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CVR > Lung Function Testing > Flashcards

Lung Function Testing Flashcards

1
Q

Measured values for lung function testing

A

FEV1
FVC
flow volume curve
Peak expiratory flow (PEF)
Lung volumes
Transfer factor estimates
[compliance]

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2
Q

FEV1

A

the maximal volume of air that a subject can expel in one second from a point of maximal inspiration.

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3
Q

FVC

A

Forced vital capacity
Total volume of air breathed out
Forced breathing out

the maximal volume of air that a subject can expel in one maximal expiration from a point of maximal inspiration.

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4
Q

Forced expiration

A

Volume/time plot AND flow/volume plot
Breathe in to total lung capacity (TLC)
Exhale as fast as possible to residual volume (RV)
Volume produced is the vital capacity (FVC)

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5
Q

Flow/volume plot

A

Re-plot the data showing flow as a function of volume
PEF: peak flow
FEF25: flow at point when 25% of total volume to be exhaled has been exhaled

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6
Q

FEF25

A

flow at point when 25% of total volume to be exhaled has been exhaled

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7
Q

PEF (peak expiratory flow)- rate

A

Single measure of highest flow during expiration
Peak flow meter, spirometer

Gives reading in litres/minute (L/min)
Very effort dependent
May be measured over time, by giving a patient a PEF meter and chart

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8
Q

Other ways to measure RV and TLC

A

Gas dilution
Body box (total body plethysmography)

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9
Q

What do expiratory procedures measure

A

VC

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10
Q

FRC

A

Functional residual capacity

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11
Q

Tidal volume average value at rest in warmth

A

500 ml

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12
Q

Gas dilution

A

Get patient to breathe in a known volume of gas
Then measure volume of dilution
Gives total lung volume
Measurement of all air in the lungs that communicates with the airways
Does not measure air in non-communicating bullae
Gas dilution techniques use either closed-circuit helium dilution or open-circuit nitrogen washout

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13
Q

How long does it take for the majority of the air to leave the lungs

A

1s

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14
Q

Which gas is used in closed-circuit dilution

A

Helium

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15
Q

Which gas is used in open-circuit washout

A

Nitrogen

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16
Q

Total body plethysmography

A

Alternative method of measuring lung volume (Boule’s law), including gas trapped in bullae
From the FRC, patient ‘pants’ with an open glottis against a closed shutter to produce changes on the box pressure proportionate to the volume of air in the chest
The volume measured (TGV) represents the lung volume at which the shutter was closed

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17
Q

Vital capacity

A

Total volume breathed out to residual capacity

Volume that can be exhaled after maximum inspiration (ie. maximum inspiration to maximum expiration)-
average 4.5L
• Inspiratory reserve volume + tidal volume + expiratory reserve volume
• Often changes in disease
• Requires adequate compliance, muscle strength and low airway resistance
In young = similar to FVC
In older = higher the FVC due to reduced elastic recoil of lungs and closure of respiratory bronchioles

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18
Q

What is measured by total body plethysmography

A

FRC (functional residual capacity)
Inspiratory capacity
Expiratory reserve volume
Vital capacity

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19
Q

Total lung capacity

A

Vital capacity + residual volume

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20
Q

Transfer estimates

A

Carbon monoxide used to estimate TLCO, as has high affinity for haemoglobin

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21
Q

What is TLCO the overall measure interaction of

A

alveolar surface area
alveolar capillary perfusion
physical properties of the alveolar capillary interface
capillary volume
haemoglobin concentration, and the reaction rate of carbon monoxide and hemoglobin.

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22
Q

Transfer estimates - single 10s breath-holding technique

A

10% helium, 0.3% carbon monoxide, 21% oxygen, remainder nitrogen.
DLCO - known conc. inhaled —> hold breath for 10s —> expired conc. measured

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23
Q

Transfer estimates- alveolar sample obtained

A

DLCO is calculated from the total volume of the lung, breath-hold time, and the initial and final alveolar concentrations of carbon monoxide.

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24
Q

What value can you not directly measure

A

Residual volume

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25
Q

Compliance of the lung

A

Change in volume per unit change in pressure gradient between the pleura and the alveoli; (transpulmonary pressure)

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26
Q

Static compliance

A

Can be measured during breath-hold
A measure of distensibility

A lung of high compliance expands more than one of low compliance when exposed to same trans-pulmonary pressure

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27
Q

Disadvantages of gas dilution

A

Doesn’t show parts of diseased lungs

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28
Q

Dynamic compliance

A

Can be measured during regular breathing
Measured during tidal breathing at end of inspiration and expiration when lung is apparently stationary
Similar to static compliance in normal lungs
Reduced compared to static compliance in airway obstruction

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29
Q

What is the affinity of CO for haemoglobin compared to O2

A

x400 higher affinity

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30
Q

Abnormal values - FEV1

A

Compare with predicted value
80% or greater “normal”
Above the lower limit of normal for that patient (LLN)
Above mean minus 1.645 SD

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31
Q

Abnormal values - FVC

A

Compare with predicted value
80% or greater “normal”
Above the lower limit of normal for that patient (LLN)
Above mean minus 1.645 SD

Low value indicates likely Airways Restriction

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32
Q

FVC <80% predicted

A

Low value indicates airways restriction

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33
Q

Abnormal values FEV1/FVC ratio

A

Abnormal ratio <0.7 = airways obstruction

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34
Q

Asthma

A

Asthma is a variable condition
Typified by variable wheeze and shortness of breath, and normal periods in-between
Typified by airways obstruction and PEF variation (in later stages)
Typified by reduced mid expiratory flows
Typified by good response to treatments

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35
Q

Airways restriction

A

FVC < 0.8
Volume problem: pulmonary fibrosis —> decreased lung compliance —> decreased expansion

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36
Q

Airways obstruction

A

FEV1/FVC ratio< 0.7
Flow problem: COPD, asthma —> decreased airflow—> hyperinflation

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37
Q

FEV1 asthma

A

Normal or reduced

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38
Q

FVC asthma

A

Normal

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39
Q

TLCO and KCO asthma

A

Normal or elevated

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40
Q

Amplitude % maximum asthma

A

Normal up to 8%
Asthma > 15-20%

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41
Q

Amplitude % mean asthma

A

> 20%

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42
Q

Asthma typical blood gases

A

PaO2 = normal
PaCO2 = low
pH - normal or elevated
HCO3- = normal

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43
Q

PEF asthma

A

Typically variable, increased diurnal variation of 20%

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44
Q

MEF asthma

A

Low, typically ‘scalloped’ shape to the flow-volume curve

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45
Q

eNO

A

High

46
Q

R(AW)

A

High when airway narrowing present

47
Q

COPD

A

COPD is a progressive condition
Typified by wheeze and shortness of breath on exercise, progressively worse with time
Intermittent exacerbations
Typified by airways obstruction and lack of significant PEF variation
Typified by reduced mid expiratory flows
Typified by partial or poor response to treatments

48
Q

FEV1 COPD

A

Reduced significantly

49
Q

FVC COPD

A

May be normal or reduced

50
Q

PEF COPD

A

Typically not variable

51
Q

PEF

A

Peak flow measurements

52
Q

MEF

A

Maximal expiratory flow

53
Q

MEF COPD

A

Low, typical ‘scalloped’ shape to the flow-volume curve

54
Q

TLC COPD

A

High or normal

55
Q

DLCO and KCO COPD

A

Low

56
Q

eNO COPD

A

Normal

57
Q

R(AW) COPD

A

High

58
Q

R(AW)

A

Airway resistance

59
Q

COPD typical blood gases

A

PaO2 = low
PaCO2 = high in type 2 respiratory failure
Low in type 1 respiratory failure
pH = normal
HCO3- = may be elevated if chronic acidosis

60
Q

1 pack year

A

1 packet of cigarettes per day for a year

61
Q

eNO

A

Exhale of nitrous oxide

62
Q

Dynamic hyperinflation

A

increase in end-expiratory lung volume (EELV) that may occur in patients with airflow limitation when minute ventilation increases (e.g. during exercise, hypoxia, anxiety etc.)

Dynamic hyperinflation occurs when end expiratory lung volume (EELV) or FRC is unable to return to the resting volume, resulting in a positive end-expiratory pressure (PEEP).

63
Q

Asbestosis

A

Pulmonary fibrosis due to asbestos

64
Q

FEV1 asbestosis

A

Reduced significantly

65
Q

FVC asbestosis

A

Reduced significantly

66
Q

PEF asbestosis

A

Typically not variable

67
Q

MEF asbestosis

A

Low or normal

68
Q

TLC asbestosis

A

Reduced

69
Q

DLCO and KCO asbestosis

A

Low

70
Q

eNO asbestosis

A

Normal

71
Q

R(AW) asbestosis

A

No typical change

72
Q

Typical blood gases of asbestosis

A

PaO2 = low
PaCO2 = low
pH - normal
HCO3- = low

73
Q

Mixed airways obstruction and restriction

A

FEV1/FVC ratio < 0.7 AND low FVC

74
Q

Tidal volume

A

Volume that enters and leaves with each breath, from a normal quiet inspiration to a normal quiet expiration
Average 0.5L

Changes with pattern of breathing e.g. shallow breaths vs deep breaths
Increased in pregnancy

75
Q

Inspiratory reserve volume

A

Extra volume that can be inspired above tidal volume, from normal quiet inspiration to maximum inspiration
Average is 2.5 L

Relies on muscle strength, lung compliance (elastic recoil) and a normal starting point (end of tidal volume)

76
Q

Expiratory reserve volume

A

Extra volume that can be expired below tidal volume, from normal quiet expiration to maximum expiration
Average 1.5L

Relies on muscle strength and low airway resistance
Reduced in pregnancy, obesity, severe obstruction or proximal (of trachea/bronchi obstruction)

77
Q

Residual volume

A

Volume remaining after maximum expiration
Average 1.5L
Cannot be measured using spirometry

78
Q

Inspiratory capacity

A

Volume breathed in from quiet expiration to maximum inspiration
Average 3L
Tidal volume + Inspiratory reserve volume

79
Q

Functional residual capacity

A

volume remaining after quiet expiration
- average 3L
• Expiratory reserve volume + residual volume
• Affected by height, gender, posture, changes in lung compliance. Height has the greatest influence.
Prevents lung collapse

80
Q

Total lung capacity

A

Volume of air in lungs after maximum inspiration-
average 6L
• sum of all volumes
• Restriction < 80% predicted
• Hyperinflation > 120% predicted
• Measured with helium dilution

81
Q

Anatomical (serial) dead space

A

the volume of air that never reaches alveoli and so never participates in respiration. It includes volume in upper and lower respiratory tract up to and including the terminal bronchioles

82
Q

Alveolar (distributive) dead space

A

the volume of air that reaches alveoli but never participates in respiration. This can reflect alveoli that are ventilated but not perfused, for example secondary to a pulmonary embolus.

83
Q

Helium dilution

A

measure total lung capacity. However, it is only accurate if the lungs are not obstructed. If there is a point of obstruction, helium may not reach all areas of the lung during a ventilation, producing an underestimate as only ventilated lung volumes are measured.

84
Q

Helium dilution process

A

After quiet expiration, the subject breathes in a gas with a known concentration of helium (an inert gas). They hold their breath for 10 seconds, allowing helium to mix with air in the lungs, diluting the concentration of helium. The concentration of helium is then measured after expiration. The volume of air which is ventilated is then calculated according to the degree of dilution of the helium.

85
Q

Nitrogen washout

A

A method for calculating serial/anatomical dead space in the conducting airways up to and including the terminal bronchioles (usually 150mL).

86
Q

Nitrogen washout process

A

The subject takes a breath of pure oxygen and then exhales through a valve which measures nitrogen levels. At first, pure oxygen is exhaled, representing the dead space volume as the air exhaled never reached the alveoli and underwent gaseous exchange.

Then, a mixture of dead space air and alveolar air is expired, meaning the detected concentration of nitrogen increases as nitrogen rich air from the dead space reaches the valve. After a few breaths, the lungs are washed out of pure oxygen, meaning that purely alveolar air is expired, with the nitrogen levels reflecting that of alveolar air. The levels of nitrogen measured over time can be used to calculate the anatomical dead space volume of the lungs.

87
Q

Capacities

A

composed of 2 or more lung volumes. These are fixed as they do not change with the pattern of breathing.

88
Q

Type 1 respiratory failure

A

• involves low oxygen, and normal or low carbon dioxide levels. (hypoxaemia (PaO2 <8 kPa / 60mmHg) with normocapnia (PaCO2 <6.0 kPa / 45mmHg))
• It usually occurs due to ventilation/perfusion (V/Q) mismatch –the volume of air flowing in and out of the lungs is not matched with the flow of blood to the lung tissue
• As a result of the ventilation/perfusion mismatch, PaO2 falls, and PaCO2 rises. The rise in PaCO2 rapidly triggers an increase in a patient’s overall alveolar ventilation, which corrects the PaCO2 but not the PaO2 due to the different shapes of the CO2 and O2 dissociation curves.

89
Q

Type 1 respiratory failure causes

A

• Occurs because of damage to lung tissue eg including pulmonary oedema, pneumonia, acute respiratory distress syndrome, and chronic pulmonary fibrosing alveoloitis.
• Causes : Reduced ventilation and normal perfusion (e.g. pneumonia, pulmonary oedema, bronchoconstriction) OR Reduced perfusion with normal ventilation (e.g. pulmonary embolism)

90
Q

Type 2 respiratory failure causes

A

Hypoventilation can occur for several reasons, including:

Increased resistance as a result of airway obstruction (e.g. COPD)
Reduced compliance of the lung tissue/chest wall (e.g. pneumonia, rib fractures, obesity)
Reduced strength of the respiratory muscles (e.g. Guillain-Barré, motor neurone disease)
Reduced respiratory drive (e.g. opioids and other sedatives)

91
Q

Type 2 respiratory failure

A

involveshypoxaemia (PaO2 is <8 kPa / 60mmHg) with hypercapnia (PaCO2 >6.0 kPa / 45mmHg).
• It occurs as a result of alveolar hypoventilation, which prevents patients from being able to adequately oxygenate and eliminate CO2 from their blood.
• This leads to PaO2 falling(due to lack of oxygenation) and PaCO2 rising(due to lack of ventilation and elimination of CO2).

92
Q

Normal residual volume in a healthy man

A

1200 ml

93
Q

eNO (exhaled nitric oxide)

A

Simple measure of nitric oxide in exhaled breath
Measure in ppb
Generally increased in asthma
Not ‘diagnostic’
A reflection of eosinophilic airway inflammation

94
Q

Normal eNO

A

<25 ppb

95
Q

High eNO

A

> 50 ppb

96
Q

What is transfer estimate

A

Ability to transfer O2 by passive diffusion from alveoli to capillaries

97
Q

FRC value

A

2.4L

98
Q

RV value

A

1.2L

99
Q

ERV value

A

1.2L

100
Q

Tidal volume value

A

0.5L

101
Q

IRV value

A

3L

102
Q

VC value

A

4.7L

103
Q

TLC value

A

5.9L

104
Q

IC value

A

3.5L

105
Q

Flow-volume graph

A

Flow is greatest at start of expiration then decreases linearly as lungs are emptied
Measured in L/min with spirometer

106
Q

Obstructive Flow-volume graph

A

Scalloped
Shifts left and kink
Decreased VC
Increased RV and TLC

107
Q

Restrictive Flow-volume graph

A

Shifts right
Decreased VC, RV , TLC

108
Q

What would be the expected V/Q ratio in the lung at the level of the 1st rib in a healthy patient

A

Greater than normal V/Q ratio- ventilation is greater than perfusion due to effect of gravity

109
Q

Which part of the lung has the lowest V/Q ratio

A

Base of lung

110
Q

What best describes the gradient of the graph of lung volume against trans-lung pressure

A

Lung compliance

111
Q

Valsalva manoeuvre

A

Breathing method which involves moderately forceful exhalation against a closed airway (I.e. closed mouth and pinching the nose)

112
Q

Breathlessness has a wide variety of causes and it is useful to measure lung volumes to investigate the cause of the disease. Which of the following statements describes the functional residual capacity?

A

The volume of gas in the lungs at the end of a normal exhalation

CVR (22 decks)

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