Value Stream Mapping
Value Stream Mapping
What is it and how can it help me?
Using this tool, a cross functional team can produce a visual map of the ‘current state' (ie how things operate now), identifying all the steps in a patient's pathway - from service user to supplies used. The team then focus on the ‘future state' which often represents a significant change in the way the system currently operates. This means that the team need to develop an implementation strategy to make the future state a reality. Using value stream mapping can result in streamlined work processes, reduced costs and increased quality.
When does it work best?
This technique can help you visualise all the stages along the patient journey. Best undertaken by a multi-disciplinary team, it helps achieve service improvements by setting goals to improve service and reduce delays.
How to use it
Drawing a current state map:
Start the process by drawing a current state map - this will help you to understand what improvements are needed, who will do them and when.
1. Using patients' views, define what value the patient gets from each part of the process eg provision of information, pain relief etc. Write this at the top of the value map so it is in the foreground at all times.
2. Walk through the patient's journey in reverse for an overview. Having identified the main steps, return with your stopwatch and map the process in more detail.
3. Draw the journey, with the starting point (referral, outpatient appointment etc) on the left and the end point on the right hand side of the paper.
4. Write each procedure down as a ‘process box' which indicates the process that the patient ‘flows through'. Each process box stops when the patient is awaiting the next stage.
5. The individual steps in the patient's journey join together from left to right. If several paths converge at various points, show this as follows:
6. As you walk through the journey, collect data that will help you determine what the future journey will look like. Include a data box below each process with the relevant measured data for each step. Time unit measurements should always be consistent, ie minutes, seconds.
The following examples are useful common system measurements that can easily be applied to health care.
Cycle time (CT): The time that elapses between one patient finishing a consultation etc and the next patient finishing a consultation.
- Value added time (VA): the time that actually adds value to the patient journey
- Changeover time (C/O): the time taken to switch from one type of process to another
- Number of people (NP) that are required to undertake a particular process
- Available working time (AT) of staff on a shift, minus breaks, which makes up the regular pattern of hourly, daily, weekly or monthly work
- Lead time (LT): The time it takes for a patient to move all the way through a process or value stream.
7. On the left of each process step, insert a triangle showing the number of patients waiting for the next process, and the time it takes to process each patient (cycle time). Thus the journey starts to look like this:
8. Next, add in the flow of information. This is shown above the pathway with arrows drawn from right to left. Straight arrows for paper-based information and lightning arrows for electronic information.
At each step in the journey, you need to consider what information is provided, where it comes from and in what form, and then record it as above on the journey diagram.
9. Now, enter whether the patient is ‘pushed' through their journey or ‘pulled' along the pathway. In most cases, this will be a push step. For example, patients are pushed from the medical assessment unit (MAU) to X-ray, and then pushed from the MAU to the wards.
The ideal end point is conversion of many of these push steps to the more efficient pull form.
NB: In this example the MAU would normally be broken down in to smaller processes. It is shown as a single process to illustrate the example.
10. The final part of the journey is the addition of a time line at the bottom of the page. Under each process and associated waiting box, insert the lead time for that process (time taken to complete it) over the value adding time in that process. You can then calculate the complete lead time for the journey, and the complete value adding time.
The future state map:
To draw a future state map and create the conditions for a lean transformation, you need to answer the following questions:
- What is the Takt time? (See below)
- What is the material flow?
- Where can we use continuous flow?
- Where can we use first in, first out (FIFO)?
- If we can't use flow, where should we use ‘supermarket pull?'
The flow of information:
- At what single point in the production chain do we trigger production?
- How much work do we release and take away?
- How do we level the production mix to support improvements?
- What process improvements are necessary? (eg reliability, quality, changeover etc)
Characteristics of a lean process
Takt time is defined as:
This is a manufacturing concept that can easily be translated to health care. It allows you to determine how many patients can be treated per unit of time so you can predict how many patients you need to see per shift to meet current demand. This involves a clear knowledge of demand and demand trends (see forecasting demand).
Value, non value and necessary but non value adding steps:
Once the current state map is complete, you should be able to determine what adds value to patient care and what doesn't. Some steps add no value but are still necessary, such as transport. You should note these and aim to reduce or eliminate them in the long term.
The notion of continuous flow is central to lean thinking. This is where the patient moves from one step in their journey to the next without delay. It is the most efficient way to manage any process as it reduces waste to a minimum.
If you are able to introduce continuous flow, the future map should show the previous process boxes being joined together as one single process box. You only require separate boxes if each process has its own separate flow which stops before another commences.
Whilst ideal, continuous flow isn't achievable in all situations. This may be because geography separates steps in the patient journey, or that some parts of the pathway have a very long lead time and are difficult to couple directly to the next stage.
When continuous flow is not possible, the next most efficient type of flow is ‘pull' or ‘the supermarket pull system'. Pull is where the next part of the process pulls patients from the one before. The following is part of the flow for investigating a patient with recurrent blackouts.
The CT scanner pulls patients through the echo process. Each time a CT is undertaken, a patient is removed from the small pool of patients between echo and CT. A card is sent to the control position which in turn sends a card to the echo to see another patient. This way a constant pool of patients is maintained between the two processes. The size of this pool should be large enough to ensure that the CT is continuously fed, even if there are disruptions in the echo process, but not so large that patients are kept waiting for a long time. This is a fine balance, but over time the aim should be to make the pool as small as possible and eventually replace it with a continuous pull system.
This simple system may seem familiar, but all too often there is no relationship between the different processes. This method enables the earlier process to control and regulate the flow. In industry, the cards used to communicate between processes are known as Kanban cards.
First in, first out (CONWIP):
Another type of flow management system is FIFO, or first in first out. (In it is known as CONWIP). You can use this system to couple activities where continuous flow or pull is impossible. It is often used if the process is rare, or if there is a great deal of variation in the cycle time.
Whilst most of healthcare is predictable, there are times when this can break down. When this happens, it is best to organise the flow according to FIFO which maximises the downstream flow, particularly through bottleneck areas. You will need to implement some form of queuing to operate FIFO, but this system should help to ensure efficiency along the whole of the patient pathway.
Flow rate is determined by the pacemaker:
Using pull systems, you will only need to schedule one point in the patient pathway, known as the pacemaker process. If combined with pull techniques, controlling this point will dictate the flow of the whole patient journey.
The process needs to occur as continuous flow - otherwise you will need multiple control sites which you will have to co-ordinate. Using a pacemaker enables you to control the flow using one simple point. This makes scheduling much simpler than trying to co-ordinate many separate processes.
Levelling the flow:
This is perhaps the most difficult concept of Lean thinking to transfer to healthcare. Used in manufacturing, levelled scheduling is the operation of a process in the lowest possible common multiple. This process is flexible and reduces the waste between stages, but it will only work if other aspects of Lean thinking are in place.
How can this concept be applied to health care? An obvious example is the provision of diagnostic services. Using levelled scheduling, you could run test A then test B then test C, rather than batching them unnecessarily. This way, patient flow is uninterrupted. You can also improve flow by using ‘right sized equipment' in the optimum location, rather than large complex machinery which encourages the ‘large batch' approach.
The way we construct surgical lists is a good example of levelled scheduling. However, a review of different areas might suggest additional processes where a levelled schedule could help. It is applicable anywhere where we currently batch and queue. You may find the Glenday Sieve - runners, repeaters and strangers useful.
You can use a learning to see value stream map to establish which strategic processes require reviewing, and in what order. You can also use the map at a process level to identify areas for improvement.
Hull Echocardiography. A classic demand and capacity study in Hull and East Yorkshire. The project team assessed demand, capacity and activity for echocardiography as a way of reducing the backlog of patients and waiting times. This baseline assessment then informed decisions on how best to go about improvements. They used a form of process mapping to understand the system.
Bicheno J (2004) ‘The New Lean Tool Box' PICSIE Books, Buckingham.
Hopp W and Spearman M (2000) ‘Factory Physics' McGraw Hill, Boston.
Rich N, Bateman N, Esain A, Massey L and Samuel D (2006) ‘Lean Evolutions' Cambridge University Press, Cambridge.
Rother and Shook (1999) ‘Learning to See'.
Womack J and Jones D (1996) ‘Lean Thinking' Simon and Schuster, New York.
Womack J and Jones D (2005) 'Lean Solutions' Simon and Schuster, New York.
This technique was devised by John Shook, who worked at Toyota for over ten years, and Mike Rother who undertakes research into Toyota and has taught at the University of Michigan. They joined forces to construct this technique as a direct result of a gap identified by Womack and Jones - that organisations needed guidance on mapping the entire value stream for products, families or services. The publication ‘Learning to See' (1999) was the result.