SPC scheme to monitor surgery duration

Abstract

AbstractA unified statistical process control (SPC) scheme is developed to monitor work‐process duration of repetitive processes (constant work content), semi‐repetitive (work content somewhat varies between cycles) and memoryless (no typical work content). As a basic paradigm to develop the new scheme, we monitor surgery duration (SD), known to represent durations of all three types of work processes. Recently, a new bi‐variate model for SD was developed and empirically validated. Based on the new model, we derive an approximation to the distribution of SD sample average and use it to construct a two‐stage SPC scheme (for a medically specified subcategory of surgeries). In the first stage, SD distributional shape, as reflected in third and fourth moments, is monitored to determine that no shape‐changing assignable causes are active (e.g., work‐content variation is stable); in the second stage, location and scale parameters are separately monitored via a traditional Shewhart scheme. Using an existent database of surgery times, application of the new scheme is demonstrated, and average‐run‐length properties explored. Extensions (like incorporating co‐variates) and generalizations are addressed.