The usability failure mode

Recommended protection

Validation

Using data of a previous patient

If the user is in charge of changing the patient data, it may happen that the user might forget to do it. As a result, a new patient might be treated using the parameters of the previous patient.

Resetting patient data

The manufacturer should provide a means, such as a two-state switch, to set the patient assignment mode. The switch modes should indicate that either a patient is assigned to the alarm system, or the alarm system is free. Apparently, these modes correspond to the 60601-1-8 Alarm Off and the intended (but not defined) Alarm On states.

The patient data should be kept as long as the alarm system is assigned to a patient, regardless whether the patient is connected or disconnected. The data should be cleared when patient is released and the alarm system becomes free.

By usability testing:

1. Attach a patient
2. Enter the patient data
3. Disconnect and reconnect the patient
4. Make sure that the patient data are still valid
5. Release the patient
6. Make sure that the patient data are erased

Startup false alarms

If the monitor is on and the patient is not connected to the sensors yet, then the system might produce false alarms

Connection mode

In addition to the patient assignment switch, the manufacturer should also provide a means, such as a two-state switch, to set the patient connection mode. When the connection mode is On, this means that alarm is enabled. Otherwise, when the connection mode is Off, this means that the alarm is disabled.

The system should alarm only when the patient is connected, namely, when the Connection switch is On.

By usability testing:

1. Attach a patient
2. Verify that the system does not produce any alarm signals
3. Connect the patient to the sensors
4. Verify that the system generates alarm signals
5. Turn on the Connected switch
6. Verify that the system stops generating alarm signals.

Using data of a wrong patient

The user might erroneously attach data of another user

Patient data validation

The system should require a unique patient id and protect from errors in entering this id.

The probability of accepted id errors should not exceed 20%