Heuristics for usability problems in medical devices34
| Heuristic | Application to the Heimlich valve |
|---|---|
| Consistency and standards ‘Users should not have to wonder whether different words, situations or actions mean the same thing’ | The term ‘chest drain’ is used by two different manufacturers to refer to either the thoracostomy tube or the chest drainage unit, creating confusion and facilitating error |
| Visibility of system state ‘Users should be informed about what is going on with the system through appropriate feedback and display of information’ | Labels on the Heimlich valve are difficult to read. The valve does not provide a clear indication of improper orientation |
| Match between system and world ‘The image of the system perceived by users should match the model the users have about the system’ | A diagram for proper orientation of the valve is not provided |
| Minimalist ‘Any extraneous information is a distraction and a slowdown’ | The manufacturer name ‘COOK’ is more prominently displayed on the valve than are the crucial orientation instructions |
| Minimise memory load ‘Users should not be required to memorise a lot of information to carry out tasks. Memory load reduces users’ capacity to carry out the main tasks.’ | Valve design does not force correct orientation, requiring the user to recall or deduce orientation information |
| Informative feedback ‘Users should be given prompt and informative feedback about their actions’ | The valve does not provide any feedback when improperly oriented, such as an indicator colour or sound. No directions are provided to guide the user to confirm correct orientation |
| Flexibility and efficiency ‘Users always learn and users are always different. Give users the flexibility of creating customisation and shortcuts to accelerate their performance.’ | Contrary to the heuristic, the valve design introduces user flexibility in the orientation of the valve and creates risk of error. |
| Good error messages ‘The messages should be informative enough such that users can understand the nature of errors, learn from errors and recover from errors.’ | The valve does not provide any feedback when improperly oriented, such as an indicator colour or sound. No directions are provided to allow the user to confirm correct orientation |
| Prevent errors ‘It is always better to design interfaces that prevent errors from happening in the first place.’ | Valve design does not force correct orientation; redesign could prevent error from occurring |
| Clear closure ‘Every task has a beginning and an end. Users should be clearly notified about the completion of a task.’ | Instructions do not include an end-of-procedure sequence of actions to confirm correct orientation of the valve |
| Reversible actions ‘Users should be allowed to recover from errors.’ | No instructions are provided to confirm correct valve orientation; such instructions could allow recovery from error |
| Use users’ language ‘The language should be always presented in a form understandable by the intended users.’ | Terms such as ‘obviate’ in the instructions may not be clear to some users. The term ‘chest drain’ is ambiguous and can refer to multiple devices. |
| Users in control ‘Do not give users that impression that they are controlled by the systems’ | Although mentioned in the instructions, labels on the valve itself do not clarify that the Heimlich valve is optional, and should be used when a one-way valve effect is desired. Users in the cases described felt obligated to use the valve to connect the thoracostomy tube to the chest drainage unit. |
| Help and documentation ‘Always provide help when needed.’ | Instructions for valve orientation and confirmation could be improved |