For the past dozen or so postings we have
been discussing the Theory of Constraints Thinking Processes with readers coming in record numbers. In this
posting I’m going to shift gears to the Healthcare field and discuss
a recently completed Process Value Stream Analysis (PVSA) project at a
hospital located in the Mid-Western part of the US. The focus of
this PVSA was in this facility’s Emergency and Cardiology Departments where
they wanted to improve one of their key performance metrics, Door to Balloon
Time (D2B). For those of you (like me before I started this engagement)
who don’t have a clue as to what D2B s, let me fill you in. Door-to-balloon
is a time measurement in emergency cardiac care (ECC), specifically in the
treatment of ST segment elevation myocardial infarction (or STEMI). The
interval starts with the patient's arrival in the Emergency Department and
ends when a catheter guide-wire crosses the culprit lesion in the Cardiac Cath
lab. In everyday language, this just means that a balloon is inflated
inside one of the heart's primary blood vessels to allow unimpeded
blood flow through the heart The clock starts ticking either
as a walk-in to the Emergency Department or in the field where a patient is
being attended to by medical personnel. This metric is enormously
important to patients simply because the longer this procedure is delayed, the
more damage occurs to the heart muscle due to a lack of oxygen to the
heart muscle. It’s damaged because the cause of this problem is typically
due to a blockage within the heart that prevents oxygen from being supplied to
the heart and without proper amounts of oxygen, muscle damage results. The inflated balloon "unclogs" the blood vessel.
1. Identify the system constraint – In a physical process with numerous processing steps, the constraint is the step with the least amount of capacity. Or another way of stating this is the step with the longest processing time.
2. Decide how to exploit the system constraint – Once the constraint has been identified, this step instructs you to focus your efforts on it and use improvement tools of Lean and Six Sigma to reduce waste and variation, but focus your efforts mostly on the constraint. This does not mean that you can ignore non-constraints, but your primary focus should be on the constraint.
3. Subordinate everything else to the constraint – In laymen’s terms this simply means don’t over-produce on non-constraints and never let the constraint be starved. In a process like the Door to Balloon time, it would make no sense to push patients into this process since they would be forced to wait excessively. But of course the hospital cannot predict when patients with heart attacks will show up needing medical attention. But by constantly trying to reduce the constraint’s time, the wait time should be continuously reduced.
4. If necessary, elevate the constraint – This simply means that if you have done everything you can to increase the capacity of the constraint in Step 2 and it’s still not enough to satisfy the demand placed on it, then you might have to spend money by hiring additional people, purchasing additional equipment, etc.
5. Return to Step 1, but don’t let inertia create a new constraint – Once the constraint’s required capacity has been achieved, the constraint could move to a new location within the process. When this happens, it is necessary to move your improvement efforts to the new constraint if further improvement is needed. What is thing about inertia? What Goldratt meant by that was to make sure things you have put in place to break the original constraint (e.g. procedures, policies, etc.) are not limiting the throughput of the process. If necessary, you may need to remove them.