it was found important to use different data collection techniques. In this study it was further found that the nature of the information from the different user groups in usability tests can differ widely. The experienced users had the competence and self-confidence to be critical and suggest improvements based on their practical experience. Whereas the novice users were important since they encountered most of the serious problems and made the most mistakes. Relevance for industry There is a need to develop viable techniques to enable manufacturers of medical equipment and hospital personnel to critically specify and evaluate usability qualities when formulating user requirements for new medical equipment.

Ultimate strength of the lumbar spine in flexion—An in vitro study

The ultimate strength in flexion of 16 lumbar functional spinal units (FSU) was determined. The specimens were exposed to a combined static load of bending and shearing in the sagittal plane until overt rupture occurred (simulated flexion-distraction injuries). The biomechanical response of the FSU was measured with a force and moment platform. Mechanical displacement gauges were used to measure vertical displacements (flexion angulation) of the specimens. Photographs were taken after each loading step for determination of horizontal displacements and the centre of rotation. The lumbar FSU could resist a combination of bending moment and shear force of 156 Nm and 620 N respectively, before complete disruption occurred. The tension force acting on the posterior structures was 2.8 kN. The flexion angulation just before failure was 20 degrees and the anterior horizontal displacement between the upper and lower vertebrae was 9 mm. The centre of rotation was located in the posterior part of the lower vertebral body. The bone mineral content in the vertebrae appeared to be a good predictor of ultimate strength of the lumbar FSU. Knowledge of the biomechanical response of the lumbar spine under different static traumatic loads is a first step to better understand the injury mechanisms of the spine in traffic accidents.

A method for studying the biomechanical load response of the (in vitro) lumbar spine under dynamic flexion-shear loads.

A method was developed to study the biomechanical response of the lumbar motion segment (Functional Spinal Unit, FSU) under a dynamic (transient) load in flexion. In order to inflict flexion-distraction types of injuries (lap seat-belt injuries) different load pulses were transferred to the specimen by means of a padded pendulum. The load response of the specimen was measured with a force and moment transducer. The flexion angulation and displacements were determined by means of high-speed photography. Two series of tests were made with ten specimens in each and with two different load pulses: one moderate load pulse (peak acceleration 5 g, rise time 30 ms, duration 150 ms) and one severe load pulse (peak acceleration 12 g, rise time 15 ms, duration 250 ms). The results showed that the moderate load pulse caused residual permanent deformations at a mean bending moment of 140 Nm and a mean shear force of 430 N at a mean flexion angulation of 14 degrees. The severe load pulse caused evident signs of failure of the segments at a mean bending moment of 185 Nm and a mean shear force of 600 N at a mean flexion angulation of 19 degrees. Significant correlations were found between the load response and the size of the specimen, as well as between the load response and the bone mineral content (BMC) in the two adjacent vertebrae. Comparisons with lumbar spine response to static flexion-shear loading indicated that the specimens could withstand higher bending moments before injury occurred during dynamic loading, but the deformations at injury tended to be smaller for dynamic loading.

Usability evaluation of a GUI prototype for a ventilator machine.

Objective. Information presentation on the monitor screen of ventilator machines affects nurses’ response and decision-making during ventilation treatment. The purpose of this study is to evaluate whether a new GUI (graphical user interface) prototype, the so-called circular display prototype can make deviations easy to detect. Method. A numerical display prototype was made and used as a reference display in the evaluation. Six task scenarios that involved parameter changes were selected to simulate a real situation under volume control (VC) mode during ventilation treatment. Usability tests with the two display designs were carried out in a usability laboratory. Twenty medical nursing students participated as test subjects in the usability tests. Results. The objective results showed that the graphical circular display had an advantage over the numerical display in interpreting parameter changes, but not in reducing the error rates for detecting the number of parameter changes or for forming an overall picture of the patient’s situation. Furthermore, the circular display prototype did not improve the detection time. Conclusions. Although the majority of the test subjects preferred the graphical circular display, the results implied that several aspects of this prototype should be improved in a future development study.

Considering the importance of user profiles in interface design

User profile is a popular term widely employed during product design processes by industrial companies. Such a profile is normally intended to represent real users of a product. The ultimate purpose of a user profile is actually to help designers to recognize or learn about the real user by presenting them with a description of a real user’s attributes, for instance; the user’s gender, age, educational level, attitude, technical needs and skill level. The aim of this chapter is to provide information on the current knowledge and research about user profile issues, as well as to emphasize the importance of considering these issues in interface design. In this chapter, we mainly focus on how users’ difference in expertise affects their performance or activity in various interaction contexts. Considering the complex interaction situations in practice, novice and expert users’ interactions with medical user interfaces of different technical complexity will be analyzed as examples: one focuses on novice and expert users’ difference when interacting with simple medical interfaces, and the other focuses on differences when interacting with complex medical interfaces. Four issues will be analyzed and discussed: (1) how novice and expert users differ in terms of performance during the interaction; (2) how novice and expert users differ in the perspective of cognitive mental models during the interaction; (3) how novice and expert users should be defined in practice; and (4) what are the main differences between novice and expert users’ implications for interface design. Besides describing the effect of users’ expertise difference during the interface design process, we will also pinpoint some potential problems for the research on interface design, as well as some future challenges that academic researchers and industrial engineers should face in practice.

Setting the Requirements for a User-Friendly Infusion Pump

The infusion pump is a commonly used piece of equipment at the Intensive Care Unit. The pumps often are from different manufacturers and have different handling characteristics. The ICU is a dynamic environment, with periods of calm interrupted by periods of very high activity and mental load. Infusion pumps are often involved in reported incidents. The purpose of this study was to set requirements for a user interface for an infusion pump, using a systematic human factors approach. The method used consisted of field studies at an ICU, a critical evaluation of two pumps presently used at this ICU and an analysis of reported incidents which involved infusion pumps. Both pumps in the evaluation had a number of latent errors. Two types of incidents relating directly to the user interface were found, both of which could be traced back to latent errors. A number of requirements were set with the purpose of reducing the risks of the two types of incidents occurring and reducing the mental load of the user. Using these requirements, a new interface for an existing volumetric pump was designed.

Exploring Maritime Ergonomics from a Bottom Line Perspective

The present paper reports a study composed of three research activities exploring the economics of ergonomics in a shipping context. First, a literature study aimed to review previous studies on the economics of ergonomics in general and within the maritime domain in particular; and moreover, to ascertain the key ergonomic factors addressed in contemporary maritime ergonomic research. Second, the concept of ergonomics was probed from a stakeholder perspective through nine semi-structured qualitative interviews. Third, structured interviews were held with representatives of ten Swedish shipping companies to investigate if the shipowners are aware of and calculate the economic effects of ergonomics.The results show that severalmodels andmethods have been developed to estimate costs and benefits of ergonomics in other industries, but no studies were found from the shipping industry.Whether thesemethods can be readily adapted to the shipping industry has to be investigated further. While contemporary maritime ergonomic literature showed a focus on physical ergonomic and health and safety issues, the results of the stakeholder interviews indicated a focus on organizational ergonomics. The Swedish shipowners calculate the costs of sick-leave, but do not estimate the economic effects of ergonomics on a regular basis.

The ultimate flexural strength of the lumbar spine and vertebral bone mineral content

Flexion-distraction injuries (lap seat-belt injuries resulting from car accidents) were simulated by exposing 16 lumbar functional spinal units (FSUs) to a combined quasistatic load of bending and shearing in the sagittal plane. The load response of the FSU was measured by means of a force and moment transducer. Displacements and angulations were measured and calculated by means of dial gauges and photographs taken after each loading step. The mean angulation between the vertebrae just before total rupture was 20 degrees. The ultimate values of bending moment, shear force, and bending stiffness were correlated with the bone mineral content (BMC), and so were the horizontal and vertical displacements determined around the yield point on the load-displacement curve.

To Develop Viable Human Factors Engineering Methods for Improved Industrial Use

Human factors engineering methodology is important for design of complex systems, such as control rooms and distributed control systems. Available methodologies are however seldom adapted to industrial needs, which limits the use of the existing human factors engineering research base. In this paper we argue that human factors engineering methods have to be developed and adapted to the engineer working under industrial project constraints. Otherwise human factors engineering is unlikely to achieve a broad industrial impact. The paper suggests how the industrial viability of methods can be improved by applying a use centered approach to method development.

Sport performance and perceived musculoskeletal stress, pain and discomfort in kitesurfing

The purpose of this study was to obtain an overview of the specific movement patterns in kitesurfing, and the participants’ perceptions of musculoskeletal stress, pain and discomfort. Task analysis and survey studies were used to provide an overview of the sport, and to identify problematic issues associated with the performance of the tasks. Three different methods were complimentary used for data collection: observations (n=8), a web questionnaire (n=206) and interviews (n=17). Participants were contacted through kitesurfing events and online forums. Their ages ranged from 16-62 years. The results showed that participants experienced high musculoskeletal stress for short times during a session (jumps, tricks and strong winds), and lower, static musculoskeletal stress over a longer time (crossing). High stress was most frequently perceived in abdominal muscles. Knees and feet were the sites most frequently experienced as painful, followed by the shoulders and elbows. This study provides additional information on the performance of kitesurfing and perceived musculoskeletal stress, pain and discomfort. The results can be used as input data to develop training methods and equipment for safe and comfortable performance.