Static Compliance Calculator
Calculate static compliance using tidal volume, plateau pressure, and PEEP. Static compliance reflects how easily the lungs and chest wall inflate when airflow is paused.
Calculate Static Compliance
Formula: Static Compliance = VT ÷ (Pplat − PEEP). Enter tidal volume in mL and pressures in cmH₂O.
Static Compliance Formula
Example: VT 450 mL, Pplat 20, PEEP 5
450 ÷ (20 − 5) = 30 mL/cmH₂O
Use the Units When You Forget the Formula
If you cannot remember what order to put the formula in, look at the units.
mL/cmH₂O
Since mL is on top, tidal volume belongs on top of the equation. Since cmH₂O is on the bottom, the pressure difference belongs on the bottom.
Static Compliance = VT ÷ (Pplat − PEEP)
How to Interpret Static Compliance
| Static Compliance | Interpretation | Common Clinical Examples |
|---|---|---|
| > 80 mL/cmH₂O | High compliance | Emphysema, hyperinflation |
| 60–80 mL/cmH₂O | Normal range | Typical adult respiratory mechanics |
| 40–59 mL/cmH₂O | Mildly decreased compliance | Early atelectasis, mild pulmonary edema |
| 20–39 mL/cmH₂O | Moderately decreased compliance | Pneumonia, ARDS, significant pulmonary edema |
| < 20 mL/cmH₂O | Severely decreased compliance | Severe ARDS, fibrotic lung disease |
Static Compliance Reflects Lung Elasticity
Static compliance is measured when airflow is absent, usually during an inspiratory hold. Because there is no flow, airway resistance does not contribute much to the measurement.
Stiff lungs. More pressure is needed to deliver volume.
Stretchy lungs. Volume enters easily, but recoil may be poor.
Avoid These Errors
PIP includes airway resistance. Static compliance requires plateau pressure.
Use Pplat − PEEP, not simply Pplat.
VT should be entered in mL. Result is mL/cmH₂O.
Compliance is a clue, not a diagnosis. Always connect it to the clinical picture.
Compare Static Compliance to Dynamic Compliance
Static compliance helps evaluate elastic properties. Dynamic compliance also includes the effects of airway resistance during flow.