Ventilation: Diffusion, Common Lung Pathologies and Lung Function Tests

Question 1

Normal adult value for residual volume

Answer 1

1200ml (20-25ml/kg)

Question 2

Normal adult value for expiratory reserve volume

Answer 2

1100mL in males

800mL in females

Question 3

Normal adult value for tidal volume

Answer 3

500mL

Question 4

Normal adult value for inspiratory reserve volume

Answer 4

1900-300mL

Question 5

What does ventilation refer to?

Answer 5

Movement of air in and our of lungs

Question 6

What are the two ways ventilation can be described as?

Answer 6

Pulmonary (minute) ventilation

Alveolar ventilation

Both measured in L/min

Question 7

What is pulmonary ventilation?

Answer 7

Total air movement into/out of lungs

Question 8

What is alveolar ventilation?

Answer 8

Volume fresh air getting to alveoli and available for gas exchange

Question 9

What does Dalton’s Law state?

Answer 9

The total pressure of a gas mixture is the sum of the pressures of the individual gases

Question 10

What is partial pressure?

Answer 10

The pressure of a gas in a mixture of gases is equivalent to the percentage of that particular gas in the entire mixture multiplied by the pressure of the whole gaseous mixture.

Question 11

What is our air a mixture of?

Answer 11

Nitrogen (79%).

Oxygen (21%).

Negligible quantities of CO2 in the air (0.03%).

Question 12

Why is there CO2 in our cells and blood?

Answer 12

We make CO2, we do NOT breathe it in.

Question 13

Why would a patient’s CO2 be increased?

Answer 13

If a patient’s CO2 has gone up it is because they can’t get rid of CO2 in their body because they’ve got some kind of respiratory pathology blocking them from exhaling it.

Question 14

What is PO2?

Answer 14

Partial pressure of oxgyegn

Question 15

What is PCO2?

Answer 15

Partial pressure of carbon dioxide

Question 16

How can alveolar PO2 and PCO2 vary?

Answer 16

Hyper and hypo ventilation

Question 17

What is the normal value for alveolar partial pressure of 03?

Answer 17

100mmHg (13.3 kPa)

Question 18

What is the normal value for alveolar partial pressure of CO2?

Answer 18

CO2 is 40mmHg (5.3kPa).

Question 19

What does the pulmonary artery do?

Answer 19

Carries deoxygenated blood away from the heart to the lungs

Question 20

What does the pulmonary vein do?

Answer 20

Carries oxygenated blood toward the heart

Question 21

What supplies bronchial circulation?

Answer 21

Bronchial arteries arising from systemic circulation to supply oxygenated blood to lung tissues

Question 22

Where does blood drain in bronchial circulation?

Answer 22

To left atrium via pulmonary veins

Question 23

What % of left heart output is in bronchial circulation?

Answer 23

2%

Question 24

What does pulmonary circulation consist of?

Answer 24

Left and right pulmonary arteries originating from the right ventricle

Question 25

Where does the entire cardiac output come from?

Answer 25

Right ventricle

Question 26

What does pulmonary circulation supply?

Answer 26

The dense capillary network surrounding the alveoli and returns oxygenated blood to the left atrium via the pulmonary vein

Question 27

How can you describe pulmonary circulation?

Answer 27

High flow, low pressure Pressure that is driving flow in pulmonary is much lower than the pressure that is driving flow in the systemic circulation.

Question 28

What is partial pressure of gas?

Answer 28

The partial pressure of gas in the alveoli is the same as the partial pressure of gas in the systemic arteries providing we’ve got nice, healthy lungs

Question 29

The rate of diffusion across the membrane is:

Answer 29

- directly proportional to the partial pressure gradient - bigger the gradient, the faster the gas will diffuse - directly proportional to gas solubility - the more soluble the gas is, the easier it is to diffuse - directly proportional to the available surface area - inversely proportional to the thickness of the membrane - most rapid over short distances - it doesn’t have so far to go

Question 30

What has a larger partial pressure gradient? Carbon dioxide or oxygen?

Answer 30

Oxygen

Question 31

What do the following abbreviations mean? A a v~ PaO2 PaCO2 mmHg kPa

Answer 31

A = alveolar a = arterial blood v~ (squiggly line on top) = mixed venous blood (eg in pulmonary artery. PaO2 = partial pressure of oxygen in arterial blood PACO2 = partial pressure of carbon dioxide in alveolar air mmHg = millimetres mercury kPa = kilopascals

Question 32

What does reduction in surface area cause?

Answer 32

Less oxygen can enter that blood so blood flowing away from an emphysemic lung has a lower partial pressure of oxygen than normal. Lower PO2 in the pulmonary vein and in the systemic arterial blood.

Question 32

What is seen in both fibrosis and emphysema?

Answer 32

An increase in partial pressure of carbon dioxide

Question 33

What does asthma cause?

Answer 33

No difficulty in gases diffusing between the alveoli and the blood. Low partial pressure of oxygen in systemic arterial blood

Question 34

To summarise: What do emphysema, fibrosis, and oedema cause?

Answer 34

Emphysema - loss of surface area Fibrosis - increased thickness of membrane Oedema - increased diffusion distance

Question 35

What are obstructive lung diseases?

Answer 35

Obstruction to air flow, especially on expiration (breathing out) - Asthma - Chronic bronchitis - COPD - Emphysema

Question 36

What are examples of restriction of lung expansion?

Answer 36

Fibrosis Infant respiratory distress syndrome Pulmonary oedema Pneumothorax

Question 37

What is spirometry used for?

Answer 37

A technique commonly used to measure lung function Measurements can be static or dynamic

Question 38

What are static spirometry results?

Answer 38

Where the only consideration made is the volume exhales - for example, “exhaled five litres” end of story

Question 39

What are dynamic spirometry results?

Answer 39

Where the time is taken to inhale or exhale a certain volume is what is being measured - more helpful - most clinical respiratory lung function testes work with expired air.

Question 40

What can spirometry measure?

Answer 40

- Tidal volume - Inspiratory reserve volume - Expiratory reserve volume - Inspiratory capacity - Vital capacity

Question 41

What is FEV1/FVC ratio?

Answer 41

Ratio of the forced expiratory volume in the first one second to the forced vital capacity of the lungs.

Question 42

What is FEV1?

Answer 42

Measures how much air you can exhale in one second

Question 43

What is FVC?

Answer 43

Total amount of air you can exhale forcefully in one breath

Question 44

What is FEV1/FVC in a healthy adult?

Answer 44

80%

Question 45

What would be seen in COPD spirometry?

Answer 45

- The rate at which air is exhaled is much slower - Total expired volume (FVC) is also reduced (FRC may be increased) - The major effect is on airways and so FEV1 is reduced to a greater extent than FVC - Significant fall in ratio also reduced

Question 46

What happens in spirometry in restrictive lung diseases?

Answer 46

Both FEV1 and FVC reduced in proportion and the ratio remains normal or may even increase.