Hydrogen Gas May Protect Brain After Cardiac Arrest - Clinical Trial
Efficacy of inhaled HYdrogen on neurological outcome following BRain Ischemia During post-cardiac arrest care (HYBRID II trial): study protocol for a randomized controlled trial
Research hubs: Brain & Nervous System · Cardiovascular System
- Evidence type
- Randomized controlled trial · Human study
- Authors
- Tomoyoshi Tamura, Kei Hayashida, Motoaki Sano, Shuko Onuki, Masaru Suzuki
- Journal
- Trials
- Year
- 2017
- PMID
- 29058596
- Study Type
- Human
- Participants
- 360
- Delivery
- inhalation
- Dose
- 2% hydrogen with 24% to 50% oxygen for 18 hours after admission via mechanical ventilation
- H₂ concentration
- 2% hydrogen with 24% to 50% oxygen
- Duration
- 3 months
- Funding
- Taiyo Nippon Sanso Corporation
- Conflicts of interest
- None declared
- Peer Reviewed
- Yes
- Cited by
- 50 (OpenAlex, as of November 2026)
- Country
- Japan
TL;DR
Scientists are testing whether breathing in a special mixture of hydrogen gas can help people's brains recover better after their heart stops and they're brought back to life. If it works, this simple treatment could help more cardiac arrest survivors wake up with healthy brains instead of permanent brain damage.
Key Finding
The HYBRID II trial is designed to test whether inhaling 2% hydrogen gas for 18 hours improves 90-day neurological outcomes in comatose cardiac arrest survivors, with the goal of increasing good neurological recovery from 50% to 65%.
Summary
This is a study protocol describing a planned clinical trial called HYBRID II that will test whether inhaling hydrogen gas helps improve brain function in people who survive cardiac arrest (when the heart stops beating). The study will enroll 360 comatose patients and randomly assign them to either breathe a mixture containing 2% hydrogen gas or regular oxygen for 18 hours after hospital admission. Researchers will measure whether hydrogen gas, combined with cooling the body to protect the brain, helps more patients recover good neurological function within 90 days.
Practical Takeaway
This is a study protocol, not a completed study with results, so no outcomes are yet available. Animal studies and a small pilot study suggested hydrogen inhalation might help brain recovery after cardiac arrest, but this large clinical trial is still underway to determine if it actually works in patients. Anyone interested in hydrogen's potential medical applications should wait for the trial results before drawing conclusions.
Abstract (excerpt)
Background: Hydrogen gas inhalation (HI) improved survival and neurological outcomes in an animal model of post-cardiac arrest syndrome (PCAS). The feasibility and safety of HI for patients with PCAS was confirmed in a pilot study. The objective of this study is to evaluate the efficacy of HI…