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BRS 6: Cardiovascular And Respiratory Medicine > 6.8: Ventilation & gas exchange > Flashcards

6.8: Ventilation & gas exchange Flashcards

1
Q

What are lung volumes

A

Discrete sections of the graph and don’t overlap

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2
Q

Capacities are

A

Sum of two or more volumes

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3
Q

Minute ventilation is

A

Volume of air expired in one minute or per minute

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4
Q

Respiratory rate is

A

The frequency of breathing per minute

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5
Q

Calculation for minute ventilation (L/min)

A

Tidal volume(L) x breathing frequency (breaths/min)

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6
Q

Definition of Alveolar ventilation is

A

Gas entering and leaving the alveoli

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7
Q

Calculation of alveolar ventilation (L/min)

A

[Tidal volume (L) - dead space (L)] x breathing frequency (breaths/min)

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8
Q

5 factors affecting lung volumes and capacities

A

Body size
Sex
Fitness
Disease
Age

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9
Q

Definition of dead space

A

Volume of air that doesn’t participate in gas exchange

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10
Q

What is the chest wall relationship

A

Chest wall has a tendency to spring outwards and the lung has a tendency to recoil inwards

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11
Q

What do pressure gradients drive

A

Flow

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12
Q

Example of negative pressure breathing

A

Normal breathing

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13
Q

Pulmonary ventilation is

A

Ventilating entire airways

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14
Q

Alveolar ventilation is

A

Ventilating alveoli

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15
Q

The pieural cavity is a

A

Partial vaccume

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16
Q

Example of positive pressure breathing

A

Ventilation / CPR

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17
Q

What does maximum ventilation involve

A

Full inspiratory muscle recruitment

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18
Q

Daltons law

A

Pressure of a gas mixture is equal to the sum of the partial pressures of gases in that mixture

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19
Q

Ficks law

A

Molecules diffuse from regions of high concentration to low concentration at a rate proportional to the concentration gradient, the exchange surface area and the diffusion capacity of the gas, and inversely proportional to the thickness of the exchange surface

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20
Q

Henry’s law

A

At a constant temperature, amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid

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21
Q

Boyles law

A

At a constant temperature, the volume of a gas is inversely proportional to the pressure of that gas

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22
Q

Charles’ law

A

At a constant pressure, the volume of a gas is proportional to the temperature of that gas

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23
Q

Tachypnoae is

A

Abnormally fast breathing rate

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24
Q

Hyperventilation is

A

Excessive ventilation of the lungs atop of metabolic demand (results in reduced PCO2 - alkalosis)

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25
Q

Difference between hyperventilation and tachypnoea

A

Decrease in CO2 in hyperventilation and increase in pH

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26
Q

Why is there a residual volume

A

Allows lungs to hold structure to prevent collapsing
Functions to keep alveoli open even after max expiration

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27
Q

Average minute ventilation of a 70kg healthy male

A

6L/min

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28
Q

What is alveolar dead space

A

Sum of volumes of alveoli which have little or no blood flowing through adjacent pulmonary capillaries

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29
Q

2 main areas of dead space found in bronchi

A

Conducting zone
Non-perfused parenchyma

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30
Q

What volume can the conducting zone typically carry in and out for adults at FRC (functional residual capacity)

A

150ml

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31
Q

Can gas exchange occur in the respiratory zone?

A

Yes
Air reaching here is equivalent to alveolar ventilation

32
Q

In adults, how much air can the respiratory zone carry in and out?

A

350ml

33
Q

Parenchyma is

A

The functional tissue of an organ as distinguished from the connective and supportive tissue

34
Q

Calculation for physiological dead space

A

Anatomical + alveolar dead space

35
Q

How to reversibly increase the amount of dead space?

A

Intubation
Anything above mouth would be dead space as gas exch cannot occur

36
Q

How to reversibly decrease amount of dead space?

A

Tracheostomy / cricothyrocotomy
Reduced amount of air passing through conducting zone

37
Q

Why are the lung-chest forces at equilibrium at FRC

A

Chest recoil = lung recoil
Where rib cage naturally recoils outwards and the lungs naturally recoil inwards

38
Q

During inspiratory muscle effort, which is higher, chest or lung recoil?

A

Chest recoil

39
Q

What process follows as lung recoil is higher than chest recoil ?

A

Expiration

40
Q

What membrane surrounds the lungs?

A

Visceral pleural membrane

41
Q

What membrane covers the inner surface of the chest wall

A

Parietal pleural membrane

42
Q

What is the pleural cavity?

A

Gap between the pleural membranes which is a fixed volume

43
Q

What does the pleural cavity contain

A

Protein-rich pleural membrane

44
Q

What is haemothorax

A

Intrapleural bleeding reduces ability to ventilate

45
Q

What occurs when you have a perforated chest wall or punctured lung?

A

Lung will collapse on itself as it recoils into preferred position due to leakage of pleural cavity,
Difficulty ventilating

46
Q

How does negative pressure breathing occur

A

Diaphragm pulled down and rib cage pulled out, reducing alveolar pressure below at,spheric so air flow into lungs

47
Q

How does positive pressure breathing occur

A

Pressure in atmosphere higher than alveolar pressure, air forced out of lungs down pressure gradient

48
Q

3 examples of positive pressure breathing

A

CPR
CPAP- continuous positive airway pressure
Mechanical ventilation

49
Q

Why is there negative pleural pressure?

A

Rib cage naturally recoiling outwards whereas lungs recoil inwards, creating negative pressure in pleural cavity

50
Q

What is transmural pressure?

A

Refers to the pressure inside relative to outside of a compartment

51
Q

What does negative transrespiratory pressure lead to?

A

Inspiration

52
Q

What does positive transrespiratory pressure lead to?

A

Expiration

53
Q

Calculation for transrespiratory system pressure

A

P(alveolar) - P(atmospheric)

54
Q

What happens to the muscles during inspiration

A

Diaphragm contracts, creating pulling force in one direction
External intercostal muscles contract, pulling rib cage in an upwards and outwards direction

55
Q

How does the composition of air breathed in change when a patient is on oxygen therapy?

A

Increase in oxygen partial pressure
Rest stay the same

56
Q

How does the composition of air being breathed in change when a patient is in a house fire?

A

Breathe in smoke:
Decrease in oxygen partial pressure
Increase in carbon dioxide partial pressure
Increase in carbon monoxide partial pressure

57
Q

How does composition of air breathed in change when a person is at high altitude?

A

Composition does not change but the volume of each gas being inhaled decreases

58
Q

How much oxygen is needed by your body at rest

A

250ml/min

59
Q

Describe the process of haemoglobin cooperativity?

A

Once an oxygen molecule binds to Hb, structure of Hb is altered so another oxygen molecule is more likely to bind and this continues until all four binding sites have been occupied

60
Q

What role does 2,3-DPG play in the role of haemoglobin

A

Metabolic product so it is found at sites where there is more respiration occurring and therefore a higher demand of oxygen
Once more oxygen molecules have bound to the Hb molecule, 2,3-DPG is more likely to bind to the Hb and this facilitates oxygen unloading

61
Q

What type of protein is haemoglobin

A

Allosteric protein

62
Q

5 conditions where there’s a right shift of oxygen dissociation curve

A

Incr. temperature
Acidosis
Bohr effect
Hypercapnia - build up of CO2 in bloodstream, affects people with COPD
Incr. 2,3-DPG (during excersise)

63
Q

4 conditions where there is a left shift of oxygen dissociation curve

A

Decr. Temperature
Alkalosis
Hypocapnia
Decreased 2,3-DPG

64
Q

In what condition is there an upward shift of oxygen dissociation curve

A

Polycythaemia - incr. oxygen carrying capacity due to more RBCs

65
Q

What conditions cause a downward shift of oxygen dissociation curve

A

Anaemia - impaired O2 carrying capacity

66
Q

What type of shift does Carbon monoxide cause in oxygen dissociation curve

A

Downward and left
Decreased capacity as oxygen cannot bind to spaces occupied by CO
Increased affinity for CO so less unloading

67
Q

What type of shift does Foetal Hb show in oxygen dissociation curve

A

Left shift
Greater affinity than adult HbA to extract oxygen from mothers blood

68
Q

What type of shift does myoglobin show in oxygen dissociation curve

A

Far left shift
Breather affinity than adult HbA to extract oxygen from circulating blood and store it

69
Q

Why is there a decrease in partial pressure of O2 in blood unloaded at tissues from when it was loaded in the lungs?

A

Venous bronchial circulation dumps blood with less O2 into it, diluting blood

70
Q

What is oxygen flux

A

Change in oxygen content in blood after it has unloaded oxygen to a respiring cell

71
Q

Outline what happens to CO2 once it’s taken up by RBCs

A

Binds to H2O with enzyme carbonic anydrase, forming carbonic acid
Acid dissociates into a proton and bicarbonate anion
Bicarbonate anion transported out of RBC and Cl- transported in, to maintain resting membrane potential - AE1
CO2 also binds to Hb at amine end to form carbaminohaemoglobin

72
Q

What makes Hb a good buffer in RBCs

A

Binds to protons from when carbonic acid dissociates and enables pH stability

73
Q

Why is O2 flux not the same as CO2 flux

A

Water produced as by-product of respiration occurring in cells that blood unloads to
CO2 flux is less than O2 flux

74
Q

CO2 gas exchange time compared to O2 at alveoli

A

Lower than O2

75
Q

How does uncontrolled type 1 diabetes affect oxygen dissociation curve

A

Shifts to the right

76
Q

How does increased tidal volume affect concentration of dissolved oxygen in the blood

A

Increases concentration

BRS 6: Cardiovascular And Respiratory Medicine (12 decks)

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