Pneumothorax + lung compliance

Question 1

Pneumothorax definition

Answer 1

• collapsed lung

- imbalance b/w inflating + deflating force

Question 2

what happens

Answer 2

• Intrapleural + alveolar + surface < elastic forces
• If gas enters the intrapleural space, the negative intrapleural pressure (a force keeping the lungs inflated) is lost
• The elastic forces (collapsing the lung) dominate, and the lung deflates

Question 3

Four types

Answer 3

1. Open – gas enters from outside body through open wound
2. Closed – gas enters from injury to lung
3. Spontaneous – small area of lung leaks for no apparent reason
4. Tension – flap of tissue acts as a valve allowing air in but not out

Question 4

Lung compliance

Answer 4

LC = a measure of how easy it is to inflate our lungs

• high compliance (too much is bad = lung disease) → easier to expand lungs
• low compliance (could be cause of lots of scar tissue + lungs filled w/ lots of fluid) → harder to expand lungs

Question 5

Lung compliance depends on:

Answer 5

Compliance depends on the

• mechanical characteristics of the lung; +
• mechanical characteristics of the chest wall.

Question 6

MECHANICAL CHARACTERISTICS OF THE LUNG

Answer 6

• At low volumes, extra work is required to overcome the surface tension in the alveoli (as walls of alveoli are stuck together)
  - Surfactant decreases surface tension, increases compliance
• At high volumes, the elastic tissue is stretched - so more effort is needed to stretch it further = low compliance

Question 7

MECHANICAL CHARACTERISTICS OF THE CHEST WALL

Answer 7

• The chest wall is compressible + distensible (movt outwards)
• At the end of a normal expiration (FRC) the inward recoil of the lung balances the outward recoil of the chest - the chest wall is at equilibrium
• The amount of effort that is required depends on the volume of the lungs + the position of the chest