Prevention of BSI and VAP Measuring Change in Outcomes Part II Ted Speroff, PhD
Using NNIS Rate Measures is a Problem for QI NNIS Rates are used in surveillance to detect outbreaks – a rise in rates! –Also, easier to make site comparisons –And easier to pool data into single rate However, the goal of QI is to decrease the rate. The area you have to work with is between the mean rate and 0. It is very hard to show improvement using rate as your measure.
Control Chart for NNIS Rate Central Line is Mean =5.0/1000 days UCL LCL = -1.7 When the lower (LCL) control limit is below zero, you have to collect data for a much longer period of time to move the LCL above zero. X-axis is Time Scale: days, weeks months To show improvement the rate will be in this area.
Solution: g Chart Change your Measure The number of days between events –Date #2 minus Date #1 Goal: to increase the number of days between events There is no upper boundary As the NNIS rate decreases, the number of days between events increases. G chart is sensitive for detecting a decrease in NNIS rate Don’t need to know the census (denominator), just the dates of infections. Thus, not dependent on the number of line-days or vent-days of your ICU.
Example Qual Saf Health Care 2005;14: Figure 3. Days between CVC-related bloodstream infections (G Chart) January 2000 – October 2004 The G chart monitors time between events. The goal is to increase time between infections, hence higher points indicate better performance. As the BSI rate decreases, there are fewer data points per year—this is reflected in shorter calendar-year bars along the top. The baseline period is from January 2000 through October 2002 (infections 1 – 39). The intervention period is from November 2002 through October 2004 (infections 40-45). During the baseline period, the number of days between infections was consistently below the upper control limit (UCL), suggesting the variation in time between infections was random and inherent to the process of CVC care. During the post-intervention period, the number of days between infections was frequently above the UCL, suggesting the intervention had introduced non-random improvements into the process of care.
Additional Rules for Control Charts Statistical Significance Single point above the UCL 2 of 3 consecutive points between 2 and 3 sigma 6 consecutive points in an upward trend 9 consecutive points above or below the central line (mean)
Excel File Template: Tabs – C-Line BSI & VAP
Reminder: Change Name of File and Save Often
First Entry: MM/DD/YYYY Date of first BSI in your ICU
Continue with Second Entry Note: Days between Events takes at least two entries
Completion of Second Entry starts the Control Chart
Baseline Data Entry From Row 20 to 42
Set Baseline: Move Cursor to Cell F20 Edit from B45 to B42
Edit of Chart Title and Data Entry Complete
VAP G Chart
VAP NNIS Worksheet
End of Part II Questions and Comments so far? Continue Part III