Pulmonary function test and role in asthma diagnosis and monitoring

Pulmonary Function Test
and Role in Asthma
Diagnosis & Monitoring
Topic Review
December 4th, 2020
Rapisa Nantanee, M.D.
Pediatric Allergy and Immunology Unit
King Chulalongkorn Memorial Hospital

Outline
• Pulmonary Function Test
• Spirometry
• Interpretation
• Asthma diagnosis
• Asthma monitoring
• PFT in COVID-19 pandemic

Spirometry
• Key Updates
• A new list of relative contraindications was added.
• Spirometers are now required to meet International Organization for Standardization (ISO)
26782 standards, but with a maximum permissible accuracy error of ± 2.5%.
• Device quality assurance procedures were updated.
• Operator training as well as attainment and maintenance of competency were addressed.
• The list of activities that patients should avoid before testing was updated.
• There is a focus on the use of devices that measure both expiration and inspiration.
• Maneuver acceptability and repeatability criteria were updated. The end of forced
expiration (EOFE) was redefined.
B. L. Graham, et al. Standardization of Spirometry 2019 Update. An Official ATS and
ERS Technical Statement. Am J Respir Crit Care Med. 2019 Oct 15;200(8):e70-e88.

Spirometry
• Key Updates (continued)
• Requirements for spirometry systems to provide uniform cues and feedback to the
operator were added.
• New withholding times for bronchodilators before bronchodilator responsiveness
testing were developed.
• A new grading system for assessment of spirometry quality was developed.
• Standardized operator feedback options that promote synoptic reporting were
developed.
• Preliminary findings derived from an international patient survey were presented.

Spirometry
• A physiological test that measures the maximal volume of air
that an individual can inspire and expire with maximal effort.
• Volume or flow as a function of time
• FVC: The volume delivered during an expiration made as forcefully and
completely as possible starting from full inspiration
• FEV1: The expiratory volume in the first second of an FVC maneuver.

Indications

Relative
Contraindications
• The forced expiratory
maneuver used in
spirometry increases
intrathoracic,
intraabdominal, and
intracranial pressures.
• The physical effort required
can increase myocardial
demand.

Relative Contraindications
• Spirometry should be discontinued if the patient experiences
pain during the maneuver.
• Patients with potential contraindications may be tested in a
pulmonary function laboratory where operators are more
experienced and there may be access to emergency care if
needed.

Laboratory Details
• Record ambient temperature, barometric pressure, and time of
day
• Quiet and comfortable environment, separated from the waiting
room and other patients being tested
• The patient should be seated erect, with shoulders slightly back
and chin slightly elevated.
• A noseclip or manual occlusion of the nostrils should be used.

Hygiene and Infection Control
• To prevent the transmission of infection to patients and staff during pulmonary function
testing.
• The operator must wash her or his hands or use an approved hand sanitizer before
contact with each new patient.
• The patient should be given an approved hand disinfectant gel or wipe upon first entry into the
testing station.
• Disposable, in-line filters for spirometers
• All disposable items, including filters, mouthpieces, noseclips, and gloves, must be disposed of at
the end of the testing session.
• Infected patients
• Reserving equipment for the sole purpose of testing infected patients
• Testing at the end of the workday
• Testing in their own rooms with adequate ventilation and appropriate protection for the operator.

https://www.wikiwand.com/en/Spirometry

Equipment
• All spirometers meet the standards contained in the current
update of ISO 26782.
• Maximum permissible error of ± 2.5%
• Standards for diffusing capacity specify a volume accuracy of ±
2%.

Display
• For optimal quality control, both volume–time and flow–volume real-time
displays are required, and operators must visually inspect the performance of
each maneuver for quality assurance before proceeding with another maneuver.
• Flow–volume graph
• Expiratory flow must be plotted upward, and expiratory volume must be plotted toward the
right.
• A 2:1 aspect ratio must be maintained between the flow and volume scales.
• Volume–time graph
• Begin at the point of maximum inspiration or 1 second before Time 0, whichever occurs
first.
• The display of the maneuver should continue to the end of the plateau or the beginning of
inspiration.

BTPS Adjustment
• All spirometry outcomes must be reported at BTPS (body
temperature, ambient barometric pressure, saturated with water
vapor).
• Changes in spirometer or flow sensor temperature can be a
source of variability.
• Spirometer temperature should be measured and not assumed to be
constant, even over the course of one testing session.

Operator Details
• Observe and engage with the patient to achieve optimal results
• Operator training and attainment and maintenance of
competency must be integrated in any spirometry testing
service.

Patient Details
• The patient’s age, height, and weight (wearing indoor clothes
and without shoes) are recorded.
• Preferable to calculate age using the date of birth and the date of the
test
• Birth sex and ethnicity
• Ethnicity categories for the Global Lung Function Initiative (GLI)
reference values are white (i.e., European ancestry), African American,
Northeast Asian, Southeast Asian, and other/mixed.

Patient Preparation
• Patients should be as relaxed as possible before and during the
tests.
• Patients should be asked to loosen tight-fitting clothing.
• Well-fitting dentures are usually left in place.
• Withhold long- and short-acting bronchodilators before testing?
• To diagnose an underlying lung condition, then withholding bronchodilators
before testing is useful.
• To determine a response to an existing therapeutic regimen, bronchodilator
medications are generally not withheld.

B. Thompson, C. G. Irvin. Middleton’s 9th ed. Chapter 42.

FEV1 and FVC Maneuver
• Test Procedure: 4 distinct phases of the FVC maneuver:
• 1) maximal inspiration
• 2) a “blast” of expiration
• 3) continued complete expiration for a maximum of 15 seconds, and
• 4) inspiration at maximal flow back to maximum lung volume
• Most of the variability in results relates to
• Inadequate and variable inspiration to TLC, ending the expiration
prematurely, and variable effort.

• 1) Maximal inspiration
• The preceding inspiration be rapid and any pause at full inspiration be minimal (≤
2 s).
• “Inspire as deeply as possible”
• Indicators of maximal inspiration include eyebrows raising or eyes widening, and
sometimes the head begins to quiver.
• 2) a “blast” of expiration
• 3) continued complete expiration for a maximum of 15 seconds, and

• 2) Maximal expiration
• At full inflation, without hesitation, the patient should be prompted to “blast,” not just “blow,” the
air from their lungs, and then he or she should be encouraged to fully expire.
• The spirometry system must signal the operator when a plateau has been reached or forced
expiratory time (FET) reaches 15 seconds.
• If the patient is able to see a volume–time trace still moving as they blow and/or a numeric or
analog display of flow in mL/s, this might help motivate them to keep blowing. Children may
benefit from incentive displays.
• 3) continued complete expiration for a maximum of 15 seconds

Acceptable

• 2) Maximal expiration
• 3) continued complete expiration for a maximum of 15 seconds
• 4) Maximal inspiration after forced expiration
• Upon completing the forced expiration, the patient should remain on the mouthpiece,
and the operator should again coach the patient to rapidly inspire to full inflation. This
will provide a measure of forced inspiratory VC (FIVC).
• Comparison of the FIVC with the FVC will provide feedback to the operator on
whether the patient began the forced expiration from full inflation.

• With appropriate coaching, children as young as 2.5 years old
with normal cognitive and neuromotor function are able to
perform acceptable spirometry.
• Specifically trained operators, child-friendly environment,
encouragement, detailed but simple instructions, lack of intimidation,
and visual feedback in the teaching

Within-Maneuver Evaluation
• The following criteria were developed as objective measures
to determine whether a maximal effort was achieved and
acceptable FEV1 and/or FVC measurements were obtained.
• However, in some cases, maneuvers that do not meet all of the
criteria may be the best that the patient is able to do on that
occasion, and although the FEV1 and/or FVC measurements
are not technically acceptable, they may be clinically useful
(i.e., “usable”).

Defines
Time 0
The back-extrapolated
volume (BEV) is the
volume of gas that has
already been expired
from maximal lung
volume to Time 0 and is
included in the FEV1
and FVC
measurements.
BEV must be <5% of
the FVC or 0.100 L,
whichever is greater.

The hesitation time, defined as
the time from the point of maximal
inspiration to Time 0 should be 2
seconds or less.
Acceptable maneuver with a
hesitation time of 0.62 s.
A hesitation time of 2.21 s which
should generate a warning and a
message to instruct the patient to
blast out immediately when
completely full.

- A large BEV will usually result in an erroneously high FEV1.
- Patients with upper airway obstruction or neuromuscular disease are often
unable to initiate a rapid increase in flow, and the BEV limit may be exceeded.
- The operator must have the ability to override the BEV acceptability
designation for such patients.

Within-Maneuver Evaluation
• BEV must be <5% of the FVC or 0.100 L, whichever is
greater.
• The hesitation time should be 2 seconds or less.
• The rise time from 10% to 90% of peak flow should be ≤150 ms.
• But may be greater than this in a maneuver in a patient with upper
airway obstruction.

End of forced expiration (EOFE)
• To ensure that a true FVC has been achieved.
• Achieving 1 of the following 3 recommended indicators of EOFE is
required:
1. There is less than a 0.025-L change in volume for at least 1 second (a “plateau”).
OR
2. The patient has achieved an forced expiratory time (FET) of 15 seconds. OR
3. The patient cannot expire long enough to achieve a plateau (e.g., children with high
elastic recoil or patients with restrictive lung disease). - repeatedly achieve the
same FVC.
• The FVC must be greater than, or within the repeatability tolerance of, the largest FVC
observed before this maneuver in the current testing set.

• Acceptable FEV1 measurement may be obtained from a
maneuver with early termination after 1 second.
• For children aged 6 years or younger, an acceptable FEV0.75
(the forced expiratory volume in the first 0.75 s) may be
obtained from a maneuver with early termination after 0.75
seconds.
• No requirement for a minimum FET.

• FEV1 and FVC measurements from a maneuver with FIVC – FVC >
0.100 L or 5% of FVC, whichever is greater, are not acceptable.
• If the volume of the maximal inspiration (i.e., FIVC) after EOFE is greater than
FVC, then the patient did not start the maneuver from TLC.
• A cough during the first second of the maneuver can affect the
measured FEV1 value, and the FEV1 from such a maneuver is
neither acceptable nor usable.
• However, the FVC may be acceptable.

• Glottic closure or early termination, such as inspiration or
coming off the mouthpiece, renders FVC unacceptable.
• If it occurs in the first 1 second, renders FEV1 unacceptable and
unusable.
• The first 0.75 seconds - FEV0.75 unacceptable and unusable.
• Obstruction of the mouthpiece (e.g., by the tongue being
placed in front of the mouthpiece, by teeth in front of the
mouthpiece, or by distortion from biting) may affect the
performance of either the device or the patient.

• Maneuvers conducted with an erroneous zero-flow level will
either under-or overestimate FEV1 and FVC.
• Both FEV1 and FVC neither acceptable nor usable.
Not acceptable/usable

Operator feedback
• The spirometry system software must provide explicit feedback
to the operator indicating FEV1 and FVC acceptability at the
completion of each maneuver.
• The operator must have the ability to override the
acceptability designation.
• Because the operator may note a leak, a cough, inadequate inspiration
or expiration, or a faulty zero-flow level that was not detected by the
software.

Between-Maneuver Evaluation
• The goal of each prebronchodilator testing set and post-
bronchodilator testing set is to achieve a minimum of three
acceptable FEV1 and three acceptable FVC measurements.
• If these criteria are not met in three maneuvers, additional trials must
be attempted, up to eight maneuvers in adults, although more may
be done in children.

BEV must be <5% of the FVC or 0.100 L,
Repeatability criteria
- Age > 6 yr: The difference between the largest and the next
largest FVC and FEV1 is ≤ 0.150 L
- Age ≤ 6 yr: The difference between the largest and the next
largest FVC and FEV1 ≤ 0.100 L or 10% of largest FVC,

Bronchodilator Responsiveness
Testing
• A determination of the degree of improvement of airflow in
response to bronchodilator administration
• If the aim of the test is to determine whether the patient’s spirometric
lung function can be improved with therapy in addition to their
regular treatment -- may continue with regular medication before the
test.
• If the test is used for diagnosis or to determine whether there is any
change in spirometric lung function in response to bronchodilators --
withhold bronchodilators before baseline testing.

Testing
Inhaled
corticosteroids and
leukotriene
modifiers need not
be withheld.

Testing
• Because normal baseline spirometry does not rule out a bronchodilator
response, all initial spirometry done for diagnostic reasons should be
performed before and after bronchodilator administration.
• Thereafter the clinician may choose to perform spirometry without bronchodilator
responsiveness testing, but it is important to consider baseline variability in lung
function when making this decision.
• Monitoring lung function by serial spirometry, especially in patients with
obstructive lung disease, may be more useful by following
postbronchodilator values.

Testing
1. Performs prebronchodilator spirometry to achieve three
acceptable FEV1 and FVC measurements.
2. Bronchodilator is administered.
3. Three or more additional post-bronchodilator acceptable FEV1
and FVC measurements

When using an MDI in young children
(< 5 years) the use of a facemask has
been suggested during tidal breathing
bronchodilator inhalation.

- 5 mg of albuterol sulfate inhalation
solution is nominally equivalent to 400
μg by MDI, and 1 mg of ipratropium
bromide inhalation solution is nominally
equivalent to 80 μg by MDI (54, 55).
- The driving gas should be air.
Routine use of 100% oxygen as the
driving gas for a jet nebulizer for
bronchodilator responsiveness testing
is not recommended.

Testing
• The 2005 ATS/ERS Spirometry Standards example used a dose of
400 μg albuterol or 160 μg ipratropium by MDI to ensure that the
response was high on the dose–response curve.
• A combination of ipratropium bromide and albuterol has demonstrated an
increased response compared to either of the individual agents alone in
identifying responsiveness in COPD patients.
• When using ipratropium only, the recommended wait time is 30 minutes.

Reported Values
• The largest FVC and the
largest FEV1
• FEV1/FVC
• The largest value from
maneuvers meeting the
acceptability criteria for FEV1.
• FIVC, PEF.
• FET from the maneuver with
the largest FVC.

Reported Values
• Children aged 6 years or younger have relatively large
airways compared with their lung volume and may complete
expiration in <1 second.
• FEV0.75 should be reported and if FET is >1 second, then FEV1 should
also be reported.
• The mean forced expiratory flow, midexpiratory phase (FEF25-
75), may be reported from the maneuver with the largest sum of
FEV1 and FVC.

Grading the Quality of the Test
Session

Classification of ventilatory function
patterns
• Obstructive defects
• Restrictive defects
• Mixed obstructive/restrictive defects
• Non-specific ventilatory patterns
Borg BM, et al. Interpretation of Lung Lunction–A step by Step Guide.
2014 Oxford Wiley Blackwell.

Spirometry
parameters
alone

Normal Restrictive
ventilatory
pattern
Suboptimal
effort
Obstruction
with gas
trapping
Gas trapping and
hyperinflation

Analysing the shape of the flow–volume curve
Normal Normal Airway
obstruction
with almost
complete
reversibility
Airflow
obstruction
Restriction Obstruction

Upper airway obstruction
Normal Intrathoracic upper airway
obstruction
Fixed upper airway
obstruction
Extrathoracic
upper airway
obstruction.

D. Czovek. Kendig’s Disorders of the Respiratory Tract in Children, 9th ed. 2019. Chapter 11.

M. Gallucci, et al. Front. Pediatr. (2019) 7:54.

Lung function testing during COVID-19
pandemic and beyond
• Lung function tests (LFTs) often generate aerosols in the form
of droplets due to patients coughing and testing often requires
generation of high minute ventilation and flow rates.
• LFTs therefore pose a considerable risk for the spread of infection to
individuals and surrounding surfaces within and around the test areas
even in asymptomatic patients.
Recommendation from ERS Group 9.1 (Respiratory function technologists /Scientists)
https://ers.app.box.com/s/zs1uu88wy51monr0ewd990itoz4tsn2h

Lung function testing during COVID-19
pandemic and beyond

Recommendations for Pandemic Phase -
Level 1 safety
• We do not recommend any patients with symptoms of COVID-19 or flu like
symptoms are tested under any circumstances at this time.
• Postpone all routine testing during the critical phase of this crisis.
• COVID patients must not be tested for a minimum of 30 days post
infection.
• For highest risk patients requiring essential testing, lung function
should be carried out in a negative pressure room and using equipment
only for purpose of high risk or infected patients.
• Exercise testing, nebulisation, bronchial challenge tests, and other aerosol
generating procedures should be postponed at this time.

Recommendations for Post Peak Phase -
Level 2 safety
• All testing procedures can be reintroduced with extra
precautions (Full PPE and appropriate mask should be guided
by local policy).
• Exercise testing, nebulisation, bronchial challenge tests, and
other aerosol generating procedures should be limited to
specific equipment and testing rooms.
• Use filters to minimise escape of aerosol from the exhalation ports
when using nebulisers.

Recommendations for Post Pandemic
Phase - Level 3 safety
• Return to Pre-COVID-19 standards for the delivery of lung
function services.

Pulmonary function test and role in asthma diagnosis and monitoring

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