Biomedical Engineering Reference
In-Depth Information
PMS Evaluation
Market intelligence
Customer comments
Market literature
Clinical meetings
Clinical papers
Changes in treatments
Trends and norms
Technical papers
Quality statistics
Regular meeting
No change
Figure 12.1
A typical PMS outcome meeting.
A process control chart captures this data and plots the information sequentially. Consider
the data that normally exists at the foot of every patient's hospital bed: the temperature
graph. The nurse will take your temperature every so often and plot this on a chart; if
the graph is on a constant rise warning bells ring (not literally!). It is a very graphical
way of illustrating errors that vary with time. Your process control chart must have your
upper and lower limits of acceptance and then the data is plotted sequentially. Figure 12.2
illustrates a typical chart taken from inspections of the bio-burden of a device before it is
The main aim of Figure 12.2 is to demonstrate the power of this type of chart, even though it
is simple. The horizontal axis is the sample, sequentially. The vertical axis is the
measurement taken (in this case it was the bio-burden of a device after manufacture). The
vertical line is only there to show that something has changed. Prior to this sample the values
of bio-burden had no real pattern; they varied between upper and lower limits randomly.
However, after the line it is clear to see that there is something going on. The bio-burden
seems to be on a steady increase. We can use this information to investigate before failure
occurs. The instigator for this growth could have been a machine change, a personnel
change, or simply a lack of attention to detail. In this case it was due to a new machinist who
was taking the drawings literally and not finishing the component to the same level as their
predecessor and hence creating a place for bio-burden to stick. This led to a drawing change
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