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103 Theme 4 - Lungs > Measuring lung function > Flashcards

Measuring lung function Flashcards

1
Q

How does a patient take a spirometry test?

A
  • Can be done slowly or “forced”
  • Most often done as forced expiration

FVC or “Tiffeneau” manoeuvre

  • Take a deep breath in
  • Don’t hold your breath
  • Put your lips round the outside of the tube

and blow out as hard as you can

for as long as you can

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2
Q

How do you interpret spirometry results?

A

A patient’s PFT values (except the FEV1/FVC ratio) are compared to predicted values, which are derived from a healthy population of people of the same gender and of similar age and height

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3
Q

What does this spirometry graph show?

A

Age-related loss of lung elasticity -> decline in FVC and FEV1

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4
Q

What do spirometry results vary by?

A

Vary by gender, height, and age

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5
Q

What is classed as an abnormal spirometry result?

A

Abnormal result: any result < 80% of the predicted value

Or: any results < lower limit of normal

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6
Q

What does this show?

A

Normal spirometry result

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7
Q

What is the lower limit of normal?

A

The lower limit of normal (LLN) is taken to be equal to the 5th percentile of a healthy, non-smoking population

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8
Q

What FEVI/FVC ration shows obstruction?

A

FEV1/FVC ratio: should exhale > 70% of FVC in first second

If FEV1/FVC < 0.7, then obstruction is present

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9
Q

What does this spirometry show?

A

Obstruction

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10
Q

What does this spirometry show?

A

Severe obstruction

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11
Q

What type of graph is this?

A

Flow Volume loop

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12
Q

What does the lilac line show?

A

Early Airflow Obstruction

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13
Q

What does early airway obstruction look like on an expiratory flow-volume loop?

A

PEFR may be normal

Mid-Expiratory Flow Rate usually more affected

Lilac line

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14
Q

What does the orange line show?

What type of graph is this?

A

Severe Airflow Obstruction

Expiratory Flow-Volume Loop

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15
Q

What does the orange line show?

What type of graph is this?

A

Extra-Thoracic Obstruction (including tracheal stenosis, retrosternal goitre, etc)

Expiratory flow-volume loop

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16
Q

What do flow-volume loops indicate?

A

Flow volume loops can indicate where obstruction is located in the tracheobronchial tree

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17
Q

Complete the diagram on what the obstruction is in these flow-volume loops

A
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18
Q

What are the benefits of peak flow rate?

A

Easy to perform

Easy to maintain device

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19
Q

What are peak flow rates used for?

A
  • Diagnosis – asthma, not COPD
  • Monitoring day to day variation
  • Picking up exacerbations
  • Assessing response to treatment
20
Q

The peak flow rate test is mandatory for which patients?

A

Asthma ptients on nebulised medicine

21
Q

What does this graph show?

A

Peak expiratory flow

Morning dips shouldn’t be there - went with inhaled corticosteroids

consistent with diagnosis of asthma

22
Q

What is the equation for flow?

A

Flow = (Pressure gradient) / (Raw)

Raw - airway resistance

23
Q

What is the equation for airway resistance?

A
24
Q

What could cause a decrease in the radius of an airway?

What is the consequence of this?

A
  • Mucous or other obstruction
  • Bronchoconstriction
  • Compression (from a mass)

Increased resistance

25
Q

How can lung volumes be measured?

A

Cannot be obtained from spirometry

Methods of measurement

  • Helium dilution
  • Plethysmography “Body Box”
26
Q

What are the 4 volumes that can be measured?

A

TV – tidal volume

IRV – inspiratory reserve volume

ERV – expiratory reserve volume

RV – residual volume

27
Q

What are the 4 capacities that can be measured?

A

TLC – total lung capacity

VC – vital capacity, slow (SVC) or forced (FVC)

FRC – functional residual capacity

IC - inspiratory capacity

28
Q

Complete the diagram on lung volumes and capacities

A
29
Q

What graph is this?

A

Relaxation pressure volume curve

30
Q

Complete the diagram of the Relaxation pressure volume curve?

A
31
Q

What are the features of restrictive lung disease?

A
  • Reduced TLC, FRC, and RV
  • Preserved tidal volume
  • Reduced IRV / inspiratory capacity

Reduced vital capacity (FVC and SVC)

32
Q

What does each colour represent?

A
33
Q

What combination of colours is -

Inspiratory capacity

Functional residual capacity

Vital capacity

Total lung capacity

A
34
Q

What condition does this indicate?

A

Fibrotic lung disease

35
Q

What are the causes of restriction and deceased lung volumes?

A
  • Alveolar filling process (e.g. pneumonia)
  • Lung tissue disease: Fibrotic lung disease
  • Pleural disease: pneumothorax, large pleural effusion, fibrosis of pleural tissue (“trapped lung”)
  • Chest wall disease (e.g. kyphoscoliosis)
  • Weakness (due to nerve and/or muscle disease)
36
Q

What does the second x-ray show?

A

Hyperinflation

37
Q

What causes hyperinflation in COPD?

A

In emphysema: loss of elastic recoil -> Cl curve plateau occurs at a larger volume -> increased TLC

38
Q

What condition does this show?

A

COPD

39
Q

Where does gas exchange occur?

A

Takes place at alveoli

40
Q

What factors influence gas exchange?

A
  • Depends on adequate ventilation of alveoli
  • Influenced by alveolar surface area and thickness of alveolar membrane
41
Q

What is the purpose of gas exchange?

A
  • Delivers oxygen to blood where it combines with Hb
  • Gets rid of CO2 into exhaled air
42
Q

What are the causes of abnormal gas exchange?

A
  • Airway disorders (asthma & COPD)
  • Alveolar destruction (emphysema)
  • Fibrotic lung disease (idiopathic lung fibrosis, asbestosis etc)
  • Abnormal ventilatory control
  • Abnormal environment (altitude)
43
Q

How is gas transfer (diffusing capacity) measured?

A
  • CO diffuses like Oxygen
  • CO binds to Hb and is carried away
  • Inhale known volume of gas with low concentrations of CO and Helium
  • Hold breath for known time
  • Measure CO and He in expired air

Helium dilution gives alveolar volume

44
Q

What is the effect of pulmonary diseases on total lung capacity (TLCO)?

A

Note: conditions of reduced surface area (first 3 listed) and increased thickness (scarring/inflammation)

45
Q

What is the effect of cardiovascular /haematological disease on total lung capacity (TLCO)?

A
46
Q

Name 4 other lung function tests used in clinical practice

A
  • Assessment of airway ‘reversibility’
  • Assessment of ventilation
  • Fitness to fly
  • Respiratory muscle assessment

103 Theme 4 - Lungs (21 decks)

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