Introduction to Spirometry
What is spirometry?
A test of lung function
Spirometry measures air movement into or out of
the lungs:


How much (eg FVC or VC) and
How quickly (eg FEV1 or FEF25–75%)
Measurement is made with a spirometer

Measures respired volume and flow
Peak expiratory flow measured by a peak flow
meter is no substitute for full spirometry
Why do spirometry?
In general practice


Diagnosis, e.g. asthma and COPD
Monitoring
Lung function test of choice for:


National Asthma Council Australia
Australian Lung Foundation
Test requirements
Test is relatively ‘easy’ to perform but


Requires repeated maximal effort and cooperation
Involves a vigorous breathing manoeuvre
Clinically useful results can only be obtained with


Reliable and correctly calibrated equipment
Experienced and trained personnel
ATS/ERS (2005) provides recommendations
Definitions
TLC (total lung capacity):

Maximum volume of air that can be contained in the
lungs
VC (vital capacity):

Maximum volume of air that can be expired ‘slowly’
following a full inspiration
FVC (forced vital capacity):

Maximum volume of air exhaled with maximally forced
effort from a position of maximal inspiration
Definitions cont.
FEV1 (forced expired volume in one second):

Volume of air that can be forcefully expired in the first
second of a maximal FVC manoeuvre
FEV1/FVC (or FER, forced expiratory ratio):

FEV1 expressed as a percentage (or fraction) of the
FVC
Definitions cont.
FET (forced expiratory time):

Time required to perform the FVC manoeuvre
FEV6 (forced expiratory volume in six seconds):

Maximum volume of air that can be expired with
maximally forced effort in six seconds
PEF (peak expiratory flow):

Largest expiratory flow achieved during the forced
expiratory manoeuvre initiated at full inspiration
Definitions cont.
RV (residual volume):

Volume remaining in the lung after a maximal
exhalation
Volume–time (spirogram)
FET
FEF25-75%
Volume
VC
FEV1
FVC
FEF25-75%
FET
FEV1/FVC (FER)
FVC
FEV1
0
1
Time (seconds)
Flow–volume curve
PEF
FEF50%
Flow
PEF
FEF50%
FEF75%
FVC
(FEV1 & FEV1 FVC)
Shape Analysis
(FEV6)
FEF75%
0
Volume
FVC
Spirometry: a repeatable test
PEF is effort dependent
Maximum expired flow soon after PEF is reached
is effort independent
Maximum expired flow depends on the physical
characteristics of the airways + parenchyma
(and respiratory muscle strength) at time of
testing
Contraindications and
Complications
Contraindications
Recent eye surgery
Recent thoracic and abdominal surgery
Aneurysms (eg cerebral, abdominal)
Unstable cardiac function
Haemoptysis of unknown cause
Pneumothorax
Chest and abdominal pain
Nausea and diarrhoea
Complications
Requires maximal effort which may result in:






Transient breathlessness
Oxygen desaturation
Syncope
Chest pain
Cough
Incontinence
In patients with poorly controlled asthma:


Forced manoeuvre can also induce bronchospasm
Progressive decrease in FEV1 with successive blows
Performing Spirometry
Pre-test preparation
Prepare the spirometer
Age, gender, ethnicity
Measure the patient’s height without shoes
Ask about smoking, recent illness, medication use, etc.
Wash hands
The test is performed in the seated and upright position


Patient should maintain the upright posture throughout the test
*Use of a nose clip is recommended
Explain the test in a clear and concise manner
Demonstrate the manoeuvre:

This will overcome most patient-related problems
Test performance
Open circuit method
Inhale completely and rapidly
*Nose clip/peg
Pause <1 sec
Seal lips around the mouthpiece
Blast air out as fast and as far as possible until
completely empty, or until unable to blow any
longer
Test performance cont.
Vigorous verbal encouragement/coaching is
essential for the patient to continue to exhale to
the end of the manoeuvre (eg “keep going”)
Obtain at least 3 technically acceptable blows
(usually not more than 8 blows are required)
Check test repeatability and perform more blows
as necessary
Start-of-test criteria
Start of test determined by back extrapolation
Back extrapolated volume should be <5% of FVC
or 0.150 L, whichever is greater
PEF should be achieved with sharp rise and
occur close to start of expiration
ie short rise time (less than 10 msec)
These criteria presume a full inhalation prior to
commencing the expiration

Back extrapolation
Volume
Back Extrapolation Line
1
Extrapolated
volume
0
0
Zero time
1
Poor
Start
Time
Back extrapolated volume
<5% of FVC or 0.150 L,
whichever is greater
Must have acceptable FVC
to determine 5% threshold
End-of-test criteria
The patient can’t or shouldn’t continue blowing

Determined by patient or person conducting the test
No change in volume (<0.025 L) for 1 sec, and
the patient has exhaled:


for 3 s in children aged <10 years
for 6 s in patients aged 10 years
Blowing for >15 sec rarely changes clinical
decisions
Acceptability criteria
For each blow:
Meet start and end criteria
Observe that patient understood instructions and
performed well with:




Maximum inspiration
Good start
Smooth continuous exhalation
Maximal effort
Acceptability criteria cont.
There should be no evidence of:








An unsatisfactory start to expiration (extrapolated
volume)
Cough during the first second
Cough that interferes with accurate measurement
Early termination of expiration
Valsalva manoeuvre (glottic closure) or hesitation that
causes a cessation of airflow
A leak
An obstructed mouthpiece
An extra breath being taken during the blow
Flow
Volume
Acceptable spirometry
0
Time
Good reproducibility
Rapid start
Maximum continuous expiratory effort
Volume
Volume
Troubleshooting: poor spirograms
Good effort
Cough*
Sub-maximal effort
*FEV1 may be valid
0
Time
0 1
0
Actual FVC
Actual FVC
Not full prior
to blow
0
Premature termination
or glottic closure
Poor start
0
0
Troubleshooting: poor flow–volume
Flow
Good effort
Sub-maximal
effort
Cough
Volume
Not full prior
to blow
Poor start
Early termination or
glottic closure
Poor quality spirometry
Common causes
Lack of tester knowledge/experience
Lack of patient understanding/compliance






Patient not completely ‘full’ at the start
Sluggish initial start to blow
Premature termination of blow
Tongue occlusion
Glottic closure
Cough – especially during the first second
Poor quality spirometry cont.
Common causes cont.
Lack of knowledge/compliance cont.





Vocalisation during the blow
Poor posture
Results not repeatable
Leak (eg around mouthpiece)
Inaccurate and poorly maintained spirometer
Inaccurately measured or entered patient details
(eg gender, height)
Repeatability criteria
Obtain at least 3 technically acceptable blows



Each of the 3 should meet start and end criteria
Repeatability is a key to good quality spirometry
Superimposing curves helps determine repeatability
FEV1 and FVC

The largest and next largest values need to agree
within 150 mL of each other
Choosing results
Largest FEV1 from acceptable and repeatable
manoeuvres (valid FEV1 can be taken from blows
without valid FVC)
Largest FVC from acceptable and repeatable
manoeuvres
Application of criteria
Perform FVC manoeuvre
No
Met within-blow acceptability criteria?
Yes
No
Achieved 3 acceptable blows?
Yes
No
Met between blow repeatability criteria?
Yes
Determine largest FVC and largest FEV1
Select blow with largest sum of FVC + FEV1 to
determine other indices
Store and interpret
Assessment of reversibility
Not valid if patient just used bronchodilator (BD)
Ideally:


Short acting -agonist BD not used within 4 hrs of test
Long acting -agonists BD stopped 12 hrs prior to test
To assess bronchodilator reversibility:




Perform pre-BD spirometry
Administer BD (eg 4 puffs salbutamol) with MDI/spacer
Wait 10 min salbutamol,
Repeat spirometry (3 acceptable/repeatable)
Calculation of reversibility
FEV1 is the most commonly used index to quantify
reversibility
Positive BD response is an increase in FEV1 (or FVC) of
12% and 200 mL
Interpretation of Spirometry
Spirometry – Interpretation
Take home messages:

Someone can have airflow obstruction but a normal FEV1

If the FER is reduced, then there is airflow obstruction

Interpretation is more difficult in the very old and very young

Different severity classifications are used – no worldwide
standard
Interpretation
? What is normal
Some people use <80% of predicted mean
Should use 95% Confidence Interval
Age, Height, Ethnicity - the major predictors of lung
function
Previous results are the most useful
Start
FER < LLN
No
(F)VC < LLN
No
Within normal limits
Yes
(F)VC < LLN
No
Obstructive
ventilatory
defect
Yes
Mixed
obstructive / restrictive
defect
Yes
Restrictive
ventilatory
defect
Spirometry Interpretation - Degree
Obstruction
Restriction
Lower value of FEV1%pred & FER%pred
> 70%
Yes
Yes
(F)VC > 65%
Mild
No
No
Yes
> 55%
Yes
Moderate
No
No
Yes
> 40%
No
Very Severe
(F)VC > 40%
Severe
COPDX Severity Classification
Obstruction
Asthma
Other
COPD

Bronchiectasis

Cystic Fibrosis


Bronchiolitis
Cystic lung disease
Restriction
Pulmonary


ILD
Other parenchymal
lung
Pseudo
Extrapulmonary

Neuromuscular

Chest wall

Lung resection

Morbid obesity

Gas trapping
Spirometry e.g. 25y/o man
LLN
Pre BD
Post BD
FEV1
2.80 (69%)
3.45 (85%)
4.22 (84%)
4.45 (89%)
66%
78%
(> 3.0)
FVC
(> 4.10)
FER
(> 73%)
Mild airflow obstruction - 23% improvement post BD
Consistent with asthma
Spirometry e.g. 80y/o woman
LLN
Pre BD
Post BD
FEV1
0.91 (69%)
0.99 (75%)
1.22 (65%)
1.24(66%)
75%
80%
(> 0.80)
FVC
(> 1.12)
FER
(> 69%)
Spirometry is within normal limits
Spirometry e.g. 65y/o man
LLN
Pre BD
Post BD
FEV1
0.80 (39%)
1.08 (53%)
2.18 (76%)
2.28(79%)
37%
47%
(> 1.51)
FVC
(> 2.08)
FER
(> 71%)
Very severe airflow obstruction with a partial
improvement following BD.
Consistent with COPD
Spirometry e.g. 65y/o man
LLN
Pre BD
Post BD
FEV1
0.80 (39%)
1.08 (53%)
1.81 (63%)
2.06 (72%)
44%
51%
(> 1.51)
FVC
(> 2.08)
FER
(> 71%)
Mixed obstructive/restrictive defect with severe airflow
obstruction and a partial improvement following BD.
Consistent with COPD and ? Gas trapping
Spirometry e.g. 49y/o man
LLN
Pre BD
Post BD
FEV1
0.80 (36%)
0.82 (37%)
1.01 (34%)
1.00 (32%)
79%
82%
(> 1.85)
FVC
(> 2.51)
FER
(> 71%)
Severe restrictive defect
Medicare- Current
Spirometry item 11506

Measurement of respiratory function involving a
permanently recorded tracing performed before and
after inhalation of bronchodilator

Must perform the test before and after bronchodilator

Must be able to provide a hard copy of the results
Medicare- *Proposed