Understanding Variation in Cardiopulmonary Bypass: Statistical Process Control Theory

Cardiopulmonary bypass (CPB) is a complex clinical process that takes place within an extremely complex care deliver system. During the past 50 years, many technicaland device-related improvements have been implemented. However, there remains enormous opportunity to improve. As has been shown in other industries, understanding variation is the key to improvement of any process, and Statistical Process Control Theory (SPCT) is a powerful method for studying variation. SPCT was first described and used by Walter Shewart in the 1930s to improve telephone component production at Bell Laboratories (1). Shewhart's hypothesis was that production quality improves when front-line workers are informed and empowered with information necessary for that improvement. He invented control charts as a method for transforming data concerning variation into understandable information. With the application of this theory in the form of control charts, Shewhart provided production workers with a deeper understanding of the variation in their production system.