Which statement best describes static lung compliance?

Which statement best describes static lung compliance?

• A. The rate of air flow into the lungs.
• B. The maximal inspiratory pressure generated.
• C. The amount of air in the lungs after a normal breath.
• D. The ease with which the lungs expand for a given pressure.

Answer: (D)

Static lung compliance describes how distensible the respiratory system is when there is no air moving. It is the change in volume for a given change in transpulmonary pressure under conditions of zero flow, typically measured during an inspiratory hold. In practice, clinicians estimate it as the tidal volume divided by the driving pressure (plateau pressure minus PEEP). The higher the compliance, the easier the lungs expand for a given pressure; the lower the compliance, the stiffer the lungs require more pressure to achieve the same volume. This concept is distinct from ventilation flow or muscle strength: the rate of air flow into the lungs reflects airway resistance, while maximal inspiratory pressure gauges inspiratory muscle strength, and the amount of air after a normal breath relates more to tidal volume or functional residual capacity, not how easily the lungs expand per unit pressure.

Static lung compliance describes how distensible the respiratory system is when there is no air moving. It is the change in volume for a given change in transpulmonary pressure under conditions of zero flow, typically measured during an inspiratory hold. In practice, clinicians estimate it as the tidal volume divided by the driving pressure (plateau pressure minus PEEP). The higher the compliance, the easier the lungs expand for a given pressure; the lower the compliance, the stiffer the lungs require more pressure to achieve the same volume. This concept is distinct from ventilation flow or muscle strength: the rate of air flow into the lungs reflects airway resistance, while maximal inspiratory pressure gauges inspiratory muscle strength, and the amount of air after a normal breath relates more to tidal volume or functional residual capacity, not how easily the lungs expand per unit pressure.