UFMEA analysis to the design of an apparatus that monitors, among other things, patient pressure and breathing.

1. Description of the device – brief characteristics

The design of an apparatus to monitor a patient’s blood pressure and saturation (and other important parameters) for hospital use was analysed. The device was to be operated by nurses, who turn it on and then set alarm levels to respond to alarming changes in the patient’s vital signs. In the event of an abnormality, the device should generate an alarm to prompt a response from the medical staff.

2. Purpose of the UFMEA analysis

The aim of the User Failure Modes and Effects Analysis (UFMEA) was to identify potential user failures when using the device and to assess their impact on patient safety and the effectiveness of vital signs monitoring. The analysis aimed to minimise the risk of user failure by introducing appropriate prevention in terms of preparation for use of the device, as well as in terms of design changes to the device.

3. The UFMEA analysis process

Identification of potential user failures

The UFMEA analysis starts by describing all the actions that the user performs when operating the device – on this basis, a list of possible failures (failure mode) is established. As part of this phase of the analysis, the following potential failures are identified, among others:

  • setting alarm levels too high/low: the nurse may set alarm levels too high or too low, which can lead to a delay in responding to the risk (e.g. detecting a critical drop in blood pressure too late). Potential causes (failure cause) for this failure were identified as, among others, a scale that is not very legible, a poorly chosen typeface where the numbers 1 and 7 look very similar, potentiometers that are set too close (when setting parameter 2, the previously correctly set parameter 1 can be inadvertently moved);
  • failure to connect the device to the patient: if the device is not properly connected to the patient, parameter monitoring will not be reliable. The cause of this failure could have been, among other things, the unusual design of the clamp, which, although it appeared to be fastened, did not ensure that the sensor adhered properly to the body;
  • failure to switch on the device: failure to switch on the device to ensure data collection and alerting as required. Potential causes were considered to include the design of the switch, which, when toggled incompletely, could retract to the ‘zero’ position and make a sound suggesting correct inclusion (‘snap’).

Assessing the impact, detectability and likelihood of failure

In the UFMEA analysis (as in any version of FMEA), risk assessment took into account:

  • probabilities of the cause of the failure – how often a particular user failure is likely to occur in practice;
  • the severity of the consequences – what will be the consequences of the failure for the patient, the user himself, as well as for the hospital (e.g. legal and financial liability);
  • detection capabilities – whether and how easy it will be to detect a problem before the patient is affected.

Each of the above risk factors (probability of occurrence, severity and detectability) was scored on a scale from 1 (lowest risk) to 10 (highest risk). The study used a risk assessment based on the RPN indicator (the product of the three risk factors) and the SxO matrix. This allowed the required improvement actions to be identified.

Planning of improvement activities

Based on the UFMEA analysis, a number of actions were proposed (here, due to the product design phase, these were preventive measures), including:

  • change in the design of the switch – this is to ensure that the unit is unambiguously switched on or off.
  • changing the font in the descriptions – for unambiguous reading.
  • system for assessing the correctness of levels set – if levels are set that are assessed as abnormal, the system requires confirmation by the nurse.
  • change the bracket design – this is to clearly show the nurse whether the sensor has a chance of adhering to the patient or whether it will definitely be loose.

On top of this, a number of new points have been proposed for the user manual, which identifies risks that should be clearly discussed during training on the use of the device.

Summary

The analysis not only provided an opportunity to introduce the device into the US market, where the FDA organisation explicitly requires a UFMEA for every newly introduced medical device. Above all, it showed the weaknesses of both the design and the pre-designed user manual. It turned out that the device was functional, well-functioning in terms of electronics and full of interesting features, but that the company’s designers knew their product well enough not to be wrong in its trial applications, so that they did not see the potential risks of an under-designed design. The UFMEA analysis allowed them to ‘step into the shoes’ of their customers and show what problems they might encounter.