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8. Respiratory > Lung Function Testing > Flashcards

Lung Function Testing Flashcards

1
Q

List 3 spirometry tests/graphs.

List 8 other lung function tests.

A

SPIROMETRY:
Lung volumes
Time/volume plots
Flow/volume plots

OTHER LUNG FUNCTION TESTS:
Peak flow (PEF)
Reversibility tests
Bronchial provocation
Transfer factor
Residual lung volumes
Pulse oximetry
Alveolar oxygen equation
Arterial blood gases
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2
Q

How would you define a spirometry test?

What would you tell the patient when doing one? (3)

A

Forced expiratory manoeuvre from total lung capacity, followed by a full inspiration; measured as the best of 3 acceptable attempts (within 5% of each other)

METHOD:

  1. Take a big breath in as far as you can
  2. Blow out as hard as you can for as long as possible
  3. Then take a deep breath in
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3
Q

List 4 disadvantages of spirometry.

A

Needs appropriately trained technician
Effort and technique dependent
Affected by patient frailty
Can’t be done if patient is too unwell

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4
Q

List 5 lung volumes which can be directly measured by spirometry.

A 
Inspiratory reserve volume
Inspiratory capacity
Expiratory reserve volume
Tidal volume (VT)
Vital capacity (VC)
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5
Q

List 3 volumes which can be calculated from spirometry tests.

A

Total lung capacity
Residual volume
Functional residual capacity (FRC)

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6
Q

What is the difference between inspiratory reserve volume (IRV) and inspiratory capacity (IC)?

A

INSPIRATORY RESERVE VOLUME (IRV):
Volume between PEAK tidal volume and volume after full inspiration

INSPIRATORY CAPACITY (IC):
Volume between END tidal volume and volume after full inspiration
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7
Q

What is the vital capacity (VC)?

A

Maximum amount of air a person can expel from the lungs after maximum inhalation

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8
Q

What is the expiratory reserve volume?

A

Volume between end tidal volume and the volume after full expiration

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9
Q

How do you calculate the total lung capacity (TLC)?

A

TLC = vital capacity (VC) + residual volume (RV)

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10
Q

What is the functional residual capacity (FRC)?

A

Amount of air left in the lungs after a normal breath (i.e. at the end tidal volume)

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11
Q

Which 2 graphs can be plotted with spirometry results?

A

Time/volume plot

Flow/volume loops

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12
Q

Draw a time/volume plot.

A

See poster

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13
Q

Draw a flow/volume loop.

A

See poster

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14
Q

Which 4 measurements can be taken from a time/volume plot?

How?

A

Peak expiratory flow (PEF)
-Extrapolate a line from beginning of plot; calculate gradient

Forced expiratory volume in 1 second (FEV1)
-Find volume at 1 second on the graph

Forced vital capacity (FVC)
-Plateau level of graph

FEV1/FVC ratio

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15
Q

Which measurement can be taken from a flow/volume loop?

A

Vital capacity

-Distance between the two x-axis intercepts

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16
Q

On a flow/volume loop, what are the 2 parts of the expiratory limb?

Briefly explain the physiology behind each.

A

Effort dependent part

  • Initial expiration requires effort to forcefully exhale
  • This creates the maximum rate of flow in the flow/volume loop

Effort independent part

  • After maximum expiratory flow is reached, the rest of the lung volume is exhaled automatically (due to pressure differences)
  • Flow is highest in the terminal bronchioles, so by the time air reaches the central airways, flow decreases
  • Therefore flow decreases on the loop
17
Q

What is predicted FEV1 adjusted for? (5)

A 
Age
Gender
Race
Height
Atmospheric values
18
Q

What is a normal % predicted FEV1?

A

Depends on individual - because predicted FEV1 is just an estimate, therefore doesn’t reflect true lung function

As long as % predicted FEV1 remains the same as it’s always been, it’s normal

19
Q

What is a normal FEV1/FVC ratio?

A

70+%

20
Q

How do you do reversibility testing on the lungs?

What do the
results indicate?

A

METHOD:

  1. Measure spirometry
  2. Give nebulised/inhaled salbutamol
  3. Measure spirometry 15 minutes after

RESULTS:
Reversible if:
-More than 15% improvement in FEV1
-More than 400ml improvement in FEV1

21
Q

When doing serial peak flow tests (PEFR), what do you look for? (3)

A

Diurnal variation
Variation over time
PEFR response to steroids

22
Q

How do you measure transfer factor? (Also called: TLCO, KCO, DLCO)

A
  1. Patient is given a single breath of CO (very low concentration)
  2. CO has a high affinity for Hb, so it will easily diffuse into the blood
  3. Measure the amount of CO breathed out
    a. Then calculate the amount of CO absorbed (this is the transfer factor)
23
Q

List 4 features which affect the transfer factor.

A

Alveolar surface area
Pulmonary capillary blood volume
Haemoglobin concentration
V/Q mismatch

24
Q

List 4 possible causes of a decreased transfer factor.

List 1 possible cause of an increased transfer factor.

A 
DECREASED TRANSFER FACTOR:
Emphysema
Interstitial lung disease
Pulmonary vascular disease
Anaemia

INCREASED TRANSFER FACTOR:
Polycytaemia

25
Q

What are the 2 methods of measuring residual lung volume?

A

Helium dilution

Body plethysmography

26
Q

How do you carry out helium dilution, to find out residual volume? (2)

A
  1. Ask patient to inspire a known quantity of inert gas (which is NOT absorbed)
  2. Measure the amount breathed out
    a. The difference is equal to the residual volume
27
Q

How do you carry out body plethysmography, to find out residual volume? (3)

A
  1. Ask patient to carry out respiratory manoeuvres in a sealed box
  2. This causes changes in air pressure
  3. Using the Archimedes principle, you can then derive lung volumes
28
Q

Describe the disadvantages of pulse oximetry. (2)

Give examples of when each might affect measurement of O2 sats.

A

Depends on adequate perfusion; inaccurate in:

  • Shock
  • Heart failure

Does not measure CO2 levels, therefore does not measure ventilation; inaccurate in:

  • Acute asthma
  • COPD
  • Hypoventilation
29
Q

What is the normal saturation of haemoglobin in the body?

A

66%

30
Q

What is the alveolar oxygen equation?

A

Alveolar oxygen = (inspired oxygen concentration) - (1.25 x pCO2)

31
Q

What is a normal alveolar-arterial (A-a) oxygen gradient?

What can cause a high alveolar arterial oxygen gradient? (1)

A

Normal: <2-4 kPa

High gradient: V/Q mismatch

32
Q

Briefly describe a systematic approach to arterial blood gas analysis. (3)

A
  1. Look at pO2 (normal: 8 kPa)
  2. Look at pCO2
    a. If low: type 1 respiratory failure
    b. If high: type 2 respiratory failure
  3. Look at H+ levels
    a. If high: acidosis
    b. If low: alkalosis
  4. Look at HCO3- levels
    a. Consider compensation of acid/base balance
33
Q

Describe an obstructive pattern on lung function tests. (3)

A

FEV1/FVC: <70%

Flow/volume loop:

  • “Church and steeple”
  • Lower PEF

Time/volume plot:

  • Slow-rising plot
  • Lower FEV1
  • Lower FVC
34
Q

Describe a restrictive pattern on lung function tests. (3)

A

FEV1/FVC: normal

Flow/volume loop:

  • Normal shape
  • Smaller size/area
  • Reduced FVC

Time/volume plot:

  • Normal shape
  • Smaller/shorter plot
  • Reduced FEV1
35
Q

List 6 causes of a restrictive pattern on lung function tests.

A 
Interstitial lung disease
Kyphoscoliosis
Previous pneumonectomy 
Neuromuscular disease
Obesity
Poor effort/technique

8. Respiratory (14 decks)

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