Boots 2006.

Methods	Randomized parallel study comparing HME to HH.
Participants	Inclusion criteria: people requiring mechanical ventilation for ≥ 48 hr. Mean age: HME 59 years, HH 60 years. Exclusion criteria: presenting history which suggested need for hot water humidification, e.g. airway haemorrhage, asthma or airway burns. Mean APACHE II score: HME 20, HH 20. Setting: ICU, Australia.
Interventions	HME (hygroscopic): Humid‐Vent (Gibeck) changed every 24 hr or more frequently if required. n = 190. HH (heated wire): MR730 (Fisher & Paykel, single heated wire) set at 37 ºC or MR290 (Fisher & Paykel, double heated wire) set at 40 ºC. n = 191. Circuit unchanged for duration of ventilation. Time in study (median): HME 6 days, HH 8 days.
Outcomes	Artificial airway occlusion. Mortality. VAP. LOS (ICU) ‐ no SD. Cost ‐ no SD.
Notes	Funding: Teleflex, Wayne, PA. and Fisher & Paykel.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated.
Allocation concealment (selection bias)	Unclear risk	Not stated.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated.
Incomplete outcome data (attrition bias) All outcomes	Low risk	100% follow‐up.
Selective reporting (reporting bias)	Low risk	Protocol not available but all primary outcomes reported.
Other bias	High risk	Participants in HME group ventilated for a significantly shorter period (i.e. HME 6 days, HH 8 days).