3. The work of breathing

Question 1

Work

Answer 1

Force x Distance Moved

Pressure x Volume Change

Question 2

Elastic

Answer 2

Ability to return to original shape if deformed

Question 3

Compliance

Answer 3

“Stretchability”

1/Elastance

Question 4

High compliance

Answer 4

easy to distend, not return forcefully

Question 5

Low compliance

Answer 5

difficult to distend, return forcefully

Question 6

Optimum level in health

Answer 6

Lung inflation = high compliance

Lung deflation = low compliance

Question 7

Loss of elastin

Answer 7

Emphysema (obstructive disease)

Increased compliance

Increased resistance

Increased work

Decreased interdependence

Decreased lung tissue

Question 8

Increased collagen (and elastin)

Answer 8

Fibrosis (restrictive disease)

Increased work

Decreased compliance

Question 9

Law of Laplace

Answer 9

P = 2T / r

Question 10

Problem with Laplace

Answer 10

When 2 alveoli of unequal size connected Smaller alv will collapse and larger one inflates

Question 11

Solution to problem

Answer 11

Surfactant molecules

Form a monolayer

decreases surface tension

Stabilises alveolar size

Question 12

Obstructive lung disease

Answer 12

High resistance

Slow & deep

Minimise airflow work

Question 13

Restrictive lung disease

Answer 13

decreased compliance

Fast &shallow

Minimise elastic work

Question 14

3 general types of Chronic Obstructive Pulmonary Disease (COPD)

Answer 14

Asthma

Chronic bronchitis

Emphysema

Question 15

4 Restrictive lung diseases

Answer 15

Fibrosis

Scoliosis

Asbestosis

Silicosis

Question 16

What is the normal value for O2 saturations (SaO2)?

Answer 16

>97%

Question 17

Normal FEV1/FVC

Answer 17

>70%