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Blood, Heart and Lungs > Basic Lung Function Testing > Flashcards

Basic Lung Function Testing Flashcards

1
Q

Why do we perform lung function tests?

A

1) Detect if lung disease is present
2) Quantify the severity of the lung disease
3) Assess the effectiveness of intervention eg. surgical, therapeutic, pharmacological
4) Pre-operative evaluation
5) Assess the extent of airways reversibility
6) Assess the extent of airway hyper sensitivity

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2
Q

When is Peak Expiratory Flow measured?

A
  • PEF on it’s own is not generally a good diagnostic tool unless it is performed serially
  • Serial PEFs are used in asthma to assess for diurnal variation
  • Also used in occupational situations to check for any differences between PEF at work and at home
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3
Q

How would you measure serial PEFs for asthma?

A
  • Asthma: Perform 4 readings per day for 2 weeks
  • Occupational asthma: Perform 8 readings per day for 4 weeks.
  • Diurnal variation can be calculated in a number of ways:
    e. g. : Highest PEF-Lowest PEF / predicted PEF (%)
  • 15-20% on most days would be indicative of asthma.
  • Generally performed pre bronchodilator for analysis.
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4
Q

What is spirometry?

A

An objective measurement of lung function.

Measures lung size (VC & FVC).
Measures airway calibre (FEV1).
Indicates airflow obstruction (FEV1/FVC).
Measures Flow (PEF)

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5
Q

Define Vital Capacity

A

Maximum volume blown out steadily, following a full inspiration.

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6
Q

Define Forced Vital Capacity

A

Maximum volume blown out as hard as possible, following a full inspiration

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7
Q

Define Forced Expiratory Volume in 1 second (FEV1)

A

Volume of air blown out in the first second of a forced blow out. Important to look at ratio of first second compared to rest.

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8
Q

Define Peak Expiratory Flow

A

Maximum flow rate achieved within first 100ms following a full inspiration.

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9
Q

What would you ask patient to avoid on the day of spirometry tests?

A
  • Smoking 24hrs prior to testing
  • No alcohol consumption within 2hrs
  • Eating a substantial meal
  • Wearing clothing that restricts full chest expansion
  • Performing vigorous exercise within 30 mins
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10
Q

What is a restrictive disease?

A

Reduced volume in the lungs due to inability of lungs to expand.

1) Intrapulmonary diseases
- Pulmonary fibrosis
2) Extra-pulmonary conditions
- Obesity
- Rib cage deformity (scoliosis)
- Respiratory muscle weakness.

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11
Q

What is an obstructive disease?

A

Persistent slowing of airflow during breathing.

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12
Q

How would you know there is airway obstruction?

A

Low FEV1/FVC ratio

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13
Q

What are the parameters used to check for extra thoracic airway obstruction?

A
  • Empey index (FEV1/PEF) >8.0
  • MEF50/MIF50 >1.0
  • VISUAL INSPECTION OF FVL
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14
Q

How does FEV1 change in restrictive or obstructive diseases?

A

Reduced in restrictive

Reduced in obstructive

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15
Q

How does FVC change in restrictive or obstructive diseases?

A

Reduced in restrictive

Can be reduced in severe obstruction

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16
Q

How does FEV1/FVC change in restrictive or obstructive diseases?

A

Normal in restrictive

Reduced in obstructive

17
Q

How does VC change in restrictive or obstructive diseases?

A

Reduced in restrictive

Normal in obstruction unless very severe

18
Q

How does PEF change in restrictive or obstructive diseases?

A

Normal to high in restrictive, but can be reduced.

Mostly reduced in obstruction

19
Q

Give some examples of restrictive diseases

A
  • Sarcoid
  • Fibrosis
  • Kyphosis
  • Heart failure
  • Tumour
  • Obesity
20
Q

Give some examples of obstructive diseases

A
  • COPD
  • Asthma
  • Emphysema
  • Bronchiectasis
  • Cystic Fibrosis
  • Tumour
21
Q

What static lung volumes are measured?

A

Total lung capacity (TLC), Functional Residual Capacity (FRC) and Residual Volume (RV)

22
Q

How would you measure the static lung volumes (TLC, FRC, RV)?

A
  • Can be measured by using helium dilution, nitrogen washout or body plethysmpgraphy
  • Provides the only way to see true restriction (by reduced TLC and FRC) due to intra pulmonary (fibrosis) or extra pulmonary conditions (obesity)
  • Shows hyperinflation (increased FRC and TLC) and increased RV (gas trapping), due to loss of elasticity (emphysema)
  • % RV to TLC in normal subjects should be <40%
23
Q

Why perform gas transfer?

A

1) Gives information about how the alveoli gas exchange is working
2) We measure transfer coefficient (KCO) and derive TLCO (Transfer factor/diffusing capacity) from: KCO x VA
- VA=single breath measurement of TLC using helium
- KCO is measured using carbon monoxide
- Corrected values are corrected for haemoglobin – lower Hb levels=lower KCO

24
Q

What is the equation to calculate TLCO?

A

TLCO = KCO x VA

25
Q

What would you expect the pulmonary function test (PFT) to be in a healthy individual?

A

PFT = FEV1/FVC x 100

You would expect it to be around 80%

26
Q

What would you expect the pulmonary function test (PFT) to be in an individual with an obstructive disease?

A

PFT = FEV1/FVC x 100
Their FEV1 would be decreased
So you would expect PFT to be <80%

27
Q

What would you expect the pulmonary function test (PFT) to be in an individual with a restrictive disease?

A

PFT = FEV1/FVC x 100
Their FVC would be decreased
So you would expect PFT to be >80%

28
Q

What is a typical tidal volume in a healthy individual?

A

500ml

29
Q

What is the total lung capacity TLC in an average adult male?

A

6 litres

30
Q

How does the flow-volume loop change in obstructive disease?

A

1) The whole loop shifts to the left because there is an increased FRC and TLC due to gas trapping
2) There is a characteristic ‘kink’ in the forced expiration due to the obstruction

31
Q

How does the flow-volume loop change in restrictive disease?

A

The whole loop shifts to the right because there is a reduced TLC

Blood, Heart and Lungs (33 decks)

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