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functional residual capacity
Physiology:
- volume remaining in the lungs after a normal, passive exhalation
- represents the point of the breathing cycle where the lung tissue elastic recoil & chest wall outward expansion are balanced & equal
- inward & outward lung compliances are balanced
- work to inflate the lungs is the lowest
- total amount of air in a person's lungs at the lowest point of their tidal volume
- combination of the expiratory reserve volume & the residual volume
- cannot be measured directly using spirometry; has to be calculated
Reference interval:
- in a normal individual, this is ~ 3 liters
- it is position-dependent
- greatest when upright, decreasing when supine or prone, even more so in Trendelenburg & head down positions
- functional residual capacity increases slightly with age
General
static lung volume
References
- Hopkins E, Sharma S
Physiology, Functional Residual Capacity
StatPearls [Internet]. Dec 26, 2022
NLM, NCBI Bookshelf
https://www.ncbi.nlm.nih.gov/books/NBK500007/