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Does the use of heat and moisture exchangers rather than heated humidifiers affect the incidence of ventilator associated pneumonia?

 

Brief Bottom Line statement.  No difference in invasively diagnosed VAP rates between patients having heat & moisture exchangers or heated water humidification in a small, underpowered study.
Level of evidence: 1+

 

Citation:

Dreyfuss D. Mechanical ventilation with heated humidifiers or heat and moisture exchangers: effects on patient colonization and incidence of nosocomial pneumonia.

Am. J. Respir. Crit. Care Med, 1995; 151: 986-992.


Lead author's name: D Dreyfuss

 

Three-part Clinical Question:

Patients: intensive care patients requiring mechanical ventilation > 48h

Intervention: heat & moisture exchanger v. heated humidifier

Outcome: incidence of ventilator-associated pneumonia (= purulent sputum + new infiltrate on chest X-ray + positive quantitative culture of bronchoscopically obtained specimen / positive blood cultures)

 

Search Terms: Intensive care, critical care, mechanical ventilation, ventilator associated pneumonia, nosocomial pneumonia, heat & moisture exchanger, heated humidifiers, controlled trial

 

The Study: Randomised controlled trial, “blinded”, intention-to-treat analysis

.

The Study Patients: 131 intensive care patients requiring mechanical ventilation > 48h


Control group 70 patients had heated humidifier, all analysed


Experimental group 61 patients had heat & moisture exchanger, all analysed

 

The Evidence:

 

Outcome

Time to Outcome

CER

EER

RRR

ARR

NNT

Ventilator-associated pneumonia

48h after stopping mechanical ventilation

0.114

0.098

0.140

0.016

NS

95% Confidence Intervals:

NS

NS

¥

 

Comments:


Patients in this trial were randomised to the treatment groups and all were followed up. The radiologist was blinded, but apparently not the person making the diagnosis of ventilator associated pneumonia. The diagnosis of VAP depended on a combination of clinical, radiological and microbiological features. Analysis was done on an intention-to-treat basis.

 

Both groups were similar at the start of the trial and were treated equally, apart from the experimental intervention. Outcomes included duration of ventilation and incidences of ventilator tubing colonisation and nosocomial pneumonia.

 

No power calculation was done, but appropriate statistical tests were made. No significant difference was found in the VAP rates in this small, but rigorous study comparing two means of humidification. It is possible that the study was not powerful enough to detect such differences. 

 

Appraised by: David Swann. Consultant, Royal Infirmary of Edinburgh.
Email: d.g.swann@ed.ac.uk

 

Kill or Update By: December 2009

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