static and dynamic compliance

• related: basic understanding of ventilators
• tags: #permanent #pulmonary

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• basic understanding of ventilators
  • static and dynamic compliance

Static compliance less than 20 is good.

$\frac{T_v}{P_{plat}-PEEP}$

Dynamic compliance measures airway resistance (e.g. small ET tube)

$\frac{T_v}{P_{peak}-PEEP}$

Dynamic compliance is the volume change divided by the peak inspiratory transthoracic pressure. Static compliance is the volume change divided by the plateau inspiratory pressure minus the PEEP. With the initiation of an inspiratory breath, the transthoracic pressure gradient increases to a peak value. This increase is a function of elastic resistance of the lung and chest wall as well as airway resistance. The pressure then falls to a plateau level as the gas redistributes in alveoli. Consequently, dynamic compliance is always lower than static compliance.¹

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