In clinical literature, "FI" is most commonly used as an abbreviation for two distinct medical concepts often discussed in studies:

1. Maritime Communication (AIS Application-Specific Messages)

: It is used for Area Notices (Broadcast) , which provide vessels with critical safety and navigational information.

: In many papers, the number " 22 " refers to a specific reference (e.g., Searle et al. ) used to construct the index or to specific cervical/spinal deformity indices used in geriatric assessments.

: Many gastrointestinal and epidemiological studies focus on FI.

: In cooling system specifications (such as those for heat exchangers), FI-22 can identify a specific secondary cooling water flow indicator channel, often used to monitor flow rates in gallons per minute (gpm).