How to Measure Lung Function
Dr Will For (Senior Lecturer) [email protected]
Cardiff School of Pharmacy and Pharmaceutical Sciences
The aim of this module is to facilitate student learning regarding the principles and
practise of measuring lung function. In addition, practise providing guidance in the
use of a spirometer.
Last updated 17/11/2016
How to Measure Lung Function
Generic/Clinical Skills Content Example Slide
Thursday 13th February 2014
£1bn could be saved by NHS over next
decade if doctors diagnosed chronic lung
diseases earlier
Doctors are failing to make an early diagnosis in 85 per cent of chronic lung
diseases, which kill 25,000 people in the UK every year….
…..found that in 85 per cent of cases, the patient had visited their GP or a clinic
with symptoms which might have indicated COPD, up to five years before an
actual diagnosis was made.
.. said that the first signs of lung disease should prompt further tests, including
with a spirometer…. but that his was not happening in nearly enough cases.
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How to Measure Lung Function
Aims & Outcomes
The aim of this module is to facilitate student learning regarding the principles and practise of measuring lung function. In
addition, practise providing guidance in the use of a spirometer
Learning Outcomes
At the end of the session the student should be able to:
 Outline the theoretical underpinning for FEV 1, including the physiological background.
 Recognise the profile of a typical COPD patient.
 Recognise the profile of a typical Asthma patient
 Identify the key features of a spirometer.
 Carry out a simple spirometery test using the equipment provided.
 Recognise any deficiencies in own knowledge and plan for self-directed remediation of these.
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How to Measure Lung Function
Important Parameters
Two Important Parameters
Lung Capacity
 How much air can be inhaled
 Reduced by RESTRICTIVE airway disease
Air Flow
 How quickly air can be moved out or into the lung
 Air flow reduced by OBSTRUCTIVE airway disease
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How to Measure Lung Function
Measuring
The best way to measure lung function is SPIROMETRY
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How to Measure Lung Function
Measuring
Instructions
1. Record physical data, age, height, gender
2. Put fresh mouthpiece on the pneumotachograph
3. Ideally patient should be standing
4. Inhale as much as you can
5. Exhale as QUICKLY as you can for AS LONG as you can
6. Encourage patient to keep breathing out
7. Repeat twice more and use best reading
8. No not repeat more than 8 times
How to Measure Lung Function
Measuring
Source: Spirometry in practice: A practical guide to spirometry in primary, 2nd edition
The BTS COPD consortium
Last updated 17/11/2016
How to Measure Lung Function
Measuring
FEV1
FVC
FEV1/FVC%
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How to Measure Lung Function
Measuring
Key Parameters
FEV1 – Forced Exhaled Volume in 1 Second
 Amount of air exhaled in 1 second
 Affected by airway diameter
 Predict ‘healthy’ values by age, gender and height
FVC – Forced Vital Capacity Definition
 Total amount of air that can be exhaled
 FVC + Residual Volume = Lung Capacity
 Predict ‘healthy’ values by age, gender and height
FEV1 / FVC ratio
 Does not require tables, FEV1 values adjusted to FVC
 Ratio <0.7 indicates airway obstruction
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How to Measure Lung Function
Measuring
Example Table of ‘Normal’ Values
FEV1 (L) Male
Express value as % of normal
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How to Measure Lung Function
Measuring
Height
Age
Male
38 - 41 FVC
5'3"
160cm
3.81
5'5"
165cm
4.10
5'7"
170cm
4.39
5'9"
175cm
4.97
5'11"
180cm
4.96
6'1"
185cm
5.25
6'3"
190cm
5.54
Years FEV1
42 - 45 FVC
3.20
3.71
3.42
3.99
3.63
4.28
3.85
4.57
4.06
4.86
4.28
5.15
4.49
5.43
Years FEV1
46 - 49 FVC
3.09
3.60
3.30
3.89
3.52
4.18
3.73
4.47
3.95
4.75
4.16
5.04
4.38
5.33
Years FEV1
50 - 53 FVC
2.97
3.50
3.18
3.79
3.40
4.07
3.61
4.36
3.83
4.65
4.04
4.94
4.26
5.23
Years FEV1
54 - 57 FVC
2.85
3.39
3.07
3.68
3.28
3.97
3.50
4.26
3.71
4.55
3.93
4.83
4.14
5.12
Years FEV1
58 - 61 FVC
2.74
3.29
2.95
3.58
3.17
3.87
3.38
4.15
3.60
4.44
3.81
4.73
4.03
5.02
Years FEV1
62 - 65 FVC
3.62
3.19
2.84
3.47
3.05
3.76
3.27
4.05
3.48
4.34
3.70
4.63
3.91
4.91
Years FEV1
66 - 69 FVC
2.51
3.08
2.72
3.37
2.94
3.66
3.15
3.95
3.37
4.23
3.58
4.52
3.80
4.81
Years FEV1
2.39
2.60
2.82
3.03
3.25
3.46
3.68
These values apply to Caucasians.
Reduce values by 7% for Asians and by 13% for Afro-Caribbeans
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For men over 70 years predicted values are less well
established but can be calculated from the equations
below (height in cms; age in years):
FVC = (0.0576 x height) –(0.026 x age) – 4.34
(SD: ± 0.61 litres)
FEV1 = (0.043 x height) – (0.029 x age) – 2.49
(SD: 0.51 litres)
Adapted Source: Spirometry in practice: A practical guide to
spirometry in primary, 2nd edition
The BTS COPD consortium
How to Measure Lung Function
Measuring
Adapted Source: Spirometry in practice: A practical guide to spirometry in primary, 2 nd edition - The BTS COPD consortium
Last updated 17/11/2016
How to Measure Lung Function
How to Differentiate Between Asthma & COPD Diagnosis?
How to differentiate between asthma and COPD diagnosis?
I’m just
so
confused
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How to Measure Lung Function
Clues in Medical History
History
COPD
Asthma
Age
Over 35
Any age
Dyspnoea varies
A little
A lot
Onset of dyspnoea
Gradually
Sudden bouts
Dyspnoea at rest
Uncommon
Common
Smoking history
> 20 pack years
Variable
Wheezing as a child
Uncommon
Common
Productive cough
For many years
Associated attacks
Morning coughing fits
Common
Uncommon
Nocturnal cough wakes
Uncommon
Common
Family history
Uncommon
Usually
Steroid responsiveness
Weak
Strong
Anticholinergic response
Usually good
Beta-agonists better
Beta-agonist response
Anticholinergics better
Very good
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How to Measure Lung Function
Clues in Medical History
SPIROMETRY
FEV1
FEV1/FVC
Asthma
Intermittent
>80% predicted
Normal
Mild persistent
>80% predicted
Normal
Moderate persistent
60%–79% predicted
Reduced ≤5% from normal
Severe persistent
<60% predicted
Reduced >5% from normal
Strong reversal with inhaled bronchodilator
COPD
Mild
≥80% predicted
<0.7
Moderate
50%–79% predicted
<0.7
Severe
30%–49% predicted
<0.7
Very severe
<30% predicted or <50%
predicted plus chronic
respiratory failure
<0.7
Limited reversal with inhaled bronchodilator
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How to Measure Lung Function
Ventilatory Pattern
Restrictive Ventilatory Pattern:
Due to conditions where lung volume is reduced – e.g. Fibrosing alveolitis, scoliosis. The FVC and FEV1 are reduced
proportionately:
 FCV reduced <80%
 FEV1 reduced
 FEV1 / FVC normal
Obstructive Ventilatory Pattern:
Due to conditions in which airways are obstructed due to diffuse airways narrowing of any cause – e.g. asthma, COPD,
extensive bronchiectasis, cystic fibrosis, lung tumours.
The FVC and FEV1 are reduced disproportionately:
 FCV normal or reduced
 FEV1 reduced <80%
 FEV1 / FVC reduced <70%
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How to Measure Lung Function
Summary Points
 Decreased FEV1/FVC percentage indicate obstructive disease
 Decreased FVC indicate restrictive disease
 Airway function is complex and affected by many factors
How to Measure Lung Function
Spirometry Video
Video Sourced from:
http://www.youtube.com/w
atch?v=s8pXdtp_Duw&featu
re=player_detailpage
This test ought to be carried out while the patient is standing unless they are dizzy
How to Measure Lung Function
Web Resources
http://www.asthma.org.uk/
http://www.brit-thoracic.org.uk/guidelines-and-quality-standards/copd-guidelines/
http://www.brit-thoracic.org.uk/guidelines-and-quality-standards/asthma-guideline/
Last updated 17/11/2016