Loss of H2 concentration in IV bags. Bag A (with soft and thin wall) vs. Bag B(with hard and thick wall). H2 enriched IV bags were hanged in the air by itself (bare), or in another bag filled with water, or bare but after the gas in the bag evacuated to leave fluid only (no gas/fluid level). The bare bag still retained more than 90% of initial concentration at the end of regular infusion (30 min). Delayed desaturation occurred with the IV bag in another water-filled bag during the infusion but the set up and infusion was rather cumbersome.