Hang Yi, Yu Feng
This study investigated how the hydrogen–oxygen (H2–O2) gas mixture (2:1 by volume) as an alternative particle carrier could enhance aerosolized medicinal delivery efficiency to the peripheral lung (i.e., generation 13-to-alveoli region) compared with air. Employing an experimentally validated computational fluid particle dynamics model, this paper predicted and compared pulmonary air-particle vs H2–O2-particle transport and deposition in a representative human respiratory system, using multiple particle sizes (i.e., 1, 5, and 10 μm) and breathing patterns (12, 16, and 20 breaths per min with a fixed tidal volume of 500 ml). Results show that using the H2–O2 gas mixture rather than air produces lower Reynolds numbers, reducing turbulence intensity and flow resistance in the respiratory system under all three breathing patterns investigated in this study. It also creates a milder mechanical ventilation environment with lower wall shear stress, thereby minimizing airway irritation. Accordingly, inertial impaction and turbulence-driven deposition in the upper airways decreased, allowing more particles to reach the peripheral lung. Across all cases, the H2–O2 mixture allows more particles to reach the peripheral lung, improving delivered efficiency by up to 9.16%. Simulations further reveal that slower breathing (i.e., lower breathing frequency) and smaller particle size (i.e., 1 μm) can further enhance particle delivery efficiency to the peripheral lung. The findings mentioned above confirm the potential of the H2–O2 gas mixture as carrier to enhance drug delivery to small airways via inhalation therapy compared with air alone. Nevertheless, before clinical translation, potential adverse health effects, such as risks of hyperoxia, require further in vivo evaluation.