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 - lacking power, pseudo-randomisation)

Citation: Branson R, et al. Comparison of 3 humidification techniques during mechanical ventilation: patient selection, cost and infection considerations. Respiratory Care 1995; 41: 809-16

Lead author's name: Richard Branson

Three-part Clinical Question:

Patients: Intensive care patients ventilated for more than 1 day, suited for use of heat and moisture exchange filters (i.e. no bloody nor sticky secretions, not severely hypothermic)

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=54; all analysed

Experimental group (HME) n=49; all analysed

The Evidence:

Outcome	Time to Outcome	CER	EER	RRR	ARR	NNT
VAP	?	0.11	0.12	-0.1	-0.011	n.s.
VAP	95% Confidence Intervals:			-1.2 to 1	-0.135 to 0.113	n.s.

Comments: Patients in this trial were pseudo-randomised to the treatment groups according to their hospital number. 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.

No comparative data is given about patient characteristics or co-interventions. Outcomes included incidences of bacterial colonisation, nosocomial pneumonia and tracheal tube occlusion. Pneumonia diagnosis was based on fever + purulent sputum + radiographic changes + tracheal aspirate cultures.

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

This study was not powered to look at differences in nosocomial pneumonia and did not find any.

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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