Queue, Demand, Capacity, Variation and Flow

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Queue, Demand, Capacity, Variation and Flow

• Essential measures for clinicians and managers

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The queue

• Queues occur where demand has not been dealt with
  resulting in a backlog of work.
• The main reasons why queues develop is the
  mismatch between the variation in demand and
  capacity at specific times

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The queue

• The NHS is a classic queue system
• We place patients in queues all the time
• some patients are in multiple queues

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The queue

• Every time the demands exceeds the capacity a
  queue is formed but
• Whenever capacity exceeds demand the extra
  capacity is lost or it is filled from the queue
  often at short notice
• Filling slots at short notice can lead to longer
  waiting times and distort clinical priorities

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Managing the queue - using evidence based tools

• Ensure an element of patient choice in the
  booking process
• Use referral information services or referral
  management services
• Ensure waiting list data is accurate
• Reduce unnecessary carve out

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Managing the queue

• Take unnamed referrals refer to a service not a
  clinician
• Pool referrals
• Pool waiting lists
• See people in clinical and date order

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Defining demand, capacity activity and queue

• Demand on the services is all the requests or
  referrals into the service from all sources
• Capacity is all of the resources required to do
  the work and includes staff and equipment
• Activity is the work done, it is the throughput
  of the system
• Backlog is the demand which has not been dealt
  with the queue or waiting list

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Demand and capacity definitions
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Measuring demand, capacity activity and queue

• Why is it important to understand the four
  measures of demand, capacity, activity and queue?
• To identify the bottleneck or constraint in the
  care process
• To increase capacity at the stage of the process
  where it will create the greatest outcome
• To reduce inappropriate demand to the constraint
• To redesign services or plan services

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Measuring demand, capacity, activity and queue

• Must be measured in the same units of time for
  the same period i.e. hourly, over a 24 hour
  period, weekly or monthly
• It is not possible to compare two or more items
  unless they are measured in the same unit of time
• It is important to compare the four measures on a
  single graph

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Measure demand

• Multiply the number of patients referred from all
  sources by the time taken in minutes to process a
  patient
• Understand your demand what it is (shape) and
  where it comes from (source)

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Manage demand

• Right person, right place, right time
• Understand and manage activity and capacity to
  meet changes in demand i.e. seasonal variation

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Measure capacity

• Multiply the number of pieces of equipment by the
  time available in minutes available to the people
  with the necessary skills to use it

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Measure activity

• Multiply the number of patients processed by the
  time in minutes it took to process each patient

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Measure the backlog or queue

• Multiply the number of patients waiting by the
  time it will take in minutes to process a patient

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Compare the four measures

• Convert the data on demand, capacity, activity
  and backlog or queue onto a common line graph

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If av. Demand av. Capacity, variation mismatch
queue
Cant pass unused capacity forward
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Understanding flow

• In the NHS flow is the movement of patients,
  information or equipment between departments,
  staff groups or organisations as part of their
  pathway of care
• Whilst process mapping looks at care processes
  from the patients perspective, flow analysis
  looks at the care process from a unit or
  departmental perspective

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Flow modelling

• Supports service improvement at specific
  bottlenecks or constraints, in specific clinical
  areas, or across whole health systems
• This tool will not tell you what should change
  process mapping helps with identifying that
• Flow modelling will show how well scarce
  resources are being used and how much room there
  is for improvement

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How to build the flow model

• Define the patient group to be analysed and
  define the start and end points of the flow map
• In straightforward care processes a process map
  and process times will provide sufficient
  information to examine patient flow
• The Unscheduled Care Collaborative made
  extensive use of flow mapping and modelling

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Understanding variation

• Why is it important to understand variation
• Because the mismatch between the variation in
  demand and capacity is one of the main reasons
  that queues occur in the NHS

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What variability?

• GP
• Number of patients
• Number of problems
• Investigations
• Length of appointments

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What variability?

• Outpatients
• Number of referrals
• Number of staff
• Investigations needed
• Length of consultation

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What variability?

• Ward
• -Length of pre-admission stay
• -Length of post-op stay
• -Intensity of nursing required
• -Staffing levels

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Variability

• Theatre
• Number of cases
• Length of cases
• Anaesthetic time
• Recovery time
• Turnaround time

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Bed availability - an example of the problem of
variation
IN-PATIENT STAY
ADMISSION
DISCHARGE
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We always bring our hips in on Tuesday !
IN-PATIENT STAY
ADMISSION
DISCHARGE
Variation in patient pathways and processes. E.g.
in Length of Stay
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Understanding demand and capacity by hour of the
day
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Analysing variation

• Statistical Process Control
• Two types of variation
• Common cause that which is natural and to be
  expected
• Special cause which produces unusual or
  unexpected variation

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Statistical process control

• Two basic charts
• The run chart a line graph an ideal method of
  comparing sets of data
• The control chart also run charts but with two
  distinct differences i.e.

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Any questions?