Document Number # QH-GDL-391:2013
Static Lung Volume
Measurement by body plethysmography, helium dilution, and nitrogen
washout methods
Respiratory Science
Custodian/Review Officer:
Chief Allied Health Officer
Version no: 1.0
Applicable To:
All Health Practitioners performing adult
and paediatric spirometry
Approval Date: DD/MM/YYYY
Effective Date: 26/11/2012
Next Review Date: 26/11/2013
1. Purpose
This guideline provides recommendations regarding best
practice to support high quality measurement of static
lung volumes and capacities using body
plethysmography, helium (He) dilution and nitrogen (N2)
washout methods throughout Queensland Health
facilities.
2. Scope
This guideline provides information for all health
practitioners who perform static lung volume testing in
adult and paediatric patients over 7 years of age.
For more thorough evaluation of lung function, spirometry
should be performed before static lung volume
measurements.
3. Related documents
Authority:
Chair – State-wide Clinical Measurements
Network
Approving Officer
Chief Allied Health Officer
Supersedes: New Documentl
Key Words: spirometry, spiro, respiratory,
measure, spirogram, spirometric,
bronchodilator, flow-volume loop, peak
flow, lung volume, SLV
This guideline is primarily based on the following
documents:
Miller, M. R., R. Crapo, et al. (2005). General
considerations for lung function testing. European
Respiratory Journal 26(1): 153-161. 1
Wanger, J., J. L. Clausen, et al. (2005).
Standardisation of the measurement of lung volumes.
European Respiratory Journal 26(3): 511-522. 2
References from alternate sources of information have
been identified in this document.
Policy and Standard/s:
Accreditation References:
EQuIP and other criteria and standards
Informed Decision-making in Healthcare (QH-POL346:2011) 3
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Procedures, Guidelines, Protocols
Australian Guidelines for the prevention and control of infection in healthcare
(CD33:2010) 4
2005 American Thoracic Society and European Respiratory Society (ATS/ERS)
guidelines 1, 2, 5
Queensland Health Guideline: Spirometry (Adult) 6
Queensland Health Guideline: Spirometry (Paediatric)
Forms and templates
Nil
4. Guideline for performing static lung volume measurements
4.1. Emergency Protocol
Follow relevant Hospital and Health Service protocols or procedures in the event of an
emergency.
4.2. Infection Control Procedures
Testing patients with confirmed or suspected communicable diseases may pose a risk
to staff and other patients due to potential cross-infection. See Appendix 1 for detailed
infection control procedures.
Adhere to relevant Hospital and Health Service infection control protocols or
procedures at all times and in all facets of lung volume testing. Specific infection control
procedures pertaining to lung volume testing are outlined in Appendix 1: Infection
Control Procedures.
Australian Guidelines for the prevention and control of infection in healthcare
(CD33:2010) 4
4.3. Gaining Consent
Gain consent in accordance with Queensland Health’s Informed Decision-making In
Healthcare Policy 3.
4.4. Identifying Indications and Contraindications for performing static lung
volume measurements
Indications for performing static lung volume measurements
Static lung volume measurements have a variety of uses including:
assisting with diagnostic evaluations 7
monitoring and assessment of pulmonary function 8
evaluating disability or impairment 8
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providing public health information.
For further indications refer to Appendix 2: Purposes for performing spirometry and static
lung volume measurements.
Contraindications for performing static lung volume measurements
The following are contraindications for spirometry testing 9, which is performed prior to
static lung volume measures:
Some conditions may pose a relative danger to a patient or affect the validity of spirometry
performance and results. These include, but are not limited to the following:
unstable cardiovascular status, unstable angina, recent myocardial infarction (within
one month), or pulmonary embolism
haemoptysis of unknown origin
recent pneumothorax
thoracic, abdominal, or cerebral aneurysms
recent thoracic, abdominal or eye surgery
acute disorders such as nausea or vomiting
severe respiratory distress
physical limitations
cognitive impairment, dementia.
In addition to the above contraindications, the below contraindications apply to static lung
volume measures:
Body Plethysmography
With respect to total body plethysmography, such factors as claustrophobia, upper
body paralysis, obtrusive casts, intravenouslines or any factor that can limit the
patient’s access into the box.
Patients over 150kg should be tested with caution. Refer to manufacturer’s
recommendations for maximum weight limit.
If the patient is unable to weight bear on their own and move from wheelchair to the
body plethysmograph unaided, and when wheelchair accessible plethysmograph is not
available. (In this situation enquire with the requesting physician if the test is necessary
for the patients treatment, and offer helium dilution or nitrogen washout techniques as
an alternative test)
Temporary interruption of supplemental oxygen and intravenous fluids.
Note: Body plethysmography measures the total compressible gas volume in the thorax,
and its accuracy is not affected by the presence of poorly ventilated airspaces.
Note: Body plethysmograph can be repeated within a short period of time. There is no
long recovery time between manoeuvres as required in the gas dilution method.
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Nitrogen washout (absolute contraindication)
Patients currently receiving Bleomycin treatment 10
Note: The helium dilution and nitrogen washout methods underestimate absolute lung
volumes in patients with airflow obstruction because some areas of lung are insufficiently
ventilated. For example, in patients with emphysema, or with bullous disease the lung
volumes with these techniques are usually underestimated.
4.5. Facilities and equipment
Testing Facilities
Ensure clearly defined rooms are available, particularly for patients with confirmed or
suspected communicable diseases, and immuno-compromised patients. Specific
infection control procedures are outlined in Appendix 1: Infection Control Procedures.
For paediatric patients, the testing environment should be child–friendly 11
Spirometer (incorporated into the static lung volume equipment)
Ensure the technical specifications for spirometers or pneumotachs for the
measurement of lung volumes and forced inspiratory and expiratory volumes comply
with the ATS/ERS guidelines 1, 2.
Ensure helium dilution flow is greater than 7 L.s-1; for nitrogen washout 0 - 6L.s-1.
General supplies:
Stadiometer, scales, tape measure
Validated 3L-volume calibration syringe
In-line bacterial/viral filter mouthpiece and nose clip
Plethysmograph
Plethysmograph (body box) with specifications that comply with the ATS/ERS
guidelines 2.
NOTE: There are several types of plethysmographs. Refer to Appendix 3: General
principles of static lung volume measurements for further information.
Nitrogen Washout
Nitrogen washout equipment and associated accessories with specifications that
comply with the ATS/ERS guidelines 2.
Medical Grade 100% oxygen
Calibration gas cylinder (approx. 16% O2, 4% CO2).
Helium Dilution
Helium dilution equipment and associated accessories with specifications that comply
with the ATS/ERS guidelines 2.
Medical Grade 100% oxygen
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Helium cylinder with appropriate gas mixture and according to manufacturer’s manual.
4.6. Training requirements
All health professionals performing spirometry should as a minimum complete the
Queensland Health Spirometry Training Program or another spirometry training to an
equivalent standard 12.
4.7. Preparing for the test
4.7.1. Key measures and terminology
Static lung volume is the volume of gas within the lung and can be measured using body
plethysmography, helium dilution and nitrogen washout techniques. These methods
measure various capacities and volumes as shown in Figure 1: functional residual
capacity (FRC), total lung capacity (TLC), vital capacity (VC, IVC or EVC), inspiratory
capacity (IC), tidal volume (TV), residual volume (RV), expiratory reserve volume (ERV)
and inspiratory reserve volume (IRV). The FRC and VC (IC plus ERV) are the key
components in the measurement of static lung volumes from which RV and the TLC can
be derived.
Figure1. Spirogram showing the main lung volumes and capacities that are measured or
derived during the measurement of TLC taken from Wagner (2005). 2
For more detailed principles underpinning the three techniques see Appendix 3: General
principles of static lung volume measurements and Section 5: Definitions of terms.
4.7.2. Preparing equipment and ensuring quality control
See Appendix 4: Quality Control Procedures.
Refer to relevant manufacturer’s operations manual for equipment calibration,
preparation and quality control guidelines.
For pneumotach calibration, refer to Appendix 4: Quality control procedures.
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Ensure adequate warm-up period of at least 30 min.
Perform daily calibration according to manufacturer’s instructions.
Attach new in-line viral/bacterial filter mouthpiece for each patient.
Adjust the dead space volume, according to manufacturer’s instructions; particularly if
other than regular mouthpieces are used.
4.7.3. Preparing the patient
Ensure all infection control measures are carried out prior to testing, particularly hand
washing for both patients and personnel performing static lung function testing. See
Appendix 1 for further infection control details.
The patient’s details such as name, hospital identification number, date of birth,
gender, weight, height, ethnic origin and indications for the test will already be recorded
on the system as it is recommended that spirometry is performed prior to performing
static lung volumes.
Patient preparation regarding medications is as per the Queensland Health Guideline:
Spirometry (Adult and Paediatric documents); as spirometry is performed prior to lung
volume measurements.
Tight clothing, braces or vests may restrict full chest expansion and should be
loosened or removed 1.
Interruption of supplemental O2 is necessary during measurements of body
plethysmography and nitrogen washout. If it is safe to do so, supplemental O 2 should
be discontinued for at least 10 minutes before beginning the N2 washout test. In such
patients, prior to performing the test and whilst disconnected from the supplemental
oxygen, continuous monitoring of oxygen saturation should be performed. If this cannot
be done safely, the interval of time off O2 must be recorded, and the results interpreted
with caution.
The patient should be clearly instructed in the procedure prior to the commencement of
the test and also be provided with ample opportunity to ask questions or receive
clarification regarding the test and its requirements.
Dentures should be left in place unless they interfere with the testing procedure or the
patient’s ability to perform the procedure as required 2.
Instruct the patient to place the nose clip on the nose, and mouth over the mouthpiece
ensuring a tight seal is maintained during testing. A flanged rubber mouthpiece can be
used if the patient is unable to maintain a tight seal.
4.8. Plethysmography 2
The patient should be seated comfortably in the plethysmograph with legs uncrossed
and feet flat on the ground. Adjust the seat height or the level of the mouthpiece so that
the patient does not need to flex or extend the neck.
Inform the patient that the plethysmograph door will be closed during the test and they
will be able to hear test instructions through the intercom. They should also be shown
how to open the door of the box from the inside.
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Explain the procedure in detail and demonstrate the panting technique emphasising the
frequency of the panting, between 0.5 - 1 Hz (1-2 pants per second). Advise the patient
that the cheeks need to be supported by both hands and the nose clip must be in place
during the manoeuvre.
Close the plethysmograph door and ensure that the microphone is functional.
Activate the software program according to the manufacturer’s instructions and allow
the instrument an appropriate period for the thermal transients to stabilise and the
patient to relax.
Adjust the volume scale if necessary to accommodate larger or smaller TLC
measurements.
Instruct the patient to place the nose clip on, their mouth over the mouthpiece, ensuring
a tight seal, and to commence normal tidal breathing until there is a stable end-tidal
expiratory volume displayed (usually 3-10 breaths).
When the patient is at or near FRC, the shutter is closed at end-tidal expiratory volumeexpiration for 2-3 seconds during which time the patient is instructed to gently pant at a
frequency of 0.5-1 Hz (1-2 pant per second), supporting their cheeks with both hands
(to minimise puffing of cheeks).
Advise the patient to continue panting against the shutter.
Record 3-5 technically satisfactory panting manoeuvres. These are displayed as a
series of almost superimposed straight lines on the pressure-volume plot.
The FRCpleth measurement is the volume of intrathoracic gas measured when airflow
occlusion occurs at FRC. Dependent on the system software a correction can be made
for a switch in/switch out error (i.e. shutter not closed at FRC). Refer to manufacturer’s
instructions.
Option 1
When the shutter is opened instruct the patient to expire fully to RV, then steadily
inspire to TLC, before returning to normal tidal breathing. This is the FRCpleth – ERV –
IVC linked manoeuvre (i.e. the patient stays on the mouthpiece for the entire
manoeuvre).
If necessary the patient can rest between linked FRCpleth – ERV – IVC manoeuvres.
Option 2
When the shutter is opened instruct the patient to breathe normally to ensure the
baseline end-tidal expiratory volume has not changed (normally due to a leak at the
mouthpiece during panting). When satisfied the baseline end-tidal expiratory volume is
unchanged, instruct the patient to inspire fully to TLC then steadily expire to RV. This is
the FRCpleth – IC – VC linked manoeuvre (i.e. the patient stays on the mouth piece for
the entire manoeuvre).
If necessary the patient can rest between linked FRCpleth – IC – VC manoeuvres.
Option 3
Note: Only use option 3 if options 1 and 2 cannot be performed by the patient
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Perform FRCpleth only. This can then be coupled with separately measured IC/ERV-VC
linked manoeuvres, which may be performed with the plethysmograph door open.
Perform at least three repeatable panting manoeuvres and three acceptable VC
manoeuvres the two largest of which are within 0.15L (see acceptability and
repeatability criteria below and the Queensland Health Guidelines: Spirometry (Adult
and Paediatric).
Note: For individuals who cannot pant, follow the paediatric instructions outlined below for
an alternative manoeuvre.
Note: During rest periods, the door may be opened, if necessary. Ensure appropriate
equilibration time elapses before resuming the test. Consult equipment manufacturer’s
instructions.
4.8.1. Paediatric test procedure
2
Children able to perform spirometry will be capable of performing the FRCpleth test.
Older children are usually able to perform methods 1 and 2 above. In young children
who cannot perform the panting manoeuvre an alternative is to perform a rapid IC
manoeuvre against a closed shutter which is described below. In this case the TGV
must be calculated using the complete TGV computation equation. For a detailed
explanation see Appendix 5: Complete TGV computation equation.
A parent/carer may accompany the child in the plethysmograph, and if this is the case,
the mass of the accompanying person must be accounted for 13.
The patient should be seated comfortably in the plethysmograph and without the need
to flex or extend the neck when on the mouthpiece.
The patient should be informed the door will be closed during the test and there is an
intercom so they will be able to hear test instructions. Also show how easily the box
can be opened.
If there is an accompanying person, instruct them to cease breathing during the shutter
occlusion 13.
Explain the manoeuvre which is a rapid inspiration against the closed shutter.
Close the plethysmograph door and ensure that the microphone is functional.
Activate the software program according to the manufacturer’s instructions and allow
the instrument an appropriate period for the thermal transients to stabilise and patient
to relax.
Volume scale can be adjusted if necessary to accommodate larger or smaller TLC
measurements/volumes.
Instruct the patient to place the nose clip on nose, mouth over the mouthpiece,
ensuring a tight seal, and to commence normal tidal breathing until there is a stable
end- expiratory volume displayed (usually 3-10 breaths).
When the patient is at or near FRC, the shutter is transiently closed at end-expiration
for 0.5-1 second during which time the patient is instructed to rapidly inspire. The
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duration of the attempted inspiration must be less than 0.8 sec to avoid problems due
to thermal drift 14.
Encourage the child to keep the mouth over the mouthpiece.
When the shutter releases, instruct the child to inspire fully, followed by an expired vital
capacity.
Remove the mouthpiece and rest briefly before a repeated attempt.
4.8.2. Analysing the plethysmography results
The graphic results for each manoeuvre should be reviewed using the appropriate tools in
the software. Adjustments can be made manually if necessary to alter the TLC, FRC and
RV lung subdivisions. The FRCpleth slopes can also be manually altered to achieve the line
of best fit if the software default measurements are incorrect.
4.8.3. Determining acceptability and repeatability of the results
Vital Capacity (VC)
See Appendix 6: Determining acceptability and repeatability criteria for spirometry.
FRCpleth
Within manoeuvre criteria
Individual panting manoeuvres are deemed acceptable if:
The panting manoeuvre shows a closed loop without drift or artefact. If thermal
equilibrium has not been reached the loop tends to be open and to drift across the
screen.
Stable end-tidal expiratory level is reached in 3-10 breaths
Shutter should be activated near FRCpleth (i.e end-tidal volume)
Panting frequency is approximately 0.5-1 Hz.
Pressure changes of ±10cmH2O (this should be within the range over which the
transducers were calibrated i.e. the tracing does not go off the screen otherwise
inaccuracies in measurements may occur)
Each pant should superimpose with little thermal drift.
Ideally a VC manoeuvre should be performed following each FRCpleth measurement,
however this may prove difficult in some patients (see Option 3).
FRC measurements should be linked to technically satisfactory ERV/IVC or IC/VC
manoeuvres.
Between manoeuvre criteria
At least 3 FRCpleth values that agree within 5% (difference between the highest and
lowest value divided by the mean is ≤ 0.05) 2.
For the VC manoeuvre acceptability and repeatability criteria see Appendix 6:
Determining acceptability and repeatability.
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4.8.4. Reporting plethysmography results
All volumes are to be reported at BTPS conditions and in litres (L) to two decimal
places.
The final report should include:
—
Scientist’s comments regarding acceptability and repeatability of the data.
—
Software version (if applicable).
—
Date, time and results of most recent calibration.
—
Identification of reference values used.
Option 1
Reported FRCpleth is the mean of at least 3 acceptable FRCpleth values in litres (L) to two
decimal places.
Reported VC is taken from the largest acceptable and repeatable VC manoeuvres.
Reported RV is the reported FRCpleth minus mean of the acceptable ERVs that are
linked to successful FRCpleth -ER-IVC trials.
Reported TLC is the reported RV plus the largest of the technically acceptable IVC.
Option 2
Reported FRCpleth is the mean of at least 3 acceptable FRCpleth values in litres (L) to
two decimal places.
Reported VC is taken from the largest acceptable and repeatable VC manoeuvres.
The largest VC may also be quoted from a previous spirometry manoeuvre which has
been performed during the same testing session
The TLC is reported as the mean of the 3 acceptable FRCpleth plus the largest linked
IC.
Note: The best & second best IC should be within 150ml.
The RV is reported as the mean TLC minus the largest technically acceptable VC.
4.9. Multiple breath Nitrogen washout (adult and paediatric patients) 2
The patient should be asked if they have a perforated eardrum and, if so, an ear plug
should be used. The patient should be assessed for current Bleomycin use as this is an
absolute contraindication to performing the Nitrogen Washout procedure.
It is imperative that the Nitrogen (N2) Washout is performed after any CO diffusion
measurements as breathing the 100% oxygen associated with this test can significantly
reduce calculated DLCO and KCO.
The patient should be seated comfortably with feet flat on the ground and without the
need to flex or extend the neck when on the mouthpiece.
Explain the procedure in detail emphasising the need to avoid leaks by maintaining a
tight seal around the mouthpiece. If a flanged rubber mouthpiece is used the dead
space volume will need be altered according to the manufacturer’s instructions.
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Instruct the patient to place the mouth over the mouthpiece, ensuring a tight seal, and
ensure that the patient has a nose clip in place during the entire procedure.
Activate the software program according to manufacturer’s instructions and instruct the
patient to breathe normally until a stable baseline end-tidal expiratory volume is
established.
When the end tidal volume is stable and at FRC, the patient is turned “into” the system
so that 100% O2 is inspired rather than room air.
Instruct the patient to perform an IC-VC manoeuvre. This can be performed before or
while breathing the 100% oxygen. Consult manufacturer’s instruction for further
guidance.
Monitor the N2 concentration. This may be displayed as a function of FRC volume, as
well as total washout volume or number of breaths. Consult manufacturer’s instruction
for further guidance.
A change in inspired N2 of >1% or a sudden large increase in expired N2 concentration
indicates a leak. In this case, the test should be terminated and the problem should be
rectified.
Display the patient’s tidal volume and end-tidal CO2% in real time.
Instruct the patient to continue normal tidal breathing and to keep the mouth seal tight.
Continue testing until the N2 concentration falls below 1.5% for at least three
successive tidal breaths. Gas mixing may be facilitated by asking the patient to take a
large inhalation from the mouthpiece approximately every minute.
If the test continues for greater than 7 minutes and N2 stability (N2 < 1.5%) is not met,
the test should be terminated. This condition indicates poor alveolar gas mixing and
test results should be interpreted with caution.
Allow double the washout time before repeating the test. For example, if the test takes
4 minutes, then wait 8 minutes before repeating the nitrogen washout 15.
4.9.1. Determining acceptability and repeatability of Nitrogen washout results
VC
Repeatability of VC from 2 tests should be within 0.15L for adults and 0.1L for
paediatric patients.
See Appendix 6: Determining acceptability and repeatability for spirometry.
FRCN2
At least 2 acceptable and repeatable manoeuvres must be performed.
No evidence of leaks in the system (a change in inspired N2 of >1% or a sudden large
increase in expiratory N2 concentration)
N2 concentration is <1.5% for at least three successive tidal breaths before terminating
the test.
Repeatability of TLC, FRCN2 and RV from 2 tests should be within 5% (no greater than
10%)
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4.9.2. Reporting Nitrogen washout results
All volumes are to be reported at BTPS conditions and in litres (L) to two decimal
places.
The final report should include:
—
Scientist’s comments regarding acceptability and repeatability of the data.
—
Software version (if applicable).
—
Date, time and results of most recent calibration.
—
Identification of reference values used.
Reported FRCN2 should be the mean of technically acceptable results that agree within
10%.
Reported RV is the reported FRCN2 minus the mean of the technically acceptable
ERVs that are linked to technically acceptable FRCN2 determinations.
Reported value for TLC should be the reported value for RV plus the largest of the
technically acceptable IVC.
If only one acceptable measurement of FRCN2 is made then caution should be used in
the interpretation and a note as such should be made in the report.
4.10. Multiple breath Helium dilution
The patient should be asked if they have a perforated eardrum and, if so, an ear plug
should be used.
The patient should be seated comfortably with legs uncrossed and feet flat on the
ground and without the need to flex or extend the neck when on the mouthpiece.
Explain the procedure in detail emphasising the need to avoid leaks by maintaining a
tight seal around the mouthpiece. If a flanged rubber mouthpiece is used the dead
space volume will need be altered according to the manufacturer’s instructions.
Instruct the patient to place the mouth over the mouthpiece, ensuring a tight seal, and
ensure that the patient has a nose clip in place during the entire procedure.
Activate the software program according to the manufacturer’s instructions and instruct
the patient to breathe normally until a stable baseline end-tidal expiratory volume is
established.
When the end-tidal expiratory volume is stable and at FRC the patient is turned “into”
the system (i.e. connected to the test gas) and should be instructed to continue
breathing regular tidal breaths.
Continual adjustment of O2 flow should be made to compensate for O2 consumption
otherwise significant errors in the FRC calculation can result. Helium concentration
should be regularly monitored.
Instruct the patient to continue normal tidal breathing whilst maintaining a tight seal
around the mouthpiece.
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Continue testing until the change in helium concentration is <0.02% in 30s. The test is
usually complete within 10 min even in severely obstructed patients. (Normal nonobstructed persons will take about 3-4 min to equilibrate.)
The patient should be turned “out” of the system (disconnected from the test gas).
Instruct the patient to exhale slowly and maximally to RV followed by a maximal
inspiratory effort to TLC and then a return to normal tidal breathing. This is the linked
FRCHe -ERV-IC manoeuvre.
At least one technically satisfactory measurement should be obtained. However, if
more than one measurement is made it must be performed at least 5-10min after the
patients has been breathing room air depending on the degree of airways obstruction
16
.
4.10.1. Paediatric test procedure
For younger children it is recommended that at least two technically satisfactory
measurements are performed 2.
4.10.2. Determining acceptability and repeatability of Helium dilution
Vital Capacity (VC)
See Appendix 6: Determining acceptability and repeatability for spirometry.
FRCHe
If more than one measurement is made FRCHe values should be the mean of
technically acceptable results that agree within 10% of each other 2.
Helium concentration should be stable before testing. If falling baseline is noted check
for leaks e.g. loose seal on the mouthpiece, a hole in the bag or circuit, nose clip not
secure.
Rebreathing pattern should be even. Successive breaths will show a gradually falling
end-tidal expiratory level as oxygen is consumed. Addition of oxygen should return
breathing to close to the baseline.
If tidal breathing is irregular, ERV may be overestimated or underestimated, giving a
lower or higher RV.
A VC manoeuvre along with its subdivisions ERV and VC should be performed during
the same testing session.
Adequate time (between 5-10min) should be allowed between tests for complete
washout of helium from the patient’s lungs.
FRCHe values should be consistent with spirometry results, and if not, may have
resulted from leaks or inaccuracy or malfunction of the gas analyser.
4.10.3. Reporting results of Helium dilution
All volumes are to be reported at BTPS conditions and in litres (L) to two decimal
places.
The final report should include:
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—
Scientist’s comments regarding acceptability and repeatability of the data.
—
Software version (if applicable).
—
Date, time and results of most recent calibration.
—
Identification of reference values used.
—
Reported FRCHe should be the mean of technically acceptable results that agree
within 10%.
—
Reported RV is the reported FRCHe minus the mean of the technically acceptable
ERVs that are linked to technically acceptable FRCHe determinations.
—
Reported value for TLC should be the reported value for RV plus the largest of the
technically acceptable IVCs.
—
If only one acceptable measurement of FRCHe is made then caution should be used
in the interpretation and a note as such should be made in the report.
4.11. Quality Control Procedures
Quality control procedures specific to spirometry testing are detailed in Appendix 4: Quality
Control Procedures. Daily validation (calibration checks), weekly biological control testing,
and data analysis are the minimum quality control requirements.
The following is performed in addition to the Quality Control procedures outlined in the
Queensland Health Guidelines: Spirometry 6, 11
If a gas transfer has been performed prior to static lung volumes, check that the
Alveolar Volume (VA) is smaller than the TLC. If an irregularity is found make sure all
other parameters fit the clinical picture e.g. the VA could be significantly less than the
TLC due to obstructive airways disease.
Check that the VC obtained during body plethysmography is the same or within 0.15L
of the VC obtained during spirometry testing.
For N2 washout appropriate corrections for tissue and body fluid elimination of N 2
should be made (see Appendix 3: General Principles of static lung volume
measurements)
For He dilution ensure patients are at FRC when they are connected to the test gas. If
not at FRC then a correction must be made before reporting results 2. Consult the
manufacturer’s instruction.
4.11.1. Calibration
Perform calibration for each technique according to equipment manufacturer’s instructions.
For all methods:
3 L syringe for volume verification of spirometer performed at least daily 6.
Periodic servicing of equipment by the manufacturer is recommended.
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For body plethysmograhy:
Mouth and box pressure transducers should be calibrated daily.
Plethysmograph signal should be calibrated daily using a volume signal of similar
magnitude and frequency as the respiratory movements during testing.
Regular check of the plethysmograph leak time constant is recommended. See
manufacturer’s instructions for frequency of check.
A validation of accuracy of the plethysmograph using an automated Isothermal Lung
Simulator. See manufacturer’s instructions for use and frequency. Alternate methods
for validation are described elsewhere 2.
For nitrogen washout:
2 point (0 & 4% CO2; 16 & 100% O2) calibration of gas analysers should be performed
at least daily. Check manufacturer’s recommendations.
Calibration check should be performed before each patient by setting the N2 analyser
to zero using 100% 02 and then exposing the analyser to room air which should be
within 0.5% of the expected reading for room air (i.e.78.08%)
For helium dilution:
2 point (0 and full scale) calibration of gas analysers performed daily.
Before each patient the status of the CO2 absorbers should be checked.
Weekly checks of helium meter stability (drift should not exceed 0.02% in 10 min.)
Weekly checks of helium meter linearity. If stable over several months then checks only
need to be performed quarterly or semi-annually.
Consult equipment manufacturer’s instruction manual for further calibration
requirement.
4.11.2. Biological control characterisation and data analysis
Body Plethysmograhy
At least fortnightly, measure FRCpleth and related RV and TLC on at least two biological
controls 2:
Calculate mean, standard deviation, and coefficient of variation for FRC, TLC, and RV.
FRC and TLC values that differ by >10%, and RV values that differ by >20% from
previously established means for each subject suggest errors in measurements.
Refer to Appendix 4: Quality Control Procedures for analysis of the data and how to
characterise the biological controls.
Nitrogen washout and helium dilution
Testing of at least two biological controls should be performed at least fortnightly.
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5. Definition of Terms
Definitions of key terms are provided below.
Term
Name
FRC
Functional Residual Capacity The volume of gas present in the lung at end
(L)
expiration during tidal breathing 2
ERV
Expiratory Reserve Volume (L)
The volume of gas that can be maximally
exhaled from the end-tidal expiratory level
during tidal breathing 2
IC
Inspiratory Capacity (L)
The maximum volume of gas that can be
inspired from FRC 2
VC
Vital Capacity (L)
IVC
Inspiratory Vital Capacity (L)
The volume change at the mouth between the
positions of full inspiration and complete
expiration 2
EVC
Expiratory Vital Capacity (L)
IRV
Inspiratory Reserve Volume (L) The maximum volume of gas that can be
inhaled from the end-tidal inspiratory level
during tidal breathing 2
RV
Residual Volume (L)
The volume of gas remaining in the lung after
maximal exhalation 2
TV
Tidal Volume (L)
The volume of gas inhaled or exhaled during
the respiratory cycle 2
TGV
VTG
Description
or Thoracic Gas Volume (L)
The absolute volume of gas in the thorax at
any point in time and any level of alveolar
pressure 2
TLC
Total Lung Capacity (L)
Refers to the volume of gas in the lungs after
maximal inspiration, or the sum of all volume
compartments 2
VA
Alveolar Volume (L)
Total volume of gas available for exchange
with blood under prevailing circumstances.
Expressed as the lung volume less the volume
of the conducting airways 17
DL,CO
Diffusing capacity for carbon Also known as transfer factor of the lung for
monoxide
CO; product of the KCO and VA 18
KCO
Transfer coefficient of the lung
Diffusing capacity for carbon monoxide per unit
of alveolar volume i.e. DL,CO/VA 18
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6. Consultation
Key stakeholders (position and business area) who reviewed this version are:
Queensland Health Respiratory Working Party: Michael Brown (Director of Respiratory
& Sleep Sciences, Royal Brisbane and Women’s Hospital), Andrew Coates (Chief
Respiratory Scientist, Mater Health Services), Annette Dent (Scientific Director,
Respiratory Science, The Prince Charles Hospital), Janine Ferns (Respiratory/Sleep
Scientist-Advanced, Cairns Base Hospital), Leanne Rodwell (Respiratory Scientist,
Royal Children’s Hospital), Irene Schneider (Respiratory Sciences Clinical Educator,
Respiratory Working Party Chair, The Prince Charles Hospital), Jessica Wilson
(Respiratory Scientist, Respiratory Working Party Assistant Chair)
Clinical Measurements Advisory Group (CMAG) for Clinical Education and Training.
State-wide Clinical Measurements Network (SWCMN)
Queensland Health Respiratory Laboratory Managers: Chris Brown (Respiratory and
Sleep Scientist – Advanced, The Townsville Hospital), Barry Dean (Respiratory
Scientist, Royal Children’s Hospital), Brenton Eckert (Scientific Director, Princess
Alexandra Hospital), Ryan Harle (Respiratory Scientist – Laboratory Manager, Logan
Hospital), Andrew Southwell (Senior Clinical Measurement Scientist - Respiratory,
Redcliffe/Caboolture), Joanne Wex (Manager- Clinical Measurements, Rockhampton
Base Hospital), Debbie Zagami (Respiratory Scientist-Laboratory Manager, Gold Coast
Hospital)
Queensland Health Respiratory Laboratory Clinical Directors: Scott Bell (Thoracic
Program Medical Director, The Prince Charles Hospital), Anthony Matthiesson
(Director Respiratory and Sleep Unit, The Townsville Hospital), Stephen Morrison
(Director of Thoracic Medicine, Royal Brisbane and Women’s Hospital), Brent Masters
(Director, Queensland Children’s Respiratory Centre), Graham Simpson (Director of
Thoracic Medicine, Cairns Base Hospital), David Serisier (Director, Respiratory
Medicine, Mater Health Service), Pathmanathan Sivakumaran (Director, Respiratory
Services, Gold Coast Hospital), Khao Tran (Respiratory Physician, Logan Hospital), Dr
Craig Hukins (Director, Department of Respiratory and Sleep Medicine, Princess
Alexandra Hospital)
State-wide Respiratory Clinical Network (SWRCN), Deb C. Hill (Network Coordinator,
State-wide Respiratory Clinical Network & Principal Project Officer, Clinical Networks
Team, Patient Safety & Quality Improvement Service, Centre for Healthcare
Improvement)
7. Guideline Revision and Approval History
Version
No.
1.0
Modified
by
Amendments
authorised by
Approved by
Dane Enkera - Chair State-wide Clinical Measurements
Network
Brett Duce - Chair Clinical Measurements Advisory
Group (for clinical education)
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8. Appendices
Appendix 1: Infection Control Procedures
The aim of infection control is to provide a better understanding of infections and their
modes of transmission to staff. It is also important in maintaining a safe working
environment for staff and patients to help prevent disease transmission during pulmonary
function testing.
General Hygiene guidelines:
Poor hygiene practice not only increases patient morbidity but also increases patient
mortality. Lung function testing equipment has the ability to spread or transmit blood borne
and airborne pathogens (droplets and other particles containing microbes being released
in the air) e.g. tuberculosis (TB), chicken pox respiratory syncytial virus (RSV), human
immunodeficiency virus (HIV) and hepatitis. The majority of the patient population would
not be affected but individuals who are immune-compromised are far more likely to
develop complications 4.
If an active respiratory infection has been identified in a patient then the test request
should be confirmed with the requesting medical officer.
Transmission of pathogens
1, 8
:
Transmission of pathogens can occur via a number of different routes including: patient staff, staff – patient, patient – patient, staff – staff, patient – equipment and staff –
equipment.
ATS/ERS guidelines 1 define direct and indirect contact with regards to pulmonary function
testing and transmission of pathogens as follows:
Direct contact:
(From person to person)
There is the potential for transmission of upper respiratory disease,
enteric infections, and blood-borne infections through direct contact.
Although hepatitis and HIV transmission are unlikely via saliva,
disease transmission is a possibility when there are open sores on the
oral mucosa, bleeding gums, or haemoptysis. The most likely surfaces
for contact are mouthpieces and the immediate proximal surfaces of
valves or tubing.
Indirect contact:
(Via animate and inanimate objects)
There is potential for transmission of TB, various viral infections, and
possibly, opportunistic infections and nosocomial pneumonia through
aerosol droplets. The most likely surfaces for possible contamination
by this route are mouthpieces and proximal valves and tubing.
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Prevention and Precautions:
Standard precautions should be followed at all times. Disease prevention or cross
contamination can be prevented by addressing the following issues regarding the source
and the transmission of pathogens:
ensuring a clean environment
proper hand-washing techniques
sterilisation and disinfection of equipment including valves and tubing
use of in-line bacterial/viral filters safety mouthpieces
personal protective equipment (e.g. gloves, gown, masks etc)
isolation of infected patients (Source Isolation)
precautions with testing patients with open sores or haemoptysis
isolation of susceptible patients (Protective Isolation).
Hands should be washed between patients and immediately after direct handling of
mouthpieces, tubing, breathing valves or the interior surfaces of equipment. Gloves should
be worn at all times when handling contaminated equipment or where surfaces are
suspected of holding pathogens which could be potentially transmitted. Gloves also offer
another barrier of defence for staff with open cuts or sores which need to be covered to
prevent contamination and/ or transmission of disease pathogens.
Volume and flow-based spirometers:
Disposable in-line filters are an effective and less expensive method of preventing
equipment contamination. In-line filters have been shown to remove microorganisms from
the expiratory air stream and thus prevent their deposition as aerosol nuclei on spirometer
surfaces. The use of in-line filters does not eliminate the need for regular cleaning and
decontamination of lung function equipment. When using equipment with inspiratory and
expiratory manoeuvres, in-line bacterial/ viral filters should be used and disposed of after
every patient (single patient use).
Closed circuit
A volume based spirometer in which a closed circuit technique has been used should be
flushed between subjects with room air at least five times over the entire volume range of
the spirometer to enhance clearance of droplet nuclei. The breathing tube or mouthpiece
should be decontaminated or changed between patients.
Open circuit
If the patient or subject only exhales into the spirometer, only the portion of the circuit
through which re-breathing occurs must be decontaminated between patients.
Alternatively a disposable sensor may be used and decontamination of sensors and
mouthpieces can be avoided. A low resistance disposable one-way valve mouthpiece may
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be used to prevent inhalation from an open circuit. This mouthpiece needs to be disposed
of between patients.
Common transmissible infectious diseases often seen in the Respiratory Laboratory
include:
Hepatitis B
Hepatitis C
Tuberculosis (TB)
Human Immunodeficiency Virus (HIV)
Pseudomonas cepacia
Cytomegalovirus (CMV)
Varicella Zoster Virus (VZV).
The ATS/ERS 1 recommends extra precautions are taken for patients with known
transmissible infectious diseases.
Reserve equipment for the sole purpose of testing infected patients.
Test infected patients at the end of the day, allowing time for the equipment to be
disassembled and disinfected.
Test patients in their own rooms with adequate ventilation and appropriate protection
for the technician. A negative air conditioned room is ideal for this situation and aids in
the prevention of cross contamination.
Place patients in a separate area apart from other patients, not in open waiting areas.
Provide patients with surgical masks and instruct them to wear the masks. Provide
patients with tissues and instructions on covering their mouth and nose when coughing
or sneezing.
Environmental engineering controls such as ventilation, air filtration or ultraviolet
decontamination of air should be used to help prevent disease transmission where spread
is by droplet nuclei as seen in tuberculosis.
Cleaning and Disinfecting Procedures
Mouthpieces, nose clips, and any other equipment coming into direct contact with mucosal
surfaces should be disinfected, sterilized, or, if disposable, discarded after each use.
Although the optimal frequency for disinfection or sterilization of tubing, valves, or
manifolds has not been established, any equipment surface showing visible condensation
from expired air should be disinfected or sterilised before reuse whenever the potential for
cross contamination exists.
Manufacturer’s recommendations regarding the cleaning and disinfection of equipment
must be consulted in order not to cause damage with the wrong cleaning procedure. Heat
sterilisation or cold sterilisation chemicals can damage flow sensors, tubes and/ or seals.
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Manufacturers should describe the recommended chemicals and concentrations as well as
the PPE required by the staff undertaking the cleaning and disinfection procedure.
However, Queensland Health infection control requirements supersede the manufacturer’s
recommendations so long as the equipment will not be damaged by these procedures.
All materials must be cleaned of debris before undergoing the disinfection process. There
are four main categories of sterilization and disinfection. ; These are described below 8.
Heat
Heat is the universally employed and most reliable form of sterilization and is listed below
in order of efficiency:
Steam under pressure (autoclave)
Steam at atmospheric pressure
Boiling water
Dry heat under pressure
Dry heat at atmospheric pressure
Water below boiling point (pasteurization).
Cold liquid
Glutaraldehydes disinfect by interrupting metabolism and reproduction in microorganisms
by binding to amino groups of proteins. These agents are bactericidal, tuberculocidal,
fungicidal and viracidal in 10-30 minutes and sporicidal in 10hours. Many of these agents
require special precautions. Comply with the material safety data of the product.
Gas
Ethylene oxide (ETO) is the alkylating agent used extensively in gas sterilisation. However
this agent is unsafe for the environment and requires stringent material preparation and
monitoring.
Other liquid disinfectants
Other disinfectant liquids include alcohol, quaternary ammonium compounds, acetic acid,
formaldehyde, phenols, iodine, chlorine, and hydrogen peroxide.
1. Acetic acid solutions, quaternary ammonium compounds, and household bleach may
be used for disinfecting respiratory equipment. However, studies have not been
performed to verify the usefulness of these agents.
2. Alcohol and hydrogen peroxide may be used for skin cleaning and disinfection.
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Appendix 2: Purposes for performing static lung volumes
Purposes for performing spirometry 9:
Diagnostic indications
evaluate symptoms, signs or abnormal laboratory tests – abnormal lab tests
measure the effect of disease on pulmonary function – pulmonary dysfunction
screen individuals at risk of having pulmonary disease – risk stratification
assess pre-operative risk – pre-operative assessment
assess prognosis – prognostic indicator
Monitoring indications
assess therapeutic intervention
describe the course of diseases that affect lung function
monitor people exposed to injurious agents
monitor for adverse reactions to drugs with known pulmonary toxicity
Disability/Impairment Evaluations
assess patients as part of a rehabilitation program
assess risks as part of an insurance evaluation
assess individuals for legal reasons
Public Health
epidemiological surveys
derivation of reference equations
clinical research
Purposes for performing static lung volume measurements (in addition to the above
purposes for performing spirometry):
Diagnostic:
4
evaluate symptoms, signs or abnormal laboratory tests and confirm restrictive
ventilatory defects
diagnose hyperinflation and gas trapping as may occur in patients with obstructive lung
disease
diagnose, evaluate and monitor diseases which involve the lung parenchyma (eg.
those associated with dusts, drug reactions, or sarcoidosis)
differentiate types of lung disease processes characterized by airflow limitation that
have similar forced expiratory volumes
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aid in the interpretation of other lung function tests (lung elastic recoil pressure,
instantaneous ventilatory flows, gas transfer factor).
Monitoring and assessment: 5
assess response to therapeutic intervention (e.g., drugs, transplantation, radiation,
chemotherapy, and lobectomy and lung volume reduction procedures/surgery)
make preoperative assessments when indicated
quantify the amount of non-ventilated lung
evaluate and monitor:
—
pulmonary disability
impairment and disability associated with interstitial lung diseases and chronic
obstructive airway diseases
—
pulmonary effects of radiation therapy, chemotherapy agents (eg Bleomycin) or
other drugs known to induce pulmonary dysfunction
—
—
pulmonary involvement in systemic diseases.
Public health:

epidemiological surveys

derivation of reference equations

clinical research.
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Appendix 3: General Principles of static lung volume measurements
Body plethysmography
The measurements made using body plethysmography are based on Boyle’s Law, which
states that, under isothermal conditions, if a given mass of gas is compressed or
decompressed, the gas volume decreases or increases and the gas pressure changes so
that the product of the gas volume (V) and gas pressure (P) is constant. This relationship
is described by the following equation:
P1V1 = P2V2
During body plethysmography the thoracic volume can be obtained by measuring the
changes in the following:
VTG
PB
VTG
PBoxCal
PMouthCal
K
Where:
VTG = thoracic gas volume (V2) measured at FRC
PB = barometric pressure (P1)
VTG = slope of the displayed line equal to P/ V
PBox Cal = box pressure transducer calibration factor
PMouthCal = mouth pressure transducer calibration factor
K = correction factor for volume displaced by the subject
Types of body plethysmographs
1. Constant – volume plethysmograph (variable-pressure plethysmography)
2. Constant – pressure plethysmograph (variable-volume plethysmography)
3. Flow plethysmography
More detailed reviews of the theory are available
19
.
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Multiple-Breath Nitrogen Washout
The principle of the method is that N2 is washed out of the body by the patient after a
period of breathing 100% oxygen. The first inspiration of 100% O2 is taken from FRC and
the expired volume is collected over a 7 minute period. The N2 concentration in the expired
gas gradually falls during the test and washout until it reaches a value of <1.5% . FRC is
calculated using the following formula 17:
FRC
FE N 2 final ExpiredVolume N 2tissue
FA N 2 alveolar1
FA N 2 alveolar2
Where:
FEN2final
=
Fraction of N2 in volume expired
FAN2alveolar1
=
Fraction of N2 in alveolar gas initially
FAN2alveolar2
=
Fraction of N2 in alveolar gas at end
N2tissue = Volume of N2 washed out of blood/tissues
For each minute of O2 breathing, approximately 30 to 40 mL of N2 are removed from the
blood and tissue. Therefore:
N2tissue = 0.04 x T (where T is time of the test).
The final FRC is then corrected to BTPS.
Determination of indices for reporting
TLC =
Average of all FRC + Best IC
VC =
The highest VC measured from spirometry or lung volume measurements
RV =
Calculated TLC – Best VC
FRC =
Average of all trials
IC
Largest IC of all trials (* best and second best must be within 10%)
=
VTG =
Average of all trials
ERV =
Average of all trials
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Multiple-breath Helium Dilution
The subject breathes from a closed circuit a gas mixture containing 9.5% helium, 35%
oxygen with a nitrogen balance. The gas mix equilibrates gradually with the resident gas in
the lungs. The helium concentration falls progressively, stabilising once mixing is
complete. In normal healthy individuals this is achieved in 5-10minutes, but in patients with
airway disease mixing is much slower and the endpoint much less definite. During
rebreathing, CO2 is absorbed by a Sodalime scrubber and oxygen is added continuously
to maintain a constant overall volume of the system (equipment+lungs). The volume
measured is that at which the subject is switched into the circuit, FRC + V D, where VD is
the sum of the apparatus and anatomic dead spaces. The total amount of helium (He)
equals the product of its concentration and the volume (V) in which it is distributed. The
initial fractional concentration of He (F1He) in the circuit (V1) falls after switching, reaching
an equilibrium concentration F2He. The total amount of helium is unchanged.
F1 He
F2 He
V1
VD
FRC
V2
Calculation:
Therefore
V1.F1He (amount of He)
= V2.F2He (amount of He)
= (V1 + FRC + VD).F2He
FRC + VD
=V1(F1He – F2He)
F2He
At the end of the procedure the subject takes a full inspiration from a spirometer and
expires fully back into the spirometer. The inspiratory capacity recorded is added to FRC
to give TLC and the VC is subtracted from the TLC to give the RV.
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Appendix 4: Quality Control Procedures
Quality control must be conducted to ensure the precision and accuracy of the test
equipment, test procedure and the results collected. It includes the regular maintenance
and calibration of equipment and the regular testing of biological controls to validate
testing equipment and test procedures. All results of quality control testing should be
recorded and analysed so that any problems can be identified and rectified as soon as
they arise. Quality control processes that conform to a “best practice model” are outlined
below 8.
Instrument maintenance
Regular preventative maintenance must be performed by the operator to anticipate
problems with the equipment before they occur. These should be done daily, weekly,
monthly or yearly depending on the recommendation of the manufacturer.
checking volume-displacement spirometers for leaks and linearity
checking tubing for tears
electrical safety
Corrective measures include unscheduled action required to correct the instrument failure
and can be performed by the manufacturer, hospital bioengineer or the operating staff.
Maintenance logs must be kept and include dates and types of tasks conducted along with
instructions on what action is to be taken if a problem is identified and needs to be
rectified. At a minimum the following record should be kept:
problem or troubleshooting log
preventative maintenance list/log
calibration log
quality control log
New Instrumentation verification and validation must be performed on all new equipment
before patient testing begins.
Instrument Calibration
To have confidence in the data that is generated during spirometry testing, the spirometer
must be regularly calibrated for volume, linearity and timing. Depending on the type of
spirometer used, some or all of these parameters need regular validation.
Calibration syringe 5
The calibration syringe should be stored at the same temperature and humidity as the
testing site, away from direct sunlight and heat sources. This is best achieved by
storing the syringe close to the spirometer.
A calibration syringe should be used to check the volume calibration of spirometers and
must have an accuracy of ±15mL or 0.5% of the full scale, whichever is greater. For
most spirometers the syringe volume required is 3L.
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A calibration syringe should be validated yearly to ensure accuracy. For specific details
refer to the manufacturer’s recommendations.
A calibration syringe should be checked monthly for leaks by attempting to empty it
with the outlet occluded. This should be performed at more than one volume.
Perform inspection of adjustable or variable stops, if they exist, especially if the syringe
has been dropped or damaged.
Use of the syringe on a large number of machines distinguishes between instrument
problems and problems with the syringe.
Procedure for validation (calibration checks)
Volume validation ensures that the spirometer is within calibration limits (+/-3% of the
true volume, usually 3L where a 3L syringe is used).
Volume validation should be performed at least daily, or after every 10 patients in a
busy service 20.
Recalibration may be indicated and BTPS correction factors updated if the temperature
changes more than 50° C 1.
In-line bacterial/ viral respiratory filters must be in place during the validation if they are
used during testing 12.
For volume-based spirometers 5
Check spirometer for leaks daily by applying a constant positive pressure of
≥3.0cmH20 (0.3 kPa) with the spirometer outlet occluded at the mouthpiece, preferably
with the mouthpiece in place. A volume loss of 30ml after 1min indicates a leak and
needs addressing.
—
Perform validation at least daily with a calibration syringe (the volume of the syringe
will depend on the type of spirometer being used). Check manufacturer’s guidelines for
details.
—
A volume linearity check should be performed quarterly (1L increments with a
calibrating syringe over entire volume range). The procedure is detailed in the
ATS/ERS guidelines 9. The check is considered accurate if the minimum volume
accuracy requirements are met for all volumes tested, i.e. measured volume should be
within ±3.5% (this value includes the 0.5% syringe accuracy limit of the reading or
65ml, whichever is greater).
—
—
The following method can be used to check the linearity for each volume tested:
% Error = Expected Volume – Measured Volume X 100
Expected Volume
Where:
Expected volume = the actual volume of the syringe
Measured volume = the result recorded for the test
Perform timer checks quarterly for spirometers with mechanical recorder time
scale. Using a stopwatch, an accuracy of 2% must be achieved.
—
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For flow-based spirometers 5:
Perform validation at least daily with a 3L syringe. Check manufacturer’s guidelines
for details.
—
A 3.00 L syringe should be injected at three different flow rates between 2 and 12
L.s-1 (with 3L injection times of ~6sec and < 0.5 sec); minimum volume accuracy
should be within 3.5% at all flows.
—
For spirometers that use disposable flow sensors, a new unused sensor should be
tested daily.
—
A flow linearity check of pneumotachs weekly ensures that minimum volume
accuracy is met for the entire range of flows measured (low-, mid-, high-flows). If the
spirometer meets volume accuracy requirements of ±3.5 ml for all flow rates tested
then it meets the requirements for linearity.
—
Quality Control Analysis
Data from calibrations and other quality control procedures must be analysed regularly in
order to be useful and contribute to quality assurance procedures. The results analysed
must be obtained in a stable laboratory environment using the same calibration syringe,
calibration procedure, biological standard or control material (eg. 3L syringe).
Biological Control is a healthy, non-smoking individual, usually a staff member, that is
regularly tested and becomes the reference standard for the quality control program.
Biological control characterisation
Biological controls must initially be “characterised” according to the “gold standard” testing
procedures before the data becomes the “reference standard”. The biological control’s
lung function must be measured as accurately as possible under ideal conditions to
determine a baseline value. All subsequent testing of the biological control is compared to
this baseline value. Characterisation determines the variability of the biological control
under the most ideal conditions.
Characterisation requires that:
FEV1, VC, FVC volumes are measured according to ATS/ERS guidelines for
acceptability and repeatability5.
The subject is free of symptoms or known respiratory disease that may cause
variability in lung function results.
Data is collected at least 10 times over a 1-2 week period under the above conditions
to assess variability of the individual’s data.
The mean for each measured parameter becomes the reference standard or the
“correct value”.
Biological control data analysis
Day to day variations in physiological function of the biological control occur even under
ideal testing conditions. The variability is used to set the “control limits for the test”, and
allows identification of data that is “out of control”, and is determined by the following
steps:
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record FEV1, FVC, VC for the 10 or more test manoeuvres performed
for each parameter measured calculate mean and standard deviation (SD)
the mean value during gold standard testing is the “correct value” for the biological
control
the standard deviation (SD) can now be used to set the control limits, where, mean ±
1.96 x SD gives a confidence interval of 95%, this means that approximately 95% of
the values will be between ± 2SD of the mean.
The biological control results, collected on a regular basis, can be plotted on a LevyJennings plot (see Graph 1) and interpreted using the Westgard rules. Westgard rules
can be used to define specific limits for biological control results when compared with
the “gold standard” testing results and to help determine if quality assurance responses
need to be enacted, as follows 8:
When one control observation exceeds the mean ±2 SD, a "warning" condition
exists
—
When one control observation exceeds the mean ±3 SD, an "out of control"
condition exists
—
When two consecutive control observations exceed ±2 SD, an "out of control"
condition exists
—
When four consecutive control observations exceed the mean ±1 SD in the same
direction, an "out of control" condition exists
—
When 10 consecutive control observations fall on the same side of the mean, an
"out of control" condition exists
—
—
Generally, the following rules apply:
—
the ±2 SD limits are considered warning limits
—
values between 2 and 3 SD limits indicate an error and the procedure should
be repeated
—
values beyond ±3 SD are considered unacceptable and the testing system
should be evaluated.
Biological control testing procedure
Routine biological control testing is performed weekly.
Routine biological control testing is performed under the same condition as routine
patient testing according to ATS/ERS guidelines 5.
Graph the biological control result on a Levy-Jennings Plot (see Graph 1), which has
horizontal lines running across it to indicate the mean, as well as one, two and
sometimes three standard deviations either side of the mean (derived from the
characterisation of the biological control). These provide visual feedback of whether
control values are “in” or “out of control”.
Westgard rules are then used to determine if any quality assurance procedures need to
be enacted.
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Levy -Jennings Plot (VC)
Graph 1. Example of a LevyJennings plot showing the mean
and one and two standard
deviations derived from biological
control characterisation. The
observation points are VC results
obtained from a biological control.
In this example, no quality
assurance procedures need to be
enacted.
3.28
3.26
3.24
VC (L) Result
3.22
3.2
3.18
3.16
3.14
3.12
3.1
3.08
0
2
4
6
8
10
12
Observation number
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Appendix 5: Complete TVG computation equation.
For young children, where the rapid IC manoeuvre against a closed shutter is used to
measure FRC, the plethysmograph should be set to “VTG on Inspiration only” mode. Not
“VTG by occlusion”. It is essential that the complete rather than the simplified version of
the VTG computation equation be used in the calculation of VTG.
i.e.
TGV=-(ΔV/ΔP)xPalv2x(Palv1/PB)
as opposed to
TGV=-(ΔV/ΔP)xPB.
Not using the complete formula will result in an error of about 5%. If a computerized
system is used for such measurements, the user must confirm that the complete equation
is used by the computer during such measurements 2, 14.
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Appendix 6: Determining acceptability and repeatability of FEV1, FVC and VC
measurements
Extract taken from Queensland Health Guideline: Spirometry (Adult)
6
Clinically useful spirograms must be acceptable (i.e meet the criteria that comprises a
good quality manoeuvre) and repeatable (i.e the two highest FEV1, FVC and VC from
three acceptable manoeuvres are in close agreement).
A spirogram is “acceptable” if the following are met:
Start of Test Criteria
begins from full inspiration
has a rapid start of test, that is, the back extrapolated volume (BEV) is <5% of FVC or
0.15L, whichever is greater (see Appendix 7: Determination of back-extrapolation
volume). If the manoeuvre has an obviously hesitant start then the trial should be
terminated early to avoid unnecessary prolonged effort.
Middle of Test Criteria
No obstruction, hesitation or artefact impeding the blow including:
a. Cough during the first second of exhalation
b. Glottic closure that influences the measurement
c. Early termination or cut-off
d. Effort that is not maximal throughout
e. Air leaks at mouth
f. Obstructed mouthpiece (due to tongue or teeth in front of the mouthpiece, or
mouthpiece deformation due to biting).
Note: See below for examples of volume-time and flow-volume spirograms.
End of Test Criteria
Continuous maximal expiratory blow for ≥6 sec in duration
A plateau in the volume-time curve (i.e. no change in volume (<0.025L) for a 1 second
period)
The patient cannot or should not continue to exhale 5.
How to ensure repeatability between individual spirograms
After three acceptable spirograms have been obtained, the following checks are used to
assess for repeatability:
The two largest values of FVC or VC must be within 0.150L of each other
The two largest values of FEV1 must be within 0.150L of each other
For patients with an FVC or VC of ≤1.0L the two largest FVC or VC and FEV1 values
must be within 0.100L of each other
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A minimum of three acceptable manoeuvres should be saved and utilised for
analysis/interpretation.
Peak expiratory flow (PEF)
During spirometry testing PEF is measured in conjunction with FEV1 and FVC and can be
used to indicate maximal patient effort.
Note: PEF can also be measured independently using a Peak Flow Meter. Refer to
ATS/ERS guidelines (2005) 5.
Examples of volume-time and flow-volume spirograms
Figure 1. Examples of unacceptable volume – time spirometry results compared with a
good effort 21
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Figure 2. Examples of unacceptable flow-volume spirometry loops compared with an
acceptable effort 21
9. Suggested Readings and References
9.1. Suggested readings
Cooper BG. 2010. An update on contraindications for lung function testing. Available
from: http://www.ncbi.nlm.nih.gov/pubmed/20671309.
22
Johns DP and Pierce RP. 2007. Pocket Guide to Spirometry. 2nd edition, McGraw-Hill
Australia. 21
Quanjer PH. Become an Expert in Spirometry: Lung function indices. Available from:
http://www.spirxpert.com/indices7.htm 23_ENREF_16
Queensland Health Spirometry Training Program. Available from:
https://ilearn.health.qld.gov.au/login/index.php 24
9.2. References
1.
Miller MR, Crapo R, Hankinson J, Brusasco V, Burgos F, Casaburi R, et al. General
considerations for lung function testing. Eur Respir J. 2005 Jul;26(1):153-61.
2.
Wanger J, Clausen JL, Coates A, Pedersen OF, Brusasco V, Burgos F, et al.
Standardisation of the measurement of lung volumes. Eur Respir J. [Review]. 2005 Sep;26(3):51122.
3.
Queensland Health. Informed decision making in health care2012: Available from:
http://www.health.qld.gov.au/consent/default.asp.
4.
National Health and Medical Research Council. Australian Guidelines for the Prevention
and Control of Infection in Healthcare. National Health and Medical Research Council; 2010 [cited
2012 12/09/12]; CD33:[Available from: http://www.nhmrc.gov.au/node/30290.
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5.
Miller MR, Hankinson J, Brusasco V, Burgos F, Casaburi R, Coates A, et al.
Standardisation of spirometry. Eur Respir J. [Practice Guideline]. 2005 Aug;26(2):319-38.
6.
Queensland Health. Queensland Health Guideline: Spirometry (Adult)2013: Available from:
http://www.health.qld.gov.au/qhpolicy/docs/gdl/qh-gdl-386.pdf.
7.
Quanjer PH, Tammeling GJ, Cotes JE, Pedersen OF, Peslin R, Yernault JC. Lung volumes
and forced ventilatory flows. Report Working Party Standardization of Lung Function Tests,
European Community for Steel and Coal. Official Statement of the European Respiratory Society.
Eur Respir J Suppl. [Review]. 1993 Mar;16:5-40.
8.
American Thoracic Society. Pulmonary Function Laboratory Management and Procedure
Manual 2nd ed. Wanger J, Crapo R, Irvin C, editors: American Thoracic Society; 2005.
9.
American Association for Respiratory Care. AARC Clinical Practice Guideline: Spirometry,
1996 Update. Respiratory Care. 1996;41(7):629-36.
10.
Therapeutic Goods Administration. Bleomycin. Australian Government; 2013 [cited 2012
21/02/2012) ]; Available from:
https://www.ebs.tga.gov.au/ebs/picmi/picmirepository.nsf/PICMI?OpenForm&t=pi&q=Bleomycin.
11.
Queensland Health. Queensland Health Guideline: Spirometry (Paediatric)2013: Available
from: http://www.health.qld.gov.au/qhpolicy/html/index-a.asp.
12.
Swanney MP, Eckert B, Johns DP, Burton D, Crockett AJ, Guy P, et al. Spirometry Training
Courses – A Position Paper of the Australian and New Zealand Society of Respiratory Science and
the Thoracic Society of Australia and New Zealand. 2004: Available from:
http://www.anzsrs.org.au/spirotrainingposition.pdf
13.
Lindemann H. Body plethysmographic measurements in children with an accompanying
adult. Respiration. [In Vitro]. 1979;37(5):278-81.
14.
Coates AL, Peslin R, Rodenstein D, Stocks J. Measurement of lung volumes by
plethysmography. Eur Respir J. 1997 Jun;10(6):1415-27.
15.
Salamon E, Gain K, Hall G. Wait time effect on repeat multiple breath nitrogren washout
FRC. [Paper presented at: European Respiratory Society Annual Congress; 2010 September 1822; Barcelona, Spain ]: European Respiratory Society,; 2010 [16/02/2012]; Available from:
https://www.ersnetsecure.org/public/prg_congres.abstract?ww_i_presentation=48377.
16.
Brown R, Leith DE, Enright PL. Multiple breath helium dilution measurement of lung
volumes in adults. Eur Respir J. [Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.]. 1998 Jan;11(1):246-55.
17.
Ruppel G. Manual of pulmonary function testing. St. Louis, Mo.: Mosby; 1998.
18.
Macintyre N, Crapo RO, Viegi G, Johnson DC, van der Grinten CPM, Brusasco V, et al.
Standardisation of the single-breath determination of carbon monoxide uptake in the lung. Eur
Respir J. 2005 Oct;26(4):720-35.
19.
Cotes JE, Chinn DJ, Miller MR. Lung Function Physiology, Measurement and Application in
Medicine. 6th ed: Blackwell Publishing; 2006.
20.
Pellegrino R, Viegi G, Brusasco V, Crapo RO, Burgos F, Casaburi R, et al. Interpretative
strategies for lung function tests. Eur Respir J. [Practice Guideline]. 2005 Nov;26(5):948-68.
21.
Johns D, Pierce R. Pocket Guide to Spirometry. 2nd ed: McGraw-Hill Australia; 2007.
22.
Cooper BG. An update on contraindications for lung function testing2010: Available from:
http://www.ncbi.nlm.nih.gov/pubmed/20671309.
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23.
Quanjer P. Become an Expert in Spirometry. [cited 2012 14/12/2012]; Available from:
http://www.spirxpert.com/indices7.htm.
24.
Queensland Health. Queensland Health Spirometry Training Program. 2012 ed:
Queensland Health; 2012.
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