Functional Residual Capacity
Overview
- The functional residual capacity (FRC) is the volume left in the lungs after passive expiration, i.e. without use of accessory muscles.
Significance
- A marker of compliance of the lungs and chest wall.
Increased FRC
- Increased functional residual capacity indicates increased lung compliance.
Causes of Increased FRC
- Erect posture
- Advanced age
- Emphysema
- Asthma
Reduced FRC
- Reduced functional residual capacity indicates decreased lung compliance.
Causes of Reduced FRC
- Supine position
- Pulmonary fibrosis
- Obesity
- Abdominal swelling
- Muscle relaxants
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