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Systems I - respiratory > Ventilation and compliance > Flashcards

Ventilation and compliance Flashcards

1
Q

What is tidal volume (TV)?

A

The volume of air breathed in and out of lungs in each breath (500ml)

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2
Q

What is expiratory reserve volume (ERV)?

A

The max volume of air which can be expelled from the lungs at the end of a normal expiration (1100ml)

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3
Q

What is inspiratory reserve volume (IRV)?

A

The max volume of air which can be drawn into the lungs at the end of a normal inspiration (3000ml)

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4
Q

What is residual volume (RV)?

A

The volume of gas left in the lungs at the end of maximal expiration (1200ml)

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5
Q

What is vital capacity (VC)?

A

Tidal volume + inspiratory reserve volume + expiratory reserve volume (4600ml)

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6
Q

What is total lung capacity (TLC)?

A

Vital capacity + residual volume (6L = 3L in each lung))

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7
Q

What is inspiratory capacity (IC)?

A

Tidal volume + inspiratory reserve volume (3500ml)

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8
Q

What is functional residual capacity (FRC)?

A

Expiratory reserve volume + residual volume (2300ml)

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9
Q

What is the FEV1:FVC ratio?

A

The fraction of forced vital capacity expired in 1 second

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10
Q

What is the purpose of residual volume?

A

So that the alveoli don’t collapse no matter how much we breathe out

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11
Q

What is anatomical dead space?

A

The volume of gas occupied by the conducting airways; not available for gas exchange. Around 150ml in each breath. Doesn’t mix with air in alveoli

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12
Q

What is pulmonary (minute) ventilation?

A

Total air movement in and out of lungs (tidal volume and respiratory frequency)

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13
Q

What is alveolar ventilation?

A

Fresh air getting to alveoli and therefore available for gas exchange. Measured in L/min

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14
Q

What is ventilation?

A

Movement of air in and out of lungs

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15
Q

What is partial pressure?

A

Pressure exerted by a specific gas in a mixture of gases

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16
Q

What is the value of alveolar PO2?

A

100mmHg (13kPa)

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17
Q

What is the value of arterial PO2?

A

100mmHg (13kPa)

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18
Q

What is the value of alveolar PCO2?

A

40mmHg (5kPa)

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19
Q

What is the value of arterial PCO2?

A

40mmHg (5kPa)

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20
Q

What happens to the 500ml O2 we breathe in?

A

Only 350ml of it reaches the alveoli, 150ml gets trapped in the dead space. This 150ml becomes stale air and is breathed out in the next expiration along with 350ml of fresh air

21
Q

What is another term for increased/decreased alveolar ventilation?

A

Increased - hyperventilation

Decreased - hypoventilation

22
Q

What happens to alveolar PO2 and PCO2 during hyperventilation

A

PO2 increases and PCO2 decreases

23
Q

What happens to alveolar PO2 and PCO2 during hypoventilation?

A

PO2 decreases and PCO2 increases

24
Q

Why is alveolar PO2 lower than atmospheric PO2?

A
  1. Air gets humidified by upper airways so water vapour dilutes down oxygen content
  2. Rest of the difference is due to continual uptake of O2 by pulmonary capillaries and continual diffusion of CO2 out of capillaries into alveoli
25
Q

What is surfactant and what is it’s role?

A

Detergent-like fluid produced by type II pneumocytes.

Reduces surface tension on alveolar membrane

26
Q

Where does surface tension occur?

A

Where there is an air-water interface and refers to the attraction between water molecules.
Example - water droplets on windows don’t fall vertically, falls in zig zag motion because of attraction to other water molecules due to surface tension

27
Q

What force does water droplet attraction create?

A

Creates an inward directed force which would cause alveoli to collapse if no surfactant

28
Q

4 main points about surfactant

A
  1. Increases lung compliance (stretchability outwards)
  2. Reduces lung’s tendency to recoil
  3. Makes breathing easier
  4. More effective in small alveoli because surfactant is more concentrated
29
Q

What is the law of LaPlace?

A 
P = 2T/r
P = inwardly directed pressure
T = surface tension
r = radius
30
Q

What is compliance?

A

The change in volume relative to change in pressure. Represents stretchability of lungs (not elasticity)

31
Q

What is high/low compliance?

A

High compliance - large increase in lung volume for small decrease in intrapulmonary pressure

Low compliance - small increase in lung volume for large decrease in intrapulmonary pressure

32
Q

What must the pressure required to inflate the lungs overcome?

A

Airway resistance

33
Q

What is compliance determined by?

A

Elastic forces, surface tension and airway resistance

34
Q

What happens to compliance in emphysema?

A

Super compliance - easy to get air in but no elastic recoil so can’t get air back out

35
Q

Why does it require a greater change in pressure from FRC to reach a particular lung volume during inspiration than during expiration?

A

Because we have to overcome elastic recoil (tissue inertia) and surface tension during inspiration

36
Q

How is expiration affected in emphysema?

A

Loss of elastic recoil means expiration requires more effort and is harder

37
Q

Where in the lung is there a bigger change in volume for any given change in pressure?

A

Bigger change in base than apex

38
Q

What happens to alveolar ventilation from base to apex of a lung?

A

Decreases

39
Q

What happens to compliance from base to apex of a lung?

A

Decreases due to alveoli at the apex being more inflated at FRC; alveoli at base are compressed between lung and diaphragm so more compliant on inspiration

40
Q

Features of obstructive lung disease

A
  1. Obstruction of air flow, particularly on EXPIRATION
  2. Increased airway resistance
  3. Examples - asthma, COPD
41
Q

Features of restrictive lung disease

A
  1. Lung expansion restricted on INSPIRATION
  2. Expiration unaffected
  3. Loss of lung compliance
  4. Examples - fibrosis, respiratory distress syndrome, pneumothorax
42
Q

What test can be used to identify abnormal lung function?

A

Spirometry

43
Q

What does spirometry measure?

A

Measures what we can physically inhale/exhale

44
Q

What are the two classes of spirometry measurements and what is the difference?

A

Static - only considers volume exhaled

Dynamic - measures time taken to exhale a certain volume

45
Q

What is the forced vital capacity (FVC)?

A

The amount of air which can be forcibly exhaled after taking in the deepest breath possible

46
Q

What does FVC help determine?

A

The presence and severity of lung disease

47
Q

What are the normal values of FEV1 and FVC?

What is the normal FEV1:FCV ratio?

A

FEV1 - 4L
FVC - 5L
FEV1:FVC = 80%

48
Q

What happens to FEV1 and FVC in obstructive lung disease?

A

Both drop but FEV1 drops more than FVC so FEV1;FVC ratio is reduced

49
Q

What happens to FEV1 and FVC in restrictive lung disease?

A

Both fall fairly equally so FEV1:FVC ratio is still constant or increased

Systems I - respiratory (5 decks)

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