Hoffmann 1995a.

Methods	Randomised controlled trial
Participants	44 participants with ISSHL for more than 6 months
Interventions	Control (22): air breathing at 1.5 ATA for 45 minutes daily, 5 days each week for 3 weeks HBOT (22): 100% oxygen breathing at 1.5 ATA on the same schedule as controls
Outcomes	Improved hearing and tinnitus
Notes	Rank 2 for sample size (chronic hearing loss): power > 80% to detect an increase in proportion of participants with significant return of hearing
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of randomisation not clear "forty‐five patients....were randomised into a HBO group and a control group"
Allocation concealment (selection bias)	Unclear risk	No mention of any attempt to conceal allocation
Blinding (performance bias and detection bias) All outcomes	Low risk	Patients and outcome assessors blind "In order to exclude uncontrolled placebo effects, the control group were dealt completely in the same manner as the HBO group ...in the chamber."
Incomplete outcome data (attrition bias) All outcomes	Low risk	One patient lost, no explanation
Selective reporting (reporting bias)	Low risk	No indication of missing outcomes
Other bias	Low risk	No obvious other sources of bias