LUNG VOLUMES AND
CAPACITIES, FEV1/FVC
RATIO
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Dr Lukubi Lwiindi
Physiology Unit
04/05/2015
LECTURE 2: SPIROMETRY,
SPIROMETRY; USED TO MEASURE LUNG
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VOLUMES ON A SPIROGRAM IN PULMONARY
FUNCTION TESTS
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SPIROMETRY
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PULMONARY FUNCTION TESTS
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Spirometry
Body Plethysmography (Body Box)
Body Box + Dlco
Metacholine Challenge text(MCT)
Cardiopulmonary Exercise Test (Ergospirometry)
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WHAT INFORMATION DOES A
SPIROMETER YIELD?
A spirometer can be used to measure the
following:
FVC and its derivatives (such as FEV1, FEF
25-75%)
 Peak expiratory flow rate
 Maximum voluntary ventilation (MVV)
 Slow VC
 IC, IRV, TV and ERV
 Pre and post bronchodilator studies in assessing
effective treatment in asthmatics

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The amount of air that moves into the lungs with each
inspiration (or the amount that moves out with each
expiration) is called the tidal volume.
The air inspired with a maximal inspiratory effort in excess of
the tidal volume is the inspiratory reserve volume.
The volume expelled by an active expiratory effort after
passive expiration is the expiratory reserve volume, and the
air left in the lungs after a maximal expiratory effort is the
residual volume.
The space in the conducting zone of the airways occupied by
gas that does not exchange with blood in the pulmonary
vessels is the respiratory dead space.
The forced vital capacity (FVC), the largest amount of air that
can be expired after a maximal inspiratory effort, is frequently
measured clinically as an index of pulmonary function. It gives
useful information about the strength of the respiratory
muscles and other aspects of pulmonary function
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LUNG VOLUMES & CAPACITIES
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LUNG VOLUMES AND CAPACITIES
The fraction of the vital capacity expired during the
first second of a forced expiration is referred to as
FEV1 (formerly the timed vital capacity).
The FEV1 to FVC ratio (FEV1/FVC) is a useful tool in
the diagnosis of airway disease.
The amount of air inspired per minute (pulmonary
ventilation, respiratory minute volume) is normally
about 6 L (500 mL/ breath x 12 breaths/min).
The maximal voluntary ventilation (MVV) is the
largest volume of gas that can be moved into and
out of the lungs in 1 min by voluntary effort. The
normal MVV is 125 to 180 L/min.
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SPIROMETER AND LUNG VOLUMES/
CAPACITIES
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MINUTE AND ALVEOLAR VENTILATION
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Minute ventilation: Total amount of air moved into and out
of respiratory system per minute
Respiratory rate or frequency: Number of breaths taken
per minute
Anatomic dead space: Part of respiratory system where
gas exchange does not take place
Alveolar ventilation: How much air per minute enters the
parts of the respiratory system in which gas exchange
takes place
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Restrictive Disease:
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RESPIRATORY DISEASES
Makes it more difficult to get air into the lungs because of ‘stiff
lungs’
 They “restrict” inspiration.
 Decreased VC; Decreased TLC, RV, FRC
 Includes:

Fibrosis
Sarcoidosis
Muscular diseases
Chest wall deformities
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Obstructive Diseases;
 Make it more difficult to get air out of the
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RESPIRATORY DISEASES
lungs because of obstruction in airways.
 Decrease VC; Increased TLC, RV, and FRC
 Includes:
Emphysema
Chronic bronchitis
Asthma
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PFTS: FEV1, FVC AND THEIR RATIO
 Interpretation
of Spirometry involves looking at the
absolute values of FEV1, FVC, and FEV1/FVC.
 Then comparing them with predicted values, and
examining the shape of the spirograms.
 Patients
should complete three blows that are
consistent and within 5% of each other—many
electronic spirometers automatically provide this
information.
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 The
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FEV1/FVC RATIO
ratio of FEV1/FVC is normally between 0.7 and 0.8.
 Values below 0.7 are a marker of airway obstruction, except
in older adults where values 0.65–0.7 may be normal.
 In people over 70 years old, the FEV1/FVC ratio may need
to be lowered to 0.65 as a lower limit of normal.
 Conversely, in people under 45, using a ratio of 0.7 may
result in under-diagnosis of airway obstruction.
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Forced Expiratory Volume (FEV1)

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SPIROMETRY
FEV1 is used in conjunction with FVC for:
Simple screening
Response to bronchodilator therapy
Response to bronchoprovocation
Detection of exercise-induced bronchospasm
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FEV1/FVC
FEV1/FVC x 100
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 FEV1% =
Useful in distinguishing between
obstructive and restrictive
pulmonary disorders.
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Forced Expiratory Volume Ratio (FEVT%)

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SPIROMETRY
Normal FEVT% Ratios for Health Adults
FEV 0.5% = 50%-60%

FEV 1%
= 75%-85%
FEV 2%
= 90%-95%
FEV 3%
= 95%-98%
FEV 6%
= 98%-100%
Patients with obstructive pulmonary disease have reduced
FEVT% for each interval
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COPDS AND FEV1/FVC RATIO
A
decrease FEV1/FVC ratio is the
“hallmark” of obstructive disease
FEV1/FVC <70%
FEV1 is reduced more than the decrease in
FVC.
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
Patients with restrictive disease often have normal or
increased FEVT% values
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RESTRICTIVE LUNG DISEASES AND
FEV1/FVC RATIO
FEV1 and FVC are usually reduced in equal proportions
 The
presence of a restrictive disorder may
by suggested by a reduced FVC and a
normal or increased FEV1/FVC ratio.
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