L4. The dynamics of ventilation Flashcards
Define compliance of the lung
Compliance is the change in volume/ change in pressure. It is a measure of how stretchable a bag is- inflate. It is inversely proportional to elasticity.
Compliance of the lung is different for inhalation vs exhalation. On inhalation, there is a certain pressure needed to overcome the collapsed airways so it is less compliant than in exhalation.
How does elasticity contribute to recoil force - the passive force of expiration
Elasticity of the lungs: ability for lungs to recover its original size and shape after deformation. This is due to elastin in the parenchyma attached to hollow airway which is stretched.
What is surface tension and how does it contribute to recoil force - the passive force of expiration
Surface tension is where atoms at the liquid (water) gas interface exhibit stronger attractive intermolecular attractive forces- this pressure acts to collapse the alveoli, allowing it deflate.
It reduces compliance.
What is the role of lung surfactant
A phospholipid lung surfactant from type 2 alveolar cells is produced when the lungs are stretched during inspiration. This liquid is used to go between some of the water atoms to interrupt their molecular surface tension to help reduce it enough that the lungs don’t need to overcome super high pressures to inflate
Compare the relationship of Chronic obstructive pulmonary disease (COPD) and Fibrosis and compliance
COPD: smoking reduces elastin fibres so easier to inflate = increased compliance, harder to deflate back to FRC.
Fibrosis: stiffening of lung due to collagen- needing more pressure inflate= decreased compliance.
