Copd and spirometry.pdf

ORIGINAL ARTICLES
CLINICAL GUIDELINE
Guideline for Office Spirometry in Adults, 2004
South African Thoracic Society Standards of Spirometry Committee: E M van Schalkwyk, C Schultz, J R Joubert, N W White
Objective. To provide clinical guidelines for office spirometry Conclusions. The indications for spirometry must be specific and clear. Spirometry equipment must meet internationally Options. More stringent guidelines are required for diagnostic accepted performance standards and carry proof of validation. Equipment must be regularly calibrated and Outcomes. To minimise variations in standard practice and maintained. Individuals performing spirometry must be improve the quality and usefulness of spirometry in the adequately trained and demonstrate a high level of competence. Subject preparation, testing and quality control Evidence. Recommendations are based on key international of results must be carried out according to published publications as well as research publications regarding guidelines. Finally, test results must be interpreted according reference values for South Africans.
to current diagnostic guidelines, taking into account the Benefits, harm and costs. The medical, social and economic purpose of the test, appropriateness of reference values and benefits and costs of standardisation of office spirometry in South Africa were considered in the recommendations.
S Afr Med J 2004; 94: 576-587.
Validation. The document has been reviewed and endorsed bythe South African Thoracic Society.
1. Abbreviations
guidelines for the standardisation of spirometry.2-4 Morerecently, selective South African reference standards have ATPS = ambient temperature, ambient pressure, saturated with become available for the normal range of forced vital capacity water vapour; ATS = American Thoracic Society; BTPS = body (FVC) and forced expiratory volume in 1 second (FEV1). 5-10 This temperature, ambient pressure, saturated with water vapour; statement is prompted by increased utilisation of office ECSC = European Community for Steel and Coal; ERS = spirometry in South Africa and a perceived need for simplified European Respiratory Society; FEV1 = forced expiratory guidelines for use at primary contact level, i.e. in the clinic or volume in 1 second; FVC = forced vital capacity; LLN = lower practice. Diagnostic and research lung function laboratories limit of normal; PEF = peak expiratory flow; RSD = residual will require more comprehensive guidelines than proposed in standard deviation; SATS = South African Thoracic Society; TLC = total lung capacity; VC = vital capacity.
3. Definitions
2. Introduction
Spirometry. Spirometry is one of a number of tests to evaluate
Spirometry is an essential part of a complete respiratory respiratory function. The basic spirometric procedure involves evaluation, but inadequate standards and variations in the measurement of gas volume and rate of airflow during a standard operating procedures exist that reduce its clinical maximal, forced expiration. The mechanical properties of the usefulness.1 Good quality spirometry necessitates a competent airways, lung, pleura, chest wall and respiratory muscles all operator, accurate and reliable equipment and a co-operative patient. Furthermore, it involves a series of standard Spirometer. Spirometers operate on one of two principles:
procedures and quality control checks to produce technically • Volume-type spirometers determine volume directly and satisfactory results. Finally, the results take reference standards have the advantages of low cost and ease of operation.
into account and are interpreted with consideration of the However, data processing and storage capacity may be limited, unless the spirometer contains a microprocessor.
Various authorities have published comprehensive • Flow-type spirometers make use of a flow-sensor (pneumotach) to derive volumes. They are computerised, Corresponding author: Dr E M van Schalkwyk, Department of Medicine,
provide quick reference values, produce flow-volume loops Stellenbosch University, PO Box 19063, Tygerberg, 7505, e-mail
emvs@sun.ac.za
enabling instant pattern recognition and can usually store July 2004, Vol. 94, No. 7 SAMJ
ORIGINAL ARTICLES
large data sets. On the other hand, they require greater time curves (Fig. 1a) and flow-type devices generate flow- expertise to operate, calibrate and maintain.
volume curves (Fig. 1b). Newer flow-type spirometers can Spirogram. Spirograms are the graphic displays produced by
spirometers. In addition to graphs, they provide the measured Measurements. Depending on type and level of
values (observed), the reference values (predicted) and the sophistication, spirometers can produce a range of measurements measured values expressed as a percentage of the reference that may assist in the clinical interpretation of results: values (% predicted). Volume-type devices generate volume- • Vital capacity (VC): VC is the total volume of gas inhaled from the position of maximal expiration or exhaled from theposition of maximal inspiration. It is measured with a relaxed/slow breathing manoeuvre either during inspiration or expiration. VC is expressed in litres (BTPS). BTPS refers toa standardised volume at normal body temperature (37°C) atambient pressure, saturated with water vapour.
• Forced vital capacity (FVC): FVC is the maximum volume of gas exhaled from the position of maximal inspiration bymeans of a rapid, maximally forced expiratory effort, • Forced expiratory volume in 1 second (FEV1): FEV1 is the volume of gas exhaled during the first second of the FVC manoeuvre,expressed in litres (BTPS).
• FEV1/FVC%: FEV1/FVC% is observed FEV1 expressed as per cent of observed FVC (FEV1/FVC × 100).
• Peak expiratory flow (PEF): PEF is the maximum flow generated with a FVC manoeuvre, expressed in litres per second (BTPS).
Measurements of FVC, FEV1 and FEV1/FVC% are the minimum required for diagnostic interpretation of results. VC measurements are useful for evaluating dynamic collapse of small airways as found in emphysema.
Calibration. Calibration is the process whereby the accuracy
(truthfulness) and precision (repeatability) of a device such as aspirometer are tested and corrected using a gold standard such as a calibration syringe with a standard volume.
Validation. Validation is the process of establishing and
certifying the accuracy and precision of a device.
Operator. The term operator refers to the person performing
4. Indications for spirometry
Specific and clear indications for spirometry are helpful in theinterpretation of results. The most frequent clinical indications for spirometry are listed below:• To confirm a diagnosis in: • Individuals with suspected obstructive or • To grade respiratory impairment in.
• Medico-legal cases (e.g. assurance or disability) • Individuals on treatment action plans (e.g. COPD) • Individuals for lung resection, and individuals for thoracotomy or upper-abdominal surgery if they Fig. 1. (a) Volume-time, and (b) flow-volume curves. In the flow-type spirometer FEV1 is a derived value. It can only be read from the flow- volume graph if a 1-second timer is displayed. July 2004, Vol. 94, No. 7 SAMJ
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• To monitor changes in lung function in: volume or flow) and linearity (consistency) of the entire system • Individuals with chronic respiratory diseases — to from the measuring components to the recording and display evaluate responses to treatment and disease components. The American Thoracic Society (ATS) has published minimal performance criteria for diagnostic and • Workers regularly exposed to substances known to cause monitoring spirometers and guidelines for validating equipment using waveform-generated calibration syringes.2 Selective ATS recommendations for diagnostic spirometers are provided in Tables I and II. Table II provides standards for • Individuals with persistent respiratory symptoms, graph output. Manufacturers should follow these guidelines to including shortness of breath (dyspnoea), chest ensure that spirometers provide accurate data that are tightness, wheezing, coughing, sputum production and comparable between different settings and over time.
Commercially available devices for monitoring of FEV1 and PEF • New employees with potential for exposure to have disadvantages for office spirometry because they may be substances known to cause respiratory diseases — less accurate, usually cannot be calibrated to ensure their performance, and graphical displays may be absent or • Workers with significant exposure to substances inadequate for evaluation of test quality. known to cause respiratory diseases.
Spirometry is frequently applied in the occupational • The BTPS-correction facility that meets ATS standards: The environment for surveillance purposes. Its sensitivity and volume of exhaled gas is measured outside the body at specificity for detecting early disease varies and a screening ambient conditions, designated ATPS (ambient temperature, programme should be tapered to the specific needs of the ambient pressure, saturated with water vapour). These gas workplace. For example, early changes of COPD or asbestosis measurements are corrected to reflect conditions inside the are detectable with spirometry, whereas early changes of lung (BTPS). Without this facility, mathematical correction silicosis are better detected with chest radiography. For occupational asthma, because of its varying nature, arespiratory symptoms questionnaire is frequently combinedwith spirometry in screening or surveillance programmes.
Table II. Minimum scale factors for spirograms*
5. Specifications for spirometers
5.1 Proof of validation
Spirometers may lack accuracy and precision. Prospective *For the flow-volume curve exhaled flow is plotted upwards and exhaled volumetowards the right in a 2:1 ratio.
purchasers of equipment should seek its proof of validation.
Accuracy depends on the resolution (minimal detectable Table I. Selective minimum volume and flow criteria for diagnostic spirometers
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• Facility to generate real-time spirograms — to enhance occluded. Any volume change greater than 10 ml after 1 minute indicates a leak. Faults are corrected and calibration repeated.
• Stated source(s) of reference values and facility to select or 5. Remaining problems are logged and referred to the • Computer-driven technical quality indicators that meet ATS The use of biological standards such as, for example, the standards (computer automatically evaluates test quality operator for daily volume calibration (biological calibration) based on pre-programmed criteria and gives prompts). cannot replace the use of a calibration syringe. Lung function • Printing facility for record-keeping purposes.
testing involves a ‘system’ consisting of three main • Adequate facility to save large numbers of tests and test components: spirometer, operator and test subject. Each of quality indicators where needed, for example, for these can be a source of variation in measurements and syringe calibration is required in order to isolate the device. Biological • Availability of after-sales service.
standards are useful for testing software irregularities such as, In addition to mechanical validation, spirometers can also for example, inconsistencies in the calculation of predicted be tested in real-life situations involving human subjects.12 values. Also, when they are used in conjunction with a SATS recommend that independent professional advice physical standard (calibration syringe), biological standards are from a registered pulmonology training laboratory or the useful to test the proficiency of operators.
Spirometry Training and Certification Committee of the South In addition to daily volume calibration, spirometers must be African Thoracic Society (SATS) be obtained before a new maintained routinely according to the manufacturer’s specifications. This includes the cleaning of pneumotachs atleast once a week (more frequently if there is visible 5.2 Calibration
condensation), as they are particularly sensitive to moisture All diagnostic spirometers must be volume-calibrated at least and secretions. Other components of the spirometer, for daily using a calibrated syringe with a volume of at least 3 l to example the time clock, must also be calibrated from time to ensure that they remain accurate during use. During industrial time. For these and other maintenance functions the surveys in which a large number of subject manoeuvres are manufacturer must routinely check spirometers at least 6 - 12- performed, calibration must be checked each morning and at least twice during the day. In circumstances where thetemperature may change markedly over the day, for example 6. Responsibilities of operators
in field surveys, more frequent temperature corrections arenecessary. Calibration involves the following steps: 6.1 Skills
1. The spirometer is switched to calibration mode (to Operators must have an understanding of the principles prevent BTPS-correction because room air is injected). Room underlying the measurement and equipment operation. They temperature and barometric pressure readings are entered. In must also be able to ensure optimal subject co-operation, the absence of a barometer, barometric pressure readings can provide acceptable, reproducible results and recognise common be obtained from the local airport or weather bureau. abnormalities. Training of pulmonary medical technologists 2. Calibration syringe size is specified. A 3 l syringe is includes this competency and competency to perform recommended. Currently, the use of 2 l and 1 l syringes is not advanced lung function tests and laboratory quality assurance.
The SATS is in the process of developing a curriculum, training 3. The calibration syringe is connected to the spirometer and materials and a means of certification of proficiency in the maximum volume of air injected. Flow-type spirometers performing spirometry for people other than pulmonary are calibrated by injection of the maximum volume from the syringe at least three times, each time at a different speed, tocover a range of flow rates. Calibration is complete when the 6.2 Quality assurance
recorded volumes are within 3% or 50 ml, whichever is the A quality assurance programme is critical to ensure a well- greater, for each flow rate tested. In the event of in-line functioning spirometry laboratory.13 This may be difficult to (antimicrobial) filters being used, calibration should be done attain in a routine clinical practice. At a minimum, a with a filter installed. The quality of the filter must be such calibration and maintenance log as well as electronic or hard that the spirometry system still meets ATS standards.
copies of whole spirograms must be kept so that accuracy and 4. Volume-type spirometers are checked for air leaks if the precision of past tests can be verified. Additionally, standard measured volume remains outside the acceptable range. A leak operating procedures should be documented and kept for can be detected by applying a slight constant positive pressure with the calibration syringe while the spirometer outlet is July 2004, Vol. 94, No. 7 SAMJ
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6.3 Infection control
the day will allow for overnight decontamination of Various components of the spirometry system, including equipment. (Note: indications for spirometry in known mouthpieces, nose clips, pneumotachs, valves and tubing, are potential vehicles for transmission of infection to subjects and For decontamination/sterilisation procedures, consult the staff. Transmission of upper respiratory tract infections, enteric user manual or contact the infection control unit or lung infections and blood-borne infections such as hepatitis and function laboratory at an academic hospital near you.
HIV, can potentially occur through direct contact when testsubjects have open sores in the mouth, bleeding gums or 7. Preparation of subjects
haemoptysis. Tuberculosis and viral and nosocomial infectionscan also occur, indirectly, through inhalation of aerosol droplets 7.1 Exclusion criteria
from the spirometer or surroundings. The type of testmanoeuvre determines whether inhalation from the spirometer The main exclusion criterion for spirometry in routine clinical takes place. This has a major influence on the extent of practice is current respiratory infections in individuals for infection control needed. An expiratory manoeuvre without impairment/disability assessment. Respiratory infections can inhalation from the spirometer reduces the potential for cross- cause temporary lung function impairment and spirometry, if infection dramatically and is the method of choice for mass required, should be done only once infections, including Infection control recommendations for expiratory
7.2 Personal information
manoeuvres without inhalation from the spirometer:
• Spirometry should be performed in a well-lit and ventilated
The following information is required for reference purposes (section 9.2) and must be entered into the programme: weight • Hands must be washed immediately after direct handling of and standing height, age, sex and race. For height and weight mouthpieces or other potentially contaminated spirometer measurements the subject should be barefoot and wear only parts, and between subjects, to avoid operator exposure and light clothing. It is also useful for interpretation purposes to cross-contamination. Gloves should be worn for personal record the time of last bronchodilator use and smoking status.
protection if there are open cuts or sores on the operator’shands.
7.3 Positioning and preparation
• A clean disposable mouthpiece or a disinfected re-usable The subject must be made to feel comfortable. Shelter him/her mouthpiece must be used for every test subject. Any other from other subjects to minimise inhibitions or distractions.
spirometer part coming into direct contact with mucosal Loosen tight clothing. Leave well-fitting dentures in, but surfaces must be decontaminated/sterilised.
remove loose-fitting ones. Test the subject sitting upright on a • Spirometers must be cleaned regularly according to the firm chair with his/her chin slightly elevated and neck slightly manufacturer’s recommendations and the frequency of tests extended. This posture should be maintained during the done. Any part with visible condensation from expired air forced expiration. Discourage excessive bending at the waist.
must also be decontaminated before re-use.
Use of a nose clip is strongly recommended. Instruct the Additional infection control recommendations for
patient when to insert the mouthpiece, for example, at the end manoeuvres involving inhalation from the spirometer system
of maximal inspiration. Ensure that the subject does not bite or part of the system:
the mouthpiece too hard, that the lips are sealed tightly around • In-line filters must be used and replaced after each subject, it, and that the tongue does not obstruct the mouthpiece in any • Involved parts of the system (i.e. spirometer, breathing Ensure maximum subject co-operation. Submaximal efforts tubes and resistive element of the pneumotach) must be are a frequent cause of abnormal results. Explain techniques in decontaminated/sterilised/flushed after each subject.
simple terms and demonstrate them to the patient. For (Note: re-calibration is necessary every time a system has example, explain that: ‘I am going to have you blow into the machine to see how big your lungs are and how fast the air Special precautions for patients with haemoptysis or
comes out. It does not hurt but requires your co-operation and known transmissible infections such as tuberculosis:
lots of effort.’ Explain and demonstrate the use of a nose clip • In-line filters must be used routinely (even if expiratory and mouthpiece. Remind the patient of a few key points. ‘Be manoeuvres are performed exclusively) with sterilisation of sure to take as deep a breath as possible, blast out hard and do not stop blowing until I tell you to do so.’ Give feedback about • Equipment must be decontaminated/sterilised/flushed the performance, encourage and describe what improvements completely after each case. Testing such cases at the end of July 2004, Vol. 94, No. 7 SAMJ
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8. Execution of tests
be expelled from the lungs), lasting until the volume-timecurve has clearly reached a plateau or the flow-volume 8.1 Test manoeuvres
curve has progressively returned to zero flow. Test manoeuvres are determined in part by the setting and All technically unsatisfactory trials must be rejected.
level of sophistication of the spirometer: Common patterns are illustrated in Figs. 2 - 4. • Expiratory-only method. For reasons of ease, cost and
infection control this method is recommended for mass 8.2.2 Reproducibility
screening. It consists of a FVC test with or without a slow Suboptimal effort by the test subject is a frequent cause of VC test. For the FVC test, the test subject is required to diminished lung function results. Ensuring reproducibility of inhale maximally before inserting the mouthpiece and test results is a way of verifying that the test subject co- starting the test. Expiration must be rapid, forceful and operates fully and provides maximal effort. Reproducibility is complete, lasting at least 6 seconds. If significant defined as two curves in which the difference in FVC and obstruction is demonstrated, proceed with a slow VC test.
FEV1, respectively, do not exceed 0.2 l. Reproducibility is The slow VC test is preceded by a maximal inspiration, the usually evident from the spirogram at a glance (Fig. 5). Testing mouthpiece is inserted and the patient then breathes out ina relaxed fashion and for as long as possible. Allow for upto 15 seconds. Only the VC is recorded. The rationale forperforming a slow VC test is as follows: the slow VC provides additional information on the characteristics of the obstructivedefect. A reduction in FVC compared with slow VC suggests dynamic collapse of unsupported airways during forced expirationleading to air trapping. This pattern is typically seen in • Inspiratory-expiratory method. With this method both
inspiration and expiration are recorded to generate a flow-volume curve on a flow-type spirometer. Typically, after insertion of the mouthpiece, a period of quiet breathing isfollowed by a complete expiration, a rapid, forceful and complete inspiration and finally, a rapid, forceful andcomplete expiration. Some programmes prompt for an expiratory manoeuvre followed by an inspiratory manoeuvre. However, the first method is recommended,because this will reveal air trapping as described in the previous section. Reduced FVC compared with forced,inspiratory VC is suggestive of air trapping.
8.2 Test quality
The final step in ensuring data quality is the evaluation ofspirograms for acceptability and reproducibility. 8.2.1 Acceptability
A technically acceptable FVC trial (Fig. 1) must exhibit the
following qualities:• A ‘crisp’, unhesitating start.
• PEF of the flow-volume curve achieved within the first 25% of the volume expired from maximum inspiration. (Most individuals are able to produce PEF within the first 15% of • A continuous smooth exhalation without artefacts caused by coughing, variable effort, second inhalations or leaks Fig. 2. (a) Volume-time, and (b) flow-volume curves exhibiting • A complete exhalation (to the point where no more air can cough artefacts (X) that can influence observed FVC and FEV1. Volume-time graphs are better for evaluating end-of-test quality. July 2004, Vol. 94, No. 7 SAMJ
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must continue until a minimum of three technically acceptableFVC trials have been obtained, at least two of which are reproducible. However, no more than eight trials should beperformed during a single session, because fatigue induced by repeated FVC trials can lead to reduced results. Subjects withasthma sometimes demonstrate spirometry-inducedbronchoconstriction leading to a progressive reduction in lung function with successive trials. This finding will be of interestto the clinician and all acceptable curves should be kept for reporting. Failure to obtain reproducibility after eight trialsmust be documented, but selection of the best curve mayproceed. Fig. 4. (a) Volume-time curve exhibiting a slow rise and the end-of-test not reaching a plateau, and (b) flow-volume curve with a latepeak flow and an abrupt end-of-test. Failure to demonstratereproducibility will confirm these as submaximal efforts. 9. Interpretation of results
9.1 Selection of the best test
For diagnostic purposes, the best spirogram must be inspected,i. e. the graph with the largest sum of FVC and FEV1. For impairment or severity grading the highest values recorded for FVC and FEV1 must be selected from all acceptable curves,including the post bronchodilator curves, even if they come 9.2 Reference standards
Fig. 3. (a) Volume-time, and (b) flow-volume curves exhibiting An individual’s observed results are evaluated for glottis closure (X) resulting in premature termination of effort andreduced observed FVC. abnormalities against predicted results derived from a normal July 2004, Vol. 94, No. 7 SAMJ
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reference population. The comparison is made as per cent result in an increased rate of abnormal results in clinically observed/predicted. Predicted values for FVC and FEV1 are calculated from equations based on age, height and gender The use of prediction equations based on studies carried out because these characteristics are the most important in South Africa, has been investigated.18 Indigenous equations, determinants of lung and airway size in healthy individuals.14-17 as detailed in Table IV, are, where available, recommended for Office spirometers are typically programmed with prediction population screening, surveillance and medico-legal purposes.
equations derived from the study of Caucasians, such as the However, it is acknowledged that the application of these European Community for Steel and Coal (ECSC) (Table III).17 predicted values in every context where spirometry is used Caucasians, when compared with indigenous populations, may present practical difficulties. Alternatively, office usually show higher FVC and FEV1, but similar or lower spirometers usually have a facility for application of a FEV1/FVC%. The use of inappropriate predicted values can correction factor such as 0.9 for adjusting predicted values forCaucasians with a view to their being used for indigenouspopulations. Adjusted per cent predicted can be calculated While the use of such correction factors is acceptable, when understood as an approximation, use of the recommended prediction equations is the preferred option. Operators must familiarise themselves with their spirometers regarding these Table III. ECSC prediction equations* from Quanjer et al.17
*Valid for age 18 - 70 years. Between age 18 and 25 years substitute age 25 in the equation. The lower limit of normal (LLN) is the lower 5th percentile: predictedvalue – 1.64 × RSD.
†80% predicted is an accepted alternative LLN.
H = standing height (m); A = age (years); RSD = residual standard deviation.
Table IV. Prediction equations* from Louw et al.5 (African men)
and Mokoetle et al.8 (African women)
*The lower limit of normal (LLN) is the lower 5th percentile: predicted value – 1.64 × Fig. 5. (a) Volume-time, and (b) flow-volume curves each RSD. 80% is an acceptable alternative LLN.
H= standing height (m); A = age (years); RSD = residual standard deviation. demonstrating three acceptable FVC trials, only #2 and #3 of whichare reproducible. July 2004, Vol. 94, No. 7 SAMJ
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9.3 Diagnosis and severity grade
9.3.1 Algorithm
The major aims of interpreting spirometric results are toconfirm the clinical diagnosis and to estimate the severity ofthe disease. An algorithm is presented (Fig. 6) for categorisingspirometric results as obstructive, normal or restrictivepatterns. The algorithm employs three variables, namelyFEV1/FVC%, % predicted FVC and % predicted FEV1. Theinterpretative strategy proposed is based on publishedguidelines,19 but the lower limit of normal (LLN) forFEV1/FVC% has been adapted to conform to current diagnosticguidelines for chronic obstructive pulmonary disease (COPD).20 The LLN for FEV1/FVC%, FVC and FEV1, is the 5th percentile (see Tables III and IV). Eighty per cent predicted isan acceptable alternative LLN for FVC and FEV1. The use of afixed percentage for the LLN for FEV1/FVC% (usually 70% or75%) is a pragmatic clinical approach, but has limitations. Forscreening purposes it may be more accurate to use the 5thpercentile to minimise misclassifications of borderline values. Areduced FEV1 should always be regarded as abnormal. Whenthis is the only finding on the spirogram, further investigations,including a bronchodilator test, may be necessary to define theabnormality (see Fig. 6).
Non-clinicians such as, for example, occupational health nurses can use the algorithm to identify cases for referral. Theexperienced clinician will use this information in combinationwith pre-test information, including the indications for testing,and his/her knowledge about the case to make a final clinicaldiagnosis.
Are the reference values appropriate? Yes further tests indicated, including BD test) Fig. 6. An algorithm for categorising spirometric results is Fig. 7. Flow-volume curves exhibiting typical (a) reversible presented. The observed FEV1/FVC is expressed as a percentage and obstruction in an asthmatic, and (b) non-reversible obstruction in a the lower limit of normal (LLN) is defined as 70%. FVC and FEV1 person with COPD (black = pre-bronchodilator, grey = post- are based on per cent predicted (%pred) and LLN defined as 80% bronchodilator, broken line = reference standard). July 2004, Vol. 94, No. 7 SAMJ
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9.3.2 Obstructive defect
• Diffuse conditions of lung parenchyma causing stiffness of An obstructive ventilatory defect is defined as a the lung (e.g. interstitial lung disease with fibrosis, disproportionate reduction in maximal airflow from the lung with respect to the maximal volume that can be displaced from • Conditions causing reduced communicating lung volume the lung. The experienced clinician will readily recognise a (e.g. lung resection, occlusion of a main bronchus, post- pattern of expiratory airflow limitation on the flow-volume tuberculous lung destruction and space-occupying lesions curve (Fig. 7). The diagnosis of an obstructive defect should be followed up with a bronchodilator test to examine the nature of Restrictive abnormalities are often over-diagnosed because the obstruction. Severity of obstruction is graded according to of poor effort by the patient (Figs 3 and 4) or the use of the worst affected spirometric parameter, usually % predicted inappropriate prediction equations. Nevertheless, diagnostic FEV1. Mild obstructive defects could be missed if there is interpretation of a reduced FVC can be difficult and referral to under-estimation of FVC due to unacceptable end-of-test a specialist must be considered after exclusion of obvious 9.3.3 Restrictive defect
9.3.4 Obstruction with reduced FVC
A restrictive ventilatory defect is characterised physiologically This pattern consists of reduced FEV1/FVC% and FVC and is by a reduction in total lung capacity (TLC) as determined by usually found in obstructive conditions such as, for example, advanced lung function testing. One may infer a restrictive severe emphysema or asthma, but a combination of an defect when FEV1/FVC% is normal or high (non-obstructive) obstructive and restrictive condition can produce a similar and FVC is reduced (Fig. 8). The severity of the restrictive result. Other VC manoeuvres (section 8.1) and a defect is graded according to TLC when available, otherwise it bronchodilator test (Fig. 7), performed in the office, can assist is graded according to the worst affected spirometric in further defining the underlying disease. The severity of the parameter, and usually % predicted FVC.
defect is graded according to the indicator showing the most A range of conditions can reduce FVC per se: severe defect, usually % predicted FEV1.
• Conditions impeding movement of the chest wall (e.g. pain, 9.3.5 Bronchodilator response
pleural thickening or effusion, neuromuscular weakness, The purpose of a bronchodilator test is to determine whether skeletal abnormality or hyperinflation with air trapping as airway obstruction, as measured by spirometry, is reversible with inhaled beta-2 agonists (Fig. 7). A bronchodilator test canbe standardised as follows: 1. Two reproducible FVC trials are obtained from the test 2. Two puffs (400 µg) of salbutamol or equivalent are 3. A waiting period of at least 10 minutes is introduced.
4. Two reproducible FVC trials are again obtained.
5. The best post-bronchodilator FEV1 is evaluated for a significant improvement of at least 200 ml and 12% from thebest pre-bronchodilator FEV1. Per cent improvement in FEV1can be calculated using the formula: [FEV1 pre-BD - FEV1 post-BD/ FEV1 pre-BD] × 100 The post-bronchodilator FVC trials must be done at least 10 minutes after administration of the bronchodilator, but ideallyonly after 20 - 30 minutes, as this is the time of maximum effectof most short-acting bronchodilators. Both the pre- and post-bronchodilator FEV1 must be reproducible; otherwise aresponse cannot be confidently interpreted as such. For anaccurate interpretation of a negative response, subjects must have been weaned from short-acting bronchodilators for atleast 4 hours and long-acting bronchodilators and theophyllinefor at least 12 hours, if medically possible. A number of Fig. 8. Flow-volume curve exhibiting a typical restrictive pattern ina person with sarcoidosis (broken line = reference curve). The factors, including the dose of bronchodilator, recent prior ‘shoulder’ on the down-slope of the expiratory curve was reproducible bronchodilator medication and timing of the post- (not demonstrated). It represents a normal physiological bronchodilator FVC trials can influence the magnitude of the phenomenon of the expiratory curve. July 2004, Vol. 94, No. 7 SAMJ
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Table V. Guide for grading* spirometric results with a view to quantifying respiratory impairment
*Impairment grade is allocated according to the worst affected parameter. Refer to a pulmonologist if impairment grade and clinical assessment do not agree.
response significantly. Each practice should decide on a guidelines aimed primarily at quantifying functional 9.3.6 Grading respiratory disease severity
9.4 Reporting
The main indications for grading respiratory disease severity Spirometry reports must contain the following information: are to quantify respiratory impairment/disability for medico- • Identification of subject and date of testing.
legal purposes, and to optimise and standardise treatment • Personal information (see section 7.2) and origin of Guidelines for grading spirometric impairment correlate • Numerical values and graphs to assess acceptability and different lung function tests, including spirometry, with the reproducibility (at least two curves, but preferably three).
ability to perform physical activities.21 For this purpose criteria for spirometry, performed in the office, are included (Table V) The report should refer to lung function and not disease for use in conjunction with the algorithm. LLN for FEV1/FVC% (e.g. ‘obstructive lung function defect without reversibility’ has been adapted to conform to current diagnostic guidelines rather than ‘chronic obstructive lung disease’), unless the for chronic obstructive pulmonary disease (COPD).20 A reporter is a clinician and has full clinical details to make an severity grade is awarded according to the worst affected parameter. The grading of obstruction should be based on thepost-bronchodilator values.
In most cases simple spirometry will be sufficient for 10. Spirometry Training and
evaluating respiratory impairment. However, if discordance is Certification Committee
found between spirometry and the stated level of dyspnoea orclinical evaluation, additional lung function tests may be For further information on training opportunities, readers may indicated and the subject must be referred to a specialist with contact the Chair, Spirometry and Training Certification diagnostic lung function facilities. Further tests might include Committee, South African Thoracic Society, PO Box 16433, carbon monoxide diffusing capacity (DLCO) and/or exercise testing. In addition to spirometry, DLCO is clinically one of themost useful tests of lung function. It is especially useful in 11. Acknowledgement
interstitial lung diseases, including the pneumoconioses, wheregas transfer at alveolar level might be affected The Standards of Spirometry Committee of the SATS drafted disproportionately to the mechanical properties of the lung.
this document. The SATS Council adopted it in August 2001.
Another factor that needs to be considered during the clinical The working group wishes to thank all reviewers for their evaluation is the potential contribution of extra-pulmonary input and the staff of the lung function laboratory at Tygerberg disease, for example, ischaemic heart disease, to total Hospital for help with graphic material.
impairment. Also, because of its varying nature, the usualspirometric criteria do not apply to asthma as far as assessment 12. References
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