Here is another question emailed to me by a reader, so I'm answering it here (with the reader's permission and removing any identifying details):
I am currently faced with a problem with scheduling breast biopsies. The next available appointment is over a month out. My imaging director's solution is more people, rooms, and equipment. This is a traditional solution and I won't allow it.
My question: how do I calculate patient demand? The schedule includes all mammos and must be coordinated with Ultrasound schedules. I can look at the daily schedule but we are meeting that, all the while patients continue to pile up. Can you help me get my arms around patient demand for this type of service?
If capacity (cases per day) is less than patient demand, we will see “patients piling up” in a backlog of appointments. If capacity is consistently less than demand, then the backlog of patients grows and the waiting times will grow.
Looking at the scheduled number of patients per day basically tells us capacity, not demand. However, I've seen cases where the number of patients seen per day was actually LESS than real capacity because of problems in the scheduling processes.
To estimate or measure demand, we need to know how many appointment requests are actually coming in each day and each week. How many phone calls or faxes are being received? How many patients are being added to that backlog?
Even then, we have to be careful because some offices might call and then NOT schedule an appointment based on the quoted appointment wait time. We'd call these “balks” in Industrial Engineering and queuing theory. You've “balked” if you've ever given up and waited away from a long line at a Starbucks or an amusement park.
Demand = # of appointments requested per day + # of appointments “balked” at because of long wait times
Let's say we are currently scheduling and seeing 20 patients per day, but 24 appointment calls come in each day, with one person balking. We need to figure out how to see 24 patients per day.
At the one hospital I'm thinking of, they improved the scheduling process so that the length of appointment schedule slots matched up with the length of actual appointments. Due to disconnects between departments (scheduling and the MRI area), they had scheduled some procedures for 90 minutes when they really only took 60. Changing the schedule didn't change the real capacity (which was limited by the number of machines, people, and hours per day)… but it allowed them to do more scans per day.
Once the effective capacity (the number of procedures per day) is greater than the number of appointment requests coming in, the backlog will start going down. Waiting times will get shorter, which will reduce “balks.”
The reader who asked the question is right that we shouldn't automatically jump to “more people and more machines” until we are absolutely sure that is necessary. Sometimes we can increase capacity by adding some daily overtime or some Saturday appointments… as a short-term measure for bringing our backlog down more quickly.
Lean is about making sure capacity (throughput) matches demand. That's what creates good flow and what leads to the most timely patient care.
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