Prevention of BSI and VAPMeasuring Change in Outcomes

Part IITed 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.

ExampleQual Saf Health Care 2005;14:295-302

0

50

100

150

200

250

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

Infection Number

Da

ys

Be

twe

en

Infe

cti

on

s

UCL = 109 days

Mean = 27 days

Intervention

2000 2001 2002 2003-2004 Year:

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 ChartsStatistical 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/YYYYDate of first BSI in your ICU

Continue with Second EntryNote: Days between Events takes

at least two entries

Completion of Second Entrystarts the Control Chart

Baseline Data EntryFrom Row 20 to 42

Set Baseline: Move Cursor to Cell F20

Edit from B45 to B42

Edit of Chart Title and Data EntryComplete

Print

VAP G Chart

VAP NNIS Worksheet

End of Part II

Questions and Commentsso far?

Continue Part III