Kirton 1997.

Methods	Randomized parallel study comparing HME to HH.
Participants	Inclusion criteria: people requiring mechanical ventilation. Mean age: 47 years. Exclusion criteria: ventilated elsewhere. Respiratory diagnosis: not stated. Severity: not stated. Setting: trauma ICU, USA.
Interventions	HME (hydrophobic): BB100‐F (Pall). n = 140. HH (heated wire). n = 140. Time in study: until removal of ETT, time not stated.
Outcomes	Artificial airway occlusion. Nosocomial pneumonia. Cost ‐ no SD.
Notes	All 6 lost to follow‐up appeared to have been in HME group. Funding: University of Miami and Jackson Memorial Hospital.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Randomization was by a random number generated from a personal computer."
Allocation concealment (selection bias)	Unclear risk	Not stated.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	"Laboratory and chest radiograph interpretation were blinded."
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear whether the 6 lost to follow‐up included in analysis.
Selective reporting (reporting bias)	Low risk	No protocol available, 2 of the 3 primary outcomes, i.e. airway occlusion and pneumonia, reported but mortality not reported.
Other bias	Unclear risk	None identified but potential differences between groups not reported.