RESPIRATION
Dr. Zainab H.H
Dept. of Physiology
Lec.5,6
Pulmonary Function Tests
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Assessed by spirometry.
Subject breathes into a closed system in
which air is trapped within a bell floating in
water.
The bell moves up when the subject exhales
and down when the subject inhales.
As the person breathes in & out through a
tube connecting the mouth to the spirometer,
the bell containing air moves up & down
Pulmonary Function Tests
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The bell is attached by a pulley to a pen that
writes on paper attached to a rotating drum
A downward pen deflection represents
expiration & an upward pen deflection
represents inspiration
The recording is known as spirogram
Spirometer
Pulmonary Function Tests
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Normal range:
 Male = 5.7 liters
 Female = 4.2 liters
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500 ml of air are inspired and expired
At end of quiet expiration, the lungs still contain 2,200
ml of air
Gas exchange continues during expiration
Maintains constant gas content
Pulmonary Function Tests
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The spirogram shows 4 lung volumes & 4 lung
capacities
Values given are for adult males (70 kg)
Normal values of lung volume & capacities
depend on:
1. Age
2. Sex
3. Posture
4. height
Lung Volumes
1.
Tidal Volume (TV): volume of air inhaled
or exhaled with each breath = 0.5 L
2.
Inspiratory Reserve Volume (IRV):
maximum volume of air that can be inhaled
after a normal tidal volume inhalation = 3L
Lung Volumes
3. Expiratory Reserve Volume (ERV) - the
maximum amount of gas that ca be expired
during forced breathing in addition to tidal
volume = 1.1L
4. Residual Volume (RV) - the volume of gas
remaining in the lungs after a maximal
expiration = 1.2L that keep the alveoli open.
Lung Capacities
1. Inspiratory Capacity (IC) - the maximum
amount of gas that can be inspired after a normal
tidal expiration
IC = TV + IRV = 3.5 L
2. Functional Residual Capacity (FRC) - the
amount of gas remaining in the lungs after a
normal tidal expiration.
FRC = ERV + RV = 2.3L
Lung Capacities
3. Vital Capacity (VC) - the maximum amount of
gas that can be expired after a maximum
inspiration
VC = IRV + TV + ERV (= IC + ERV)
4. Total Lung Capacity (TLC) - total amount of
gas in the lungs after a maximum inspiration
TLC = TV + IRV + ERV + RV (= IC + FRC) or
(= VC + RV) = 5.8L
Note
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Volumes and capacities cannot be measured
directly with spirometer are:
FRC
RV
TLC
Functional residual capacity is determined by
nitrogen wash-out method or helium dilution
method and then residual volume and total lung
capacity are calculated.
Maximal Voluntary Ventilation
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Also called maximal breathing Capacity
largest volume of gas that can be
moved into and out of the lungs in 1
minute by voluntary effort
Equals to 125 – 170 L/min.
Factors Affecting Lung
Volumes and Vital Capacity
1.
2.
3.
4.
Body build or physique
Position of the body
Strength of respiratory muscles
Pulmonary compliance
Restrictive and Obstructive
Disorders
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Restrictive pulmonary/lung diseases
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Expansion of lungs restricted & compliance of lungs 
i.e.,
 Fibrosis
 Pulmonary edema
Obstructive pulmonary diseases
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Airflow limitation (resistance is high), i.e.,
 Chronic obstructive pulmonary diseases (COPD)
 Asthma
Forced Expiratory Volume
in 1st second (FEV1)
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FEV1 (Forced expiratory volume in 1st second):
Volume of forced vital capacity (FVC) exhaled in
the first second of expiration
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Normal ratio of FEV1/FVC ~ 0.8 or 80%
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In obstructive pulmonry diseases, ratio is  70%
Maximal inspiration
Maximal expiration
or normal
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Which of the following is/are decreased
in both restrictive and obstructive lung
diseases:
vital capacity,
FEV1,
FEV1/FVC?
In obstructive airways
disease.
 The increase in
intrapleural pressure may
act to compress airways
proximal to the alveoli 
further obstruction with no
increase in expiratory flow
and air-trapping distally.
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