Queue, Demand, Capacity, Variation and Flow

Essential measures for clinicians and managers

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

The queue

• The NHS is a classic queue system

• We place patients in queues all the time

• some patients are in multiple queues

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

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”

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

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

Capacity= what we could

do

Demand and capacity definitions:

Activity = what we did

Demand = All requestsfor a service

= what we should do

Waiting list, queue= what we should have done

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

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

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)

Manage demand

• Right person, right place, right time

• Understand and manage activity and capacity to meet changes in demand i.e. seasonal variation

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

Measure activity

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

Measure the backlog or queue

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

Compare the four measures

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

If av. Demand = av. Capacity, variation mismatch = queue

time

Demand Capacity

Queue

Can’t pass unused capacity forward

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demand capacity activity 80% of variation in demand

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

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

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

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

What variability?

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

What variability?

• 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

Variability

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

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 !”

Emergency Demand - Decision to admit/hour

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Understanding demand and capacity by hour of the day

Discharged patients/hour

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Emergency & Elective Admissions April-November 2002

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EmergencyAdmissions

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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

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.

Any questions?