Compare this to how things are often done in the NHS: huge amounts of time and resources are spent designing a large new system which when implemented works poorly. Staff feel like their views were not considered and that the changes have been ‘done to them’. If only they had started small, learning what worked and didn’t before scaling up…you can hopefully imagine the difference.
Therefore it is perfectly legitimate to try your first PDSA cycle on a single patient, or a single outpatient clinic, or a single ward round, or a single TTO, or a single GP consultation. As long as efforts are made (using PDSA) to learn as much as possible, then it’s ideal. The scale can be increased, if we suspect a change is working well.