Performance of Unmodified Mechanical Ventilators With 2% Hydrogen Gas Mixtures.

Background: Molecular hydrogen (H2) is a breathable gas that has been shown to have anti-oxidative, anti-inflammatory, and anti-apoptotic properties that may positively impact ischemia-reperfusion injury. The provision of 2% H2 through unmodified mechanical ventilators may facilitate the clinical translation of H2 as a therapeutic in critical illness. The effect of 2% H2 on ventilator performance is unknown. Methods: Unmodified Maquet Servo-i, Maquet Servo-u, Dräger Evita Infinity V500, and Dräger Evita Babylog VN500 ventilators from clinical stock were tested in an experimental closed system using certified, premixed air and O2 containing 2% H2 gas. Wall air and O2 supply were used as control. Ventilator settings were varied across the spectrum of neonatal to adult settings. End points included (1) difference between set and delivered tidal volume (VT) (Douglas method), (2) difference between set versus delivered O2 concentration, (3) delivered H2 concentration (gas chromatography), and (4) ventilator pre-use check malfunction. Correlation between set and measured end points were quantified by linear regression analysis and bias by Bland-Altman analysis. Results: During H2 administration, the average bias in measured versus set VT was within ± 10% for all ventilators except for the Babylog VN500, which exhibited an average bias of -89.2% (95% CI -107.0 to -71.3). The average bias in measured FIO2 was within ± 10% of set for all ventilators. Except for the Babylog VN500, all ventilators passed the pre-use check. Conclusions: Unmodified Servo-i, Servo-u, and Evita V500 ventilators deliver 2% H2 mixtures with acceptable accuracy in VT and FIO2. The Babylog VN500, which uses hot-wire anometry and a higher set operating temperature, exhibits unacceptably inaccurate delivery of VT with H2 mixtures.