Lung Compiance

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Pulmonary compliance, or lung compliance, is a measure of the lungs ability to stretch and expand. In clinical practice it is seperated into two different measurements, static compliance and dynamic compliance. The calculating of lung compliance demonstrates the relationship between changes in volume and changes in pressure within the airways. This measurement is important because it can often be one of the first warnings of a developing lung disease.

Static Compliance

Static Compliance is the measuring of the lung compliance when the lungs are stationary. This can be accomplished by using an inspiratory hold maneuver and taking a measurement of the plateau pressure. Plateau pressure represents the lowering of the lung pressure caused by the additional expanding of the lungs after no more volume is added.

Static Compliance Equation

\begin{align} {C_{stat}}=\frac{V_t}{P_{plat}-PEEP} \end{align}

Dynamic Compliance

Dynamic compliance represents the lung compliance during both inhalation and exhalation. This measurement uses peak pressure rather than plateau pressure, as in the static compliance equation, in order to show lung compliance while the lungs are in motion.

Dynamic Compliance Equation

\begin{align} {C_{dyn}}=\frac{V_t}{PIP-PEEP} \end{align}