Respiratory Physiology 3.4- lung function tests and common lung conditions

Question 1

Obstructive vs. restrictive lung disease?

Answer 1

obstructive- obstruction of air flow, especially on expiration

restrictive- restrictive of lung expansion

Question 2

Why are obstructive lung disorders felt particularly on expiration?

Answer 2

Because during inspiration the physical forces on the lung are such that the lung is being expanded, airways being expanded.
And so diameter of those airways increases and we get a reduction in resistance to airflow.

Whereas on expiration, the chest wall is being compressed. And therefore we also have compression of the airways and therefore any pathologies are aggravated on expiration because the airways are being further compressed by the physical forces that we experience on expiration.

Question 3

Give examples of obstructive lung disorders?

Answer 3

asthma

(Chronic Obstructive Pulmonary disease)
-chronic bronchitis
-emphysema

Question 4

Describe asthma?

Answer 4

inappropriate constriction of the bronchial smooth muscle
- expiration harder

Question 5

Describe bronchitis?

Answer 5

inflammation of the bronchi
-expiration harder

Question 6

Describe emphysema?

Answer 6

destruction of the alveoli
loss of elasticity
-expiration harder

Question 7

What are restrictive lung disorders accompanied by?

Answer 7

loss of lung compliance

Question 8

What is needed when there is a restriction of lung expansion?

Answer 8

invest more effort in inspiration in order to get the same change in volume

Question 9

Do restrictive lung diseases impact on expiration or inspiration?

Answer 9

impact on inspiration because they restrict lung expansion

Question 10

Give examples of restrictive lung disorders?

Answer 10

fibrosis

infant respiratory distress syndrome

oedema

pneumothorax

Question 11

Describe fibrosis?

Answer 11

fibrous tissue gets laid down around the elastic tissue in the lungs.
Fibrous tissue resists stretch

idiopathic- origin of the disease is unknown or unspecified

Question 12

Describe asbestosis?

Answer 12

individuals who have been exposed to asbestos dust over a long period of time .
Leads to a stiffening of the lung

Question 13

Describe infant respiratory distress syndrome?

Answer 13

babies born prior to 36 weeks suffer from infant respiratory distress syndrome because they have an increase in surface tension.

Lung less willing to expand on inspiration because of that increase in surface tension

Question 14

Describe oedema?

Answer 14

fluid building up around the alveoli.
Fluid creates a pressure that resists inflation of the alveoli.
Resists lung expansion.

Question 15

Describe pneumothorax?

Answer 15

Occurs where you get air introduced to pleural cavity.
Pushes apart the parietal pleural membrane from the visceral pleural membrane.
Lung that is no longer related to the chest wall and diaphragm.
Complete loss of lung expansion.

Question 16

Describe spirometry?

Answer 16

technique commonly used to measure lung function

Question 17

What are the two classes of spirometry?

Answer 17

static - the only consideration made is the volume exhaled or inhaled

dynamic- where the time taken to exhale a certain volume is what is being measured

Question 18

What can’t be measured by spirometry?

Answer 18

residual volume
total lung capacity
functional residual capacity

as involves residual volume

Question 19

Describe FEV1 / FVC?

Answer 19

FEV1- forced expiratory volume in one second
(in fit, healthy, young adult males: 4.0L)

FVC- forced vital capacity - total amount of air that you can expire over whatever time
(in fit, healthy, young adult males: 5.0L)

Question 20

What is FEV1 to FVC ration in a healthy adult male?

Answer 20

80%

Question 21

What is normal ratio of FEV1/FVC? regardless of sex

Answer 21

80%

Question 22

Describe FEV1/ FVC in obstructive lung diseases?

Answer 22

takes much longer to get all air out because there is obstruction to air flow.
Reduced volume of air being expired in the first second and we also tend to have a total reduction in the total expired air aswell.
Ratio less than normal.
FRC may be increased.

Question 23

Describe FEV1/FVC in restrictive lung diseases?

Answer 23

Not much air in the lungs to start with because of the restriction of expansion.
FEV1 decreases but only because there’s less air in the lungs in the first place- air that is flowing is flowing at a normal rate as there is no obstruction to air flow.
FEV reduced and your FVC reduced.
Ratio normal or slightly increased.

Question 24

What are the limitations of the FEV1/FVC ratio?

Answer 24

Obstructive: both FEV and FVC fall but FEV more so, so ratio is reduced

Restrictive: both FEV and FVC fall so ratio remains normal, or may even increase, despite severe compromise of function

Question 25

Describe pressure-volume relationship and compliance in inspiration?

Answer 25

compliances increases as we move through the inspiratory phase.
Compliance is pretty low at the start of inspiration.
Increases greatly at end of inspiration

Question 26

Why do we require a greater change in pressure (from FRC) to reach a particular lung volume during inspiration, than to maintain that volume during expiration?

Answer 26

Overcome lung inertia during inspiration (overcome the reluctance of our tissues to change their shape)

Overcome surface tension during inspiration

During expiration compression of the airways means more pressure is required for air to be pushed out.

Question 26

Describe pressure-volume relationship and compliance in expiration?

Answer 26

compliance is low at start of expiration but then increases significantly once intrapleural pressure reaches about -0.4kPa.
Compliance increases towards end of expiration