Pilgramm 1985.

Methods	Randomised controlled trial
Participants	1. Acute hearing loss (< 14 days since onset). 37 patients with hearing loss and/or tinnitus, 18 allocated to HBOT group and 19 to control. 2. Chronic hearing loss (14 days to 1 year since onset). 51 patients with hearing loss and/or tinnitus; 26 allocated to HBOT, 25 to control.
Interventions	Control: vasodilator therapy: 500 ml of 10% dextran‐40 and sorbitol 5% daily for 14 days, plus daily naphtidrofuryl hydogenaxalate 600 mg and vitamin B orally HBOT: as above, plus 60 minutes daily breathing 100% oxygen at 2.5 ATA for 10 days
Outcomes	Improvement in average hearing threshold by audiometry and improvement in tinnitus. Both assessed at 4 weeks from presentation.
Notes	Translated in detail by MP Rank 5 for sample size (acute hearing loss): power to detect mean hearing improvement of 20 dB more in active group than control > 80%
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated sequence "All patients were randomized into a specific treatment group by computer and were maintained in these groups."
Allocation concealment (selection bias)	Unclear risk	No description of allocation concealment
Blinding (performance bias and detection bias) All outcomes	High risk	No description of blinding for any party
Incomplete outcome data (attrition bias) All outcomes	High risk	6 individuals withdrew from treatment but it is not clear if they contributed to the analysis
Selective reporting (reporting bias)	Low risk	No indication of missed outcomes
Other bias	Low risk	No other obvious source of bias