There are multiple definitions:

1. reticulocyte production index(English)

   • Erythrocyte, Hematology

2. REM predominance index(English)

   • while OSA is a REM sleep-related problem in the majority of children, there is a significant subset of children with NREM predominance of obstructive events. This finding highlights the importance of considering sleep state distribution of events in studies of the pathophysiology and outcomes of OSA in childhood
   • NREM, OAHI, OSA, REM, PSG
   • Sleep medicine, Pediatrics
   • https://doi.org…69.2009.00760.x

3. regional perfusion index(English)

   • calculated as the ratio of the regional TcPO2 to the reference TcPO2
   • TcPO2, TKA, DVT, OA, RA
   • Hemodynamics, Wound care, Ratio-based metric
   • https://doi.org…58863x04vm539oa
   • https://doi.org…nee.2011.10.002

4. Reference Point micro-Indentation(English)

   • detects differences between cortical bone from the femoral neck of healthy, osteoporotic fractured and osteoarthritic hip replacement patients
   • OA
   • Skeleton and bone (formation), Aging, Injury, Biomaterials
   • https://doi.org…bbm.2017.06.036