FRC
= residual volume + expiratory reserve volume
= volume of gas in the lungs after normal expiration
= lung volume where elastic recoil of chest and lung are in equilibrium (but in opposite directions)
Increased FRC (in general) results from:
- Decreased inward lung recoil
- Increased outward chest recoil
- Bronchoconstriction/airway obstruction
- Lung hyperinflation
Differential diagnosis for increased FRC:
Obstructive lung disease (higher end-expiratory volumes -> hyperinflation -> ↑FRC)
- Emphysema
- Asthma
- Bronchiectasis
- Exercise (↑RR/Tidal volume may not allow for sufficient lung emptying -> hyperinflation)
- Age (associated with a gradual loss of elastic lung tissue)
- PEEP/CPAP
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