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

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

Bottom Line: This is a small inconclusive trial

Level of evidence: 1^- (RCT with a high risk of bias - lack of power)

Citation: Martin C, et al. Heat and moisture exchangers and vaporizing humidifiers in the intensive care unit Chest 1990; 97: 144-9.

Lead author's name: C Martin

Three-part Clinical Question:

Patients: Intensive care patients ventilated for more than 1 day

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: ICU patients ventilated for more that 24hrs.

Control group (Heated humidifier) n=42; all analysed

Experimental group (HME) n=31; all analysed

The Evidence:

Outcome	Time to Outcome	CER	EER	RRR	ARR	NNT
VAP	Study period	0.19	0.065	0.66	0.125	n.s.
VAP	95% Confidence Intervals:			-0.12 to 1	-0.022 to 0.272	n.s.

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 incidences of bacterial colonisation, nosocomial pneumonia and tracheal tube occlusion.

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

The most worrisome outcome was the incidence of tracheal occlusion (6 in the experimental group v. 0 in the control group). One death occurred in the experimental group as a result of tracheal tube occlusion. However the Pall Ultipor filter 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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