Anne van Dalen

240 I Chapter 9 to reach the Six Sigma level of system performance. 3 The term ‘Six Sigma’ comes from statistics, specifically from the field of statistical quality control, which evaluates process capability. The concept of Six Sigma was originally developed by Motorola engineers in the 1980s, to provide greater resolution in measuring and decreasing defects in every product, service, and transactional process. It helped to optimise operational processes, by reducing process output variation. 5 In statistical terms, Six Sigma refers to 3.4 defects per million opportunities (i.e. nearly perfect). The formula repre- sents the variation about the process average (mean), hence the expectation that the first six standard deviations (sigma) of production variability fall within acceptable failure limits. 5,6 The fundamental objective of the Six Sigma methodology is the implementation of a structured data-driven strategy, focusing on reduction of variation and process improvement. 6,7 A balance between error prevention, detection, handling, and learning is crucial. The operating theatre remains an environment that often lacks comprehensive data capture, robust monitoring strategies, and process evaluation, causing a knowledge gap on perioperative process optimisation. 8 Currently, most quality and safety improvement ap- proaches in healthcare focus on retrospective data and post hoc error analysis to identify poor quality, resulting in recall bias, low compliance, and a lack of detail. Objective multisource data monitoring systems are needed. The Six Sigma framework includes five steps: define, measure, analyse, improve, and control (DMAIC). 6 In healthcare, organisations need first to recognise that human error cannot be completely avoided. Instead, events that may lead to errors ought to be spotted early, analysed, and reduced. Using a system approach, procedures are standardised so that, for example, specific protocols (e.g. use of name stickers or the WHO Surgical Safety checklist) help minimise the chance of human error occurring. 9,10 It is important, as well, that operating theatre teams using this approach are often able to overcome unexpected events and deviations, achieving good outcomes. This is termed system resilience, meaning that the team is able to adapt successfully before, during, or after safety threats occur, despite conditions that could lead to failure. 11,12 The positive consequences of increased transparency about errors ought to be highlighted,