practical and applied aspects of spirometry

1. SPIROMETRY

2. PY 6.8 DEMONSTRATE THE CORRECT TECHNIQUE TO
PERFORM & INTERPRET SPIROMETRY.
• SLOs: After attending lecture & studying the assigned
materials, the student will:
1.
2.
State the principles of recording of Spirometry.
Define & draw different lung volumes & capacities.
3.Explain FEV (TVC) correctly with its clinical
significance.
4. Demonstrate the correct procedure of recording

3. RELEVANCE
•Although many sophisticated tests are available for
assessing respiratory functions
•VC is a simple & useful measurement for assessing
the ventilatory functions of the lungs in health &
disease.

4. MEASUREMENT
VC may be measured either on a Simple Spirometer or
Recording Spirometer.
A.Simple Spirometer (student Spirometer also called
vitalograph)
B.Recording Spirometer (lung volume & capacity) &
C.Wright’s peak flow meter

7. TYPES OF LUNG FUNCTION TESTS
Lung function tests are of two types:
1. Static lung function tests
2. Dynamic lung function tests.

8. 1. STATIC LUNG FUNCTION
TESTS
•Static lung function tests are based on volume of air that
flows into or out of lungs.
•These tests do not depend upon the rate at which air
flows.
•Static lung function tests include static lung volumes and
static lung capacities.

9. PARAMETERS THAT ASSESS
VENTILATION
• Lung volumes and capacities
- the volume of the air in lungs changes considerably during a
respiratory cycle.
For convenience 4 lung volumes and 4 lung capacities are
distinguished:
• The maximum volume to which a lung can be expanded has been
divided into four non-overlapping volumes
Tidal volume (TV), Inspiratory Reserve Volume (IRV),
Expiratory Reserve Volume (ERV), & Residual Volume (RV).

10. LUNG
CAPACITIES
• Lung capacities are combination of two or more pulmonary
volumes and include;
1.VITAL CAPCITY (VC = TV+ ERV + IRV), FORCED VITAL
CAPCITY (FVC), FORCED EXPIRED VOLUME (FEV).
2. INSPIRATORY CAPACITY (IC = TV + IRV)
3.FUNCTIONAL RESIDUAL CAPACITY (FRC = RV + ERV)
TOTAL LUNG CAPACITY (TLC = VC + RV)

11. DYNAMIC LUNG FUNCTION TESTS
•Dynamic lung function tests are based on time,
• i.e. the rate at which air flows into or out of lungs.
•These tests include forced vital capacity, forced expiratory
volume
•Dynamic lung function tests are useful in determining the
severity of obstructive and restrictive lung diseases.

12. Apparatus Required
• Recording Spirometer
• Nose clips
• Potassium permanganate solution/Spirit to clean mouth piece
• Graph paper

13. Recording Spirometer
The recording spirometer,
which is electrically
driven, is used to provide
a graphic record (called
spirogram) of various lung
volumes and capacities.
Pulley
chain
Outer cylinder
Pen marker attachedto
counter weight
Kymograph
Bi Directional Valve to connect
mouthpiece with atmospheric
air/ spirometer
Controlpanel for
kymograph
O2 inlet
Water
outlet
Corrugatedrubber tube with
mouthpiece
2 corrugated rubber tube
one for inspiration ,other
for expiration each with
unidirectional valve

15. After familiarizing the subject with the apparatus, start taking the
readings as
described below
• Connect the subject to the spirometer and allow her/him to breathe quietly for a
short time.
• Then start the kymograph at the speed of 60 mm/ min and record the excursions
of the pen writer for about a minute. Note that the upstrokes are inspirations and
down strokes expirations.
• This record of tidal breathing will be used for calculating the rate of respiration,
tidal volume (TV) and minute ventilation (minute volume; MV).
• TV- Volume of air breathed in or out during quiet respiration. Normal- 500 ml
• Minute ventilation: Volume of air inspired or expired out of the lungs in one
minute. MV = TV x RR = 500 x 12= 6L/min.
Upstroke- inspiration
Downstroke- expiration
TV

16. Recording of Inspiratory reserve volume(IRV) and inspiratory capacity(IC)
• IRV: It is the maximal volume of air which can be inspired after completing a
normal tidal inspiration i.e. inspired from the end inspiratory position. Normal:
2000-3000 ml
• IC: It is the maximal volume of air which can be inspired after completing tidal
expiration i.e. from the end expiratory position.
• IC= TV+ IRV Normal: 2500-3500 ml
• To record IRV, ask the subject to breathe in as deeply as possible after a quiet
inspiration. IRV + TV will give IC. Record a few tidal breaths afterwards.
IC

17. Recording of Expiratory reserve volume(ERV)
• Expiratory Reserve Volume (ERV). It is the extra amount of air that can be
expelled (expired) by forceful expiration from the spontaneous end-expiratory
point, i.e. over and above the normal tidal expiration. Normal: 750-1100 ml.
• To record ERV, ask the subject to breathe out as forcefully as possible after a quiet
expiration.

18. Recording of Vital capacity (VC)
After few tidal breaths, subject is asked to inspire as deeply and as fully as possible
to fill the lungs, then subject is asked to expel all the air that he can with maximum
effort into the spirometer.

19. THE LUNG VOLUMES AND CAPACITIES THAT CANNOT BE
MEASURED ON A SPIROMETER
Residual Volume (RV): It is the amount of air that remains behind in the lungs after
a maximum voluntary expiration. It amounts to 1300 ml.
• The lungs cannot be emptied out completely of air even with maximum effort.
So, The lung capacities that have RV as their component, cannot be measured on a
spirometer. These include
• Total lung capacity (TLC): It is the volume of air that is present in the lungs at the
end of a deepest possible inspiration. It is a measure of VC + RV, and amounts to
6Litres.
• Functional residual capacity (FRC): This is the amount of air remaining in the lungs
at the end of a normal (quiet) expiration. FRC= ERV + RV
• It amounts to about 2300-2500ml .

20. Precautions
• Subject should not face the recording spirometer during
recording.
• All lung volume and capacities are measured from the end
that is expiratory position.
• Make sure that there is no leak (of air) from the vitalograph
and spirometer.

22. •Residual volume and the functional residual capacity
cannot be measured by spirometer and can be
determined
•by three methods:
1. Helium dilution technique
2. Nitrogen washout method
3. Plethysmography.

23. TIMED VITAL CAPACITY (TVC) OR FORCED VITAL
CAPACITIES (FVC)
•Forced vital capacity is the volume of the air that
can be expired rapidly with a maximum force
following a maximum inspiration.
•The volume of air expired can be timed by
recording the vital capacity on a spirograph moving
at the known speed.

24. •Components of TVC or FVC
(i) Forced expiratory volume in 1 s (FEV1).
- It represents the volume expired in the first second of a FVC.
- Estimation of FEV1 is the most commonly used screening test for
airway diseases.
• The FEV1 is actually a flow rate: its unit are L/s.
• FEV1% is the percent of FVC expired in 1 s (i.e. FEV1% =
• FEV1/FVC × 100) normally FEV1% is about 80% of the
• FVC (Fig. 5.2-8A).

27. Clinical application.
Useful in distinguishing between restrictive and obstructive lung
diseases:
1.Patients with restrictive lung disease (e.g. kyphoscoliosis and
ankylosing spondylitis) have a reduced FVC but are able to
achieve relatively high flow rates; therefore their FEV1% exceeds
80% (Fig. 5.2-8B).
2.Patients with obstructive lung disease (e.g. bronchial asthma)
have low flow rates as a result of high airway resistance therefore
their FEV1% is abnormally low (Fig. 5.2-8C).

29. THANK YOU . . .