Ventilation and compliance (physiology)

Question 1

What is the tidal volume

Answer 1

The volume of air inspired and the volume of air expired (they are equal)

Question 2

What are the volumes of the lung during a tidal volume sequence

Answer 2

1.5L-3L-2.5L

Question 3

What is the vital capacity

Answer 3

The maxiumum amount of air which can be breathed out or in

Question 4

What is the residual volume

Answer 4

The air left in the lungs which remains even when the maximum amount if air is exhaled

Question 5

Vital capacity + residual volume =

Answer 5

Total lung capacity

Question 6

What are the two types of ventilation?

Answer 6

Minute ventilation and alveolar ventilation

Question 7

How do you work out minute ventilation

Answer 7

Tidal volume (ml/breath) x respiratory rate (breaths/min)

At rest this should be roughly 5L/min

Question 8

How do you work out alveolar ventilation?

Answer 8

(Tidal volume - dead space*) x respiratory rate

This takes into account the areas of the lungs where no gas exchange occurs.

Will be lower than the minute ventilation
*dead space = volume of the conducting airways ~150ml)

Question 9

Give 2 examples of lung function tests

Answer 9

Spirometer

Peak flow meter

Question 10

What are the main parameters used to measure lung function

Answer 10

Forced vital capacity - max volume exhaled

Forced Expiratory Volume in 1sec FEV¹- will be 80% of FVC

Question 11

List the 3 obstructive lung diseases and explain their impact on lung function tests

Answer 11

COPD (emphysema, chronic bronchitis), asthma, CF

• FEV¹ reduced due to increased resistance in obstructed airways. It will be <80% of FVC
• FVC normal

Question 12

Give an example of a restrictive lung disease and explain its impact on lung function tests

Answer 12

Fibrosis

FVC is reduced when compared to healthy lungs (there is restricted movement due to stiffening or the lungs)
FEV¹ is >80% FVC

Question 13

What is lung compliance

Answer 13

A measure of how well the lungs change volume

Question 14

What two characteristics does healthy lung tissue possess

Answer 14

Elasticity (elastin) and strength (collagen)

Question 15

In a healthy individual, what does an increase in transpulmonary pressure lead to

Answer 15

An increase in lung volume in

Question 16

In an individual with emphysema, what does the same increase in transpulmonary pressure lead to

Answer 16

A larger increase in volume due to the loss of alveolar tissue, loss of elasticity and loss of elastic recoil. This is know as high compliance

Question 17

In an individual with oedema, pneumonia or fibrosis what does the same increase in transpulmonary pressure lead to

Answer 17

A much smaller increase in volume. This is known as low lung compliance

Question 18

Explain the impact fibrosis has on lung compliance

Answer 18

Reduced lung compliance due to an increased expression of collagen and inflammation

Question 19

Explain the concept of lung surfactants

Answer 19

Type II cells in the lung produce surfactants
They are a complex mixture of lipids and proteins
They decrease surfactants tension at air/liquid interface in the alveoli - aiding breathing

Question 20

What is the link between premature babies and lung surfactants

Answer 20

Premature babies have under developed type II cells meaning they have reduced surfactqnt production. This increases surface tension and is known as newborn respiratory distress syndrome

Question 21

What is the link between lung compliance and arthritis

Answer 21

Painful disorders affecting movement of the ribs and spine make breathing difficult so reduce compliance

Question 22

Lung compliance =

Equation

Answer 22

Change in lung volume/change in transpulmonary pressure

Question 23

Why is it important to have optimal ventilation and blood flow within the lungs

Answer 23

To maximise uptake of O2 and release toxic CO2. If this isn’t optimised it can cause shortness of breath, headache, dizziness and liss of consciousness

Question 24

Describe the impact emphysema has on lung tissue

Answer 24

Degradation of alveolar and bronchiole walls and capillaries
The release of protease enzymes by leukocytes also damages tissue

Question 25

What percentage of cases of emphysema are caused by smoking

Answer 25

80-90%

Question 26

Describe the impact emphysema has on gaseous exchange

Answer 26

The breakdown of alveolar tissue reduces surface area available for gaseous exchange. In diseased alveoli less O2 is able to diffuse effectively into capillaries reducing uptake of O2 into the body

Question 27

What is the treatment for emphysema

Answer 27

Oxygen (only in severe cases when FEV¹<30%FVC)