simple understanding of spirometry

1. SPIROMETRY
9/26/2020
1dessalegn yemam

2. objective
At the end of this session learners are expected to;
 Know what spirometry is
 Understand indication and contraindication to perform
spirometry
 Know measurements of spirometer
 Understand spirometric measurement interpretation
9/26/2020
2
dessalegn yemam

3. Introduction
 Spirometry is the term given to the basic lung
function tests that measure the air that is expired and
inspired using Spirometer.
 Spirometer is an instrument that measures and
records the volume of inhaled and exhaled air, used
to assess pulmonary function. The computer
connected to spirometer converts the signal into
numerical values and graphical images called a
spirogram.
9/26/2020
3
dessalegn yemam

4. Con’t…
 Spirometer was invented by John Hutchinson
(1811-1861) – surgeon in London.
 He observed that the volume of air that could be
exhaled from the lungs when completely inflated
(Vital Capacity or VC) was a good indicator of an
individual's longevity.
 When this measure was compromised, premature
death was expected.
9/26/2020
4
dessalegn yemam

5. Con’t…
 There are different types of spirometer. According to
their property, spirometer can be;
 Water / Dry
 Closed / Open
 Volumetric / Pneumotachometer
 Pneumotachometer is the most commonly used
spirometer
9/26/2020
5
dessalegn yemam

6. Indication and contraindication for spirometer
application
 Spirometer is indicated mainly for;
Diagnostic
Monitoring
Evaluation of deterioration/disability
Public health
Clinical research
9/26/2020
6
dessalegn yemam

7. Diagnostic
 Evaluation of respiratory symptoms or signs,
 Measurement of the effect of the disease on lung function ,
 Screening of subjects at risk of lung disease
 Risk evaluation for surgical procedures
 Estimation of severity and prognosis in respiratory diseases or diseases
of other organs that affect respiratory function,
 Assessment of health status before beginning strenuous physical activity
programs 9/26/2020
7
dessalegn yemam

8. Monitoring
 Evaluation of the effect of therapeutic interventions,
 monitoring the course of diseases that affect lung
function,
 Monitoring persons exposed to substances that are
potentially toxic for the lungs, including drugs
9/26/2020
8
dessalegn yemam

9. Evaluation of deterioration/disability
 Rehabilitation programmes,
 Evaluation of dysfunction for medical insurance and
legal assessments (social security, expert reports,
etc.)
9/26/2020
9
dessalegn yemam

10. Contraindication
 Absolute
Haemodynamic instability
Pulmonary embolism (until adequately anticoagulated)
Recent pneumothorax (2 weeks after re-expansion)
Acute haemoptysis
Active respiratory infections (tuberculosis, norovirus, influenza)
Recent myocardial infarction (7 days)
Unstable angina
Aneurism of the thoracic artery that has grown or is large in size (>6 cm)
Intracranial hypertension
Acute retinal detachment
9/26/2020
10
dessalegn yemam

11. Con’t…
 Relative
Children under 5–6 years old
Confused or dementia patients
Recent abdominal or thoracic surgery
Recent brain, eye or ear, nose or throat surgery
Acute diarrhoea or vomiting, nausea
Hypertensive crisis
Dental or facial problems that impede or make it difficult to
insert and hold the mouthpiece
9/26/2020
11
dessalegn yemam

12. Spirometer measurement
 Spirometer measures and records the volume of
inhaled and exhaled air to assess pulmonary
function.
 There are two types of lung volume: static and
dynamic lung volume.
 There are four static respiratory volumes (lung
volume). When two or more respiratory volumes are
added we call it respiratory capacities.
9/26/2020
12
dessalegn yemam

13. Con’t…
9/26/2020
13
Tidal volume (TV); is Amount of air inhaled or exhaled in one breath during
relaxed, quiet breathing.
Inspiratory reserve volume (IRV); is the Amount of air in excess of tidal
inspiration that can be inhaled with maximum effort or Volume of gas inspired
over normal tidal inspiration (45ml/kg).
Expiratory reserve volume ( ERV) ; Volume of gas forcefully expired after
normal tidal expiration or Amount of air in excess of tidal expiration that can be
exhaled with maximum effort (15ml/kg).
Residual volume (RV); is Volume of gas remaining in lungs after a forced
expiration (15-20ml/kg). It is Amount of air remaining in the lungs after maximum
expiration; keeps alveoli inflated between breaths and mixes with fresh air on next
inspiration.
dessalegn yemam

14. Con’t…
 RV is not measured by spirometer. Because
spirometer measures the volume of air that moves in
and out of the lung.
 The other lung volumes are measured by spirometer
and the spirogram is recorded
9/26/2020
14
dessalegn yemam

15. Con’t…
9/26/2020
15
dessalegn yemam

16. Con’t…
 The summation of two or more lung volumes is called lung capacities.
There are four lung capacities.
 Vital capacity (VC); Amount of air that can be exhaled with maximum
effort after maximum inspiration (ERV + TV + IRV); used to assess
strength of thoracic muscles as well as pulmonary function. It is around
4700 ml or (60-70ml/kg).
 Inspiratory capacity (IC); is Maximum amount of air that can be inhaled
after a normal tidal expiration (TV + IRV). It is about 3500 ml.
 Functional residual capacity (FRC); is the Amount of air remaining in
the lungs after a normal tidal expiration (RV + ERV). It is about 2400 ml or
30ml/kg.
 Total lung capacity (TLC); volume of gas in lungs at the end of maximal
inspiration. It is about 5900 ml (80ml/kg).
NB;A spirometer is unable to measure TLC, FRC and RV. 9/26/2020
16
dessalegn yemam

17. Dynamic lung volume
 The forced expiratory volume in one second (or FEV1);
represents the volume of air exhaled during the first second of
a forced expiration.
 The forced expiratory flow between 25% and 75% of FVC
(FEF 25-75)
 The forced vital capacity (FVC); volume of forced exhaled
air after maximal inhalation
 The Tiffeneau index (ratio of FEV / FVC x 100). This
percentage is important in identifying airways obstruction.
Airflow obstruction will occur if FEV1 <80% predicted and
FEV1/FVC <70%7
9/26/2020
17
dessalegn yemam

18. Con’t…
9/26/2020
18
dessalegn yemam

19. Con’t…
 These spirometric
measurements are
important to evaluate
pulmonary function and
to know whether lung
problem is obstructive
or restrictive
9/26/2020
19
dessalegn yemam

20. The main difference between vital capacity and forced vital capacity
 we use Slow
maneuver:
 Quiet breathing,
 Full inspiration,
 Complete exhalation
 we use Forced
maneuver:
 Quiet breathing,
 maximal inspiration,
 rapid and complete
expiration,
 rapid and deep
inspiration 9/26/2020
20
vital capacity forced vital capacity
dessalegn yemam

21. Measurement of TLC, FRC and
RV
 functional residual capacity is measured by means of
a helium dilution method.
9/26/2020
21
A spirometer of known volume is filled with air mixed with helium at a known
concentration. Before breathing from the spirometer, the person expires normally.
At the end of this expiration, the remaining volume in the lungs is equal to the
functional residual capacity. At this point, the subject immediately begins to
breathe from the spirometer, and the gases of the spirometer mix with the gases of
the lungs. As a result, the helium becomes diluted by the functional residual
capacity gases, and the volume of the functional residual capacity can be calculated
from the degree of dilution of the helium, using the following formula
dessalegn yemam

22. Con’t…
Where
FRC is functional residual capacity,
CiHe is initial concentration of helium in the
spirometer,
CfHe is final concentration of helium in the
spirometer, and
ViSpir is initial volume of the spirometer.
 RV= FRC-ERV
 TLC= VC + RV
9/26/2020
22
dessalegn yemam

23. Interpretation of spirometric
result
9/26/2020
23
 Once pulmonary function test done with spirometer is
reported, the next task is interpreting the result and
identify the pathologies and establish differential
diagnosis.
 To interpret the result, and identify the pathologies and
establish differential diagnosis, we use the following
steps;
1) Assess the validity or interpretability of the result
2) Assess the value of FVC, FEV1 and FEV1/FVC , and
group lung pathology based on their value
3) See for reversibility test and static lung volume
4) Establish DX or DDX dessalegn yemam

24. Con’t…
I. Assess the validity or
interpretability of the result
Start- should be quick, sudden
and without hesitation
Expiratory maneuver should be
continuous without artifact,
cough
End of maneuver should not be
an abrupt interruption
9/26/2020
24
dessalegn yemam

25. Con’t…
9/26/2020
25
dessalegn yemam

26. 9/26/2020
26
dessalegn yemam

27. Con’t…
9/26/2020
27
ii. Assess the value of FVC, FEV1 and FEV1/FVC, and group lung pathology based
on their value
If FVC normal, FEV1 normal, absolute FEV1/FVC >0.7, it is normal spirometry
If FVC normal or decreased, FEV1 decreased, absolute FEV1/FVC <0.7, it is
Obstructive ventilatory impairment
If FVC decreased, FEV1 decreased or normal, absolute FEV1/FVC >0.7, it is
restrictive ventilatory impairment
If FEV1, FVC and FEV1/FVC all are decreased, it is mixed lung disease
dessalegn yemam

28. Con’t…
9/26/2020
28
iii. See for reversibility test and static lung volume
 If Obstructive ventilatory impairment is suggested, we will perform bronchodilator challenge
test or reversibility test.
1. Bronchodilators should be withheld; Short-acting for the previous 6 hours, long-
acting for 12 hours, and sustained release theophylline for 24 hours.
2. FEV1/FVC should be measured before bronchodilator
3. The bronchodilator should be given by metered dose inhaler, ideally through a spacer.
A nebulizer may be used but generally larger doses are delivered by this route. 400
µg salbutamol, up to 160 µg ipratropium, or the two combined.
4. FEV1/FVC is measured 15-20 minutes after bronchodilator is given.
5. Calculating bronchodilator reversibility (% FEV1 Reversibility)
dessalegn yemam

29. Con’t…
9/26/2020
29
% FEV1 Reversibility =
Post −bronchodilator FEV1−Pre bronchodilator FEV1
Pre bronchodilator FEV1
X 100
dessalegn yemam

30. Con’t…
 From reversibility test, we may get three possibilities:
1. The FEV1 increases of> 12% and 200 ml from baseline
returning to normal values (> 80% predicted):
OBSTRUCTION FULLY REVERSIBLE (typical
bronchial Asthma)
2. FEV1 increased by 12% or 200 ml from baseline but
remains <80% predicted and FEV/FVC<70:
OBSTRUCTION PARTIALLY REVERSIBLE (typical of
partially reversible COPD)
3. Increases FEV1 <12% or 200 mL from baseline:
OBSTRUCTION NOT REVERSIBLE (typical of COPD is
not reversible)
9/26/2020
30
dessalegn yemam

31. Con’t…
9/26/2020
31
 If the patient’s initial PFT results indicate a restrictive
pattern or a mixed pattern that is not corrected with
bronchodilators, the patient should be referred for full
PFTs with DLCO testing.
 DLCO is a quantitative measurement of gas transfer
in the lungs.
 Diseases that decrease blood flow to the lungs or
damage alveoli will cause less efficient gas
exchange, resulting in a lower DLCO measurement.
dessalegn yemam

32. Con’t…
9/26/2020
32
During the DLCO test, patients inhale a mixture of helium (10%), carbon monoxide (0.3%),
oxygen (21%), and nitrogen (68.7%) then hold their breath for 10 seconds before exhaling. The
amounts of exhaled helium and carbon monoxide are used to calculate the DLCO. Carbon
monoxide is used to estimate gas transfer instead of oxygen due to its much higher affinity for
hemoglobin.
dessalegn yemam

33. Con’t…
9/26/2020
33
IV. Establish DX or DDX
DLCO results Differential diagnosis
High DLCO; Asthma, left-to-right intracardiac shunts, polycythemia, pulmonary hemorrhage
Normal DLCO with restrictive pattern; Kyphoscoliosis, morbid obesity, neuromuscular
weakness, pleural effusion
Normal DLCO with obstructive component; α1-antitrypsin deficiency, asthma, bronchiectasis, chronic
bronchitis
Low DLCO with restriction; Asbestosis, berylliosis, hypersensitivity pneumonitis, idiopathic
pulmonary fibrosis, Langerhans cell histiocytosis (histiocytosis X), lymphangitic spread of
tumor, miliary tuberculosis, sarcoidosis, silicosis (late)
Low DLCO with obstruction; Cystic fibrosis, emphysema, silicosis (early)
Low DLCO with normal PFT; Chronic pulmonary emboli, congestive heart failure, connective
tissue disease with pulmonary involvement, dermatomyositis/polymyositis, inflammatory bowel
disease, interstitial lung disease (early), primary pulmonary hypertension, rheumatoid arthritis,
systemic lupus erythematosus, systemic sclerosis, Wegener granulomatosis (also called
granulomatosis with polyangiitis) dessalegn yemam

34. Con’t…
9/26/2020
34
American Thoracic Society Grades for Severity of a Pulmonary Function Test
Abnormality
Severity FEV1 percentage of predicted
Mild > 70
Moderate 60 to 69
Moderately severe 50 to 59
Severe 35 to 49
Very severe < 35 FEV1
dessalegn yemam

35. 9/26/2020
35
Algorithm for Spirometry interpretation
dessalegn yemam