Airborne nanoparticle exposure is increasingly recognized as a significant contributor to oxidative stress, mitochondrial dysfunction, and low-grade systemic inflammation-factors that impair postoperative recovery. The World Health Organization and European initiatives such as the Human Exposome Project have highlighted the clinical importance of the exposome, defined as the totality of environmental exposures influencing health throughout life.

EOX is a CE-certified air regeneration system designed to modify the indoor exposome through a dual mechanism: advanced filtration and controlled emission of bioavailable anions using cold atmospheric plasma (CAP). Its multistage filter removes particulate matter, pathogens, and volatile organic compounds, while the anionic plasma phase modulates cellular oxidative balance and metabolic function.

Experimental and clinical data indicate that exposure to EOX improves mitochondrial efficiency, increases ATP production, and reduces oxidative protein damage. EOX has also been shown to influence molecular pathways involved in stress adaptation and repair, such as the HIF-1α-VEGF-EPO axis and protein synthesis signaling (e.g., mTOR-p70S6K). These mechanisms may collectively enhance tissue recovery, vascularization, and metabolic resilience in the postoperative setting.

The present study investigates the effects of EOX in hospitalized postoperative patients, evaluating both subjective (sleep quality, well-being) and objective (vital signs, metabolomics, microbiota composition) endpoints. The central hypothesis is that EOX induces a beneficial hormetic response-an adaptive reaction to mild environmental stressors-reflected by improved clinical recovery and biomarker modulation (e.g., succinate reduction, increased ATPase activity). The goal is to assess whether EOX can serve as an effective environmental intervention to support physiological healing and improve the quality of inpatient recovery.

Inclusion Criteria:

• Adults aged ≥18 years, regardless of sex.
• Undergoing elective general surgery, preferably hepatobiliary procedures.
• Hospitalized for at least 4 days postoperatively in Unit 69 (HUFJD).
• Able to provide written informed consent.
• Considered to have medium or high risk of oxidative stress or mitochondrial dysfunction.

Exclusion Criteria:

• Surgery within the previous 6 months, either outpatient or inpatient.
• Diagnosed psychiatric or neurological disorders, including epilepsy.
• Active progressive cancer or chronic inflammatory disease.
• Cognitive impairment or inability to comply with study procedures.
• BMI ≥30 kg/m² (obesity class I or higher).

This is a quadruple-blind study (participant, care provider, investigator, outcomes assessor). The masking is ensured by installing EOX devices in all rooms, regardless of group allocation. Devices appear identical, emit no distinguishable noise, light, or heat, and all display a powered-on light indicator. Only the manufacturer knows which units are active or inactive (placebo). Room assignment is determined by hospital admission scheduling, not influenced by study personnel. Neither patients nor clinical or research staff are aware of the device's operational status, ensuring complete masking throughout the intervention.