Compliance is the ease at which the lungs and thoracic cage expand and is dependent on the elasticity of the tissues involved.
Compliance determines the change in volume for any given change in pressure.
Compliance = ∆V/∆P (ml/cmH2O)
Hence, that ∆P is the pressure needed to vanquish the elastic recoil of the lung to be able to fit a certain volume. It is called the Elastance (PElast) and is the reverse of compliance (compliance = 1/PElast)
In mechanically ventilated patients with normal lungs, the respiratory system’s compliance is 50-100 mL/cmH2O.
[az_toggle_section] [toggle title=”What is the compliance of your patient’s lungs if they accomodate 500mL of air for every 14cmH2O, and how would you describe your patient’s compliance? ” id=”tgl-1″] Compliance = ∆V/∆P (ml/cmH2O)
Compliance = 500mL / 14 cmH2O = 35-36 mL/cmH2O
Your patient has a poor compliance, well below 50mL/cmH2O. [/toggle] [/az_toggle_section]