Nursing Practice
Practice educator
Respiratory
Keywords: Spirometry/Lung function/
COPD/asthma
●This
article has been double-blind
peer reviewed
The first in a two-part series explores the purpose and technique of the spirometry test
Understanding
spirometry
In this article...
How to decide if a patient is suitable for spirometry testing
Definitions of lung function measurements
How to perform a spirometry test and which device to use
S
pirometry is a method for measuring the speed and volume of
airflow and is seen as the “gold
standard” of testing lung function (Levy et al, 2009). This article is the
first in a two-part series. It describes the
definitions of lung function measurements, how to perform spirometry testing,
which patients are suitable for the test, and
which type of spirometer to use.
Patient selection
The most common reason for undertaking
spirometry is to help diagnose COPD,
asthma and pulmonary fibrosis. It is also
used to assess disease progression in these
conditions, as well as in cystic fibrosis and
bronchiectasis. Spirometry testing should
be used for patients presenting with undiagnosed respiratory symptoms, such as
dyspnoea, wheeze and cough. It should also
be used for those with suspected COPD, a
smoking history and: chronic cough;
breathlessness on exertion; daily wheezing;
or a history of winter chest infections.
Spirometry should also be used to monitor patients who have COPD, asthma or
Box 1. spirometer
features
● The spirometer should have a volume/
time graph displaying lung airflow so that
any technical errors can be detected
● It should have a flow volume loop to
provide information about both phases of
respiration
● It should produce the predicted values
other chronic respiratory conditions (Levy
et al, 2009).
Patients with the following conditions
are not suitable for spirometry testing:
» Known or suspected respiratory infection;
» Haemoptysis of unknown origin;
» Pneumothorax;
» Myocardial infarction in the previous
month;
» Uncontrolled hypertension or pulmonary embolism;
» History of haemorrhagic cerebrovascular event;
» Recent thoracic, abdominal or eye
surgery;
» Nausea, vomiting or pain;
» Confusion or dementia;
» Recent middle-ear infection.
Patients with these conditions may be
tested using spirometry if a health review
shows it is appropriate, but only after discussion with a clinician who is experienced in spirometry (Levy et al, 2009).
How to perform spirometry
Before performing spirometry, the
patient’s condition should be stable and
based on the person’s age, height, sex and
ethnicity. Predicted values are based on
measurements in white people. Modern
machines have a correction factor for
different ethnic groups
● It should show measured values as a
percentage of predicted values and should
also be able to calculate reversibility
testing results
● The device should have an integral
14 Nursing Times 25.10.11 / Vol 107 No 42 / www.nursingtimes.net
5 key
points
1
Spirometry
testing is most
commonly used to
help diagnose
COPD, asthma and
pulmonary fibrosis
Spirometry
testing should
be used for
patients with
undiagnosed
respiratory
symptoms and for
those with a history
of smoking and
suspected COPD
Spirometry
testing is
contraindicated in
some conditions
2
3
4
Before a test,
patients should
avoid smoking,
alcohol, strenuous
exercise or a heavy
meal
Good
technique is
essential to ensure
optimal results
5
Patients must sit for
spirometry testing
they should not have had a chest infection
for at least six weeks. Features of the
spirometer are outlined in Box 1.
Preparing the patient
Before a spirometry test, patients should
be advised to avoid smoking, alcohol,
strenuous exercise or a heavy meal. They
should wear loose-fitting clothing,
ensure they arrive in good time for the
memory to record data, and should be
able to produce a hard copy and/or have
the facility to download to a computer
● All spirometers require calibration or
verification with an annually certificated
calibration syringe. The machine should
be serviced annually, or as per manufacturer’s recommendations
Source: Levy et al (2009)
Fig 1. Consistent spirometry
results
6
Volume (litres)
5
4
3
2
1
1
2
3
4
Time (seconds)
5
6
Fig 2. volume/time graph
(Spirograph)
5
FVC
Volume (litres)
4
3
FEV1
2
1
0
0
1
2
3
Time (seconds)
4
5
Fig 3. Expiratory flow volume
graph
Expiratory flow
rate (L/s)
Maximal expiratory flow
FVC
Volume (litres)
Fig 4. Flow volume loop
Flow (L/s)
PEF
FEF25
FEF50
FEF75
Volume (L)
FVC
FEV1
16 Nursing Times 25.10.11 / Vol 107 No 42 / www.nursingtimes.net
The mean flow
between FEF25 and
FEF75 is often the first
parameter to decline
in respiratory disease
Box 2. Lung function
measurements
recorded with a
spirometer
● FVC: The volume of air, measured in
litres that can be forcibly expelled from
the lungs following maximal inspiration.
Patients should aim for an expiration
lasting a minimum of six seconds
● FEV1: This is the speed of air forcibly
expelled from the lungs in the first second
from maximal inspiration
● FEV1/FVC ratio (FEV1%): The percentage of the FVC expired in the first second
of maximal forced expiration following full
inspiration
● Vital capacity (VC): The total expired
volume after maximal inspiration, also
known as relaxed vital capacity (RVC) or
slow vital capacity (SVC)
● Forced expiratory flow (FEF 25-75) or
mid expiratory flow (MEF50): Indicates
expiratory flow in the middle portion of the
FVC and the function of the lower airways
● Peak expiratory flow (PEF) or peak
expiratory flow rate (PEFR): The highest
flow achieved from maximal lung inflation
and forced expiration, measured in the
first 10 milliseconds of a forced expiration.
PEF is measured in litres per minute using
a peak flow meter
Source: Miller (2008)
appointment and have an empty bladder.
Height and weight should be measured,
and the patient should be seated for the test.
The practitioner should explain the forced
expiratory manoeuvre. This involves:
» Inhaling as deeply as possible;
» Sealing the lips around the mouthpiece;
» Blowing out as hard and fast as possible
until all the air has been expelled from
the lungs.
only performed for those patients with
conditions that cause severe obstruction.
(See part 2 for interpretation of results.)
During all spirometry testing, the practitioner should encourage the patient to
keep blowing for at least six seconds
during expiration. They should also
observe the patient to check for inadequate
inspiration or expiration.
The procedure should be carried out
three times for all measurements to give
three consistent volume–time curves. The
Performing spirometry
best two curves should be within 100ml or
Measurements recorded using a spirom- 5% of each other (Fig 1).
eter are outlined in Box 2.
Poor readings due to technique error
Before performing the test, the practi- can occur; these are outlined in Box 3 .
tioner should:
The results of lung funcBox 3. Common tion measurements are pre» Prepare the spirometer
causes of
according to manufacsented as a volume/time
technique
turer’s instructions;
graph, or spirograph (Fig 2),
errors
» Ensure the patient is
a flow/volume graph (Fig 3),
sitting upright. This is
or flow volume loop (Fig 4)
● Obstructed mouthpiece
recommended for
(Miller et al, 2005).
optimal lung expansion; ● Mouth leak
Reversibility testing
» Use nose clips or ask the ● Poorly coordinated or
slow start
Post-bronchodilator spirompatient to pinch their
● Additional inspiration
etry should be measured to
nose if relaxed vital
confirm a diagnosis of COPD
capacity is recorded. If a while performing the test
● Coughing
and
help
differentiate
relaxed manoeuvre is
● Submaximal inspiration
between asthma and COPD.
being undertaken, this
● Submaximal effort
The patient’s condition
test should be per● Abrupt finish before
should be stable before carformed first. This
rying out bronchodilator
involves inhaling deeply compete expiration
reversibility testing, and the
and breathing out gently
Source: Cooper et al (2005)
patient should stop shortto full expiration. This
acting bronchodilators six
measurement is usually
Box 4. Reversibility formula
% change (>20% positive)
Post FEV1 - pre FEV1 x 100 = % change
preFEV1
ml change (>400ml is positive)
Post FEV1 - pre FEV1 x 1000 = ml
change
hours before the test. Long-acting bronchodilators should be stopped 12 hours
before testing, and theophylline stopped 24
hours before (The Scottish Intercollegiate
Guidelines
Network/British
Thoracic
Society, 2009). A baseline spirometry test is
then performed before a bronchodilator is
administered. This is usually 400mcg salbutamol delivered by a metered dose inhaler
and spacer device (Pearce, 2011). The
spirometry test is then repeated after 15
minutes and the difference calculated using
the reversibility formula (Box 4).
Further assessment can be carried out
using steroid reversibility testing.
According to the National Institute for
Health and Clinical Excellence (2010), this
involves performing a baseline spirometry
test, administering a two-week course of
30-40mg of daily prednisolone, repeating
the spirometry test and calculating the difference using the reversibility formula.
Training
Misleading results from poorly performed
spirometry can lead to inappropriate diagnosis and treatment. The practitioner
should attend a recognised training programme, followed by a period of supervision while administering spirometry; regular quality audits of performance should
also be carried out (NICE, 2010).
Respiratory training organisations provide spirometry courses and most COPD
training courses include spirometry education. Spirometry manufacturers provide
training for using their equipment. NT
Dr Linda Pearce is respiratory nurse
consultant and clinical lead, Suffolk COPD
Services, West Suffolk Hospital
» Next week, part 2 looks at how to
interpret spirometry results
References
Cooper BG et al (2005) Practical Handbook of
Respiratory Function Testing: Part Two. www.artp.
org.uk
Levy ML et al (2009) Diagnostic spirometry in
primary care: proposed standards for general
practice compliant with American Thoracic Society
and European Respiratory Society recommendations.
Primary Care Respiratory Journal; 18: 3, 130-147.
Miller B (2008) Spirometry: A Handbook for Health
Professionals. County Down, Ireland: Rosie Spence.
Miller MR et al (2005) Standardisation of spirometry.
European Respiratory Journal; 26: 319–338.
National Institute for Health and Clinical
Excellence (2010) Management of Adults with
Chronic Obstructive Pulmonary Disease in Adults
in Primary and Secondary Care. London: NICE.
tinyurl.com/NICE-COPD
Pearce L (2011) How to teach inhaler technique.
Nursing Times; 107: 8, 16-18.
Scottish Intercollegiate Guidelines Network/British
Thoracic Society (2009) British Guideline on the
Management of Asthma. tinyurl.com/SIGN-BTS-guide
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