This study was designed as a randomized, single-blind, dose-response clinical trial consisting of six distinct arms. The first arm served as the control group, where participants received 500 mL of normal saline without any hydrogen nanobubbles, functioning as a placebo. The remaining five arms were intervention groups that received intravenous infusions of hydrogen nanobubbles (HNBs) at different doses. Specifically, participants in Arm B received 5 mL of HNB, Arm C received 10 mL of HNB, Arm D received 15 mL of HNB, Arm E received 20 mL of HNB, and Arm F received 25 mL of HNB, with each dose diluted in normal saline.

All participants underwent a total of 10 infusion sessions over a period of 5 weeks, receiving treatments twice weekly. The study was conducted under single-blind conditions. This multi-arm design allowed the researchers to systematically evaluate the dose-dependent effects of HNB therapy on cardiovascular function, blood biomarkers, and health-related quality of life.

This study investigated a novel intervention using intravenous hydrogen nanobubbles (HNBs), which are microscopic hydrogen gas bubbles encapsulated in liquid, offering enhanced stability, deep tissue penetration, and sustained antioxidant and anti-inflammatory effects. Unlike other hydrogen therapies (such as inhalation or hydrogen-rich water), this method delivers HNBs directly into the bloodstream.

Participants were randomized into six groups: one control group receiving saline and five intervention groups receiving escalating doses of HNBs (5-25 mL) over 10 intravenous infusions in 5 weeks. This intervention is distinct for its dose-response design, intravenous delivery, and combined evaluation of cardiovascular function and quality of life (SF-36)-a patient-centered approach not commonly found in similar studies.

Primary cardiovascular function outcomes included systolic and diastolic blood pressure, measured in millimeters of mercury (mmHg); heart rate, expressed in beats per minute (bpm); and left ventricular ejection fraction (LVEF), reported as a percentage. Diastolic function was assessed through early diastolic mitral inflow velocity (EVel), lateral mitral annular velocity (ELat), and septal mitral annular velocity (ESep), all expressed in meters per second (m/s). Left Ventricular Mass divided by Body Surface Area (BSA) to report Left Ventricular Mass Index in (g/m²), relative wall thickness (RWT), presented as a unitless ratio; tricuspid annular plane systolic excursion (TAPSE), interventricular septal thickness in diastole (IVSd), left ventricular internal dimension in diastole (LVIDd), and left ventricular posterior wall thickness in diastole (LVPWD), all reported in centimeters (cm).Flow-mediated dilation (FMD) (% change in vessel diameter)

The study evaluated health-related quality of life (HRQoL) using the 36-Item Short Form Health Survey (SF-36), a validated instrument consisting of eight distinct domains: General Health (GH), Physical Functioning (PF), Role Limitations due to Physical Health (PH), Bodily Pain (BP), Vitality (VT), Social Functioning (SF), Role Limitations due to Emotional Problems (EL), and Mental Health (MH). Each domain was treated as a separate outcome measure and scored individually on a scale from 0 to 100, where higher scores reflect better health status in that specific domain. In accordance with reporting standards, each SF-36 domain was analyzed and reported independently, rather than being combined into a single summary score. Although all domains share the same unit (0-100 scale), they assess different dimensions of physical and mental well-being and are therefore presented as distinct outcome variables.