The W. Edwards Deming Institute Blog

Fewer Patients-In-Process and Less Safety Scheduling; Incoming Supplies are Secondary

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Guest Post by Sami Bahri

photo of Sami Bahri

Sami Bahri

As a way to improve operations, manufacturers reduce inventory levels at all steps in a value stream. Taiichi Ohno, inventor of the “Toyota production System,” said that inventory conceals operational waste the same way water in a lake hides underlying rocks. Ohno advised reducing inventory levels to uncover waste. In healthcare, what inventory is similar to the water in Ohno’s lake?

Shigeo Shingo named “delays” the time that products spent waiting to be processed; just as my patients waited to be treated. Here is a good definition of “inventory” from the Lean Lexicon which helps to understand the similarity between patients wait and inventory wait. It defines inventory as

“Materials (and information) present along a value stream between processing steps.

Physical inventories usually are categorized by position in the value stream and by purpose. Raw materials, work-in-process, and finished goods are terms used to describe the position of the inventory within the production process. Buffer stocks, safety stocks, and shipping stocks are terms used to describe the purpose of the inventory.”

The definition describes six kinds of inventory. But, in healthcare, we can’t talk about finished goods or shipping stocks, since we cannot stock people as finished goods. Buffer stock, also refers to finished goods; it is of little importance, as well.

We are left with three categories of stock that are interesting for our purpose, the “raw materials”, “work-in-process”, and “safety stocks”.

Raw Materials: Incoming Supplies come easily to mind in this category. Their supply chain is very important, and needs to be managed carefully. However, equating the inventory reduction concept exclusively with the reduction or the control of incoming supplies would be a misinterpretation of the concept. We reduce inventory to improve operations along a whole value stream; controlling incoming supplies can achieve only a small part of this goal.

Work-In-Process (WIP): represents unfinished goods still passing through the value stream. The more products you work on at the same time, the less efficient your process flow will be.

We translated WIP as “unfinished treatment”; patients who went home, waiting for the rest of their teeth to be treated.

Manufacturers reduce Work-In-Process through the “one-piece flow,” “leveling” and “synchronization” concepts; once you start working on a piece, never stop until it’s completed. In dentistry we called it “one-patient flow.” Whenever possible, if we start treating a patient, we would like to see all the teeth treated in one appointment, without any delays between the interventions of different providers.

Treating more teeth requires longer appointment times, at a big risk, i.e., cancellations!

Cancellations can be very costly to a practice because resources—labor, machines and materials—are expensive. How can we compensate for the negative effect of cancellations? Do we over-book our schedule? If we do so and all scheduled patients showed up, our operations would become chaotic.

In manufacturing, over-booking resembles the accumulation of unfinished goods between operations in a value stream. That accumulation makes us feel safe against such things as machine breakdowns, errors in scheduling, etc. That’s why it’s called Safety Stock.

Safety Stock: The price of overbooking is certainly a lower quality of “patient experience,” and a higher stress level for healthcare providers. To avoid the negative effects of over-booking, we had to find an alternate source of patients that can fill the eventual gaps caused by cancellations. How about treating patients who came for dental cleanings? We have three hygienists, seeing around 30 patients per day, many of whom need treatment. They are always pleased if seen immediately after their cleanings; especially when a need has just been discovered. Emergency patients, also, like being treated promptly. These two sources combined, i.e. emergency patients and dental hygiene patients, are often capable of neutralizing the negative effects of cancellations.

Maybe a translation of Work-In-Process (WIP) and Safety Stock would make it more applicable to healthcare processes. WIP is similar to patients with unfinished treatment; we should probably call it Patients-In-Process (PIP). Safety Stock is like patients waiting in the dental chairs for provider availability; should we call it “Safety Scheduling?”

In service, the main inventory to be reduced is service itself not the physical supplies associated with it. I hope you would figure out what “WIP” and “safety stocks” mean to your own operations, and to work on eliminating them.

The perspective of “inventory reduction” should not be taken lightly! If we focus on reducing the number of Patients-In-Process (PIP) and on reducing Safety Scheduling, treatments would flow efficiently and outcomes would improve.

Improving the value stream allows our practice, using Lean Dentistry, to improve results for patients. For instance, in the past if a patient had a problem with a tooth, we would have diagnosed the issue, prescribed medication for pain and infection if needed, and scheduled them to return on another day to have the problem fixed.

Now that we apply Lean Dentistry, we can diagnose and treat problems on the same day, so you don’t need impressions, temporaries, or extra appointments. A restoration that used to take weeks to complete can now be finished in hours.

image of the cover of Follow the Learner

Dr. Sami Bahri was born in Lebanon where he received his dental degree from Saint Joseph Jesuit University. He spent three years in Paris, France specializing in dental prosthetics, and upon his return to Lebanon, he started teaching dentistry. In 1990, he moved to Jacksonville, FL and co-founded Bahri Dental Group with his brother, Dr. Gaby Bahri.

In 2007, after a presentation at the Shingo Prize Conference he received the title of “World’s First Lean Dentist.”

Dr. Sami Bahri wrote Follow the Learner:The Role of a Leader in Creating a Lean Culture. The book has won the 2010 Shingo Prize for Research and Professional Publication Award. The book describes how the Bahri Dental Group, transformed their work and their thinking from a traditional batch-and-queue approach to one focused directly on the needs of the patient, not on the needs of the practitioners.

Single Patient Flow: Applying Lean Principles in Healthcare (DVD) by Dr. Sami Bahri was awarded the Shingo Research and Professional Publication Award in 2013.

Related: Dentist Drills Down to the Root Causes of Office WasteLean Dentist podcastsWhat’s Deming Got to Do With Agile Software Development and KanbanWe Don’t Need to Limit Ourselves to Finding Management Ideas from Our Industry?A Trip to the Dentist That You’ll Enjoy


Categorised as: customer focus, systems thinking


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