Lung compliance

Question 1

What is lung compliance?

Answer 1

The measure of the lung’s ability to stretch and expand; calculated as the change in volume over the change in pressure (ΔV/ΔP)

Question 2

Why is lung compliance reduced in neonatal RDS?

Answer 2

Due to surfactant deficiency leading to alveolar collapse and increased surface tension.

surfactant deficiency is due to either inadequate surfactant production (problems with alveolar type II cells), or surfactant inactivation in the context of immature lungs

Antenatal betamethasone (corticosteroid injection) is primarily used to speed up lung development in preterm fetuses.

Question 3

What is the clinical significance of decreased lung compliance in ARDS?

Answer 3

Leads to stiff lungs requiring low tidal volume ventilation to prevent further injury.

Question 4

Changes in Lung Compliance; Emphysema (a form of COPD)

Answer 4

Compliance: Increased

Mechanism: Destruction of alveolar walls leads to loss of elastic recoil, making lungs more distensible.

Clinical Implication: Air trapping and hyperinflation.

Question 5

Changes in Lung Compliance; Idiopathic Pulmonary Fibrosis (IPF)

Answer 5

Compliance: Decreased

Mechanism: Fibrotic thickening of alveolar walls reduces lung elasticity.

Clinical Implication: Restrictive lung pattern with reduced lung volumes.

Question 6

Changes in Lung Compliance; Neonatal Respiratory Distress Syndrome (RDS)

Answer 6

Compliance: Decreased

Mechanism: Surfactant deficiency leads to alveolar collapse and increased surface tension.

Clinical Implication: Difficulty in lung expansion, requiring ventilatory support.

Question 7

Changes in Lung Compliance; Acute Respiratory Distress Syndrome (ARDS)

Answer 7

Compliance: Decreased

Mechanism: Inflammatory exudates and alveolar damage reduce lung compliance.

Clinical Implication: Severe hypoxemia requiring lung-protective ventilation strategies.

Question 8

Relationship Between Lung Compliance and Elasticity

Answer 8

Lung compliance and elasticity are inversely related.

High compliance → Low elasticity
- Lungs are easy to inflate but don’t recoil well.
- Example: Emphysema

Low compliance → High elasticity
- Lungs are stiff and resist inflation, but they recoil forcefully.
- Example: Pulmonary fibrosis