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Study notes - Respiratory > * Physiology 2 (Lecture 3) > Flashcards

* Physiology 2 (Lecture 3) Flashcards

1
Q

What is anatomical dead space?

A

The volume of inspired air that remains in the conducting airways where it cannot be involved in gas exchange (it is expired unchanged)

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2
Q

What does pulmonary ventilation (L/min) =?

A

Tidal volume (L/breath) X respiratory rate (breath/min)

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3
Q

Why is alveolar ventilation?

A

The volume of air that is going to exchange gases with the blood

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4
Q

Approximately how much of the airway is dead-space?

A

150ml

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5
Q

What is the equation for alveolar ventilation?

A

(Tidal volume - dead space) X respiratory rate

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6
Q

What 2 types of dead space can you get?

A

Anatomical/ airway dead space (air left in airways which doesn’t reach alveoli and therefore doesn’t take part in gas exchange)
Alveolar dead space (alveoli not perfused)

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7
Q

What is pulmonary ventilation?

A

The volume of air breathed in and out per minute

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8
Q

What 2 things can be done to incase pulmonary ventilation e.g. during exercise?
What way is more advantageous?

A

Increase depth (tidal volume)
Increase breathing rate
Increasing depth of breathing (due to dead space)

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9
Q

What does the transfer of gases between the body and atmosphere depend upon?

A

Ventilation (rate at which gas is passing through the lungs)

Perfusion (rate at which blood is passing through the lungs)

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10
Q

What is the V/Q ration?

A

Measurement used to assess the efficiency and adequacy of the matching of two variables: “V” – ventilation – the air that reaches the alveoli. “Q” – perfusion – the blood that reaches the alveoli.

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11
Q

V/Q ratio at the bottom of the lungs?

A

Less than 1 (higher blood supply)

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12
Q

V/Q ratio at the top of the lungs?

A

more than 1 (higher ventilation)

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13
Q

How well does ventilation and perfusion in the lung normally match?

A

Not exactly the same but usually does matter except sometimes in disease (where the alveolar dead space could increase significantly)

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14
Q

What is alveolar dead space?

A

Ventilated alveoli which are not adequately perfused with blood

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15
Q

What is the physiological dead space?

A

Anatomical dead space + alveolar dead space

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16
Q

What normal happens regarding ventilation perfusion match in the lungs?

A

Local controls act on the smooth muscles of airways and arterioles to match airflow to blood flow

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17
Q

What does the accumulation of CO2 in the alveoli cause?

A

Due to increased perfusion = decreases airway resistance leading to increased airflow

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18
Q

What does an increase in alveolar O2 conc. lead to?

A

Due to increased ventilation therefore causes pulmonary vasodilation increasing blood flow to match larger airflow

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19
Q

What does decreased O2 cause pulmonary arterioles and systemic arterioles to do?

A 
Pulmonary = vasoconstriction
Systemic = vasodilation
20
Q

What does increased O2 cause pulmonary arterioles and systemic arterioles to do?

A 
Pulmonary = vasodilation
Systemic = vasoconstriction
21
Q

What are the 4 factors that influence the rate of gas exchange across the alveolar membrane?

A

Partial pressure gradient of O2 and CO2
Diffusion coefficient for O2 and CO2
Surface area of alveolar membrane
Thickness of alveolar membrane

22
Q

What is the total pressure exerted by a gaseous picture =? (Dalton’s law of partial pressures)

A

The sum of the partial pressures of each individual component of the gas mixture

23
Q

What causes a gas to move across the cell membrane?

A

A pressure gradient

24
Q

What determines the pressure gradient for a particular gas?

A

Its partial pressure

25
Q

What is the partial pressure of a gas in a mixture of gases that don’t react with each other?

A

The pressure the gas would exert if it occupied the total volume for the mixture in the absence of other components

26
Q

What is the partial pressure gas 1 which makes up half of the picture of a gas mixer of 100kPa?

A

50kPa

27
Q

What is the partial pressure of Oxygen?

A

160mmHg (total atmospheric pressure = 760mmHg, 21% air is O2)

28
Q

What is the respiratory exchange ratio for someone eating a balance diet?

A

Ratio of CO2 produce/ O2 consumed

0.8

29
Q

What is the air in the respiratory tract saturated with?

A

Water

30
Q

How much does the water vapour pressure contribute to the total pressure in the lungs?

A

47mmHg

31
Q

What does the pressure of inspired air=?

Normal values?

A

Atmospheric pressure - water vapour pressure

760 - 47 = 713mmHg

32
Q

What does PiO2 = ?

A

713-0.21 = 150mmHg

33
Q

What does PAO2 = at a normal arterial PCO2 of 40mmHg?

A

100mmHg at see level

34
Q

What unit for pressure is used in the UK?

A

kPa (US uses mmHg)

35
Q

How to convert from mmHg to kPa?

A

Divide mmHg by 7.5

36
Q

What is the diffusion coefficient?

Does O2 or CO2 have a higher diffusion coefficient?

A

The solubility of the gas in membranes

CO2 has a higher diffusion coefficient (more soluble in membranes)

37
Q

Why is there a small difference between alveolar PO2 PAO2) and arterial PO2 (PaO2)?

A

Ventilation perfusion match is usually not perfect

38
Q

What does a big gradient between PAO2 and PaO2 indicate?

A

Problems with gas exchange in the lungs or a right to left shunt in the heart

39
Q

What is Flick’s law of diffusion/

A

The amount of gas that moves across a sheet of tissue in unit time is proportional to the area of the set but inversely proportional to its thickness (lung has a very large surface area with thin membranes

40
Q

What are alveoli made up from?

A

A single layer of flattened type 1 alveolar cells

41
Q

What circles each alveolus?

A

Pulmonary capillaries

42
Q

What happens to the rate of gas transfer as the partial pressure gradient increases?

A

Rate of transfer increases

43
Q

What happens to the rate of gas transfer as the partial pressure gradient increases?

A

Rate of transfer increases

44
Q

Why does alveolar surface area increase during exercise?

A

More pulmonary capillaries open up when the cardiac output increase
Alveoli expand as the breathing becomes deeper

45
Q

what happens to the rate of transfer as the thickness of the alveoli increases?

A

Rate decreases

46
Q

What happens to the rate of transfer as the diffusion coefficient increases?

A

Rate of transfer increases

47
Q

Despite the diffusion coefficient for CO2 being 20 times greater than that of O2, why are are approximately equal amounts of CO2 and O2 transferred across the membrane?

A

It offsets the smaller partial pressure gradient for CO2

Study notes - Respiratory (29 decks)

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