Sequential PDSA cycles vs. Simultaneous PDSA cycles

Picture of Suzie Creighton

Published on 26 September 2022 at 12:56

by Suzie Creighton

sequential PDSA cycle vs simultaneous PDSA cycle

We’ve taken a look at ‘Plan-Do-Study-Act’ (PDSA) cycles in some of our previous blogs. You can use this four-step model for improvement as a framework for changes across a wide range of industries.


In a previous article we looked at the origins of PDSAs, and how improvement heroes such as Walter A. Shewhart and Edwards Deming developed and popularised this methodology, which we still use today in order to create quality process improvements.


From its roots in scientific methodology, PDSAs provide a quick way to test out small changes and build on them. Wherever you work and whatever your environment is. Described by NHS England as: ‘a powerful tool for learning from ideas that do and don’t work’, in this blog, we’re going to take closer look at the different types of PDSA cycles - both sequential and simultaneous - and the pros and cons of each.



What is a PDSA cycle?

NHS England and NHS Improvement describe using PDSA cycles as a method which enables you to ‘test out changes on a small scale, building on the learning from these test cycles in a structured way before wholesale implementation. This gives stakeholders the opportunity to see if the proposed change will succeed and is a powerful tool for learning from ideas that do and don’t work. This way, the process of change is safer and less disruptive for patients and staff.’


Let’s remind ourselves of the four stages of the PDSA cycle:


  • Plan – the change to be tested or implemented
  • Do – carry out the test or change
  • Study – based on the measurable outcomes agreed before starting out, collect data before and after the change and reflect on the impact of the change and what was learned
  • Act – plan the next change cycle or full implementation.

You can read in more detail about PDSA cycles and what they involve in our blog.



What are sequential PDSA cycles?

The NHS England and NHS Improvement guide 'Plan, Do, Study, Act (PDSA) cycles and the model for improvement' looks in more detail at sequential PDSA cycles. These are PDSA cycles that follow one after the other. They are most commonly used when ‘the study reveals results that suggest a different approach is needed.’


Sequential PDSAs are part of the normal process of PDSA cycles. You finish one cycle and start the next on, working on and enhancing areas of focus as the cycles go on.


In the article ‘Using sequential Plan-Do-Study-Act cycles to facilitate implementation of a morbidity and mortality review process,’ the authors look at how ongoing PDSA cycles were helpful in improving their morbidity and mortality review process, while praising the methodology, saying the ‘flexibility of the PDSA methodology has enabled the process to be dynamic.’



What are simultaneous PDSA cycles?

Simultaneous PDSA cycles– as the name suggests – are when a number of PDSAs are carried out at the same time. This can often happen where more than one change is being tested at the same time, but when all of the changes have the same aim and in order to accomplish the same goal.


You can read more here in the IHI article: ‘Science of Improvement: Testing Multiple Changes’. It states that: ‘Simultaneous cycles may occur when the changes are more complex, possibly involving several departments.’


You might also want to watch this short video from the IHI which takes a look at simultaneous PDSA cycles.



Pros and cons of each approach?

Let’s take a look at the pros and cons of these two approaches:



Benefits of carrying out sequential PDSAs


  • You can build on each PDSA and take learning from one cycle and apply it to subsequent cycles
  • You can refine each step of the process, learn about how each cycle works and apply it to the next iteration


Disadvantages of carrying out sequential PDSAs


  • It can be time-consuming to complete and assess each cycle
  • Patients and team members may be less receptive to continual change while you are testing the cycles


Benefits of carrying out simultaneous PDSAs


  • It can help to speed up the improvement process. As improvement can be slow and methodical, it may make sense to test two changes at the same time
  • It can help you build knowledge of the system of change ideas
  • You may be able to test more ways of achieving change by carrying out several linked PDSAs. It allows a team to test more than one change simultaneously


Disadvantages of simultaneous PDSA cycles


  • It can be confusing to mix too many PDSA cycles at the same time. If you are running the QI programme, there is a lot of data and information to analyse and understand if you are running concurrent PDSA cycles
  • It is vital that any interactions between simultaneous cycles are identified, as the impact of one cycle may be altered by a change in method in another cycle
  • Keeping track of the timing of implementation for overlapping PDSA cycles is critical to being able to determine the impact of the different change ideas
  • It is really important to isolate changes when working on improvement. If PDSAs become too muddled, you may not be able to identify or isolate changes which made a difference.


So, as we’ve seen there are pros and cons associated with carrying out both simultaneous and sequential PDSA cycles. Whichever method you choose to use, if you are planning on carrying out simultaneous PDSA cycles, it might be a good idea to test on a smaller scale to start with and focus in on which changes work with each other.


It may also be worth looking into using a solution such as Life QI, which helps you track all your improvement projects – including PDSAs – and enables you to keep abreast of changes you have made and the results of these changes, in one place.


As we’ve seen, PDSAs can really help to build an organisation-wide approach to improvement. So, good luck on making small changes, which can lead to big improvements!





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