#Lean: Clarifying Push, Pull, and Flow in a Hospital; the Patient “Pulls”
Of all of the different Lean concepts, it seems that the question of “push” versus “pull” is often the most confusing for folks in healthcare. I tried to address this in my book Lean Hospitals, but I see a lot being said or written about pull that I think doesn't quite capture the concept.
This is not a question of whether we physically push or pull a patient bed as they're rolling down a hallway. That's a matter of ergonomics. What I'm talking about is the conceptual “pull” of resources (rooms, medications, doctors) when needed by the patient.
People sometimes say, “We already have pull. We pull the patient to the room when it's available.” No. That's not pull. Pull is making resources, again, when needed by the patient. Not when the resource is ready.
Before we get to the healthcare topics, please bear with me for a little bit of manufacturing context on the words push and pull.
What is “Push” in Manufacturing?
Before we can understand “pull,” we have to first understand the traditional way in manufacturing… what we call “push.”
In a “push” environment, we're generally producing goods without a real regard for actual customer demand. If you're from healthcare, this might seem silly. Why would you build products that aren't needed by customers? Why would you order supplies that aren't needed for production?
Push production is often driven by a production schedule that's created in advance, based on a forecast of actual demand. Forecasts are usually inaccurate, even with fancy computer systems. A factory or a department might have a computerized schedule that says to build 500 of something each day. The factory managers, in their silo, are often judged based on their ability to meet the schedule. So, they try to build 500 a day, even if inventories of finished products are accumulating. That manager's job is to build them… it's somebody else's job to sell them.
One of the problems with push is that inventory accumulates — either as “finished goods inventory” or “work in progress” between steps in a value stream.
Why would a factory keep building stuff if they are building more than customers demand?
One reason is that managers are afraid that machines will break down. So, if the machines are running smoothly… keep 'em running. Keep 'em cranking out parts. We'll build up inventory just in case the danged thing breaks down tomorrow. We'll use the inventory or sell the products eventually.
Another reason a factory will keep making product is to spread out their overhead costs. In some cost accounting systems, making more parts means each part is cheaper because the overhead is spread out across, say, 600 units instead of 500 units. The cost might seem lower in that one silo, but now the company has the cost of storing and moving that inventory, along with the other risks that come from holding inventory.
Examples of “push production”:
- A fast food restaurant making food and storing it under heat lamps (some of it gets thrown away)
- An automaker building an excess number of cars or trucks and forcing the dealers to take them
- The U.S. Mint producing dollar coins that far exceed customer demand
- Computer makers building product and shipping it to retailers to sit on the shelves
- Starbucks brewing batches of coffee based on a forecast
- A hospital pharmacy making IV bags based on expected usage
It's hard to find examples of “push” production in healthcare. The hospital cafeteria might do “push” production of food items (made in advance based on a forecast). Same might be true in the pharmacy. So much of what we do in healthcare is done “on demand,” that it is essentially “pull.”
Sometimes, “push” works out OK. We might have very known and steady demand. The amount pushed might happen to be the same as what's consumed by the customer. But, push often causes many problems.
What is “Pull” in Manufacturing and How Does It Help?
“Pull” is the concept of basically building in response to actual customer demand OR restocking inventories in a controlled way based on the customer's consumption of products. Pull reduces costs, improves quality, and makes sure the customer gets what they want, when they need it, in the right quantities.
Some examples of pull (or push combined with pull), based on the bullet points above
- Chipotle makes a specific burrito when pulled by the customer (but the meat and veggie components might be cooked based on push, potentially)
- Starbucks makes a specific latte or beverage based on a customer order or pull signal, but the milk might be “pushed” to the store based on forecasts
- In many stores, Starbucks can brew a single cup of coffee for you based on a pull signal, in a french press or a Clover machine.
- You special order a specific car or truck from a dealer and it's built specifically for you (possible, but it might take weeks or months, even from Toyota)… many of the “pull signals” in the auto industry are from the dealer, who is predicting what you'll want to buy
- Dell Computer, back in the day, did “build to order,” building and ordering after you ordered it on the web (but components were purchased from China based on forecasts)
Even in those examples, “pure pull” (where everything is done only in response to a customer order) is hard to find. It's easier to do “pure pull” when the production times are short and the supplier is close to the customer.
For example, let's say I wanted to buy a Toyota pickup truck that's made here in San Antonio:
- My pull signal (singing a contract with Toyota) would lead to them starting final assembly
- Final assembly would pull all of the components (stamped metal panels, plastic pieces, electronics, tires) directly from a supplier
- Some of those parts are assembled by on-site suppliers (such as dashboards and seats)
- The dashboard and seats have purchased components that might come from some distance away…
So when there's some time and distance involved, Toyota is going to have an inventory of parts. It's not longer “pure pull.” Toyota has inventory levels that are set based on the expected usage of parts (so a forecast or prediction is involved somewhat). But, the supplier is not authorized to just keep shipping parts because the forecast said so. Toyota has inventory limits and a “kanban system,” where you use some and you order some. So, the replenishment of parts is driven by actual usage… if none are used, none get replaced. That's a form of pull, as well.
Here's a video from my friends at Gemba Academy on Kanban systems:
Pull systems are helpful because they set limits on inventory levels. There's a discipline that says either:
- We have no customer demand, so we don't build or
- Inventory levels have hit their max, so we stop building
Again, in a push system, people are tempted to EXCEED inventory levels because they think that reduces cost to keep building. A Lean thinker realizes it's more costly, generally speaking, to overproduce. During the 2008-2009 financial crisis, Toyota stopped production for three months because inventory levels had gotten too high (and they didn't layoff full time workers, but that's a different story).
Here is a video by Jay Arthur about Pull and Push:
From a Toyota instructional booklet:
See, it's about “real demand.” What's the “real demand” in our hospital? Hint, if patients are waiting, real demand isn't being met. Notice also how Toyota admits they are building to dealer orders, not the end car-driving customer… but it's better than pushing cars to dealers based on our own forecasts or schedules.
The Goal is Flow – Right Care, Right Place, Right Time
Whether we have push or pull, or a combination of the two, the real goal in Lean is FLOW – matching production to consumption, matching supply to demand.
As Jim Womack, Jeff Liker, and others have taught:
Flow where you can, Pull where you must
Rather than quibbling over “push vs pull,” the real challenge for healthcare is figuring out how to improve flow by reducing waste in the system.
What Does This Mean for Healthcare?
It means we need to think about “pull” as the patient pulling resources that are needed. Doing work when patients need the care, rather than doing it when it's convenient or when we happen to have the capacity.
Not what we mean by “push” vs. “pull” – one person is pulling the bed and two are pushing it… it's not the physical movement of the patient, but the match of patient needs to the care provided.
If we move a patient from the ED to an inpatient bed because that bed was made available when the patient needed it (at a physician's admission order), then that's pull. That gets confusing, because we are moving the patient, but the patient is pulling the bed/room.
What's sometimes called “pull until full” in the E.D. is sort of pull… if a patient comes to triage and registration and they need a room, the patient is requesting a room and they get a room. The patient has “pulled” an exam room. But, if there's no doctor or nurse available, we have just moved the wait from the waiting room to the exam room… that's poor flow.
Let's say a patient needs blood work done. An order is put in and a nurse (or a phlebotomist) comes to draw blood. That's a pull — the person doing the work has been pulled and they are “pulling” blood from the patient because it's needed. Now, there might be delays in getting the blood drawn (this would be poor flow), but it's pull. The lab testing is done as a “pull” (we can;t do blood testing in advance on a specimen that doesn't exist) but it might have a long turnaround time (poor flow).
There are times when the emergency department will draw blood (“a rainbow draw,” named for the colors of the different tubes) from a patient “just in case” they are needed. This is “push,” illustrated by the fact that some of those tubes might not be needed. The push, the rainbow collection, is a workaround for slow lab turnaround times. The best fix is reducing the TATs so we can “pull” blood only when needed for the lab.
If a patient needs a bed and there's not a bed available… that's poor flow. There's a mismatch in supply and demand. If the patient is moved once a bed is made available… that's not pull.
A patient getting a same-day primary care appointment when they are sick, that's pull — the patient needs the care, so they get the care quickly. Making a patient wait months for a surgical procedure… that's bad flow.
Restocking supplies to a patient room based on yesterday's usage or a kanban signal… that's pull. A lab with a “standing order” of chemicals and reagents (the same amount every month), that's push. That same lab might have pull if they order a different amount based on usage (a “par level” system) or if they have a kanban system.
An ambulance coming in response to a 911 call… that's “pull.” A slow response time — that's poor flow.
Anyway, I hope this is a helpful discussion. Please add your comments and questions to the post below…