Spirometry: test performance and

interpretation

Prof Ellie Oostveen, lung physiologist

Antwerp University Hospital and University of Antwerp

Ellie.Oostveen@uza.be

Guidelines: the literatureATS/ERS Task Force: Eur. Respir. J. 2005 (jul-nov)

• General considerations for lung function testing. ERJ 2005: 26: 153-161

• Standardisation of spirometry. ERJ 2005: 26: 319-338 More recent: Graham et al. AJRCCM 2019

• Standardisation of the measurement of lung volumes. ERJ: 2005: 6: 511-522

• Standardisation of single breath determination of carbon monoxide uptake in the lung. ERJ 2005: 26: 720-735. More recent: Graham et al. Eur. Respir. J 2017.

• Interpretative strategies for lung function tests. ERJ 2005: 26: 948-968

Kwaliteit op het longfunctielab

Standardisation of tests

• Contra-indications: • Myocard infarction < 1 month• Rib fracture, pneumo thorax etc. (Aneurysm is

NOT a contra-indication) • Thoracic or abdominal surgery < 1 month• Suspected transmissible infection

• Suboptimal results are likely when:• Chest of abdominal pain• Oral or facial pain (due to mouthpiece?)• Stress incontinence• Dementia or confused person• Young children ATS/ERS Task Force 2019

Calibration

• Calibration with syringe (3 L):• Fast vs. slow calibration (linearity, end-of-

test criterium)

• Biological calibration (healthy subject whose values are known)

Cleaning / disinfection

• Each patient: new mouthpiece

• Disposable in-line bacterial filter • No/hardly risk of contamination

• Daily cleaning & disinfection

ATS-ERS 2005 Spirometry guidelines

Good quality spirometry implies:

• A correct performance of the individual forced expiratory manoeuvres, i.e. acceptable forced expiratory manoeuvres

• A minimum of 3 (maximally 8) acceptable forced expiratory manoeuvres which fulfill the criteria of reproducibility

A correct FVC manoeuvre

• A correct body position (head slightly extended)

• A maximal deep inspiration (with a pause < 1 s at TLC)

• A good /fast start of the forced expiration (powerful, explosive)

• Exhale as long as possible (until no air can be expired any more; expiratory flow < 25 mL/s): in adults an expiration of at least ≥ 6 s!

• No change in body position

• Repeat instructions when necessary and

• Coach vigorously and in a clear way!

Criteria for FVC acceptability

• Within the test:

• There is a good start of the FVC manoeuvre (extrapolated

volume < 5% FVC or 0.15 L, whichever is greater)

• There are no artifacts in the forced expiration (e.g. cough, air

leakage, glottis closure, no maximal effort, obstruction of

mouth piece, expiration stops too early…)

• There is a satisfactory end of the forced expiration ( ≥ 6 s.

(adults) and a plateau in the volume-time curve or if the

patient can or may not expire any longer)

A good start of the FVC manoeuvre:

“back-extrapolation”

The principle of back-extrapolation:

Extrapolated volume (EV)

Expired V

olu

me (

L)

time (s)t= 0 s

The principle of back-extrapolation: in the volume-time curve, the tangent of the steepest part is back-extrapolated in order to obtain t= 0, the start of the forced expiration.

The principle of back-extrapolation: in the volume-time curve, the tangent of the steepest part is back-extrapolated in order to obtain t= 0, the start of the forced expiration. The extrapolated volume should be < 150 mL or 5% FVC (whichever is greater)

Back-extrapolation:

• Back-extrapolation is automatically performed by the software of the spirometer.

• Thus: carefully inspect the table of results to see if the extrapolated volume (EV, …) is within acceptable limits

• If not:• throw away the FVC manoeuvre• Instruct the patient to avoid the “hesitant start”

and to immediate “blast out” after the full inspiration.

Artifacts in the Forced Expiration

Cough…Very good recognizable in the FV curveVery good recognizable in the FV curve, but hardly in the volume time curve…

Submaximal force during expiration

PEF is reached too late during expiration

Incomplete exhalation to the end of test

Consequence?

Spirometry Induced Obstruction

A systematic reduction in FEV1 with additional manoeuvres performed: FV loops show a systematic increase in obstruction

Measurement 1Measurement 2Measurement 3

Criteria for FVC acceptability

• Three criteria:

• There are no artifacts in the forced expiration (e.g. cough, air leakage, glottis closure, expiration stops too early…)

• There is a good start of the FVC manoeuvre(extrapolated volume < 5% FVC or 0.15 L, whichever is greater)

• There is a satisfactory end of the forced expiration ( ≥ 6 s. or a plateau in the volume-time curve or if the patient can or may not expire any longer)

Criteria for FVC repeatability

• Between tests:Evaluate after three correct FVC manoeuvres:• Largest and second-largest value of FVC within 0.15 L ?• Largest and second-largest value of FEV1 within 0.15 L ?

• If yes→ Ready! • If no → perform another expiration (up to 8 FVC-tests)

Examples of spirometry test

• The next slides show examples of spirometrytests

• Please evaluate if the spirometry test was of good quality!

Flow (L/s)

Volume (L)

Dhr. MVO 53 jr, 181 cm, 121 kg

pred #1 #2 #3

FVC 5.08 4.84 4.80 5.13

FEV1 3.98 3.97 4.29 4.14

FEV1/FVC

78 77 83 81

Volume (L)

Tijd (s)

Dhr. K.D.J 40 jr, 179 cm, 127 kgPred #1 #2 #3

FVC 5.32 3.53 4.86 5.23

FEV1 4.27 3.28 3.48 3.48

FEV1/FVC 81 63 67 66

Volume (L)

Tijd (s)

Flow (L/s)

Volume (L)

Mevr. H.J. 56 jr, 160 cm, 55 kgpred pre %p z-score post %p %

verschil

FVC 3.15 2.01 64 -2.57 2.07 66 3

FEV1 2.50 0.65 26 -4.86 0.76 30 17

FEV1/FVC 80 32 -4.83 37

Dhr VDB; 61 jr, 176 cm, 96 kg

Dhr VDB; 61 jr, 176 cm, 96 kg

pred pre %p Z-score

FVC (L) 2.54 1.68 66 -1.73

ESW (L) 2.11 1.42 67 -1.68

ESW/VC (%)

76 84 +1.11

Dhr VDB; 61 jr, 176 cm, 96 kg

pred pre %p Z-score

FVC (L) 2.54 1.68 66 -1.73

ESW (L) 2.11 1.42 67 -1.68

ESW/VC (%)

76 84 +1.11

TLC 6.98 4.42 63 -3.66

RV 2.42 1.67 69 -1.83

Interpretation of spirometry

When is a measured spirometry “normal”?

Interpretation scheme ATS-ERS 2005

Prediction of ‘restriction’ on based on spirometry (golden rule is: based on TLC)

FEV1/FVC

80.1-100%

FEV1/FVC

60.1-80%

FEV1/FVC

40.1-60%

FEV1/FVC

20-40%

Aaron et al. Chest 1999

Interpretation of key figures: use of reference values

How to tell whether the measured lung function of a patient is “normal”?

The optimal reference value of a patient is a lung function measurement performed in a clinical optimal phase!

Reference value = prediction for a · healthy person with· similar height,· age,· sex and· ethnical background

Reference values

Asymptomatic, lifetime non-smokers with 2 acceptable FVC manoeuvres (7429/20627 subjects: 8-80 yrs)

Hankinson et al. AJRCCM, 1999: 179-187

Hankinson et al. AJRCCM, 1999: 179-187

Reference values

Hankinson et al. AJRCCM, 1999: 179-187

Reference values

Mean value (X)

84% of the population > ( X – 1 SD )

SD

95% of the population > ( X – 1.64 SD )

Lower limit of the normal value (LNN)

When is lung function “abnormal”?

Use of LLN:

• Lower Limit of the Normal value

• Only 5% of a healthy population exhibits values below this threshold

• At the age of 35-40 years:

• Is the LLN of FEV1/VC ~70%

• Is the LLN of FVC ~ 80%predicted

• However, with increasing age, the LLN decreases, thus a fixed cut-off for FEV1/FVC (or FVC) is FALSE! This holds both for obstruction and restriction.

Reference values

Hankinson et al. AJRCCM, 1999: 179-187

Conclusion:

The use of a fixed cut-off value as the lower limit of the normal value forFEV1/FVC (< 70%) leads to:

•under-diagnosis of obstruction in younger individuals (asthma)

•over-diagnosis of obstruction in oldersubjects (COPD)!!

Global Lung Function Initiative (2012)

• 74.187 spirometry data of healthy, non-smoking subjects between 2.5 - 95 years (43% M; 72 centra uit 33 landen)• n= 57.395 Caucasians• n= 3.545 Afro-Americans• n= 4.992 North-East Asians• n= 8.255 South-East Asians

• FEV1/FVC ratio is independent of ethnicity!

Prediction Spirometry (GLI)

Quanjer et al. Eur Respir J 2012

Mean value (X)

84% of the population > ( X – 1 SD )

SD

95% of the population > ( X – 1.64 SD )

Lower limit of the normal value (LNN)

Use of LLN: Is a measured value < LLN, then z-score < -1.64

Conclusions

• Reference values for spirometry are now available for ages between 3 and 95 yearss

• They can be applied worldwide for subjects with different ethnical background

• These equations are continuous and provide, next to the predicted value, also the lower limit of the normal value (LLN = -1.64 z-score), dependent on sex, age, height, ethnicity.

• Reference values for diffusion capacity (only Caucasians) are now available for ages between 4 and 91 years

Questions?