Normobaric Oxygen Therapy in Colorectal Cancer Patients

The intervention will involve NBO as a supportive treatment for CRC patients undergoing chemotherapy. The NBO protocol consists of regular sessions in a normobaric chamber where patients are exposed to controlled oxygen levels aimed at reducing ox-idative stress, supporting erythropoiesis, and modulating immune function. Patients in the CRC group will undergo 10 NBO sessions across five weeks, with two sessions weekly. Patient's exposure to NBO conditions in group 1 (aNBO) including: oxygen levels of 32-40% (compared to about 21% in the atmosphere), pressure maintained at 1,500 hPa (about 1,000 hPa outside), carbon dioxide levels between 0.7-1.9% (compared to 0.03% in the atmosphere, and hydrogen levels between 0.5-1% (which is 10 to 20 thousand times higher than in the atmosphere). Exposure time in the NBO chamber will be the standard 2 hours with an additional 20 minutes for preparation and adaptation and 10 minutes for the finalization and decompression period. Patients' exposure to atmospheric conditions in the same NBO chamber (without normobaric conditions to provide sham-placebo intervention) in group 2 (pNBO): oxygen levels about 21%, pressure maintained at about 1,000 hPa, carbon dioxide levels about o 0.03%, and hydrogen levels about 0.00005% (0.5 parts per million, like in the atmos-phere). The primary comparator in this study is the placebo NBO group (CRC patients; n=127) for CRC patients, which serves to differentiate the specific effects of active NBO from the natural course of treatment without enhanced oxygen exposure. The patient assessment scheme contains six visits from V0 to V5 with subsequent analytical packages with detailed explanation in 2.8. section. The patient assessment schedule consists of six visits, from V0 to V5, each including specific evaluations and interventions. The study begins with V0 (prequalification/screening), where patient consent is obtained, medical history is collected, and baseline data are recorded. V1 (randomization and pre-test visit) involves the initial assessments, including anemia, stress, immune, genetic markers, and patient-reported outcomes (PROMs). Following this, the first phase of the NBO intervention (sessions 1-5) takes place over five weeks. At V2 (midpoint evaluation), the same set of assessments is repeated to track progress, followed by the second phase of the NBO intervention (sessions 6-10) conducted over the next five weeks. V3 (finalization and post-test visit) marks the completion of the intervention, with a final round of primary and secondary outcome assessments. The study then proceeds with two follow-up visits: V4 (3-months post-NBO) and V5 (6-months post-NBO), where anemia, stress, immune, genetic markers, and PROMs are reassessed to evaluate the long-term effects of the intervention.