Dynamic Compliance Calculator
Calculate dynamic compliance using tidal volume, peak inspiratory pressure, and PEEP. Dynamic compliance reflects the pressure needed to deliver volume while airflow is occurring, so it includes the effects of airway resistance.
Calculate Dynamic Compliance
Formula: Dynamic Compliance = VT ÷ (PIP − PEEP). Enter tidal volume in mL and pressures in cmH₂O.
Dynamic Compliance Formula
Example: VT 450 mL, PIP 30, PEEP 5
450 ÷ (30 − 5) = 18 mL/cmH₂O
Use the Units When You Forget the Formula
Dynamic compliance is reported in the same units as static compliance:
Since mL is on top, tidal volume belongs on top. Since cmH₂O is on the bottom, the pressure difference belongs on the bottom.
Dynamic Compliance = VT ÷ (PIP − PEEP)
How to Interpret Dynamic Compliance
| Dynamic Compliance | Interpretation | Possible Clinical Meaning |
|---|---|---|
| > 80 mL/cmH₂O | High compliance | Hyperinflation or emphysema pattern may be present. |
| 60–80 mL/cmH₂O | Normal range | Typical adult respiratory mechanics. |
| 40–59 mL/cmH₂O | Mildly decreased | Early stiffness or increased resistance may be contributing. |
| 20–39 mL/cmH₂O | Moderately decreased | May reflect lung stiffness, airway resistance, or both. |
| < 20 mL/cmH₂O | Severely decreased | Significant airway resistance, stiff lungs, or combined ventilator mechanics problem. |
Dynamic Compliance Includes Flow and Resistance
Dynamic compliance is measured during active airflow. Because flow is present, the result is affected by both elastic properties and airway resistance.
Uses plateau pressure. Best reflects lung and chest wall elasticity.
Uses PIP. Reflects elasticity plus airway resistance during flow.
This can suggest increased airway resistance, secretions, bronchospasm, kinked tubing, or high flow-related pressure.
Looking at static and dynamic compliance together helps separate stiffness from resistance.
Avoid These Errors
Dynamic compliance requires peak inspiratory pressure.
Use PIP − PEEP, not simply PIP.
Low dynamic compliance may be caused by airway resistance, lung stiffness, or both.
Static and dynamic compliance together tell a better story.
Compare Dynamic Compliance to Static Compliance
Static compliance helps evaluate elastic properties, while dynamic compliance adds the effect of airway resistance during flow.