Pulmonary function tests measure how an individual inhales and exhales air over time. Spirometry evaluates lung function through acceptability criteria, reproducibility criteria, and comparison to reference values to identify obstructive, restrictive, or mixed lung patterns. Interpretation involves assessing the flow-volume loop and volume-time curve for start and end-of-test criteria and comparing values like FEV1, FVC, and their ratio to predicted values and determination of limits of normal. A bronchodilator response test evaluates change in values after administration of a bronchodilator.

1. Pulmonary Function Test
Khagendra Jang Shah
MD, Resident
NAMS

2. Spirometry is a physiological test that measures
how an individual inhales or exhales volumes of air
as a function of time. The primary signal measured
in spirometry may be volume or flow.
 The test effort can be presented as a ‘FLOW-VOLUME
LOOP’ or as a ‘VOLUME-TIME CURVE’.

3. PRESENTATION PLAN
• Acceptability and repeatabiltiy criteria
• Reversibility criteria
• Test result selection. Best curve
• Reference values
• Advantages of LLN over % predicted
• Normal pattern
• Obstructive pattern
• Restrictive pattern

4. evaluating
spirometric results
• acceptability and repeatability criteria
• reversibility criteria for bronchodilator test
• information on reference values and
comparing the results with normal values
• normal, obstructive and restrictive patterns
of spirometry
• changes of spirometric indices over time

5. Spirometric results evaluation may be considered as a two-step process
 acceptibility criteria:
Expiratory effort show good
start of test with flow volume loop and volume time curve showing
rapid rise to PEF and good effort ,
end of test criteria met (plateau of volume for more than 1 sec is
present in all attempts and all expiratory efforts are beyonds 6 secs. No
coughing or closer of glottis seen no extra breath .
Good spirometry implies that at least three acceptable manoeuvers
should be recorded
 reproducibility criteria:
difference between the best and the second best value of FEV1 and FVC
less than 150 ml.

6. • When doing a bronchodilator test, one should be aware that both
spirometries (pre- and post- ) should be technically acceptable and
the bronchodilating agent should be properly delivered.
• pre and post values of FEV1 and FVC are analysed. A positive
response is achieved
• when the increase in postbronchodilator values is greater than 200
ml and 12% of prebronchodilator value.
• Recorded best values are compared with reference values, that are
created using results obtained from the examination of a healthy
subpopulation and have the form of equations relating respective
parameters to sex, age, height and ethnic origin.
• interpreting the results is to compare the measured value with the
lower limit of normal (LLN) – which is set at the level of 5th percentile

7. • With spirometry obstructive defect can be stated when the FEV1/
(F)VC factor is below the lower limit of normal.
• The severity of obstruction is quantified using the value of FEV1
expressed as a percentage of predicted.
• When FEV1/ (F)VC remains within normal limits and FVC is below
LLN a restrictive ventilator defect may be suspected, but confirmation
of this requires the measurement of total lung capacity (TLC) done
either by plethysmography or gas dilution method

9.  Actual measurement:
 There are three important steps (FFF) the subject has to follow in
spirometry: a) Full inspiration, b) Forceful expiration, c) Full
expiration.
 Quality control of spirometry includes
 the assessment of acceptability (within-manoeuvre evaluation
 and repeatability (between-manoeuvre evaluation) of the tests.
 acceptability criteria
1) There is a good start of the test,
2) Spirogram is free from artefacts: continuous blow as fast and as
hard as possible, without cough, variable effort, and early
termination, etc
3) There is a satisfactory exhalation.

10. The rapid start is defined as a back extrapolated volume of <5% of the FVC or less
than 0.15 l, whichever is greater.
The end of test criteria are:
• -The subject cannot or should not continue further exhalation or
• -The volume-time curve shows an obvious plateau (no change in volume: 0.025 l for >1
second) or
• -The subject has tried to exhale for at least 6 seconds (for at least 3 seconds in children <
10 yrs)

11. • The repeatability criteria are used as a guide to whether more than
three acceptable FVC manoeuvres are needed.
• The following reproducibility criteria are applied after three
acceptable spirograms have been obtained:
• 1) The two largest values of FVC must be within 0.150 l of each other,
• 2) The two largest values of FEV1 must be within 0.150 l of each
other,
• 3) If criteria 1 and 2 are not met, testing should be continued.

12. Interpretation of PFTs is usually based on comparisons of data
measured in an individual patient or subject with reference
(predicted) values based on healthy subjects.
Predicted values should be obtained from studies of
‘‘normal’’ or ‘‘healthy’’ subjects with the same
anthropometric (e.g. sex, age and height) and, where
relevant, ethnic characteristics of the patient being tested

13. Obstructive abnormalities
An obstructive ventilatory defect is a disproportionate reduction
of maximal airflow from the lung in relation to the
maximal volume (i.e. VC) that can be displaced from the lung
[45–47]. It implies airway narrowing during exhalation and is
defined by a reduced FEV1/VC ratio below the 5th percentile
of the predicted value.
The earliest change associated with airflow obstruction in
small airways is thought to be a slowing in the terminal
portion of the spirogram, even when the initial part of the
spirogram is barely affected

14. This slowing of expiratory flow is most obviously reflected in a concave
shape on the flow–volume curve.
As airway disease becomes more advanced and/or more central airways
become involved, timed segments of the spirogram such as the FEV1
will, in general, be reduced out of proportion to the reduction in VC.

15. a, b) Examples of obstructive pulmonary defects with a low (a; forced expiratory
volume in one second (FEV1) 38%; FEV1/vital capacity (VC) 46%; peak
expiratory flow (PEF) 48%; total lung capacity (TLC) 101%) or normal .
(b; FEV1 57%; FEV1/VC 73%; PEF 43%; TLC 96%) ratio of FEV1/VC. In both cases, TLC is
normal, and flows are less than expected over the entire volume range.

16. c) Example of a typical restrictive defect (FEV1 66%; FEV1/VC 80%; PEF 79%; TLC 62%). The TLC
is low and flow is higher than expected at a given lung volume.
d) Example of a typical mixed defect characterised by a low TLC and a low FEV1/VC ratio (FEV1
64%; FEV1/VC 64%; PEF 82%; TLC 72%)

17. Restrictive abnormalities
 A restrictive ventilatory defect is characterised by a reduction in TLC
below the 5th percentile of the predicted value, and a normal
FEV1/VC.
 The presence of a restrictive ventilatory defect may be suspected
when VC is reduced, the FEV1/VC is increased (.85–90%) and the
flow–volume curve shows a convex pattern.

18. Mixed abnormalities
 A mixed ventilatory defect is characterised by the coexistence of
obstruction and restriction, and is defined physiologically when both
FEV1/VC and TLC are below the 5th percentiles of their relevant
predicted values.

19. Types of ventilatory defects and their diagnoses
• Obstruction: < FEV1/VC ,5th percentile of predicted
• Restriction TLC :<5th percentile of predicted
• Mixed defect : FEV1/VC and TLC <5th percentile of predicted

20. INTERPRETATION AND PATTERNS OF
DYSFUNCTION
 In contrast with a fixed value of 0.7, the use of the 5th percentile
does not lead to an overestimation of the ventilatory defect in older
people with no history of exposure to noxious particles or gases.

21. Omitting the quality review and relying only on
numerical results for clinical decision making is a
common mistake,

23. BRONCHODILATOR RESPONSE
• Bronchial responsiveness to bronchodilator medications is an
integrated physiological response involving airway epithelium,
nerves, mediators and bronchial smooth muscle.
• to assess both the underlying airway responsiveness and the
potential for therapeutic benefits of bronchodilator therapy.
• salbutamol, are recommended. Four separate doses of 100 mg
should be used when given by metered dose inhaler using a spacer.
Tests should be repeated after a 15-min delay
• Values >12% and 200 mL compared with baseline during a single
testing session suggest a ‘‘significant’’ bronchodilatation.

24. procedures relating to bronchodilator response
• Assess lung function at baseline
• Administer salbutamol in four separate doses of 100 mg through a
spacer
• Re-assess lung function after 15 min.
• An increase in FEV1 and/or FVC ≥12% of control and ≥200 mL
constitutes a positive bronchodilator response.
• The lack of a bronchodilator response in the laboratory does not
preclude a clinical response to bronchodilator therapy

25. CENTRAL AND UPPER AIRWAY OBSTRUCTION
• Central airway obstruction and UAO may occur in the extrathoracic
(pharynx, larynx, and extrathoracic portion of the trachea) and
intrathoracic airways (intrathoracic trachea and main bronchi).
• When patient effort is good, the pattern of a repeatable plateau of
forced inspiratory flow, with or without a forced expiratory plateau,
suggests a variable extrathoracic central or upper airway obstruction.
Conversely, the pattern of a repeatable plateau of forced expiratory
flow, along with the lack of a forced inspiratory plateau suggests a
variable, intrathoracic central or upper airway obstruction. The
pattern of a repeatable plateau at a similar flow in both forced
inspiratory and expiratory flows suggests a fixed central or upper
airway obstruction.

26. a) fixed, b) variable extrathoracic, and c) variable intrathoracic airway obstruction.

29. INDICES MEASURED

30. ANNUAL FEV1?
• Used to detect sudden deterioration in lung
function
• Should precipitate action if deterioration
marked.
Normal deterioration in FEV1 thought to be
50ml/annum in none smoking individual

31. THE NORMAL CURVE
Volume Time
• The vertical scale indicates
total volume (l) the patient has
blown out
• The horizontal scale indicates
the total time (s) the patient
has been blowing out for
• Note the initial part of the
curve which is steep followed
by a gradual flattening of the
curve
• Look initial step up, mid line
platue of at least 1 sec and no
drop in last .

32. Normal Spirometry

33. THE NORMAL CURVE
Flow Volume Loop
• The vertical scale indicates litres
of air breathed out per second
(L/s) at that moment in time
• The horizontal scale indicates
total volume expired (L)
• Note the sharp peak at the
beginning of the curve followed
by an initially sharp trough that
gradually flattens out

34. • The FVC may be reduced by suboptimal
patient effort, airflow limitation, restriction
(eg, from lung parenchymal, pleural, or
thoracic cage disease), or a combination of
these.
• The lower limit of normal FEV1 is more
accurately defined by the fifth percentile of
healthy never-smokers, instead of the
traditional 80 percent of predicted .

35. (A) a healthy person (B) severe obstruction (emphysema),
(C) severe restriction from interstitial disease (radiation fibrosis), (D) upper airways obstruction
(tracheal stenosis),
E) poor effort.

36. • At least three acceptable spirograms must be
obtained.
• In each test, patients should exhale for at least six
seconds and stop when there is no volume
change for one second.
• The test session is finished when the difference
between the two largest FVC measurements and
between the two largest FEV1 measurements is
within 0.2 L.
• If both criteria are not met after three
maneuvers, the test should not be interpreted.
• Repeat testing should continue until the criteria
are met or until eight tests have been performed.

37. Restrictive Pattern
 Decreased FEV1
 Decreased FVC
 FEV1/FVC normal or increased

38. How to determine severity ?
• Close to 80 Borderline
• 65-79 Mild
• 50-64 Moderate
• < 50 severe
Obstruction:
FEV1
• Close to 80 Borderline
• 65-79 Mild
• 50-64 Moderate
• < 50 severe
Restriction
FVC

39. SPIROMETRY PATTERNS

40. TECHNIQUE PROBLEMS
Cough
• This curve suggests the patient
has coughed during a FVC
reading
• Note the peaks and troughs
that occur throughout the
curve
• This will effect the FVC reading

41. TECHNIQUE PROBLEMS
Poor Effort
• This curve suggests the patient
has not blown as hard as they
can during the FVC technique
• Note the rounded top to the
peak at the beginning of the
curve
• This will effect the FEV1
reading

42. TECHNIQUE PROBLEMS
Slow Start
• This curve suggests the patient
has started off blowing slowly
during a FVC technique
• Note the peak in L/s comes in
the middle of the curve rather
than at the beginning
• This will effect the FEV1
reading

43. TECHNIQUE PROBLEMS
Inspiration
• This curve indicates the patient
has breathed in at the
beginning of the technique
• This usually occurs when the
patient puts the filter in their
mouth before they have
finished breathing in
• Note the negative L/s reading at
the beginning of the curve
• This could effect all readings

44. TECHNIQUE PROBLEMS
Inspiration
• This curve suggests the patient
has breathed in at the end of
the FVC technique
• This usually occurs when the
patient attempts to take an
extra breath in to prolong
expiration
• Note the negative L/s at the end
of the curve
• This could effect the FVC
reading

45. Bronchodilator challenge test response
• FVC increase 200mL or
• FEV1 increase 12% or
• FEF 25-75% increase15- 25%
• “ Improved after bronchodilation”
• “Reversible airway disease”

46. BRONCHODILATOR RESPONSE
 Degree to which FEV1 improves with inhaled
bronchodilator
 Documents reversible airflow obstruction
 Significant response if:
- FEV1 increases by 12% and >200ml
 Request if obstructive pattern on spirometry

47. REVERSIBILITY
Repeat Spirometry following one of the
following (Post);
1. Salbutamol 100mcg MDI 4 puffs via spacer
2. Salbutamol 2.5mg nebuliser
Repeat Spirometry after 15-30 minutes

48. Reversibility
• Useful if diagnosis is not clear
Either;
• Measure peak flows for 14 days morning and
evening. Diurnal variation of greater than 20%
indicates asthma
• Record pre and post bronchodilator
spirometry

49. REVERSIBILITY
• An FEV1 that increases by < 400mls is likely to
have COPD
• An FEV1 that increases by > 400mls is likely to
have asthma
• However if;
– FEV1 < 80%
– Ratio < 70%
– Post > 400mls
– Obstruction is not fully reversible

50. Reversibility (Example)
Billy
• FEV1 2.34 l
• FEV1 56% of predicted
• Ratio 40%
Given Salbutamol 2.5mg nebuliser and
spirometry repeated after 30 minutes
POST
• FEV1 3.09 l
• FEV1 91% of predicted
• Ratio 71%

51. Flow Volume Loop
 “Spirogram”
 Measures forced inspiratory and expiratory
flow rate
 Augments spirometry results
 Indications: evaluation of upper airway
obstruction (stridor, unexplained dyspnea)

52. Flow Volume Loop

53. Upper Airway Obstruction
 Variable intrathoracic obstruction
 Variable extrathoracic obstruction
 Fixed obstruction

54. Upper Airway Obstruction

55. CORRECTION FACTORS
BTS Guidelines Only
Ethnic Origin Correction Factor
Caucasian 100%
Afro-Caribbean Reduce by 13% (87%)
Asian Reduce by 7% (93%)

56. PERCENTAGE OF PREDICTED
• Most frequently referred to value within the
community
• Need to be aware that this gives an absolute
value and clearly there is variability within
normality
Measured x 100 = % Predicted
Predicted

58. Lung Volumes – Patterns
 Obstructive
- TLC > 120% predicted
- RV > 120% predicted
 Restrictive
- TLC < 80% predicted
- RV < 80% predicted

59. Diffusing Capacity
 Diffusing capacity of lungs for CO
 Measures ability of lungs to transport inhaled gas
from alveoli to pulmonary capillaries
 Depends on:
- alveolar—capillary membrane
- hemoglobin concentration
- cardiac output

60. Documentation
• 1.Progress note
– Indication
– Patient effort
– Assessment
• 2. Scanned original report in Special Studies

61. Diffusing Capacity
 Decreased DLCO
(<80% predicted)
 Obstructive lung disease
 Parenchymal disease
 Pulmonary vascular disease
 Anemia
 Increased DLCO
(>120-140% predicted)
 Asthma (or normal)
 Pulmonary hemorrhage
 Polycythemia
 Left to right shunt

62. DLCO — Indications
 Differentiate asthma from emphysema
 Evaluation and severity of restrictive lung disease
 Early stages of pulmonary hypertension
 Expensive!