lecture 7 - lung mechanics

Question 1

What are the 2 forces that must be overcome to ventilate the lungs (the work of breathing)?

Answer 1

1. Elastic recoil/stiffness of the lung and chest wall
2. Airways resistance/friction to get airflow

Question 2

What is the relative interpleural pressure at rest?

Answer 2

Sub-atmospheric (less than 760mmHg)

Question 3

What is a pneumothorax?

Answer 3

Air trapped in the inter-pleural space

Question 4

What is the compliance of the lungs?

Answer 4

The elasticity/stiffness

Question 5

How does lung compliance change with lung volume?

Answer 5

As the lung is stretched with inspiration it gets harder to stretch further

Question 6

What is the biggest factor affecting lung compliance?

Answer 6

Alveolar surface tension - the surface tension exerted by the fluid lining the alveoli

Question 7

How is surface tension in the lungs reduced to reduce compliance?

Answer 7

By the production of surfactant by type II pneumocytes

Question 8

What is the main area of airway resistance in the lungs?

Answer 8

The bronchi

Question 9

What is dynamic compression of airways?

Answer 9

The collapse of airways due to increase intrathoracic pressure, i.e. breathing out