Applying Usability Test to Find the Interface Design Principle of HRV Device for Senior Users
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Home use medical device industry prospers due to the ageing society. In both physiological and psychological domain, home use medical devices have received much attention in recent years. Seniors usually feel depressed or anxious because of losing health and living abilities. They can use the heart rate variability (HRV) device in analyzing their emotional response, however the interface of commercial HRV devices are not easy for them to operate. Therefore, the usability test of these devices was introduced for the senior users. Five senior user were recruited to conduct usability test of the two commercial HRV devices: ANSWatch (Taiwan Scientific Corp.) and CheckMyHeart Handheld HRV (DailyCare BioMedical Inc.) follow the typical operation task. Then the in-depth interview were conducted to find operational failure factors. All of senior users indicated that the serious failure factors are: “unable to understand English instructions” and “unable to determine the meaning of illustration”. Four of them indicated that the minor ones are: “no appropriate guide”; “text is too small”; and “layout is not appropriate”. Three of them indicated that “illustration surface reflection” is another problem. Therefore, we suggests that the home use HRV device interface design should consider principles such as (1) the language and icon properties, (2) step guides and text properties, (3) consistency of interface configuration, (4) color scheme to improve the operational satisfaction for the senior users.
KeywordsUsability test Home use medical device Heart rate variability
With rapid development of technology, people’s life becomes more complicated and changeful. The changes in life may easily disjoin the life of older adults to the environment, making them feel anxious. Older adults with anxiety disorders tend to have high rates of depression. Anxiety also is highly comorbid with medical illness in older populations. These comorbidities can make differential diagnosis difficult as the symptoms overlap heavily and may also lead to underdiagnosis of anxiety disorders . Therefore, the self-emotional management product is important for the older adults. Many studies have suggested that physiological signal, such as electrocardiography (ECG), when accompanied with heart rate variability (HRV) analysis technique, can be applied in analyzing personal emotional response . HRV refers to the variation of heartbeat intervals, which allows people to know how heart rate is affected by the constant coactions of sympathetic and parasympathetic influence. This technology can in term reveal information concerning autonomic flexibility, which is a key factor for estimating a person’s emotional control ability. Many portable medical devices using HRV technology have been proposed, so that the users can manage their emotion easily [3, 4]. However, these devices are not designed specifically for the older population.
For the user who is not the intended target user of the product, some difficulties may arise during operation, especially when the user is older adults. Moreover, many older user maybe be afraid that their misoperation may damage the products, thus the willingness to use new products with complex functions is lower. The older adults often feel perplexed when facing technological products . In addition, visual degeneration, which is a common problem to older adults, causes difficulties in seeing the operation interface of the products. The deteriorating finger sensitivity may cause difficulty for them to operate small buttons . Some studies have proposed that usability evaluation is an useful approach to assist find operational problem when operating medical devices [7, 8], especially for the older adults . In recent years, the usability evaluation has been adopted to evaluate the operational behavior of medical device interface. In this user-based evaluation procedure, the user is asked to complete the typical operating process of the device, while the researcher observes and records the mistakes made by the users or the hesitation encountered by the users. Thus, the defects in design can be identified, and the probability of misoperation can be reduced. Therefore, this study aims at the usability of home-use medical device interface, and uses HRV device as an example to propose a principle of interface design suitable for the senior users.
Basic data of subjects
Experience in home-use medical devices
Blood pressure meter/5 years
Blood pressure meter/6 years
Blood pressure meter/2 years
Blood glucose meter/10 years
Blood glucose meter and Blood pressure meter/10 years
3 Results and Discussion
The five subjects completed the usability evaluation of the two HRV devices. In their view, the problems in the operating process were most likely to occur in the followings (brackets represents the number of subjects who agreed to the item): the English description is not understood (5 subjects) and the icon meaning is unknown (5 subjects); no operation guide (4 subjects), the text is too small to read (4 subjects), poor interface configuration (4 subjects); the icons are unclear due to interface reflection (3 subjects). The opinion agreed by less than three persons was regarded as non-essential operational issue in this study, excluded from discussion.
3.1 Language and Icon Attributes
The language barrier is an important factor in product interface design. The two commercially available HRV devices used in this study are in English. It may not be a problem to general users, but for the elderly who only read Chinese had difficulty in completing the tasks as they did not understand the operating instructions. According to our interview, different languages result in users’ operation mistakes, thus causing frustration . Among the interface button icons of “CheckMyHeart”, “M” represents “record” function, but the subjects did not associate “M” with “Memory”, resulting in operational difficulties.
The subjects indicated that the icons on the interface of HRV device should be larger, and must convey meanings clearly. In terms of the meanings of icons, the interface button icons of “ANSWatch” are shown as four footballs, and the subjects could not associate them with the functions directly, thus they had to spend much time on identifying the button functions.
3.2 Step Tips and Word Level Attribute
Both the “ANSWatch” and “CheckMyHeart” do not provide step guide, but provide good auditory feedback, allowing the users to complete the tasks. However, the subjects indicated that they need appropriate tips to help them operating an unfamiliar technological (medical) product. If there were no operation guide or feedback tips in operation, they could not complete the tasks easily [5, 10].
The subjects suggested that the words in the interface should be larger, and the word meanings should be simple and clarified. The smallest font on the “Check My Heart” screen was about 10 pt, and they need to wear presbyopia glasses to read the text. Thus, “the text is too small to read” is the important factor failing their operation.
3.3 Interface Configuration Consistency
The subjects indicated that the operation interface is easy to operate when it has high consistency. The results of this study showed that “ANSWatch” uses football icons (incomprehensible) as controllers (buttons). The subjects had to spend much time on thinking about the meanings of the icons for the first operation. However, the “ANSWatch” interface has higher space consistency, meaning each football icon corresponds to an operating function, and there are acoustic and animated operation feedbacks to the subjects. Once the subjects recognized the meaning of football button, the following tasks were easy to complete. In addition, the button position and spacing were important factors influencing the subjects’ operation . According to the subjects’ operational behavior, when they operated the commercially available HRV device with both hands, the buttons located below the screen could present their hands from covering the screen in operation. When the subjects operated buttons with their thumbs, the buttons should be separated from each other appropriately to avoid misoperation.
3.4 Interface Color Matching
The subjects indicated that the dark gray icons in the grayish background of the operation interface of “CheckMyHeart” were difficult to see. The icons were covered with bright membrane which reflects light, making it difficult for the subjects to see the button icons clearly. Therefore, the button icons should avoid using analogous colors or materials that reflect light.
This study tested the elderly on the operation of two types of home-use HRV device to analyze the product usability. The results revealed several operating problems in practical use: (1) English description is not understood, (2) icon meaning is unknown, (3) no operation guide, (4) text is too small to read, (5) poor interface configuration, (6) icons are illegible due to interface reflection. Therefore, this study suggests that the future interface design for hand-held home-use medical devices should consider (1) language barrier and icon attribute, (2) step tips and word level attribute, (3) interface configuration consistency, (4) interface color matching. The improved design to enhance the user satisfaction.
The authors appreciate Chen Ying-Hsiu and the participation of senior users. This work was sponsored under grant NSC 100-2632-H-130-001-MY2 by the National Science Council, Taiwan.
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