Ricard 1999.

Methods	Randomized parallel/cross‐over* study comparing 4 types of HME to HH. * Participants randomized to 2/5 interventions.
Participants	Inclusion criteria: people requiring mechanical ventilation. Mean age: 54 years. Exclusion criteria: not stated. Respiratory diagnosis: 58%. Mean SAPS score: 14. Setting: ICU, France.
Interventions	HME (hydrophobic): Ultipor Filter BB2215 (Pall). n = 20. HME (hydrophobic): Biomedical BB50 (Pall). n = 20. HME (hydrophobic/hygroscopic): Ultipor Filter BB100 (Pall). n = 20. HME (hydrophobic/hygroscopic): Hygrobac (DAR). n = 10. HH: Fischer‐Paykel. n = 15. Time in study: 3 hr.
Outcomes	Minute ventilation. Tidal volume.
Notes	Funding: authors declared they did not have any funding support and had no conflict of interest.
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)	Unclear risk	No protocol available but 2 respiratory variables reported for this short‐term study.
Other bias	Low risk	None identified.