Resp 5 - Lung function tests + O2/CO2 in the blood Flashcards Preview

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Flashcards in Resp 5 - Lung function tests + O2/CO2 in the blood Deck (42):
1

Define tidal volume:

The amount of air in and out at each breath
~ 0.5 L

2

Define inspiratory reserve volume:

Air volume that can be inspired 'on top of' tidal inspiration
~ 2.5 L

3

Define expiratory reserve volume:

Air volume that can be expired 'on top of' tidal expiration
~ 1.5 L

4

Define residual volume:

Volume remaining in lungs after maximal expiration
~ 0.8 L

5

Define inspiratory capacity:

Amount of air that can be inspired from the Resting Expiratory Level
~ 3 L

6

Define functional residual capacity:

Volume of air in lungs at resting expiratory volume
~ 2 L

7

Define vital capacity:

Measured from maximum inspiration to maximum expiration
~ 5 L

8

Define total lung volume:

The volume of gas at the end of maximum inspiration
~ 5.8 L

9

Define FVC:

Forced Vital Capacity
= Total volume of air that can be breathed out with maximal effort in 1 breath

10

Define FEV1:

Forced Expiratory Volume in 1 sec
= Volume of air that can be breathed out with maximal effort in 1 second (calculated from FVC)

11

How does an obstructive deficit affect:
FEV1
FVC
FEV1/FVC

FEV1 < 80%
FVC may be reduced
FEV1/FVC < 0.7

12

How does a restrictive deficit affect:
FEV1
FVC
FEV1/FVC

FEV < 80%
FVC < 80%
FEV1/FVC > 0.8

13

Give some examples of obstructive lung diseases:

- Asthma
- COPD
- Emphysema
- Chronic bronchitis
- Cystic fibrosis

14

Give some examples of restrictive lung diseases:

- Fibrosis
- Tumours
- Interstitial lung disease
- Pneumothorax
- Weak muscles (ie Muscular dystrophy)

15

What is the normal range for respiratory rate in an adult?

16-20 breaths per min

16

What changes would you see on a flow-volume loop if the patient has obstructive disease?

- Scalloped expiratory flow
- Normal expired volume
- Normal inspiratory flow

17

What changes would you see on a flow-volume loop if the patient has restrictive disease?

- Narrowed curve
- Reduced expiratory volume
- Fast expiratory flow rate
- Normal inspiratory flow

18

How can we measure the residual volume of the lungs?

Helium dilution:
- Patient breaths a known volume of gas containing a known concentration of Helium
- As patient breaths, [He] changes as it is diluted by the residual air in the lungs
(Helium is not metabolised)

19

What are the properties of Hb which facilitate O2 transport in the blood?

- 4x Haem groups
- Cooperative binding (T and R states)

20

How does a fall in pH affect the O2-Hb dissociation curve?

BOHR EFFECT
Curve shifts to right

21

How does a rise in temperature affect the O2-Hb dissociation curve?

Curve shifts to the right

22

How does an increase in 2,3-BPG affect the O2-Hb dissociation curve?

Curve shifts to the right

23

Why do red blood cells usually contain 2,3-BPG?

To stabilise deoxy-Hb, promoting O2 release at the tissues

24

How does high altitude and anaemia affect the concentration of 2,3-BPG in the blood?

Increases conc of 2,3-BPG

25

Why is it important that foetal haemoglobin binds 2,3-BPG less tightly?

Allows O2 to be passed from maternal blood to foetal blood

26

Define cyanosis:

Bluish discolouration of skin and mucous membranes due to unsaturated haemoglobin in systemic circulation, or poor circulation

27

What test specifically measures the level of haemoglobin saturation in arterial blood (bound O2)?

Pulse oximetry

28

What does pulse oximetry test, and how?

The level of haemoglobin saturation in arterial blood

Red and infared light emitting detector detects the difference in absorption of light between Oxy-Hb and Deoxy-Hb

29

What are the units of a pulse oximetry test?

% saturation

30

What is the main disadvantage of a Pulse Oximetry test?

Hint - An anaemic could have 100% O2 saturation

It doesn't measure the amount of Haemoglobin in the blood

31

What test measures the pO2 in arterial blood?

Arterial blood gas analysis

32

What are the units of an arterial blood gas analysis?

kPa

33

What does an Arterial Blood Gas Analysis measure?

PO2, PCO2 and pH of arterial blood

34

What is the normal range of [HCO3-] in the blood?

~ 22-26 mmol/L

35

What is the pKa of H2CO3 in the plasma?

pKa = 6.1

36

What is the Henderson-Hasselbach equation for plasma pH?

pH = pKa + log( [HCO3-] / (PCO2 x 0.23) )

37

What acids can be produced by the body to buffer HCO3-?

- Keto acids
- Lactic acid
- Sulphuric acid

Produces H2O and CO2 which can be removed by expiration

38

How is CO2 transported in the blood?

8% dissolves in plasma
12% as carbamino compounds (Carbaminohaemoglobin)
80% as HCO3-

39

What are the functions of carbaminohaemoglobin?

- Transport of CO2
- More formed at tissues = reduces Hb affinity for O2 = favours O2 release at tissues

40

What is the colour of Carbaminohaemoglobin?

Blue = darker venous blood

41

What is the [CO2] in whole arterial and venous blood?
In what form is the majority of CO2 transported?

[CO2] in whole arterial blood = 21.31 mmol/L
[CO2] in whole venous blood = 23.21 mmol/L
Majority of CO2 carried as HCO3- in the plasma

42

What percentage of blood is plasma vs cells?

Blood=
~ 60% plasma
~ 40% cells