# Abstract

 

## Introduction The preventive impact of hospital-acquired infection (HAI) surveillance is difficult to assess. Our objective was to investigate the effect of HAI surveillance disruption on ventilator-associated pneumonia (VAP) incidence. 

## Methods A quasi-experimental study with an intervention group and a control group was conducted between 1 January 2004 and 31 December 2010 in two intensive care units (ICUs) of a university hospital that participated in a national HAI surveillance network. Surveillance was interrupted during the year 2007 in unit A (intervention group) and was continuous in unit B (control group). Period 1 (pre-test period) comprised patients hospitalized during 2004 to 2006, and period 2 (post-test period) involved patients hospitalized during 2008 to 2010. Patients hospitalized ≥48 hours and intubated during their stay were included. Multivariate Poisson regression was fitted to ascertain the influence of surveillance disruption. 

## Results A total of 2,771 patients, accounting for 19,848 intubation-days at risk, were studied; 307 had VAP. The VAP attack rate increased in unit A from 7.8% during period 1 to 17.1% during period 2 (*P* \<0.001); in unit B, it was 7.2% and 11.2% for the two periods respectively (*P* = 0.17). Adjusted VAP incidence rose in unit A after surveillance disruption (incidence rate ratio = 2.17, 95% confidence interval 1.05 to 4.47, *P* = 0.036), independently of VAP trend; no change was observed in unit B. All-cause mortality and length of stay increased (*P* = 0.028 and *P* = 0.038, respectively) in unit A between periods 1 and 2. In unit B, no change in mortality was observed (*P* = 0.22), while length of stay decreased between periods 1 and 2 (*P* = 0.002). 

## Conclusions VAP incidence, length of stay and all-cause mortality rose after HAI surveillance disruption in ICU, which suggests a specific effect of HAI surveillance on VAP prevention and reinforces the role of data feedback and counselling as a mechanism to facilitate performance improvement. # Results 

## Study participants Of the 4,411 patients included in the surveillance of both units during the study period, 2,915 (61.1%) were exposed to mechanical ventilation during their hospital stay. Data were missing for 4.9% (n = 144) of intubated patients and were, therefore, excluded. Totally, 2,771 patients, accounting for 37,330 hospitalisation days, 26,768 intubation-days and 19,848 intubation-days at risk, were analysed. Among them, 940 (34%) were hospitalised in unit A, and 1,831 (66%) in unit B. Overall, 62% (n = 1,724) were men, and mean ± SD age was 60 ± 16 years. Totally, 61% (n = 1,694) received antibiotics at admission, 41% (n = 1,142) came from home, and 26% (n = 721) were immunosuppressed. Mean ± SD SAPSII score was 53 ± 20. All-cause in-hospital mortality was 26% (n = 712). Overall, 307 patients had VAP. The VAP attack rate was 11.1 per 100 intubated patients and the VAP incidence rate was 15.5 (95% confidence interval (95% CI) 13.8 to 17.3) per 1,000 intubation-days at risk. 

## Characteristics by group and period Table [1](#) reports the characteristics of hospitalised patients by group and period. In the intervention group with surveillance interrupted in 2007, patients hospitalised during period 2 compared to period 1 more often came from home (*P* = 0.004), were more immunosuppressed (*P* \<0.001), more often had surgery as diagnosis category (*P* \<0.001), received antibiotics less frequently at admission (*P* \<.001), were older (*P* = 0.022), and presented lower mean SAPSII (*P* \<0.001). In the control group with continuous surveillance, patients hospitalised during period 2 compared to period 1 were less likely to come from home (*P* \<0.001), were more immunosuppressed (*P* \<0.001), and received antibiotics more frequently at admission (*P* \<0.001). ::::table-wrap

::: caption
Description of the study population by period and ICU, Edouard Herriot
Hospital, Lyon (France), 2004-2010.
:::

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Characteristics Intervention group: Control group:\
Interrupted surveillance, unit A Continuous surveillance, unit B

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```
                                                 Period 1 2004 to 2006 (n = 448)    Period 2 2007 to 2010 (n = 492)   *P*       Period 1 2004 to 2006 (n = 743)   Period 2 2007 to 2010 (n = 881)   *P*
```

Categorical variable,\
n (%)

Gender, male 308 (68.8) 320 (65.0) 0.23 439 (59.1) 531 (60.3) 0.63

Patient origin 0.004 \<0.001

Home 70 (15.6) 114 (23.2) 421 (56.7) 421 (47.8)

Other unit/hospital 378 (84.4) 378 (76.8) 322 (43.3) 460 (52.2)

Immunosuppressed^a^ 153 (34) 263 (53) \<0.001 98 (13.2) 175 (19.9) \<0.001

Diagnosis category^a^ \<0.001 0.060

Medical 265 (59.2) 161 (32.7) 660 (88.8) 807 (91.6)

Surgery 183 (40.9) 331 (67.3) 83 (11.2) 74 (8.4)

Antibiotics^a^ 284 (63.4) 230 (46.8) \<0.001 397 (53.4) 629 (71.4) \<0.001

Deceased in-hospital 60 (13.5) 91 (18.8) 0.028 236 (31.9) 256 (29.1) 0.22

Continuous variable,\
mean (SD)

Age, years^a^ 56.3 (14.9) 58.5 (15.5) 0.022 61.1 (16.4) 60.7 (59.6) 0.61

SAPSII^a^ 51.7 (17.9) 45.4 (21.0) \<0.001 55.6 (19.8) 55.5 (18.8) 0.95

Length of hospital stay, days 12.2 (18.6) 15.3 (25.7) 0.038 14.8 (20.3) 12.0 (17.0) 0.0023

Length of invasive mechanical ventilation, days 7.7 (14.5) 11.3 (24.7) 0.007 11.1 (19.0) 8.5 (14.5) 0.0015

Incidence of VAP

Number of VAP 35 84 68 99

Attack rate^b^ 7.8 17.1 \<0.001 9.2 11.2 0.17



## Incidence^c^ (95% CI) 13.4 22.9 11.2 17.1<br /> (9.5-18.4) (18.4-28.2) (8.7-14.1) (14.0-20.8)

NOTE: CI, confidence interval; SD, standard deviation; SAPSII,
simplified acute physiological score II; VAP, ventilator-associated
pneumonia. ^a^ At ICU admission. ^b^ Number of VAP per 100 intubated
patients. ^c^ Number of VAP per 1,000 intubation-days.:::: 

## Duration of exposure by group and period In the intervention group with surveillance interrupted in 2007, mean length of ICU stay and of invasive mechanical ventilation was longer during period 2 compared to period 1 (*P* = 0.038 and *P* = 0.007, respectively). In the control group, the length of invasive mechanical ventilation was shorter during period 2 compared to period 1 (*P* = 0.0023). In patients who had VAP, mean ± SD length of invasive mechanical ventilation before VAP onset did not change between periods 1 and 2 in the intervention group (11.6 ± 12.5 days vs. 14.0 ± 15.0 days, respectively, *P* = 0.4) and in the control group (13.1 ± 11.6 days vs. 10.4 ± 9.9 days, respectively, *P* = 0.11). In patients who did not suffer from VAP, no difference was found regarding mean ± SD length of hospital stay between periods 1 and 2 in the intervention group (9.3 ± 11.9 days vs. 9.9 ± 14.8 days, respectively, *P* = 0.5), whereas it decreased in the control group (11.3 ± 13.0 days vs. 9.1 ± 9.9 days respectively, *P* \<0.001). 

## Outcome In the intervention group with surveillance interrupted in 2007, all-cause in-hospital mortality increased from 13.5% (n = 60) to 18.8% (n = 91) between periods 1 and 2 (*P* = 0.028). In the control group, all-cause in-hospital mortality was stable between the periods (*P* = 0.22). 

## Effect of surveillance disruption on VAP incidence The VAP attack rate rose in the intervention group from 7.8% (n = 35) during period 1 to 17.1% (n = 84) during period 2 (*P* \<0.001) (Figure [1](#)). The VAP attack rate in the control group without surveillance disruption did not change between periods 1 and 2 (*P* = 0.17). <figure> <p><img src="" /></p> <figcaption><strong>Trend of ventilator-associated pneumonia incidence in ICU, Edouard Herriot Hospital, Lyon (France), 2004-2010</strong>. NOTE: The intervention group was unit A with surveillance disruption in 2007, the control group was unit B with continuous surveillance. Period 1 (pre-test period) comprised patients hospitalized during 2004 to 2006, period 2 (post-test period) involved patients hospitalized during 2008 to 2010. During period 1, no difference in the VAP attack rate (number of VAPs per 100 intubated patients) was observed between units A and B (<em>P</em> = 0.43). During period 2, the VAP attack rate was higher in unit A compared to unit B (<em>P</em> = 0.002). In unit A, the VAP attack rate increased between periods 1 and 2 (<em>P</em> \<0.001). In unit B, the VAP attack rate did not change between periods 1 and 2 (<em>P</em> = 0.17).</figcaption> </figure> VAP incidence increased after surveillance disruption in the intervention group (incidence rate ratio (IRR) = 2.17, 95% CI 1.05 to 4.47, *P* = 0.036) independently of VAP trend (Table [2](#)), but remained unchanged in the control group (IRR = 1.37, 95% CI 0.74 to 2.55, *P* = 0.31). Additional file [1](#) reports the covariables associated with VAP occurrence after univariate analysis. After adjusting for trends, gender, age, patient origin, immunosuppression, diagnosis category, antibiotics and SAPSII at admission, the adjusted incidence of VAP rose after surveillance disruption (IRR = 2.31, 95% CI 1.03 to 5.17, *P* = 0.042), but did not change in the control group (IRR = 1.36, 95% CI 0.72 to 2.56, *P* = 0.35). ::::table-wrap
::: caption
Incidence rate ratio of ventilator-associated pneumonia for trends and
disruption in 2007 in ICU
:::

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Characteristics Intervention group: Control group:\
Interrupted surveillance, unit A Continuous surveillance, unit B

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```
                                   **Adjusted IRR of VAP (95% CI)**^a^   *P*                               **Adjusted IRR of VAP (95% CI)**^a^   *P*
```

Bivariate model

Trend, per quarter 0.98 (0.93 to 1.03) 0.45 1.01 (0.97 to 1.05) 0.69

Period

Before surveillance disruption^b^ 1.00 (Ref.) 1.00 (Ref.)

After surveillance disruption^c^ 2.17 (1.05 to 4.47) 0.036 1.37 (0.74 to 2.55) 0.31

Full model^d^

Trend, per quarter 0.98 (0.92 to 1.04) 0.43 1.02 (0.97 to 1.06) 0.50

Period

Before surveillance disruption^b^ 1.00 (Ref.) 1.00 (Ref.)



## After surveillance disruption^c^ 2.31 (1.03 to 5.17) 0.042 1.36 (0.72 to 2.56) 0.35

NOTE: CI, confidence interval; IRR, incidence rate ratio; VAP,
ventilator-associated pneumonia. ^a^After multivariate Poisson
regression. ^b^ Period 1 (2004 to 2006). ^c^ Period 2 (2007 to 2010).
^d^ Adjusted for gender, age, patient origin, immunosuppression,
diagnosis category, antibiotics and SAPSII at admission in the unit. The
two other variables, trend (per quarter) and period (period 1 vs. period
2), were forced in the model.::::


Extracted trial result:
Outcome: mean ± SD length of hospital stay between periods 1 and 2 in patients who did not suffer from VAP (continuous)
Intervention: Interrupted surveillance unit A
Comparator: Continuous surveillance, unit B
Intervention group size: 940
Intervention mean: 9.9
Intervention standard deviation: 14.8
Comparator group size: 1831
Comparator mean: 9.1
Comparator standard deviation: 9.9
Notes: Values are from post-intervention.