Infection Control & Hospital Epidemiology Pneumonia (VAP) 0.15 0.10 0.05 0.00
0 days in ICU before MV 1 days in ICU before MV 2 days in ICU before MV 3−4 days in ICU before MV >4 days in ICU before MV
0 5 10 15 20 25 30
duration of mechanical ventilation (days)
0.0 0.2 0.4 0.6 0.8 1.0
Extubation without VAP
305
0 days in ICU before MV 1 days in ICU before MV 2 days in ICU before MV 3−4 days in ICU before MV >4 days in ICU before MV
0 5 10 15 20 25 30
duration of mechanical ventilation (days)
Fig. 4. Cumulative risk (incidence) of ventilator-associated pneumonia (VAP) and extubation without VAP, stratified by days in ICU before mechanical ventilation.
Pneumonia (VAP) 0.08 0.04 0.00
first episode second episode third episode
0 5 10 15 20 25 30
duration of mechanical ventilation (days)
0.0 0.2 0.4 0.6 0.8 1.0
Extubation without VAP
first episode second episode third episode
0 5 10 15 20 25 30
duration of mechanical ventilation (days)
Fig. 5. Cumulative risk (incidence) of ventilator-associated pneumonia (VAP) and extubation without VAP, stratified by episode.
of the extubation hazard rate is also of importance because it indi- rectly determines the cumulative VAP risk. Patients who have been in the hospital for 2 ormore days before
intubation have a higherVAP risk regardless of the duration of ven- tilation.2 We distinguished the preintubation time between general hospital and intensive care and found that it is rather the timein ICU than the time in the general ward. In addition, our results indicate that the risk for VAP is higher during the second and third episodes of ventilation. Such effects, even thoughmuch less pronounced, have been reported in previous studies.8,9 The study had following limitations. First, extubation documen-
tation did not indicate whether it was a planned or unplanned extu- bation. Such a distinction would have been interesting for studying the effect of reintubation in more detail. Second, we included only adults in this analysis. Thus, the results cannot be generalized to pediatric populations. In this study, we did not distinguish between early or late onset of VAP. To investigate late-onset VAP occurring after 4 days of intubation and mechanical ventilation,2 conditional models should be used.16 Therefore, for late-onset VAP, a statistical analysismust account for the fact that patients have to be ventilated at least 4 days without acquiring a VAP; patients who acquire an early-onset VAP or were extubated within four days are not at-risk for late-onset VAP.16 Many patients receive short-term ventilation
(Fig. 1) and are therefore excluded from the risk set, and the cumu- lative risk of late-onset VAP is greater than that for early- and late-onset VAP combined (data not shown). In conclusion, we hope that our approach leads to a better risk understanding of VAP. This information may guide physicians to improve medical decisions related to the harms and benefits of the duration of ventilation.
Acknowledgments. We thank all the participating ICUs for their invaluable contribution to the data collection.
Financial support. This study was funded by the German research foundation Deutsche Forschungsgemeinschaft (grant No WO 1746/1–2).
Conflicts of interest. All authors report no conflicts of interest relevant to this article.
References
1. Chastre J, Fagon JY. Ventilator-associated pneumonia. Am J Respir Crit Care Med 2002;165:867–903.
2. Hunter JD. Ventilator associated pneumonia. BMJ 2012;344:e3325. 3. Philippart F, Gaudry S, Quinquis L, et al. Randomized intubation with polyurethane or conical cuffs to prevent pneumonia in ventilated patients. Am J Respir Crit Care Med 2015;191:637–645.
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