Figure 3.

Histogram and pie chart of classification and quantification of all enrolled reports on mechanistic investigation of gas‐mediated tissue protection. A) numbers of reports showing discernible therapeutic effect (black numbers inside the bars) were much higher than those exhibiting ineffectiveness and/or side effect (red numbers on top of the bars) for all gases examined (note: no negative reports were found for NO and O₃). B) The percentages in the chart corresponded to the number of positive reports of each gas over the total number of papers enrolled (i.e., 223). The majority of the qualified studies demonstrating therapeutic efficacy investigated biological gases (total: 83%) of hydrogen sulfide (H₂S: 55/223 = 25%) and carbon monoxide (CO: 48/223 = 22%), with xenon (Xe: 16/223 = 7%) being the most studied noble gas (group total: 17%).