Web site designed and maintained by
Chris Cairns
© SICS EBM Group 2004
|
|
|
|
Does the use of heat and moisture exchangers rather than heated humidifiers affect the incidence of ventilator associated pneumonia?
Citation: Impact of Humidification Systems on Ventilator-associated Pneumonia. A Randomized Multicenter Trial Am J Respir Crit Care Med 2005; 172: 1276–1282
Lead author's name: Jean-Claude Lacherade
Three-part Clinical Question: Patients: expected to require ventilation for more than two days Intervention: Heat & Moisture Exchange Filters v. Heated Humidifiers with wire heated circuits Outcome: Ventilator Associated
Pneumonia, diagnosed on clinical & radiological features with invasive
respiratory sampling Search Terms: Intensive care, critical care, mechanical ventilation, ventilator-associated pneumonia, nosocomial pneumonia, heat & moisture exchanger, heated humidifiers, controlled trial
The Study: Randomized
controlled trial, with blinded microbiological testing and intention-to-treat
analysis Control group n= 184; all
analysed Experimental group n= 185; all analysed
The Evidence:
1) Do the methods allow accurate testing of the hypothesis? Yes. This was a well-designed trial, using a definition of VAP that included the use of invasive respiratory sampling. The likelihood of including colonised as well as infected patients, in the outcome analysis was therefore reduced.
While the microbiologists were blinded to treatment arm, clinicians were not; they used pre-defined criteria to diagnose pneumonia. Observer bias in the diagnosis of pneumonia would seem unlikely.
A manufacturer of heated water humidifiers supported the trial. This may prejudice the validity of the trial in some minds.
The VAP rate of 27% was about twice that reported in other trials and in our own experience. Is there a reason why HMEFs may not affect VAP rates when the incidence is high?
2) Do the statistical tests correctly test the results to allow differentiation of statistically significant results? The original power calculations were based on Kirton’s findings and indicated that 500 patients were needed. After an interim analysis showed a higher than expected incidence of VAP this number was recalculated as 370 patients. This seems reasonable, but a type II error may explain the equivalent outcomes.
3) Are conclusions valid in light of the results? Yes
4) Did results get omitted, and why? No.
5) Did they suggest areas of further research? Yes, a new RCT in trauma patients.
6) Did they make any recommendations based on the results and were they appropriate? Yes, that either system may be used without an effect on VAP. This is a reasonable view.
7) Is the study relevant to my clinical practice? Yes.
8) What level of evidence does this study represent? 1+
9) What grade of recommendation can I make on this result alone? B
10) What grade of recommendation can I make when this study is considered along with other available evidence? A
11) Should I change my practice because of these results? No, one can use this study either way to promote the use of HHs or HMEFs.
12) Should I audit my current practice because of these results? VAP rates should be audited, in any case.
| ||||||||||||||||||||||
