In addition, CO2 increase was higher in patients receiving anti-Her2 treatment than those not (4.6 vs. 1.0 mmHg, p = 0.005).This group, all women with breast cancer, showed no distinguishing characteristics discussed in detail in the results section.No literature evidence was found to explain the higher CO2 retention in this predominantly trastuzumab-treated cohort.Anti-Her2 monoclonal antibodies are the backbone treatment modalities of Her2 expressing breast cancer32. This evidence concerns the gene ERBB2 and breast cancer.