Cascade of Errors

I first heard of the phrase “cascade of errors” from a friend of mine who was a private pilot.

As part of his desire to be a competent and safe pilot of private planes, he regularly read after-action reports of every airplane crash in the United States.

His thinking was that crashing an airplane had a near 100% fatality rate. So, there is no opportunity to learn from your own mistakes. You can only really learn from someone else’s mistakes.

(I often say that learning from mistakes is essential… but nowhere does it say that you’re restricted to learning only from your own mistakes.)

After reading hundreds of crash report summaries, he observed a pattern. Most airplane crashes were not caused by a single error, but typically by multiple errors… hence the phrase “a cascade of errors.”

For some reason, I found that concept fascinating. 

In the context of airplane crashes, one frequent error in the cascade was the pilot losing situational awareness. In other words, pilots were confused and misunderstood what their airplane was doing and/or didn’t fully grasp where the plane was in the sky relative to everything else.

It turns out that the concept of an error cascade is also used in the medical field. It refers to a sequence of errors that compound each other and results in an adverse outcome for patients.

The phrase “initial misdiagnosis” comes up a lot in medical error cascades.

In the book The Checklist Manifesto by surgeon Atul Gawande (one of my favorite books on building scalable operations), the author discusses the errors that occur in surgery. I was shocked at the types of errors that occur in surgery.

The two errors that stick out most in my mind are:

1. Operating on the wrong part of the patient (e.g., left leg instead of right leg);
2. Leaving surgical instruments inside the patient after stitching them back up.

I was absolutely horrified.

It is encouraging to hear that, today, surgical teams have a protocol where they make an inventory count of every object they use that may end up in the patient’s body (instruments, sponges, etc.) before surgery and then again after.

If they count 25 sponges before surgery, they will count again for those 25 sponges after the surgery ends and before closing up the patient. They count how many unused sponges remain and how many used sponges are in the surgical waste zone. If the numbers don’t match, they double-check everything and consider the possibility that they left a sponge inside the patient.

My fascination with error cascades comes from figuring out how to prevent them.

Imagine an error cascade is like a series of dominoes. If you stop the first domino from falling, or at least from falling on the second domino, you prevent all the other dominoes from falling.

What occurs to me about error cascades in aviation and those in the medical field are their similarities. The error cascades typically start from confusion or misunderstanding. You thought X to be true, but it wasn’t.

I find error cascades in business to also be similar.

People run their businesses based on what they think is true. If what they think is true actually isn’t, all subsequent actions are based on a false premise.

If you can catch the false premise early enough, you prevent the amplification of the error.

This is one of the reasons that I insist on my clients tracking their key performance indicator metrics. This is the equivalent of the airplane pilot looking at his or her instruments. It’s the same as the surgeon monitoring vital signs and keeping track of surgical equipment inventories.

When you run a business or even a department within a business, you must know what is going on.

At all times, you must maintain situational awareness.

At the simplest level, is business good or bad?

Every morning, the CEO of Costco looks at two numbers: 1) How many people walked into our stores yesterday?; and 2) What were our sales yesterday?

Every profession, every industry, every functional area has its equivalent of “the basics.”

You never go wrong taking care of the basics.

The only time you go wrong is when you think you understand, but your understanding is wrong. Then, you’re in trouble.