Video Transcript: Driver Diagrams

Bob Lloyd, PhD, Executive Director Performance Improvement, Institute for Healthcare Improvement

One of the first things an improvement team needs to understand is the level at which they’re working. Are you trying to change a large, macro-level system? That is, a whole system, a state, a province, a country? Or are you trying to change a smaller group — maybe a group of clinics, or hospitals within it? Or are you trying to deal with the micro level, and actually change one entity, one organization?

Well, when a team starts working to try to define the boundaries, it’s important to define the system that you’re trying to work in, and that system can be defined very nicely through something called a driver diagram. The driver diagram is a pictorial display of a system.

What we’re trying to do is to show the factors that cause the outcome. So we start with an aim, and that aim can be driven by what we call “primary drivers.” These are a small set of things that you believe are the primary things that cause this outcome to occur. Then, after the primary drivers, we set up a group called “secondary drivers,” and these are the things that we believe drive the primary drivers. There may be more of these than you identified with the primary drivers, and they may even have multiple influences. Sometimes they may have an influence, but we indicate them with a dashed line, indicating a weaker relationship, but nonetheless still having an impact on this one. Now we have two things impacting that.

One of the things that a driver diagram should be able to do is define the system. So let’s look at an example. Let’s say that you wanted to make a new me. How would you do that? Let’s say that the aim is to lose some weight. How would you think about the factors that lead to defining that new me? Well, simply, one thing could be “calories in” and “calories out.” Now, two primary things: the amount of calories you take in and the number of calories you expend. Now what are the things that drive those?

Well, you could look at things such as the daily intake of calories. You could look at substituting low-calorie options for food. You could look at the amount of alcohol and soda you take in. You could also look at the amount of exercise as secondary drivers.

These things all affect the calories in and out, so we have some direct effects of these two. This one has an impact on calories in and calories out — by avoiding alcohol and soda — and, finally, exercise clearly has an impact on calories out.

Now one of the things that driver diagram also allows you to do is to be able to identify measures that relate to each of these concepts because the driver diagram is essentially a description of the system you’re trying to improve and the causal variables that you think drive this outcome. So we could put “y” here as a dependent variable, and then these are independent variables x1, x2, x3, x4, x5, x6. All of these independent variables are having an effect on the outcome. But they’re concepts, and what we need to do is establish measures. So what we’ll try to do is hang our measures on each of these concepts.

A new me? How would we know that? We could measure our BMI, our body mass index. You could measure your waist size; you could measure the weight in grams, kilos, whatever the unit. Now, calories in, how would you measure that? You could actually get your daily calorie count. Calories out? You could track the number of calories burned each day.

Now if we move over to our secondary drivers, we now could look at counting the number of calories we take each day. You could even go so far as to track the daily intake of fat, sodium, and cholesterol. You could look at the percent of opportunities to use low-calorie foods. You could look at the number of alcoholic or sodas you had each week, the number of drinks. And finally you could look at the exercise, that is, you could look at the miles walked, on your bike, run, different units could be associated with miles. You could look at number of minutes you’re exercising.

The point being that now we’ve identified the system of interest we’ve identified the key drivers — the primary drivers, the secondary drivers — and now we’ve also been able to hang our measures on it. Now we define the system, it gives us the opportunity to start tracking our data and tracking how these variables, in fact, produce a new me. So the driver diagram gives us a great opportunity to think about the system we want to change and also to then start the improvement journey.