Fewer auditory alarms would improve safety

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Fewer auditory alarms would improve safety

• Judy Edworthy, Elizabeth Hellier
• University of Plymouth

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Where are alarms used?

• Operating theatres
• Intensive Therapy Units
• Hospital wards
• Most other hospital locations where there are
  patients and devices

• GPs surgeries
• Ambulances
• Free-standing equipment
• Home use devices

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The Operating Theatre
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Operating Table
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Anaesthetic Workstation
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Where do problems with alarms arise?

• Alarm handling
• False alarm rates
• Design of the alarm sounds
• Relationship between alarm sounds and their
  function

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Alarm handing

• Most of the time that alarms go off, they are
  simply reset and acknowledged
• No action results
• Typical of many environments where there is a lot
  of monitoring of equipment by operators

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Problems resulting

• Unless alarms have an automatic reset function,
  they may be switched off but then not switched on
  again for real emergencies
• Most of the alarms that are heard do not signal
  emergencies
• Handling the alarms diverts everyones attention
  from primary task

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Bad design area 1

• If the alarms are not providing important
  information, why are they used at all?
• There are repercussions
• polluting the sound environment
• distracting operatives
• makes distinguishing between critical and
  non-critical incidents more difficult

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False alarms

• Over-use of alarms for noncritical events
  effectively creates false alarms
• False alarms can also occur due to
• equipment malfunction
• inappropriate settings of trigger points
• Misunderstanding of the situation

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Responding to false alarms

• Research evidence shows that operatives will
  adapt their response rate to the perceived false
  alarm rate
• If alarm system is perceived to be 90 reliable,
  operatives will respond slightly gt 90 of time
• If alarm system is perceived to be 10 reliable,
  operatives will respond slightly gt 10 of time

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Bad design area 2

• If alarms are installed on a better safe than
  sorry logic, responses to alarms will be less,
  rather than more, reliable

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Design of alarm sounds

• What would the worst alarm sound in the world be
  like?
• Hard to localise
• Be susceptible to masking by other sounds
• Hard to remember, identify, and discriminate from
  other sounds
• Only linked to the situation it signals in a very
  obscure way

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How to design the worst alarm in the world

• Localisation Brain uses one of two mechanisms to
  localise sound - one works at low pitches and one
  works at high pitches
• So use a pitch that lies in the middle of the
  two, making it hard to localise
• Masking Sounds with few harmonics are easily
  masked
• So use poor quality acoustic signals

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Worst alarm ctd...

• Learning, remembering and discriminating
• Ear responds to change, not constancy
• People are very poor at remembering the absolute
  level of a pitch
• People are bad at remembering abstract sounds
• So use continuous beep-type tone at a fixed
  pitch

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Bad design area 3

• The continuous tone
• Hard to localise
• Susceptible to masking
• Difficult to remember, identify and discriminate
  from other tones
• Has no obvious match to the situation it is
  signalling

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Relationship between alarm sounds and function

• In areas with lots of equipment you may find
• Equipment from the same manufacturers providing
  different functions, but all equipped with the
  proprietary alarm sounds for that company
• Equipment from different manufacturers with the
  same function, but equipped with different alarm
  sounds

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Typical scenario

• Ventilators A and B have alarm sounds that are
  hard to localise BUT
• Nurse knows that Patient A is assigned to
  Ventilator X ( ping)
• Also knows that Patient B is assigned to
  Ventilator Y (beep)
• Can attend appropriate patient depending on sound

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Ideal scenario

• Both ventilators are fitted with alarms that have
  acoustic properties allowing them to be readily
  localised
• Nurses ears tell her/him which patient to attend

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Sources of error

• Patients ventilators have been changed and nurse
  does not know
• Nurse cannot tell a beep from a ping
• Ping and beep are readily masked by other
  alarm sounds

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Bad design area 4

• Alarms are assigned on an equipment-centred basis
  rather than a patient-centred basis

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Equipment changes, people dont

• Assign alarm sounds by bodily functions, not
  equipment
• Standardisation
• Main functions
• Oxygen, Ventilation, Perfusion, Temperature,
  Cardiovascular, Drug administration
• One generic alarm sound for each domain with
  urgency variants

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What needs to be done?

• Alarm philosophies need to be reconsidered
• Acoustic nature of alarm sounds needs to be
  improved
• Alarm numbers need to be reduced and standardised