This document provides information on pulmonary function testing and spirometry. It defines key lung volumes and capacities that are measured, such as FVC, FEV1, FRC, RV. Normal values for various pulmonary function tests are provided. Spirometry is described as the most common pulmonary function test used to measure breath volume and flow. The document outlines the technique for spirometry and how to interpret the results to determine if a restrictive or obstructive ventilatory pattern is present. Limitations of spirometry and contraindications to its use are also discussed.

1. Pulmonary Function Testing
Sid Kaithakkoden MD
MBBS,DCH,DipNB,MD,MRCPCH,FCPS
alavisaid@aol.com

2. Introduction
• Lung function is physiologically divided into four
volumes:
– expiratory reserve volume
– inspiratory reserve volume
– residual volume
– tidal volume.
• Together, the four lung volumes equal the total
lung capacity (TLC)
• Lung volumes and their combinations measure
various lung capacities such as functional
residual capacity (FRC), inspiratory capacity,
and VC

3. Spirometric values
• FVC-Forced vital capacity;
– the total volume of air that can be exhaled during a maximal forced
expiration effort.
• FEV1-Forced expiratory volume in one second;
– the volume of air exhaled in the first second under force after a
maximal inhalation.
• FEV1/FVC ratio-
– The percentage of the FVC expired in one second.
• FEV6-Forced expiratory volume in six seconds.
• FEF25-75%-Forced expiratory flow over the middle one half of the
FVC;
– the average flow from the point at which 25 percent of the FVC has
been exhaled to the point at which 75 percent of the FVC has been
exhaled.
• MVV-Maximal voluntary ventilation

4. Lung volumes
• ERV-Expiratory reserve volume;
– the maximal volume of air exhaled from end-
expiration.
• IRV-Inspiratory reserve volume;
– the maximal volume of air inhaled from end-
inspiration.
• RV-Residual volume;
– the volume of air remaining in the lungs after a
maximal exhalation.
• VT-Tidal volume;
– the volume of air inhaled or exhaled during each
respiratory cycle

5. Lung capacities
• FRC-Functional residual capacity;
– the volume of air in the lungs at resting end-
expiration.
• IC-Inspiratory capacity;
– the maximal volume of air that can be inhaled from
the resting expiratory level.
• TLC-Total lung capacity;
– the volume of air in the lungs at maximal inflation.
• VC-Vital capacity;
– the largest volume measured on complete exhalation
after full inspiration

6. Lung volumes and Capacities

7. Pulmonary function test Normal value (95 percent confidence interval)
FEV1
80% to 120%
FVC 80% to 120%
Absolute FEV1
/FVC ratio Within 5% of the predicted ratio
TLC 80% to 120%
FRC 75% to 120%
RV 75% to 120%
Dlco >60% to <120%
Normal Values of Pulmonary Function Tests
Dlco = diffusing capacity of lung for carbon

8. Spirometry
• Spirometry- the measuring of breath, the most
common of the Pulmonary Function Tests
• measurement of the amount (volume) and
speed (flow) of air that can be inhaled and
exhaled
• Spirometry is important tool used for generating
a pneumotachograph
• A valuable tool in assessing conditions such
asthma and cystic fibrosis

9. • Spirometry measures the rate at which the lung
changes volume during forced breathing
maneuvers
• Spirometry begins with a full inhalation, followed
by a forced expiration that rapidly empties the
lungs
• Expiration is continued for as long as possible or
until a plateau in exhaled volume is reached
• These efforts are recorded and graphed

10. Objective
• Measurements for obstructive defects (those
related to resistance to flow)
• Measurements for restrictive defects (those
related to decrease in functional lung volume)
• Measurements of diffusion defects (those that
impair diffusion of gas through the alveolar-
capillary membrane)
• Measurement of respiratory muscle function

11. Pneumotachographs
• a pneumotachograph
shows a volume-time
curve
• Y-axis shows volume
in litres
• X-axis shows time in
seconds
• a flow-volume loop
graphically depicts the
rate of airflow on the Y-
axis and the total
volume inspired or
expired on the X-axis

13. Normal spirometric flow diagram. Flow-volume curve
The smooth lines, expiratory time of greater than six seconds, and quick peak of
the peak expiratory flow rate indicate a good spirometric effort

15. FEV1
Forced Expiratory Volume
in 1 second
The amount of air forcibly exhaled
in 1 second measured in litres and
expressed as a percentage of
predicted normal for that person.
Should be >80% predicted
Reduced in resistrictive
disease and obstructed
disease if air trapping
occurs
FVC
Forced Vital Capacity
The volume of the lungs from full
inspiration to full forced expiration in
litres and expressed as a
percentage of predicted normal for
that person
Reduced in recitative and
obstructed disease. Most
closely relating to presence
of secretions andis a
predictor of morbidity and
mortality.
FEF 25-75 %
Forced Expiratory Flow
25-75 %
MMEF
Maximum Mid Expiratory
Flow
Average speed of airflow in the mid
range of expiration.
A good indicator of disease
in the middle and lower
respiratory tract.
Normal in restrictive disease
PEF
Peak Expiratory Flow
Speed of air flow generated
l/min
Does not distinguish
between obstructed and
restrictive disease and may
seriously underestimate the
degree of airflow obstruction

16. Technique
• Precede the test by a period of quiet tidal
volume breathing through the mouthpiece
usually x3 breaths
• Followed by a maximal inspiratory breath. The
volume inspired directly affects the results of the
test.
• Then exhale through the sensor as hard as
possible, for as long as possible. Initial effort can
be turned into gentle effective effort to achieve
maximal expiration.
• Maintain the seal on the mouthpiece for
inspiration

17. An Approach to Interpreting Spirometry
1. The first step is determining the validity
of the test
2. Determination of an obstructive or
restrictive ventilatory pattern
3. Grade the severity
4. Additional tests - static lung volumes,
diffusing capacity of the lung for CO2,
bronchodilator challenge

18. Validity of spirometric results
• 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

19. Determination of ventilatory pattern
• When the FVC and FEV1 are decreased, the distinction between an
obstructive and restrictive ventilatory pattern depends on the absolute
FEV1/FVC ratio
• If the absolute FEV1/FVC ratio is normal or increased, a restrictive
ventilatory impairment may be present.
– Confirmation by static lung volumes.(TLC is less than 80% – restrictive lung
disease)
• A reduced FEV1 and absolute FEV1/FVC ratio indicates an
obstructive ventilatory pattern
• Bronchodilator challenge testing is recommended to detect patients
with reversible airway obstruction
– A bronchodilator is given, and spirometry is repeated after several
minutes
– Positive if the FEV1 increases by at least 12 percent and the FVC
increases by at least 200 mL
– The patient should not use any bronchodilator for at least 48 hours
before the test

20. Spirograms and Flow
Volume Curves
Gold WM. Pulmonary function testing. In: Murray JF, Nadel JA, eds. Textbook of respiratory
medicine. 3d ed. Philadelphia: Saunders, 2000:805
Restrictive ventilatory defect
Normal spirogram
Obstructive ventilatory defect

24. Limitations
• The manoeuvre is highly dependent on patient
cooperation and effort
• Normally repeated at least three times to ensure
reproducibility
• Since results are dependent on patient
cooperation, FEV1 and FVC can only be
underestimated, never overestimated
• Spirometry will only be useful when children are
old enough to comprehend and follow the
instructions given, typically about 4-5 years old

26. Contraindications to
use of Spirometry
• Acute disorders affecting test performance (e.g.,
vomiting, nausea, vertigo)
• Hemoptysis of unknown origin (FVC maneuver may
aggravate underlying condition.)
• Pneumothorax
• Recent abdominal or thoracic surgery
• Recent eye surgery (increases in intraocular pressure
during spirometry)
• Recent myocardial infarction or unstable angina
• Thoracic aneurysms (risk of rupture because of
increased thoracic pressure)

27. Interpreting Spirometry Results

28. Indications of Spirometry
• Detecting pulmonary disease
• History of pulmonary symptoms
• Chest pain or orthopnea
• Cough or phlegm production
• Dyspnea or wheezing
• Chest wall abnormalities
• Cyanosis
• Decreased breath sounds
• Finger clubbing
• Chest radiograph
• Assessing severity or progression of
disease
• Pulmonary diseases
• Chronic obstructive pulmonary disease
• Cystic fibrosis
• Interstitial lung diseases
• Sarcoidosis
• Cardiac diseases
• Congestive heart failure
• Congenital heart disease
• Pulmonary hypertension
• Neuromuscular diseases
• Amyotrophic lateral sclerosis
• Guillain-Barré syndrome
• Multiple sclerosis
• Myasthenia gravis
• Risk stratification of patients for surgery
• Thoracic surgeries
• Lobectomy
• Pneumonectomy
• Cardiac surgeries
• Coronary bypass
• Correction of congenital abnormalities
• Valvular surgery
• Organ transplantation
• General surgical procedures
• Cholecystectomy
• Gastric bypass
• Evaluating disability or impairment