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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: Hydrophobic HMEFs prevent VAP


Level of evidence: 1+

Citation: Kirton OC, et al. A prospective, randomized comparison of an in-line heater moisture exchange filter and heated wire humidifiers. Chest 1997; 112: 1055-59

 Lead author's name: OC Kirton

 

Three-part Clinical Question:

Patients: trauma intensive care patients requiring mechanical ventilation

Intervention: hydrophobic heat & moisture exchanger v. heated humidifier

Outcome: incidence of nosocomial, ventilator-acquired pneumonia (CDC criteria)

 

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: 280 intensive care patients requiring mechanical ventilation


Control group 140 patients had heated humidifier, all analysed


Experimental group 140 patients had heat & moisture exchanger (HMEF), all analysed

 

The Evidence:

 

Outcome

Time to Outcome

CER

EER

RRR

ARR

NNT

Noscocomial pneumonia

Duration of mechanical ventilation

0.157

0.064

0.592

0.093

11

95% Confidence Intervals:

0.13-1

0.02-0.166

7-50

 

Comments:

 

Patients in this trial were randomised to the treatment groups and all were followed up during their intensive care episode. Analysis of radiographic and laboratory data was blinded. Analysis was also 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 the incidences of tracheal tube occlusion & nosocomial pneumonia.

A power calculation before the study showed that 280 patients were needed to provide a 95 % certainty of a 15% difference in the incidence of nosocomial pneumonia. Appropriate statistical tests were made to compare the incidence of nosocomial pneumonia in the two groups.

There was a reduction in the incidence of nosocomial pneumonia in the HMEF group. There was no difference in the incidence of tracheal tube occlusion.

These results are important and valid. Their applicability to general intensive care patients may be limited. The subjects of this trial were trauma victims and had a mean age of around 47 years. The incidence of nosocomial pneumonia was low (11%), but a clinically significant reduction in the rate of nosocomial pneumonia by use of the HMEF was shown. There was no evidence of harm. I see no obvious reason why we should not use similar HMEFs in general intensive care patients requiring ventilation.


 

Appraised by: Dr David Swann, Consultant, Intensive Care Unit, Royal Infirmary Of Edinburgh.

 
Email: d.g.swann@ed.ac.uk

 

Kill or Update By: December 2009

 

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