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Module 103: The Heart, Lungs and Blood > Theme 4: Lecture 2 - Measuring lung function > Flashcards

Theme 4: Lecture 2 - Measuring lung function Flashcards

1
Q

Spirometry

A

a common office test used to assess how well your lungs work by measuring how much air you inhale, how much you exhale and how quickly you exhale.

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2
Q

FVC

A

Forced vital capacity

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3
Q

Describe FVC or Tiffeneau manoeuvre

A
  • 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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4
Q

FEV1

A

Forced expiratory volume in 1 second

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5
Q

What is a normal FEV1

A

3.25 litres

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6
Q

What is a normal FVC

A

4.2 litres

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7
Q

What is a normal FEV1/FVC

A

77%

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8
Q

What are abnormal spirometry results

A
  • any result < 80% of the predicted value

- any result < lower limit of normal

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9
Q

What is the lower limit of normal

A

taken to be equal to the 5th percentile of a healthy, non-smoking population

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10
Q

When is obstruction present

A

When FEV1/FVC is less than 70%

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11
Q

Why might FEV1/FVC be unreliable in more severe obstruction

A

In severe obstruction the patient sometimes has trouble reaching a full FVC

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12
Q

What can tell us a lot more about the characteristics of air flow than spirometry

A

A flow volume loop

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13
Q

Describe an expiratory flow volume loop in early airflow obstruction

A
  • PEFR may be normal

- Mid-expiratory flow rates usually more affected

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14
Q

PEFR

A

peak expiratory flow rate

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15
Q

Describe an expiratory flow volume loop in severe airflow obstruction

A
  • Lower FVC
  • Lower PEFR
  • Lower mid expiratory flow rates
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16
Q

Describe an expiratory flow volume loop in extra thoracic obstruction

A
  • Unchanged FVC

- Flow rate plateaued

17
Q

What can flow volume loops indicate

A

Where the obstruction is located in the tracheobronchial tree

18
Q

Describe peak flow rate

A

-Easy to perform
-Easy to maintain device
-Useful for:
Diagnosis – asthma, not COPD
Monitoring day to day variation
Picking up exacerbations
Assessing response to treatment
-Mandatory for patients on nebulised Rx

19
Q

What causes a decrease in the radius of the airway

A
  • Mucus or other obstruction
  • Bronchoconstriction
  • Compression (from a mass)
20
Q

Can lung volumes be obtained from spirometry

A

No

21
Q

Methods of measurement for lung volumes

A
  • Helium dilution

- Plethysmography ‘body box’

22
Q

Characteristics of restrictive lung disease

A
  • Reduced TLC, FRC, IC and RV
  • Preserved tidal volume
  • Reduced IRV (inspiratory reserve volume) / inspiratory capacity
  • Reduced vital capacity
23
Q

Causes of restriction and decreased 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)
24
Q

Describe what happens in emphysema

A
  • Loss of elastic recoil leads to compliance curve plateau occurring at a larger volume which leads to an increased TLC
  • Occurs in COPD
25
Q

Lung volumes in COPD

A
  • Preserved TV
  • Decreased IC, ERV and VC
  • Increased FRC and TLC
  • Significantly increased RV
26
Q

Describe gas exchange

A
  • Takes place at alveoli
  • Depends on adequate ventilation of alveoli
  • Influenced by alveolar surface area and thickness of alveolar membrane
  • Delivers oxygen to blood where it combines with Hb
  • Gets rid of CO2 into exhaled air
27
Q

When does abnormal gas exchange occur

A
  • Airway disorders (asthma & COPD)
  • Alveolar destruction (emphysema)
  • Fibrotic lung disease (idiopathic lung fibrosis, asbestosis etc)
  • Abnormal ventilatory control
  • Abnormal environment (altitude)
28
Q

What is gas exchange measured as

A

CO transfer factor

29
Q

Describe how gas transfer is 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
  • He dilution gives alveolar volume
30
Q

What does a low diffusion capacity (TLCO) indicate

A

Abnormal gas exchange

31
Q

What are the pulmonary diseases that decrease TLCO

A
  • Emphysema
  • Alveolar filling process
  • Lobectomy
  • Scarring or inflammation around the alveolar wall
32
Q

What are the cardiovascular/haematological diseases that decrease TLCO

A
  • Pulmonary hypertension
  • Low cardiac output
  • Pulmonary oedema
  • Anaemia
33
Q

What causes increased TLCO

A
  • High cardiac output
  • Pulmonary haemorrhage
  • Polycythaemia
34
Q

Name 4 other pulmonary function tests used in routine clinical practice

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

Module 103: The Heart, Lungs and Blood (51 decks)

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