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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.  This is a small inconclusive trial.
Level of evidence   1+                             

 Citation: Roustan JP, et al.Comparison of hydrophobic heat and moisture exchangers with heated humidifier during prolonged mechanical ventilation. Intensive Care Medicine 1992; 18: 97-100

Lead author's name: JP Roustan

 

Three-part Clinical Question:

Patients: intensive care patients requiring mechanical ventilation

Intervention: heat & moisture exchanger v. heated humidifier

Outcome: incidence of ventilator-associated pneumonia

 

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, apparently unblinded, intention-to-treat analysis

 

The Study Patients: 116 intensive care patients requiring mechanical ventilation


Control group 61 patients had heated humidifier; all analysed


Experimental group 55 patients had heat & moisture exchanger; all analysed

 

The Evidence:

Outcome

Time to Outcome

CER

EER

RRR

ARR

NNT

Nosocomial pneumonia

Duration of mechanical ventilation

0.147

0.110

0.252

0.037

   NS

95% Confidence Intervals:

NS

NS

¥

 

Comments:


Patients in this trial were randomised to the treatment groups and all were followed up during their intensive care episode. Analysis does not seem to have been blinded, but 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 durations of ventilation & ICU stay, survival and incidences of atelectasis, nosocomial pneumonia and tracheal tube occlusion.

 

No power calculation was done, but appropriate statistical tests were made.

The only statistically significant difference in outcome was the incidence of tracheal occlusion (9 in the experimental group v. 0 in the control group).

The authors suggest that the high incidence of tracheal tube obstruction in the group treated with the Pall BB 2215 filter was related to the low thermal gradient between respiratory gases and the ambient temperature (28C in this unit in the south of France!). It should also be borne in mind that this filter was primarily designed as an anti-microbial barrier and not as a heat & moisture exchanger. It is no longer available from the manufacturer.

While this study highlights a potential problem with the use of this particular device, it was not powered to look at differences in nosocomial pneumonia.  

 

Appraised by: David Swann, Consultant, Intensive Care, Royal Infirmary of Edinburgh.


Email: d.g.swann@ed.ac.uk

 

Kill or Update By: November 2009

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