First process identified is going to sterile processing department. Second Process identified is taking instruments set for service. Third process identified is sharpening and repairing surgical instruments.
Among the three processes, two of which can be measured. Instruments set for service can be measured for their quality, sharpness and usability. Sharpened and repaired surgical instruments can also be measured for their quality, sharpness and usability. Quality and usability are attribute characteristics of instruments that are intangible. The measurement of both characteristics can be a count of the number of defects. On the other hand, sharpness is a characteristic of the instrument that can be measured using a specialized instrument such as a micrometer.
A statistical process control can be employed in order to measure the sharpness of a surgical instrument. Statistical process control or SPC is a technique for error prevention rather than error detection. The goals of SPC are to improve quality, reduce cost, increase profit and enhance competitive advantage. Steps taken to improve a process will result in fewer defects and better quality products delivered to the customer. Application of SPC can produce improvements in yield, reduce cost and increase efficiency. It can also create a high degree of visibility of process performance and can be used to determine process capabilities. Measurements will provide a comparison of performance to target objectives and assess the effectiveness of process improvements.
SPC is statistically based and built around the concept that variation in a product is always present. Inherent variations occur due to wear of tools, material hardness, machine accuracy, and operator skills. In order to control the process and reduce variations, the cause must be identified through a collection of data. Mathematical distributions characterize the collected data and predict the overall performance. Variations that are outside of the desired process distribution can be corrected by improving the process directly.
Three statistical tools shall be used to determine that the process is in control and follows a normal distribution curve. These tools include control charts, histograms, and mathematical analysis tests. Control charts are used to identify assignable causes of variations. A histogram is a graphic representation of a frequency distribution.
Control charts for variable data will be created for quantitative measurements of sharpness of surgical instruments. Control charts for attribute data will be created for qualitative measurements or counts of defects. The average value () chart and the range (R) chart will be utilized as form of control charts in tracking and identifying the causes and variations.
In making the control chart, the centerline and control limits are determined and drawn on the chart. The centerline is the average of the mean values. The purpose of the control limits on the chart is to indicate if the process is under control. It means that all are within the estimated 3 limits of the process.
An upper control limit for control chart for attributes is UCL = + 1.96 x standard deviation, while the lower control limit is LCL = - 1.96 x standard deviation, where is the total number of defects divided by the number of observations. Standard deviation is defined as S = An upper control l