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Respiriatory: Airway Disease > Pulmonary Function Testing > Flashcards

Pulmonary Function Testing Flashcards

1
Q

What are 3 types of pulmonary function test?

A
  • Effort dependent tests
  • Effort independent tests
  • Gas diffusion tests
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2
Q

What are examples of effort dependent tests?

A
  • Forced expiratory volumes/flow rates
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3
Q

How are forced expiratory volumes measured?

A

Spirometry

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4
Q

What are examples of effort independent tests?

A
  • Relaxed vital capacity
  • Helium/N2 without static lung volumes
  • Whole body plethysmography
  • Impulse oscillometry
  • Exhaled breath nitric oxide
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5
Q

What are examples of gas diffusion tests?

A
  • CO transfer factor
  • Arterial blood gases (resting)
  • SaO2 during exercise
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6
Q

How is relaxed vital capacity measured?

A

Spirometry

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7
Q

What is a forced expiratory manoeuvre?

A

From TLC to RV

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8
Q

What is the forced expiratory volume in 1 second?

A

FEV1 (litres)

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9
Q

What is the forced expiratory ratio?

A

FER = FEV1/FVC

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10
Q

What is relaxed vital capacity?

A

Patient breathes out in their own time

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11
Q

What is the normal value of FER?

A

> 75%

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12
Q

In asthma, how does FEV1, FVC and FER compare with a normal individual?

A
  • FEV1 is reduced
  • FVC is the same (just takes longer)
  • FEV1/FVC is reduced
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13
Q

In COPD, how does FEV1, FVC and FER compare with a normal individual?

A
  • FEV1 is reduced
  • FVC is reduced
  • FEV1/FVC is the same
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14
Q

Why is FEV1/FVC ratio preserved in COPD?

A

FEV1 is reduced in proportion to FVC

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15
Q

What is a volume-time curve?

A

Plots volume in litres (FVC and FEV1) against time (s)

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16
Q

What is a flow-volume curve?

A

Flow rate (l/s) plotted against forced expiratory volume (l)

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17
Q

What affects the shape of the expiratory flow-volume curve?

A
  • Volume dependent expiratory airway closure - asthma, chronic bronchitis
  • Pressure dependent expiratory airway closure - emphysema
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18
Q

What causes volume dependent expiratory airway closure in asthma?

A

Small airways close off earlier in expiration (wheeze)

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19
Q

What causes pressure dependent expiratory airway closure in COPD?

A

Small airways close off extremely early in expiration

20
Q

How is peak expiratory flow rate (PEF) measured?

A

Peak flow meter

21
Q

What are the units of peak expiratory flow rate?

A

l/min

22
Q

How does obstructive airway disease affect peak expiratory flow rate?

A

Peak expiratory flow rate is reduced in obstructive disease

23
Q

What is the FEV1/FVC ratio of someone with asthma?

A

<75%

24
Q

What is the FEV1 response to B2-agonist in asthma?

A

Increases by approx 15%

25
Q

How does restrictive airway disease affect peak expiratory flow rate?

A

Peak expiratory flow rate is normal in restrictive airway disease

26
Q

Why is peak expiratory flow rate not affected in restive airway disease?

A

In restrictive disease, no problem with conducting airways so flow rate is normal

27
Q

Why is there no FEV1 response to B2 agonist (e.g. salbutamol) in restrictive airway disease?

A

Conducting airways are normal

28
Q

What are methods of bronchial challenge testing?

A
  • Exercise (will produce bronchoconstriction - cold air)
  • Metacholine/histamine/mannitol (markers of airway hyper-responsiveness)
  • Allergens/chemicals (early and late responses)
29
Q

How is metacholine/histamine/mannitol used in bronchial challenge testing?

A

Provocative dose to produce 20% fall in FEV1

30
Q

How is exercise testing used to diagnose respiratory disease?

A
  • Fall in FEV1 or peak expiratory flow rate = asthma
  • Decrease in SaO2 during exercise in interstitial lung disease - to monitor treatment response
  • Full cardiopulmonary exercise test (CPET) - differentiate cardiac vs respiratory dyspnoea (HR vs oxygen uptake vs ventilatory rate)
31
Q

What type of test is the measurement of static lung volumes?

A

Effort independent test

32
Q

What information can helium dilution/N2 washout provide?

A

Functional residual capacity

33
Q

What is the equation for residual volume?

A

RV = FRC - ERV

34
Q

What is the equation for total lung capacity?

A

TLC = VC + RV

35
Q

When does TLC increase beyond normal values?

A

In hyperinflation - emphysema

36
Q

When does TLC decrease below normal values?

A

In restrictive lung disease - ILD

37
Q

What is the equation for gas trapping in COPD?

A

RV/TLC x 100

38
Q

What is CO transfer factor?

A

Co diffusion across alveolar-capillary barrier

39
Q

What is TLCO?

A

Total lung transfer for CO (diffusing capacity)

40
Q

What conditions can cause TLCO to decrease?

A
  • Anaemia
  • Emphysema
  • Interstitial lung disease
  • Pulmonary oedema
  • Pulmonary embolus
  • Bronchiectesis
41
Q

What can TLCO be used for?

A

To monitor treatment response in lung disease

42
Q

How is airway resistance measured?

A
  • Whole body plethysmography

* Impulse oscillometry (more common)

43
Q

What is impulse oscillometry?

A

Measures airway resistance during quiet tidal breathing at different resonant frequencies to give:

  • total resistance (5Hz)
  • central resistance (20Hz)
  • and hence peripheral airway resistance by subtraction
44
Q

What is a non-invasive marker of eosinophilic airway inflammation in asthma?

A

Exhaled breath nitric oxide measured at flow of 50ml/s (FeNO)

45
Q

Why is exhaled breath nitric oxide measurement not useful in COPD?

A

Nitric oxide suppressed by smoking

46
Q

What do high levels of NO (>35ppb) measured in exhaled breath indicate?

A

Uncontrolled asthmatic inflammation

47
Q

When is exhaled breath nitric oxide measured?

A

In adjunct to bronchial challenge to assess asthmatic inflammation - especially when spirometry is normal

Respiriatory: Airway Disease (10 decks)

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