AJTCCM VOL. 28 NO. 4 2022 181
GUIDELINE
Spirometry is required as part of the comprehensive evaluation of both adult and paediatric individuals with suspected or conrmed respiratory
diseases and occupational assessments. It is used in the categorisation of impairment, grading of severity, assessment of potential progression
and response to interventions. Guidelines for spirometry in South Africa are required to improve the quality, standardisation and usefulness
in local respiratory practice. e broad principles of spirometry have remained largely unchanged from previous versions of the South African
Spirometry Guidelines; however, minor adjustments have been incorporated from more comprehensive international guidelines, including
adoption of the Global Lung Function Initiative 2012 (GLI 2012) spirometry reference equations for the South African population.
All equipment should have proof of validation regarding resolution and consistency of the system. Daily calibration must be performed, and
equipment quality control processes adhered to. It is important to have standard operating procedures to ensure consistency and quality and,
additionally, strict infection control as highlighted during the COVID-19 pandemic.
Adequate spirometry relies on a competent, trained operator, accurate equipment, standardised operating procedures, quality control and
patient co-operation. All manoeuvres must be performed strictly according to guidelines, and strict quality assurance methods should be in
place, including acceptability criteria (for any given eort) and repeatability (between eorts).
Results must be categorised and graded according to current guidelines, taking into consideration the indication for the test.
Keywords. Spirometry, lung function, impairment.
Afr J Thoracic Crit Care Med 2022;28(4):181-192. https://doi.org/10.7196/AJTCCM.2022.v28i4.287
Spirometry is required as part of the comprehensive evaluation of
children, adolescents and adults with suspected or conrmed respiratory
diseases, including asthma and chronic obstructive pulmonary disease
(COPD), as well as for screening in certain contexts.[1] It is useful
for the general categorisation as well as grading of impairment, for
documenting potential disease progression, as well as to assess response
to interventions.[1,2] Spirometry, however, should always be interpreted
in conjunction with clinical information and the pre-test probability of
disease should inuence interpretation. Moreover, incorrect standards
and operating procedures signicantly reduce the value of spirometry
in diagnosis and screening for diseases.[1,2]
Guidelines for spirometry in South Africa (SA)have existed for
many years, with the aim of improving the quality, standardisation and
usefulness of the test itself.[1,3,4] Although the principles have remained
largely unchanged, previous guidelines have been supplanted by
comprehensive international guidelines.[2] Interpretation of spirometry
is based on reference equations used to dene normality derived from
data from healthy individuals in the same population. ere are limited
robust data from large diverse population groups in SA, with the largest
healthy dataset suggesting black South Africans may have a best t to
the GLI-Other reference equation.[5,6]
The present statement aims to provide an updated and relevant
guideline for the use of spirometry in both adults and children at
primary healthcare level in SA.
Basic equipment and denitions
Spirometry
Spirometry involves the measurement of air volumes and airflow
rates of the lung that are dependent on the physical properties of the
airways, lung parenchyma, pleura and chest wall and respiratory muscle
strength.[1,2] Practically all modern commercially available computerised
spirometers are flow-type spirometers making use of a flow sensor
(pneumotachometer) to derive volumes. ey allow for the real-time
display of expiratory and inspiratory manoeuvres as ow-volume loops,
which allow instant pattern recognition. Standard features of modern
spirometers include soware for the storage of large data sets and the
Position statement for adult and paediatric spirometry in South
Africa: 2022 update
D M Maree,1 ND Clin Tech (SA); R A Swanepoel,1 BTe ch ; F Swart,1 ND Clin Tech (SA); D M Gray,2 MB ChB, FRACP, Cert Pulm (SA)
Paeds, PhD; R Masekela,3 MB BCh, MMed (Paeds), Cert Pulm (SA) Paeds, PhD; B W Allwood,1 MB BCh, FCP (SA), MPH, Cert Pulm
(SA), PhD; R N van Zyl-Smit,4 MB ChB, FRCP (UK), FCP (SA), MMed (Int), Cert Pulm (SA), PhD; C F N Koegelenberg,1 MB ChB, MMed
(Int), FCP (SA), FRCP (UK), Cert Pulm (SA), PhD
1 Division of Pulmonology, Department of Medicine, Stellenbosch University and Tygerberg Hospital, Cape Town, South Africa
2 Department of Paediatrics and Child Health and MRC Unit of Child and Adolescent Health, University of Cape Town, South Africa
3
Department of Paediatrics and Child Health, Nelson R Mandela School of Medicine, School of Clinical Medicine, College of Health Sciences,
University of KwaZulu-Natal, Durban, South Africa
4 Division of Pulmonology and UCT Lung Institute, Department of Medicine, Groote Schuur Hospital and University of Cape Town, South Africa
Corresponding author: C F N Koegelenberg (coeniefn@sun.ac.za)
182 AJTCCM VOL. 28 NO. 4 2022
GUIDELINE
ability to express measured values as percentage predicted and z-scores,
using various reference value sets as a guide. ese spirometers generally
require greater expertise to operate, calibrate and maintain than the older
volume-type spirometers, which measured volume directly and produced
volume-time curves, but are smaller and more portable. Spirograms (Fig.
1) are graphic displays produced by spirometers and include volume-time
curves (both types of spirometer) and ow-volume curves (newer ow-
type spirometers).[1] Modern equipment also automatically superimposes
measured spirograms on predicted curves to facilitate interpretation.
Measurements
e minimum measurements that should be produced by basic oce
spirometers include:
1. Forced vital capacity (FVC): FVC is the maximum volume of gas
exhaled from the position of maximal inspiration by means of a
rapid, maximally forced expiratory eort, expressed in litres as BTPS
(body temperature, pressure, water vapour saturated). BTPS refers
to a standardised volume at normal body temperature (37°C) at
ambient pressure, saturated with water vapour.
2. Forced expiratory volume in the rst second (FEV1): FEV1 is
the volume of gas exhaled during the rst second of the FVC
manoeuvre, expressed in litres (BTPS).
3. FEV1/FVC%: This is the observed FEV1 expressed as the
percentage of observed FVC (FEV1/FVC × 100), also called the
forced expiratory ratio (FER) or the Tieneau-Pinelli index.
4. Peak expiratory flow (PEF): The PEF is the maximum flow
generated during a FVC manoeuvre, usually expressed in litres
per second (BTPS).
Additional measurements may include:
1. Vital capacity (VC): e ‘slow’ VC (sometimes referred to as SVC)
is the total volume of gas inhaled from the position of maximal
expiration or exhaled from the position of maximal inspiration.
It is measured with a relaxed/slow breathing manoeuvre either
during inspiration or expiration. VC is expressed in litres (BTPS)
and may be useful for identifying dynamic small airway collapse
in COPD patients (the slow VC will be greater than the FVC).
2. Forced expiratory volume in X second (FEVX): FEVX is the
volume of gas exhaled during the rst X second of the FVC
manoeuvre, expressed in litres (BTPS), e.g. FEV6 (volume in 6 s)
FEV0.5 (volume in 0.5 s).
3. Forced expiratory flow (FEFX%): The instantaneous forced
expiratory ow rate at the point where X% of the FVC has been
expired, e.g. at 25%, 50% and 75% (FEF25%, FEF50% and FEF75%).
ese measurements are expressed in litres per second (BTPS).
4. FEF25-75%: Average flow during the middle 50% of an FVC
manoeuvre, also sometimes referred to as the maximum mid-
expiratory ow (MMEF) expressed in litres per second (BTPS).
Accuracy, repeatability, and reproducibility
Accuracy is the truthfulness or closeness of agreement between the
result of a measurement and the true value.[2] Repeatability is the
closeness of agreement (precision) between the results of successive
measurements of the same patient carried out (provided the same
methods, instrument, observer and conditions are present), whereas
reproducibility is viewed as the closeness of agreement of the results
of successive measurements of the same item where the measurements
are carried out with changed conditions (e.g. methods, observer,
instrument, location, conditions of use, or time).[1,2]
Measurement range and equipment resolution
e measurement range is the range over which the manufacturer
indicates that the device complies with the equipment resolution,
which is the smallest detectable change in measurement.[3]
Calibration and validation
Calibration is the process whereby the accuracy and repeatability
of measurement of a device are tested and corrected using a gold
standard, e.g. a calibration syringe with standard volume. Validation
is the process of establishing and certifying that the device is correctly
calibrated.[1,2,]
Indications for spirometry
The indication for spirometry in a particular patient should be
unambiguous and should be documented in each case. Current
indications for spirometry are summarised in Table 1.
Fig. 1. (A) Volume-time, and (B) ow-volume curves. In the ow-type
spirometer, FEV1 is a derived value. It can only be read from the ow-
volume graph if a 1 s timer is displayed.
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GUIDELINE
Specications and technical preparation
for spirometry
Validation
All equipment should have proof of validation.[1,2,7] Accuracy depends
on the resolution (minimal detectable volume or ow) and linearity
(consistency) of the system, from the measuring components to the
display and graphical output. e European Respiratory Society (ERS)
and American oracic Society (ATS) Taskforce for the Standardisation of
Lung Function Testing have recommended minimal performance criteria
for spirometers and guidelines for validating equipment using waveform-
generated calibration syringes are summarised in Tables 2 and 3.[2]
Other recommendations include:
1. A BTPS-correction facility. The volume of exhaled gas is
measured outside the body at ambient conditions, designated
ATPS (ambient temperature, ambient pressure, saturated
with water vapour). ese gas measurements are corrected to
reect conditions inside the lung (BTPS). Without this facility,
mathematical correction of volumes must be done manually.
Depending on the environmental temperature, the BTPS
correction factor may be as large as 10%. Ambient temperature,
barometric pressure and time of day should therefore be
recorded.
Table 1. Indications for spirometry
Diagnostic
Evaluation of abnormal respiratory symptoms and signs (in individuals with suspected obstructive and/or restrictive lung diseases)
Measure to what extent a disease aects the respiratory system
Screening of individuals at risk, e.g. smokers, employees exposed to substances known to cause respiratory disease
Preoperative risk assessment
Assessment of prognosis
Monitoring
Assessment of interventions/treatment action plan
Monitoring the course of chronic lung diseases
Monitoring of patients exposed to injurious agents
Screen for pulmonary toxicity secondary to drugs
Evaluation of impairment
Insurance and disability
Rehabilitation
Assessment for medicolegal purposes
Public health
Epidemiological surveys and derivation of reference equations
Table 2. Selective minimum volume and ow criteria for diagnostic spirometers
Parameter Volume range (L) Accuracy* (BTPS) Repeatability† (BTPS) Flow range (L/s) Time (s) Validation method
FVC 0.5 - 8.0 ±3% of reading or
±0.050 L, whichever is
greater
±4.5% of reading or
±0.200 L, whichever is
greater
0 - 14 30 24 ATS waveforms,
3 L calibration
syringe
FEV10.5 - 8.0 ±3% of reading or
±0.050 L, whichever is
greater
±4.5% of reading or
±0.200 L, whichever is
greater
0 - 14 1 24 ATS waveforms
PEF n/a ±10% of reading or
±0.30 L/s, whichever
is greater
±5% of reading or
0.15 L/s, whichever is
greater
0 - 14 24 ATS ow
waveforms
BTPS = body temperature, pressure, water vapour saturated; ATS = American oracic Society; FVC = forced vital capacity; FEV1 = forced expiratory volume in the rst second; PEF = peak expiratory
ow; n/a = not applicable.
*Percentage deviation = 100 × (average-standard)/standard.
†Percentage span = 100 (maximum-minimum)/average.
Table 3. Minimum scale for spirograms*
Parameter
Instrument display Graphical output
Required resolution Scaling Required resolution Scaling
Volume 0.050 L 5 mm/L 0.025 L 10 mm/L
Flow 0.200 L/s 2.5 mm/L/s 0.100 L/s 5 mm/L/s
Time 0.2 s 10 mm/s 0.2 s 20 mm/s
*e correct aspect ratio for a ow v. volume display is two units of ow per one unit of volume.
184 AJTCCM VOL. 28 NO. 4 2022
GUIDELINE
2. A facility to generate real-time spirograms to enhance feedback
and subject compliance.
3. Stated source(s) of reference values and the facility to select or enter
appropriate values manually.
4. Computer-driven technical quality indicators that meet the latest
ATS standards.
5. Printing or electronic facility for record-keeping purposes.
6. Adequate facility to save large numbers of tests and test quality
indicators where needed; e.g., for occupational surveillance.
Calibration and equipment quality
control
All diagnostic spirometers must be volume-calibrated at least daily
using a calibrated syringe with a volume of 3 L (with accuracy of
±0.015 L or ±0.5% for the daily checks) to ensure that they remain
accurate during use.[1,2,7,] In some settings (e.g., industrial surveys), the
calibration should be performed twice daily. Moreover, calibration
should be repeated should the temperature change markedly (>3°C in
<30 min). Flow-type spirometers should be calibrated with at least 3
discharges within a range of ows ranging from 0.5 – 12 L/s (with the
3 L syringe this equates to calibration manoeuvres of approximately 6
s and <0.5 s), while performed in calibration mode (to prevent BTPS-
correction because room air is injected). Ambient temperature and
barometric pressure readings are entered, ideally in the room where
testing will be performed (atmospheric variables may be obtained from
the local airport or weather bureau or from weather apps). Calibration
is complete when the inspiratory and expiratory volumes for the
varying ows are within ±3%. Calibration should be done with in-line
lters installed. For linearity, a volume calibration check should be
performed weekly with a 3 L syringe to deliver 3 constant ows at a low
ow, followed by 3 at a mid-range ow and nally 3 at a high ow. e
volumes achieved at each of these ows should each meet the accuracy
requirement of ±3% (±2.5% for the spirometer itself and ±0.5% for the
calibration syringe).[2]
Volume-type spirometers must be evaluated for leaks daily (with 0.3
kPa constant pressure for 1 minute), and quarterly for volume linearity
(1 L increments with a calibrating syringe measured over the entire
volume range).[2,7]
e calibration syringes(s) should be tested annually with regard
to calibration (recalibrated if needed), and also undergo leak testing
and general servicing.[2] is should be certied by an independent
laboratory, and the quality control and calibration certicates should
be stored on site.
Further equipment quality control measures include the installation
of soware updates (this should be recorded in a logbook) and quarterly
calibration of the time clock (by mechanical recorded checks with a
stopwatch). In addition to calibration, spirometers must be maintained
according to the manufacturer’s specifications. This includes the
weekly cleaning of pneumotachs, more frequently if there is visible
condensate, as they are particularly sensitive to moisture and secretions.
It is advisable that the local supplier/manufacturer services spirometers
annually.
At a minimum, a calibration and maintenance log and electronic or
physical copies of whole spirograms should be kept, so that accuracy
and precision of past tests can be verified. Additionally, standard
operating procedures should be documented and kept for reference.
Ambient conditions
Ambient temperature, barometric pressure and time of day should
be recorded daily. Temperature is a signicant variable in spirometry
and may be measured directly by a simple thermometer or an internal
thermostat (i.e. directly by the equipment). e operator is responsible
for conrming the accuracy of temperature measurements, and it is
the responsibility of the manufacturer to describe or provide a clear
mechanism for checking the accuracy of instrument measurements.[1]
Hygiene and infection control
Rationale
There is a risk of transmitting infections, including severe acute
respiratory syndrome coronavirus 2 (SARS-CoV-2), other respiratory
viral infections, tuberculosis (TB) and bacterial infections to other
test subjects and sta during pulmonary function testing.[1,8] Virtually
all the components of the spirometry system have been implicated
as an infection control risk, and transmission can occur through
both direct and indirect contact with equipment.[1,9] Mouthpieces and the
immediate proximal surfaces of valves or tubing are the most likely sources
of contamination. e type of test manoeuvre (and specically whether
accompanied by inhalation from the spirometer) has a signicant inuence
on the extent of infection control needed. An expiration-only manoeuvre,
without inhalation from the spirometer, reduces the potential for cross-
contamination and is the method of choice for mass screening purposes.[1]
Infection control recommendations
Transmission to operators can be prevented by proper hand washing,
using barrier devices, e.g. gloves, wearing masks and using appropriate
disposable in-line lters for testing. Hands should be washed following
direct handling of mouthpieces, tubing, valves or interior spirometer
surfaces and always between patients. Operators should be supplied with
and wear a surgical mask during the test procedure and gloves when they
have open wounds or lesions on the hands, particularly when handling
contaminated equipment. N95 masks should be supplied and worn
during high-risk testing (e.g. testing during viral pandemics), and the
South African oracic Society’s position statement and practical guide to
the use of particulate ltering facepiece respirators should be adhered to.[8]
Cross-contamination should be avoided. Mouthpieces, nose clips and
any other equipment that come into direct contact with mucosal surfaces
should be disinfected, sterilised or discarded (if disposable) aer each use.
Equipment surfaces showing condensation from expired air should be
disinfected or sterilised before re-use. Manufacturers’ recommendations
should be strictly adhered to, particularly regarding the choice of
sterilising agents, as some equipment may be damaged by chemicals or
heat.[1]
Volume-based spirometers that use a closed-circuit technique, should
be ushed between subjects with room air at least ve times over the
entire volume range of the spirometer to ensure clearance of droplet
nuclei. e breathing tube and mouthpiece should be decontaminated or
changed between patients.[1]
Infection protection control measures are required: in-line disposable
lters must be used and replaced aer every subject, or the involved
parts of the system (spirometer, breathing tubes and resistive element of
the pneumotach) must be decontaminated/ sterilised/ushed aer each
subject. In-line lters are suggested, as re-calibration is necessary every
time a system has been dismantled for decontamination.[2]
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GUIDELINE
Special precautions must be taken for patients with known transmissible
infections or those with current haemoptysis. In-line lters should
be used routinely, even if expiratory manoeuvres are performed
exclusively, with sterilisation of contaminated surfaces, or equipment
decontaminated aer each case. Proper attention should also be paid
to environmental control, e.g. ventilation of the room where testing
occurs. Practical considerations include testing such cases at the end of
the day, to allow overnight decontamination of equipment.
General considerations and preparation
e patient’s sex at birth, age, self-identied ethnic group, standing height
and weight must be recorded on the day of the test, as these variables
are required for reference purposes.[10] Height and weight should be
measured with the subject barefoot (feet together), standing upright
and eyes looking straight ahead with their back against the wall or
stadiometer. Weight is taken wearing only light clothing. e weight and,
most importantly, the age and height must be accurate to one decimal
place, to avoid prediction bias.[11] e body mass index (kg/m2) should
be calculated. Smoking status and the use of any medication that can
inuence spirometry should be documented, including the type and dose
of drugs and when they were last administered.
Contraindications
The forceful generation of maximal pressures in the thorax with
the resultant impact on abdominal and thoracic organs during the
performance of spirometry, poses certain risks.[2] ere are few absolute
contraindications to spirometry, but several relative contraindications
to spirometry exist.
Major contraindication criteria: Current respiratory infections in
individuals who are not being treated, or treated <2 weeks prior to
testing, is a contraindication for assessing permanent impairment/
disability, as respiratory infections can temporarily impair lung
function.[2] Testing should be postponed in individuals with current
haemoptysis (>125 ml per day) to avoid precipitating life-threatening
haemoptysis.
Relative contraindication: Lung function testing should not be
performed within one week of an acute myocardial infarction, eye
surgery or surgery to the sinus or middle ear, or infection of either.[2]
Testing should also be postponed in patients within 4 weeks of brain,
thoracic or abdominal surgery. Patients who experience syncope with
forced and prolonged expiration should not be re-tested.[2]
Subject preparation
Patients should abstain from smoking (within 1 hour) and not perform
any vigorous exercise 60 minutes before testing.[2] e specic durations
of abstinence prior to testing or bronchodilator responsiveness testing
are summarised in Table 4. Clothing that restricts chest and abdominal
movement should also be avoided. Patients should be informed of these
requirements prior to testing, and deviations should be documented.
Subjects should be relaxed and comfortable before and during testing.
For children, an age-appropriate description of what will happen prior
to testing and, if possible, providing pictures or videos of the procedure
for them to look at in preparation, may improve success, particularly
in young children. Tight-fitting clothing should be loosened, and
distractions minimised. Well-fitting dentures can be left in place,
but loose-tting dentures are best removed. e use of a nose clip is
strongly recommended but using the ngers to pinch the nose closed is
acceptable in children and individuals where the nose clip slips o.[1]
It is imperative to use simple instructions to ensure optimal co-
operation, which may include real-time visual aids, and incentive
graphic soware on spirometers is advisable for children. An initial
period of training, particularly in children, is essential for better
results.[4] Feedback should be given regarding their performance,
and patients should be continually encouraged to ensure the best-
quality spirometry results possible (including describing potential
improvements that can be made).
Subject positioning
Spirometry may be performed either sitting or standing, and the position
should be reported.[1,,7] e sitting position is the most widely used,
primarily because of the small risk of syncope during forced expiration.
e chair should have arm rests, but not wheels. Patients should sit in
an upright position with the neck extended and the feet planted on the
oor directly in front of them.
Execution of tests
FVC and FEV1 test manoeuvres
The operator should follow the summarised procedures (Table 5).
The performance of an FVC manoeuvre has four distinct phases:
(1) maximal inspiration; (2) rapid, forceful exhalation (a ‘blast’); (3)
continued complete exhalation for a maximum of 15 s, known as end of
forced expiration (EOFE); and (4) inspiration at maximal ow back to
maximum lung volume.[2] ere are essentially two accepted procedures:
Table 4. Abstinence prior to testing or bronchodilator responsiveness testing
Activity/product Duration
Prior to testing
Caeine products, smoking, vaping, etc. Within 1 hour
Strenuous exercise Within 1 hour (patient should rest for at least 15 minutes prior to test)
Prior to testing with bronchodilator responsiveness
SABA (e.g. salbutamol) 4 - 6 hours
SAMA (e.g. ipratropium bromide) 12 hours
LABA (e.g. formoterol or salmeterol) 24 hours
Ultra-LABA (e.g. indacaterol) 36 hours
LAMA (e.g. tiotropium) 36 - 48 hours
SABA = short-acting b2-agonist; LABA = long-acting b2-agonist; SAMA = short-acting muscarinic antagonist; LAMA = long-acting muscarinic antagonist.
186 AJTCCM VOL. 28 NO. 4 2022
GUIDELINE
1. Full loop (recommended)
is allows for the recording of inspiration and expiration, and for
generating ow-volume loops (on a ow-type spirometer). e subject
assumes the correct posture, the nose is occluded, a mouthpiece is
inserted (observing that the tongue is not occluding the airway) and the
lips sealed tightly around it. e subject is instructed to inhale completely
and rapidly while being prompted by the operator with simple phrases
such as ‘more, more’; if the patient pauses at total lung capacity (TLC),
it should be for <1 s; this inspiration should be followed with minimal
hesitation by a rapid, forceful (blast) and maximal exhalation until no
further air can be expelled (while maintaining an upright posture). e
operator should, throughout the procedure, prompt and encourage
the subject to perform maximally, while monitoring for the moment
a plateau is reached or a forced expiratory time (FET) of 15 s has been
reached. Once the forced expiration has been completed, the patient
should be asked to inhale as deep and fast as possible with the same
encouragement and prompting from the operator to full lung capacity,
as with the initial inspiratory manoeuvre. When testing children, the
operator should use age-appropriate language, preferably in the rst
language of the child, be trained in testing children; and the testing
environment should be safe and child friendly. e test procedure
should be explained in simple terms and well demonstrated.[4] Where
possible visual aids should be used prior to testing, children should
be encouraged and prompted with basic instructions. Making use
of incentive devices, graphics or software can result in acceptable
performances.
2. Expiration loop only
is is oen employed for mass screening and consists of an FVC
test with or without a slow VC test. After the correct posture has
been assumed, the nose is occluded. e subject is required to inhale
completely and rapidly; this is followed by the individual placing the
mouthpiece in the mouth and sealing the lips within 2 s. e patient
is then instructed to exhale rapidly, forcefully and maximally, and the
mouthpiece can be removed at EOFE.
Quality assurance
Many within-manoeuvre (Table 6) and between-manoeuvre criteria
must be satised to ensure adequate quality:
1. Start and end of test
e start of forced expiration (’time zero’) is determined by the back
extrapolation method (Fig. 2), and defines the start for all timed
measurements.[2,7] e steepest slope on the volume-time curve is used
for manual measurements, whereas the largest slope averaged over
an 80 ms period is used for computerised back extrapolation.[1,2] e
back extrapolated volume (BEV) is the volume of air that has been
exhaled before this ‘time zero’ and is included in the FEV1 and FVC
Table 5. Procedures for recording FVC
Verify spirometer calibration
Explain the procedure to the subject
Subject preparation Enquire about medication use and smoking status
Measure height and weight without shoes
Infection control Wash hands or hand sanitiser (operator and patient)
Disposable lter
Instruct and demonstrate test Correct positioning and posture
Complete and rapid inhalation
Forced, maximal exhalation
Perform manoeuvre Closed v. open circuit (see text) with nose clip
Repeat instructions as necessary
Repeat for a minimum of 3 tests
Verify test quality Acceptability
Repeatability
Perform more attempts Maximum of 8 for adults (up to 10 children <6 years old)
is table is adapted from Graham et al.[2]
FVC = forced vital capacity.
Table 6. Within-manoeuvre acceptability criteria for the recording of FVC and FEV1
No artefacts Coughing during rst second of expiration
Glottis closure (Valsalva manoeuvre) or hesitation
Early termination or submaximal eort
Leakage
Obstructed mouthpiece
Good starts Back extrapolated volume <5% of FVC or <0.100 L (whichever is greater)
Exhalation A plateau of 1 s with volume change <0.025 L (less only if the subject cannot or should not continue)
is table is adapted from Graham et al.[2]
FVC = forced vital capacity; FEV1 = forced expiratory volume in the rst second.
AJTCCM VOL. 28 NO. 4 2022 187
GUIDELINE
measurement. e following criteria are critical to ensure that the
FEV1 comes from a maximal attempt: the hesitation time must be <2
s and the BEV must be <5% of FVC or ≤0.100 L, whichever is greater
(the previous minimum 6 s exhalation for EOFE has been updated).[2]
Current recommended EOFE criteria also include: (1) subjects cannot
exhale to achieve plateau (patients with high elastic recoil or restrictive
lung disease); in these cases, a similar FVC in repeated attempts will be
a measure of EOFE being reached. A patient should not continue further
testing owing to discomfort or the risk of syncope; or (2) the volume-time
curve shows no change in volume (<0.025 L for ≥1 s), i.e. reaches a ow
plateau. It should be noted that a closure of the glottis will result in early
termination of the manoeuvre, resulting in an unacceptable attempt; or
(3) if the patient has exhaled for 15 s, the attempt may be terminated, as
longer exhalation times rarely change clinical decisions.[2] Manoeuvres
not meeting EOFE acceptability criteria will not provide acceptable FVC
measures, but an acceptable FEV1 may be obtained from an attempt
with early termination after 1 s. Younger children often struggle to
take in a maximal breath before forced expiration. Hence the followed
expiration could be inadequate. In simple terms – the more air in, the
more air out. e most dicult part of the spirometry manoeuvre for
younger children is the complete expiration aer forced expiration, as
when their lungs feel empty, they do not understand how to keep on
applying pressure to their chest and abdomen. Ecient motivation and
demonstration must be used. In children <6 years of age, an acceptable
FEV0.75 can be obtained from an attempt terminating aer 0.75 s. It is to
be noted that a minimum exhalation time is not required.
2. Acceptability criteria
e within-manoeuvre acceptability criteria for the recording of FVC
and FEV1 are as follows: there must be no artefacts such as coughing
within the rst second of the exhalation manoeuvre, no obstruction
such as the tongue in the mouthpiece/lter, no abrupt/early termination
resulting in under-measurement of FVC, leaking by not having an
adequate seal of the mouth around the mouthpiece, nor may there be
a false/hesitant start (FIVC-FVC should be <0.100 L or 5% of the FVC
whichever is greater). Testing with an erroneous zero-ow level can
result in the measurements being under- or overestimated. Acceptable
curves must satisfy all criteria mentioned, whereas ‘usable’ curves only
need a good start (without hesitation) and to be free of coughing during
the rst second (Figs 3 - 5). e spirometry system soware must
provide explicit feedback to the operator with regard to acceptability
aer each manoeuvre but must have the ability to be overridden by the
operator.
3. Repeatability criteria
An adequate test (be it pre-bronchodilator or post-bronchodilator)
requires a minimum of three acceptable FVC and FEV1 measurements
– they do not necessarily need to be from the same manoeuvres (Fig.
6).[2] FVC repeatability is achieved when the dierence between the
largest and the next largest FVC is ≤0.150 L in subjects >6 years of
age and ≤0.100 L or 10% of largest FVC, whichever is greater for
those ≤6 years old.[2] e criterion for FEV1 repeatability is the same
as for FVC. If these criteria are not met aer 3 attempts, additional
testing must be performed, up to a maximum of 8 manoeuvres (or
until the subject cannot or should not continue or until it is obvious
that perseverance will not change the outcome).[9] For children, it
may be necessary to make more than 10 attempts at times but, if the
child tires or becomes restless, it is advisable to stop and to praise the
child for trying – this could result in better attempts in the future.
[4] When repeatability is not achieved, results should be labelled as
such.
Fig. 2. Expanded version of the early part of a subject’s volume-time
spirogram, illustrating back extrapolation through the steepest part of the
curve, where ow is peak expiratory ow (PEF), to determine the new
‘time zero’. Forced vital capacity (FVC) = 4 291 L; back extrapolated
volume (EV) = 0.123 L (2.9% FVC), back extrapolation line through PEF.
Fig. 3. Flow-volume curve exhibiting cough artefact (X) that can
inuence observed FVC and FEV1. Volume-time graphs are better for
evaluating end-of-test quality.
188 AJTCCM VOL. 28 NO. 4 2022
GUIDELINE
Test result selection
If there are a minimum of 3 acceptable manoeuvres measured and
the FVC and FEV1 are deemed as repeatable (be it for the pre- or
post-bronchodilator test), the largest FVC and largest FEV1 from these
acceptable and repeatable manoeuvres are selected irrespective from
which manoeuvre, the FEV1/FVC ratio is calculated from these 2 ‘best’
parameters. All other indices are determined from the best test which
is derived from the test with the largest sum of FVC and FEV1
Other derived indices
The PEF which is the maximum expiratory flow achieved from the
maximal forced expiration, starting without hesitation from the point of
maximal ination, is expressed in L/s.[1] PEF should be achieved within
the rst 25% of volume expired maximally from a maximal inspiration
(most subjects can achieve this within the first 15% of the expired
volume).[2] One should note, for comparison, that the PEF measured with
the Wright’s peak ow meter is in L/minute. e FEF25-75 is also known as
the maximum mid-expiratory ow. is parameter is dependent on the
validity of the FVC measurement and the degree of expiratory eort.[1,7]
Bronchodilator responsiveness test
The term ‘reversibility test’ has previously been used to denote a
signicant change which could be inferred to mean that complete
elimination of airway obstruction would occur; the term ‘bronchodilator
responsiveness test’ is now the preferred term.[2] e purpose of this test
is to determine the degree of improvement of airow in response to
bronchodilator therapy as measured by FVC and FEV1 changes.[2,7] e
choice of drug, dose and delivery mode is a clinical decision.[1, 2,7,9] If the
aim of the test is to determine whether the patient’s lung function can
improve with therapy while being on therapy, the patient is to continue
therapy as prescribed. If the aim is to aid in diagnosis using a change in
lung function owing to bronchodilator therapy, the patient must abstain
from bronchodilators prior to the test for a specied time according to
the bronchodilator in use (Table 4).
A standard bronchodilator test is performed as follows:
• e post-bronchodilator test can only be performed if the pre-test
was deemed acceptable and repeatable as described previously.
• A short-acting bronchodilator is administered after a gentle
expiration to residual volume (RV), or if not possible (for e.g., in
young children) a gentle expiration to functional residual capacity
(FRC) would be sucient. A dose of 100 mcg of salbutamol (or
equivalent) is gently inhaled in one breath to TLC. e breath is
then held for 10 s before exhaling. ree additional doses (total
dose 400 µg) are delivered at 30 s intervals. For children, the MDI
is administered through a face mask and a spacer for children <6
years and through a spacer with a mouthpiece for children >6
years. Ipratropium bromide (total dose 4 × 40 = 160 µg) can be
used as an alternative in adults.
• A waiting period of 10 - 15 minutes follows (30 minutes for
ipratropium bromide).
• ree acceptable tests of FEV1, FVC and PEF (of which 2 are
repeatable) must be performed.
• e best post-bronchodilator FEV1 and FVC are evaluated for
improvement compared with the best pre-bronchodilator FEV1 and
Fig. 4. Flow-volume curves exhibiting glottis closure (X) resulting in
premature termination of eort and reduced observed FVC.
Fig. 5. Flow-volume curve with a late peak. Failure to demonstrate
reproducibility will conrm these as submaximal eorts.
AJTCCM VOL. 28 NO. 4 2022 189
GUIDELINE
FVC. e percentage improvement in FEV1 can be calculated using
the formula: (FEV1 post-BD − FEV1 pre-BD/FEV1 pre-BD) × 100
(similarly FEV1 can be replaced with FVC in the aforementioned
formula). A signicant bronchodilator response is present if either
the FEV1 or FVC improves by 200 ml and 12%. Recent updated
recommendations suggest BDR is calculated as the change in FEV1
and FVC and is evaluated for improvement as a percentage of the
predicted; this value is calculated using the following formula:
(post-BD value − pre-BD value× 100)/predicted value.[11]
• Signicant bronchodilator responsiveness is present if either the
FEV1 or FVC improves by 200 ml and 12%, or if either FEV1
or FVC improves by >10% relative to the individual’s predicted
value for FEV1 or FVC. Owing to limited data, bronchodilator
responsiveness criteria are yet to be validated for children.[11]
In adults, there may be complete reversibility (when the post-
bronchodilator values recover to at least 80% of predicted) or
partial (when the post-bronchodilator values improve to less than
80% of predicted). Significant bronchodilator responsiveness
should always be seen in context. Although common in asthma, it
can also be detected in up to 55% of COPD subjects at some point
in their disease; similarly, asthmatics with uncontrolled airway
inammation may exhibit persistent airow limitation and not
demonstrate signicant bronchodilator responsiveness.[12]
Interpretation and reporting of results
Spirometry reference equations
Observed results should always be compared with an appropriate
reference population and expressed as percent observed/predicted.[1,2,4,7]
Predicted values for FVC and FEV1 are calculated from equations
based on age, height and sex at birth, as these parameters are
the major determinants of lung and airway size in healthy
individuals.[1, 2,7,13] Most oce spirometers are programmed with
many prediction equations derived from the study of patient cohorts.
e use of the Global Lung Function Initiative of 2012 (GLI 2012) is
currently recommended as the preferred set of predicted equations to
be used in SA.[6] e use of inappropriate predicted values can result in
a falsely increased rate of abnormal results in clinically normal people.[1]
Based on a prospective study of >3 500 healthy SA adults and children of
various ethnicities, SATS recommends the GLI 2012 reference equation
be used as follows: For SA black and mixed ethnicity populations, the
GLI ‘other’ reference equation (and not ‘black’) should be used when
performing spirometry. e GLI ‘white’ equation should be used for
white South Africans and the GLI ‘SE Asian’ for people of Indian
descent.[5,6]
Historical international guidelines for spirometry and the diagnosis
and management of chronic respiratory conditions have used 80% of
predicted FVC and FEV1 as suggested cut-o values, given the ease
of calculation and interpretation. is has recently been challenged
because of the age dependence of the percentage predicted, e.g. 80%
may be more than the lower limit of normal (>LLN) for a 45-year-old
adult but would be <LLN for a 12-year-old adolescent. From a scientic
perspective, the LLN has superior diagnostic accuracy and should be
preferentially used and always used in children and the elderly where
the xed cut-o of 80% predicted FVC and FEV1 may underestimate
disease in the young and overestimate it in the elderly.[1,10,14,15]
Categorisation of spirometric results
When interpreting spirometry, the focus should be on airow and lung
volumes to recognise patterns of altered physiology. ese results are
used to categorise physiology, but not for making a clinical diagnosis.[11]
Interpretation of spirometry should be clear, concise and informative to
help understand whether the observed result is normal and, if not, what
type of physiological impairment is most likely involved.
e initial assessment is based on a suggested algorithm (Fig. 7) that
employs three variables: FEV1/FVC%, FVC (% predicted) and FEV1
(%
predicted) or the LLN for these parameters. Pattern recognition
(see below) can also aid in this assessment. e FEV
1
/FVC% ratio of
<70% is still advocated by many as indicative of abnormality, despite the
fact that that such a crude approach may lead to an underdiagnosis in
young patients and an overdiagnosis in elderly patients, which should
be avoided.
[16]
e LLN (i.e. lower than lower 5th percentile), should
ideally be used, particularly for screening purposes and in borderline
cases.
[2]
Fig. 6. (A) Volume-time, and (B) ow-volume curves each demonstrating
three acceptable FVC trials, only #2 and #3 of which are reproducible.
190 AJTCCM VOL. 28 NO. 4 2022
GUIDELINE
An obstructive ventilatory defect is dened
as a disproportionate reduction in maximal
airflow from the lung with respect to the
maximal volume that can be displaced from
the lung, and per denition the FEV1/FVC
is <LLN.[7] e expiratory limb of the ow-
volume loop appears concave (Fig. 8), as ow
per volume is reduced. PEF is reduced, as is
the FEF25-75%. FVC can be normal or reduced.
Obstruction with reduced VC is most
oen due to air trapping, and the slow VC
may be preserved in such cases. Moreover,
plethysmography or gas distribution
assessment may then be indicated to evaluate
the residual volume (RV), total lung capacity
(TLC) and other lung-volume parameters.
A bronchodilator test should be performed
in patients with an obstructive ventilatory
defect, unless the indication for the test was
purely screening, in which case the patient
should be referred to a specialist. e Global
Initiative for Obstructive Lung Disease
(GOLD) organisation has dened COPD as
a post-bronchodilator FEV/FVC <70%; it is
now well recognised that there are patients
with clinical and imaging features of COPD
who exceed this ratio, i.e. >70%.[17,18]
A restrictive ventilatory defect is
characterised physiologically by a reduction in
TLC as determined by plethysmography or gas
distribution assessment (TLC per denition
<lower 5th percentile) and can be inferred on
spirometry when the FEV1/FVC% is normal
or high and the FVC is reduced (Fig. 9).
Several conditions can reduce FVC, including
pulmonary pathology (e.g. interstitial brosis),
chest wall and pleural disease (e.g. large
eusions) and neuromuscular diseases. Flow
is often relatively preserved in cases with
pulmonary pathology (owing to an increased
elastic recoil) but decreased in other causes.
Restrictive impairments are often over-
diagnosed, predominantly because of poor
effort (patient/operator) and inappropriate
reference values.[1]
Mixed obstructive-restrictive patterns
are sometimes seen, as some diseases (e.g.
bronchiectasis) may produce both patterns,
and some patients may have dual pathology (e.g.
COPD and interstitial pulmonary brosis). Both
the FEV1/VC and TLC should be <lower 5th
percentile. It may be challenging to categorise a
patient solely on spirometry to a mixed pattern,
and to distinguish these cases from obstruction
with reduced VC. Patients with mixed patterns
should therefore be referred to a specialist
centre for further investigations.
Variable and xed large airway obstruction
often gives rise to strikingly abnormal flow-
volume loops. Fixed obstruction causes a
‘hamburger’ spirometric pattern, so called
because of the shape of the resultant flow-
volume loop (Fig. 10). The inspiratory limb
is flattened (horizontal) with variable extra
thoracic obstruction, whereas the expiratory
limb is flattened
with variable intrathoracic
obstruction.
Grading of severity
Impaired lung function is generally graded
to quantify respiratory impairment/disability
for medicolegal purposes, and to optimise
and standardise treatment.[1] Current
guidelines suggest grading both obstructive
and restrictive ventilatory impairments
solely according to FEV1, as there is little or
no evidence for the use of FVC, VC or even
TLC as a parameter of impairment.[19] Pre-
bronchodilator FEV1 values should generally
be used when grading abnormal values (Table
7), with the exception of patients with COPD,
where post-bronchodilator values are used.
Large airway obstruction should not be graded
according to the FEV1.[1] Of note, the grading
system reported here is for general spirometry,
and differs from certain specific disease
entities, e.g. the GOLD statement for COPD.[20]
Although spirometry is oen sucient for
the evaluation of respiratory impairment,
this is not always the case, and further
investigations, e.g. carbon monoxide diusion
capacity (DLCO) and/or exercise testing may be
indicated, particularly in patients with clinical
evidence of interstitial lung disease or when a
disproportionate degree of dyspnoea is present
with a relatively preserved FEV1 and FVC.
Grading of quality of the test session
e standards are designed to help attain the
best results possible from a patient. Results
are more repeatable when all attempts are
performed maximally from maximal lung
volumes compared with sub-maximal eort
and lung volumes. A suggested grading system
(Table 8) has been developed that informs the
interpreter about the level of condence that
the spirometry results represent the best that
the patient was able to do at the time of the test
and the probability that a similar value would
be achieved should the test be repeated at a
later date.[2]
Reporting
Spirometry reports must contain the
following:
1. subject’s name
2. date and time of testing
Fig. 7. An algorithm for the categorisation of spirometry. Lower limit of normal (LLN) can be
used to replace the percentages of predicted.
AJTCCM VOL. 28 NO. 4 2022 191
GUIDELINE
3. subject’s age, sex at birth and race
4. subject’s height and weight
5. source of reference value (GLI 2012, recommended)
6. latest calibration date
7. numerical values and graphs (ow-volume as well as volume-
time) in order to assess acceptability and repeatability
8. basic categorisation.
The ATS recommends including the actual value, LLN, percent of
predicted and the z-score (optional) on a spirometry report, if possible.[11]
Note that spirometry, as outlined above, is oen used to conrm clinical
diagnoses and to grade the impairment, but should never be viewed
in isolation.[1,2] e nal assessment and interpretation of spirometry
requires knowledge of medicine and the patient’s full clinical details (e.g.
to diagnose COPD), and may also require further special investigations
(e.g. radiology, DLCO or plethysmography). Pulmonary function
technologists and related personnel should therefore reserve the basic
Fig. 8. Flow-volume curve exhibiting typical obstruction. Fig. 9. Flow-volume curve exhibiting a typical restrictive pattern.
Fig. 10. Example of xed large airway obstruction.
Table 7. Severity of any spirometric abnormality based on FEV1
Severity FEV1 (% predicted) z-score
Mild >70 -1.65 to -2.5
Moderate 60 - 69 -2.51 to -4.0
Moderately severe 50 - 59 -
Severe 35 - 49 >4
Very severe <35 -
is table is adapted from reference 2.
FEV1 = forced expiratory volume in the rst second.
192 AJTCCM VOL. 28 NO. 4 2022
GUIDELINE
interpretation to the categorisation of abnormalities and not comment
on the presence or absence of a clinically relevant disease process.
Spirometry training and certication
Basic skills
Operators must understand the principles of spirometry summarised
in this statement, be able to calibrate the equipment, ensure optimal
subject co-operation, provide acceptable repeatability results and
categorise common abnormalities (taking relevant reference values
into consideration).
Personnel
Pulmonary clinical technologists, general practitioners certied to
practise occupational health, specialist physicians and pulmonologists
are trained to perform basic spirometry. Pulmonary clinical
technologists are competent to perform advanced lung function tests,
which are best interpreted by qualied pulmonologists or specialist
physicians with an interest in respiratory medicine.
e need to train other healthcare professionals (e.g. nurses) to
perform basic spirometry is well recognised, given the paucity of
trained personnel.
Declaration. RM,BWA, RNvZS and CFNK are members of the editorial
board.
Acknowledgements. The authors thank the other members of the council
of the SATS for their assessment and approval of this manuscript.
Author contributions. The manuscript was prepared by DM and CK, and
critically reviewed by all co-authors.
Funding. None.
Conflicts of interest. None.
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ajrccm.160.6.9902042
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Accepted 6 October 2022.
Table 8. Grading system for FVC and FEV1 (graded separately)
Grade Number of measurements Repeatability: Age >6 yrs Repeatability: Age <6 yrs
A ≥3 acceptable Within 0.150 L Within 0.100 L*
B 2 acceptable Within 0.150 L Within 0.100 L*
C ≥2 acceptable Within 0.200 L Within 0.150 L*
D ≥2 acceptable Within 0.250 L Within 0.200 L*
E ≥2 acceptable
or 1 acceptable
>0.250L
n/a
>0.200 L
n/a
U 0 acceptable and ≥1 usable n/a n/a
F 0 acceptable and 0 usable n/a n/a
FVC = forced vital capacity; FEV1 = forced expiratory volume in the rst second; n/a = not applicable.
*Or 10% of the highest value, whichever is greater; this applies to patients ≤6 years only.
e repeatability grade is determined for the set of prebronchodilator and post-bronchodilator manoeuvres separately. e repeatability criteria are applied to the dierences between the two largest FVC
values, likewise with the FEV1 values. Grade U indicates that only usable but not acceptable measurements were obtained. Although some attempts may be acceptable or usable at grading levels lower than
A, the overriding goal of the operator must be always to achieve the best possible testing quality for each patient.
is table is adapted from Graham et al.[2]
