Measuring for improvement: from Toyota to thoracic surgery

Measuring quality has become a high priority in the era of managed care. Nevertheless, it can be counterproductive to use the same methods for measuring improvement in surgical procedures and processes as we use for measurement in basic research. Techniques of statistical process control have been used for many years to measure process improvement in industry and are now being applied to health care.

Examples of using statistical process control charts to monitor coronary artery bypass grafting mortality, intensive care unit admission time, and length of stay are reviewed.

The major advantage of using control chart methodology is that it allows one to determine whether the process being evaluated is in fact stable and to detect when significant or special cause variation occurs.

Summary statistics currently provided to purchasers of care and regulatory agencies do not ensure that the processes being evaluated are stable. We need to look at data over time with statistically validated methods such as control charts to better monitor our processes of care and thereby provide accurate statistics.