4. Ventilation Flashcards

1
Q

Minute ventilation

A

Volume of air expired in 1 minute or per minute

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2
Q

Respiratory rate

A

Frequency of breathing per minute

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3
Q

Alveolar ventilation

A

Volume of air reaching the respiratory zone per minute

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4
Q

Respiration

A

Process of generating ATP

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5
Q

Anatomical dead space

A

Capacity of airways incapable of undertaking gas exchange

Includes entirety of conducting airways and upper respiratory tract

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6
Q

Alveolar dead space

A

Capacity of airways that should be able to undertake gas exchange but can’t (usually due to absent/ inadequate blood flow)
e.g. hypoperfused alveoli

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7
Q

Physiological dead space

A

Sum of alveolar + anatomical dead space

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8
Q

Hypoventilation

A

Deficient ventilation of the lungs; unable to meet metabolic demand
(results in increased PO2 – acidosis)

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9
Q

Hyperventilation

A

Excessive ventilation of the lungs atop of metabolic demand

results in reduced PCO2 - alkalosis

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10
Q

Hyperpnoea

A

Increased depth of breathing (to meet metabolic demand)

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11
Q

Hypopnoea

A

Decreased depth of breathing (inadequate to meet metabolic demand)

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12
Q

Apnoea

A

Cessation of breathing

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13
Q

Dyspnoea

A

Difficulty breathing

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14
Q

Bradypnoea

A

Abnormally slow breathing rate

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15
Q

Tachypnoea

A

Abnormally fast breathing rate

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16
Q

Orthopnoea

A

Positional difficulty in breathing

e.g. when lying down

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17
Q

Tidal volume (TV or VT)

A

Volume of air inspired and expired during regular breathing (not necessarily at rest)
~500mL at rest

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18
Q

Inspiratory reserve volume (IRV)

A

Volume of air that can be inspired after a tidal inspiration

2.7 L at rest

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19
Q

Expiratory reserve volume (ERV)

A

Volume of air that can be expired after a tidal expiration.

~1.3 L at rest

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20
Q

Residual volume (RV)

A

Volume of air that cannot be emptied from the lungs, no matter how hard you expire. This is fixed because of the lung-chest wall interface.
~1.2 L

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21
Q

Equation for total lung capacity (TLC)

A

TLC = RV + IRV + TV + ERV

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22
Q

Define total lung capacity

A

Maximum capacity of the lungs

~6L

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23
Q

Functional residual capacity (FRC) equation

A

FRC= RV + ERV

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24
Q

Define functional residual capacity

A

Volume of air in the lungs following a tidal expiration at rest.
Represents the “default” volume of the lungs, when the lung recoil (inwards) and chest recoil (outwards) are in equilibrium

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25
Q

Inspiratory capacity (IC) equation

A

IC = TV + IRV

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26
Q

Define inspiratory capacity

A

Maximum volume of air the lungs can draw in from the equilibrium FRC point

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27
Q

Vital capacity (VC) equations

A
VC= TLC - RV
VC= TV + IRV + ERV
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28
Q

Define Vital capacity

A

volume of air between the maximum and minimum achievable volumes
“how much useful air you can get in that you can influence”

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29
Q

What 5 factors affect lung volumes and capacities?

A
Body size (height, shape: Taller= Bigger lungs)
Sex (Males usually= Bigger lungs)
Disease (pulmonary, neurological)
Age (chronological, physical)
Fitness (innate, training)
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30
Q

Dead space (VD)

A

Parts of the airways that don’t participate in gas exchange

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31
Q

How is anatomical dead space measured?

A

Not with spirometry

Requires dilution test

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32
Q

Describe the dilution test used to measure anatomical dead space

A

Known volume of inert gas (e.g. helium) is inspired and expired into a closed circuit. After enough breathing to equilibrate it with the air already in the airway a sample of the original volume is measured for concentration of inert gas.
The ratio of that to the original concentration, and spirometry data are used to calculate VD.
Remember: tubing connected to the airway increases the volume of anatomical dead space.

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33
Q

What reversible procedures could be performed to increase dead space?

A

Anaesthetic circuit

Snorkelling

34
Q

What reversible procedures could be performed to decrease dead space?

A

Tracheostomy

Cricothyrocotomy

35
Q

What is the volume of alveolar dead space in a healthy human?

A

Effectively 0

36
Q

Alveolar ventilation during tidal breathing (subconscious) equation

A

Valv = VT - VD

Difference between tidal volume and dead space

37
Q

Volume of pleural fluid

A

Very small (few ml)

38
Q

Intrapleural cavity pressure (PpI) in healthy individuals

A

-5 cmH2O
Always negative
due to natural recoil of chest wall and lungs

39
Q

Atmospheric pressure in cmH2O

A

0 cmH2O

40
Q

Tendency of chest wall and lung

A

Chest wall: Spring outwards
Lung: Recoil inwards
Forces in equilibrium at end-tidal expiration (FRC); neutral position

41
Q

If inspiratory muscle effort + chest recoil > lung recoil

A

Results in inspiration

42
Q

If chest recoil < lung recoil + expiratory muscle effort

A

Results in expiration

43
Q

What is the pleural cavity?

A

Gap between pleural membranes
Fixed volume
Contains protein rich pleural fluid

44
Q

What is the consequence of breaching the pleural cavity?

A

Bad

Lung relies on the pleural fluid to operate normal lung mechanics

45
Q

Haemothorax

A

Accumulation of blood in pleural cavity
Impedes lung function
Compresses the lung- less space to expand and fill with air
Harder to breath

46
Q

Pneumothorax

A

Puncture allows air into pleural cavity
Interrupts ability of lung to work as a single unit
Dissipation of ‘tension’ causes lung to recoil and chest wall to expand

47
Q

Describe how the pleural cavity allows the chest wall and the lungs to move in unison

A

Pleural cavity has a fixed volume and is at negative pressure.
“Partial vacuum”
So when the chest wall expands, the lung gets pulled with it.

48
Q

What is needed to generate airflow?

A

A pressure gradient

Air flows from high to low pressure

49
Q

What type of pressure breathing is normal?

A

Negative pressure breathing

Palv is reduced below Patm

50
Q

3 Examples of positive pressure breathing

A

Mechanical ventilation
CPR
Fighter pilots

51
Q

What are the pressures in positive pressure breathing?

A

Patm is increased above Palv

52
Q

At FRC mechanical forces of the lung are in equilibrium…

A

Needs to be imbalanced to generate airflow and stimulate ventilation
Achieved by increasing atm or intrapulmonary pressure(+)
Or by decreasing intrapleural pressure (-)

53
Q

How does the respiartory musculature decrease intrathoracic pressure?

A

By creating a partial vacuum
Diaphragm contracts down and external intercostals pull ribs up and out
Lung is elastic, expandable tissue that stretches to fill the space (maintaining intrapleural volume)

54
Q

Atmospheric pressure (Patm)

A

Always 0 cmH2O

Unless having CPR/ Ventilator

55
Q

Intrapleural pressure (Ppl or Plp)

A

-5 cmH2O at rest

Not equal along length of lung

56
Q

Intraalveolar pressure (Palv)

A

0 cmH2O at rest

57
Q

Transmural pressures (PTP)

A

Pressure inside relative to pressure outside

P inside - P outside

58
Q

Transmural pressure in lung (PTP)

A

Palv - Ppl

Difference in pressure between alveolar sacs and pleural cavity

59
Q

Transthoracic pressure in lung (PTT)

A

Ppl - Patm

Difference in pressure between pleural cavity and atmosphere

60
Q

Transrespiratory system pressure (PRS)

A

Palv - Patm

Difference in pressure between alveolar sacs and atmosphere

61
Q

Importance of transrespiratory pressure and transmural pressure

A

Dictates airflow
Negative PRS leads to inspiration
Positive PTP leads to expiration

62
Q

Describe the mechanical effect of the diaphragm

A

Pulling force in 1 direction

Like a syringe

63
Q

Describe the mechanical effect of other respiratory muscles

A

Upwards and outwards swinging force (inspiration)

Like a bucket handle

64
Q

Describe the chest wall relationship pressure-volume graph shape of a healthy lung

A

Sigmoid
In middle volume: volume that changes per unit pressure is significant (less effort to change pressure)
At extremities of volume: same unit of pressure has a less significant effect on volume

65
Q

What occurs at volume plateaus on chest wall relationship graph?

A

Changes in pressure no longer generate changes in airflow

66
Q

FVC

A

Forced vital capacity

67
Q

FEV1

A

Forced expiratory volume in 1 second

68
Q

FET

A

Forced expiratory time

69
Q

FEV1 / FVC ratio

A

Compares how much air comes out in 1 second

70
Q

FEV1 / FVC ratio in normal, restrictive and obstructive individuals

A

Normal: 73%
Restrictive: 97%
Obstructive: 53%

71
Q

Restrictive lung disease

A

Restricts capacity of lungs to fill

“bear hug” disease: bear hugs you and you try to breath

72
Q

Obstructive disease

A

Obstruction to airflow in the lungs

“Someone partly covers your mouth and you try to breath in”

73
Q

PEF

A

Peak expiratory flow

74
Q

How would you use serial PEF measurements to discriminate between asthma and COPD?

A

COPD: Stable PEF
Asthma: Variable PEF

75
Q

Flow volume loops:

Mild obstructive disease

A

Displaced to the left

Indented exhalation curve

76
Q

Flow volume loops:

Severe obstructive disease

A

Shorter curve
Displaced to the left
Indented exhalation curve

77
Q

Flow volume loops:

Restrictive disease

A

Displaced to the right

Narrower curve

78
Q

Flow volume loops:

Variable extrathoracic obstruction

A

Blunted inspiratory curve

Otherwise normal

79
Q

Flow volume loops:

Variable intrathoracic obstruction

A

Blunted expiratory curve

Otherwise normal

80
Q

Flow volume loops:

Fixed airway obstruction

A

Blunted inspiratory curve
Blunted expiratory curve
Otherwise normal