understanding variation and setting capacity. why do we get backlog and queues? because demand...
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Understanding Variation and Setting Capacity
Why do we get backlog and queues?
• Because demand exceeds activity
• Because we want to be efficient
• Because we do not take account of variation
• variation in demand• variation in capacity• the interaction between the two
3
GP Discharged!
Staff
skills
illness holiday
motivation
trainingshifts
Patients
Kit
Process
rooms not the same
supplies
machines not the same
age
sex
race education
motivation
diseaseunclear
guidelines differ
complications anaesthetics
80% is under ourcontrol
Information
transcription
transport
applications
Sources of variation in a clinical system
What variability?• GP
– Number of patients– Number of problems– Investigations– Length of appointments
• Outpatients– Number of referrals– Number of staff– Investigations needed– Length of consultation
What variability?• Ward
– Length of pre-admission stay– Length of post-op stay– Intensity of nursing required– Staffing levels
• Theatre– Number of cases– Length of cases– Anaesthetic time– Recovery time– Turnaround time
Sources of variation activity
• Identify examples of variation in your specialty
Bed availability - an example of theproblem of variation
IN-PATIENT STAYADMISSION DISCHARGE
Variation in patient pathways and
processes. E.g. in Length of Stay
Variation in Admission Patterns
- particularly for Elective Care
Variation in Discharge - By time of day- By day of week
- Seasonal variations
IN-PATIENT STAYADMISSION DISCHARGE
Variation in patient pathways and
processes.E.g. in Length of Stay
Variation in Admission Patterns -
particularly for Elective Care
Variation in Discharge - By time of day- By day of week
- Seasonal variations
“We always bring our hips in on Tuesday !”
IN-PATIENT STAYADMISSION DISCHARGE
Variation in patient pathways and
processes.E.g. in Length of Stay
Variation in Admission Patterns
- particularly for Elective Care
Variation in Discharge - By time of day- By day of week
- Seasonal variations
“We’re too busy in the morning and haven’t time to think about discharges.
They all get done in the afternoon.
Emergency Demand - Decision to admit/hour
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Time of day
Em
erg
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Understanding demand and capacity by hour of the day
Discharged patients/hour
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ts
Emergency & Elective Admissions April-November 2002
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Nu
mb
er
of
Ad
mis
sio
ns
EmergencyAdmissions
ElectiveAdmissions
time
Demand Capacity
Queue
Can’t pass unused capacity forward to next week
Variation mismatch = queue
How should we set capacity?
• Set capacity to average demand?
• Set capacity to maximum demand?
• Something else?
Setting capacity to Average demand
Wait
Seen
Capacity set as average demand
100% utilisation each day= very efficient as long as there is a queueLots of energy shuffling the queuesHigh risk if we get it wrong(clinical and financial)
Setting capacity to max demand
Poor utilisation
Large amount of wasted clinic timeVery inefficient use of resources
Wait
Seen
Capacity set as maximum demand
Solution:Flex Capacity
See today’s work today
But how do we cope with the variation in workload from day to day?
Solution:Reduce variation
Step 1:Understand why capacity and demand vary. Find the root cause
Step 2:Reduce the variation
Step 3:Set capacity to the 80th percentile (not the average)
Step 4:Flex capacity to match demand
Or
80th percentile...
50th percentil
e(median)
80th percentil
e
Variation
Lowestvalue
Highestvalue
Mean
80% of what?
• 80% of the demand falls below the line:• sort the patients/clinics into order• draw the line where 80% of the demand will fall
below, and 20% above the line
• Quick equation:minimum demand+ ((Maximum demand – minimum demand) x 0.8)
=
80% of variation in demand
A model of variability...
0
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1 21 41 61 81 101
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161
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201
week
waiti
ng
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and/
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demand waiting list waste
“The Variation Model”For model go to www.steyn.org.uk/models/demand analysis.xls
A new definition of capacity...
• Capacity is not activity
• Capacity is not “100% utilisation of every resource”
• Capacity is maximising utilisation of the constraint
• Capacity should be set at the 80th percentile of the demand
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