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Pulmonary Functions Lung Volumes
1.
2.
3.
4. Standard Tests of Lung Function
Static Lung Volumes
Spirometry: Dynamic Lung Volumes
Diffusing Capacity (DLCO)
Arterial Blood Gas (ABG)
5. Specialized Tests of Lung Function
Bronchial challenge testing
Ventilatory muscle studies
Ventilatory drive studies
Physiologic shunt studies
Cardiopulmonary exercise testing
Six minute walk
6. PFTs are really wonderful but…
They do not act alone.
They act only to support or exclude a diagnosis.
A combination of a thorough history and physical
exam, as well as supporting laboratory data and
imaging will help establish a diagnosis.
12. Static lung functions
Are the ones that do not have to do with the rate (how
long it takes) at which they are inspired or exhaled.
This is almost all the volumes and capacities:
VT
IRV
ERV
RV
VC
IC
TLC
FRC 12
14. Static lung volumes are determined using
methods in which airflow velocity does not play
a role.
The sum of two or more lung-volume
subdivisions constitutes a lung capacity.
The subdivisions and capacities are expressed
in liters at body temperature and pressure
saturated with water vapor (BTPS).
15. Static Lung Volumes
This test measures your static or absolute lung
volumes.
The most important are the
1. Total lung capacity (TLC)
2. Functional Residual Capacity (FRC).
3. Residual volume (RV).
15
21. Tidal Volume (TV)
IRV
TV
ERV
RV
IC
FRC
VC
TLC
RV
Volume of air
inspired or expired
during normal
quiet breathing
About 500ml
22. Inspiratory Reserve Volume IRV
IRV
TV
ERV
RV
IC
FRC
VC
TLC
RV
The maximum
amount of air
that can be
inhaled after a
normal tidal
volume
inspiration
=3000ml
23. Expiratory Reserve Volume (ERV)
Maximum amount
of air that can be
exhaled over
normal tidal
volume (from the
resting expiratory
level) when
person expires
forcefully
ERV= 1100ml
IRV
TV
ERV
RV
IC
FRC
VC
TLC
RV
24. Residual Volume (RV)
IRV
TV
ERV
Volume of air
remaining in the
lungs at the end
of maximum
expiration.
IC
FRC
VC
TLC
RV =1200 ml RV
RV
25. Vital Capacity (VC)
IRV
TV
ERV
The maximum
amount of air a
person can expel
from the lungs after
filling the lungs to
their maximum
extent and then
expires to the
maximum extent.
VC=4600ml
VC=IRV+TV+ERV
RV
IC
FRC
VC
TLC
RV
27. Inspiratory Capacity (IC)
IRV
TV
ERV
The amount of air a
person can breathe
in beginning at the
normal expiratory
level and distending
the lung to the
maximum amount.
IC = IRV + TV
IC= 3500ml
RV
IC
FRC
VC
TLC
RV
28.
29. Functional Residual Capacity (FRC)
IRV
TV
ERV
Volume of air
remaining in the
lungs at the end of
a normal expiration
FRC = ERV + RV
IC
FRC
VC
TLC
RV
RV
FRC= 2300 ml
30. Total Lung Capacity (TLC)
IRV
TV
ERV
Volume of air in the
lungs after a
maximum inspiration
TLC = IRV + TV + ERV
+ RV
IC
FRC
VC
TLC
RV
RV
=5800ml
31. Residual
Volume
Tidal volume
Dead space
Total
lung
capacity
Vital capacity
Expiratory reserve
volume
Tidal volume
Inspiratory reserve
volume
LUNG VOLUMES
57. The lung volumes that can be measured by simple
spirometry are the tidal volume, inspiratory reserve
volume, expiratory reserve volume, inspiratory
capacity, and vital capacity.
The static lung volumes cannot be measured by
observation of a spirometer trace and require
separate methods of measurement are the residual
volume, functional residual capacity, and total lung
capacity..
58. Lung Volumes
Determination of lung
volume
Includes the VC
(spirometry) and its
subdivisions, along
with the FRC (indirect
spirometry) – from
these TLC and other
lung volumes can be
determined
59. Lung Volumes
Direct Spirometry
– Used to measure all volumes and
capacities EXCEPT for RV, FRC and TLC
60. Volumes not measured with spirometer
– Residual volume (RV): volume of air remaining in
lungs after maximal inhalation.
– Functional residual capacity (FRC): volume of air
left in lungs after a normal exhalation.
– Total lung capacity (TLC): total volume of air the
lungs can hold.
61. Indirect Spirometry
– Required for the determination of RV, FRC and
TLC
Most often, indirect spirometry is performed to
measure FRC volume
– FRC is the most reproducible lung volume and
it provides a consistent baseline for
measurement
62. Indirect Spirometry
– Two basic approaches
1. Gas dilution
2. Body plethysmography
– Measurements are in Liter or Milliliters
– Reported at BTPS
67. Measuring Residual Volume
Can’t use a Spirometer
Use instead:
– Nitrogen Washout
– Helium Dilution Method
– Total-body Plethysmograph
68. Indirect Measurements of RV
The residual volume (and the capacities
which have it as a part – FRC & TLC) must be
measured indirectly by one of three
methods:
– Helium Dilution – Closed Circuit Method
– Nitrogen Washout – Open Circuit Method
– Body Plethysmography
69. Lung Volumes
Residual Volume
(RV):
– Volume of air
remaining in lungs
after maximium
exhalation
– Indirectly measured
(FRC-ERV) not by
spirometry
70. Measuring TLC
To measure TLC or FRC, which include RV,
spirometry is insufficient
Techniques:
– Gas dilution
– Plethysmography (body box)
71. Measurement of Lung Volumes
Two Common
Methods of
Measuring FRC
Helium Dilution Plethysmography
73. Measurements of Lung Volumes
FRC is measured generally
TLC is measured by some methods
RV is measured indirectly
74. Pulmonary Function Testing
Volumes and Capacities
Capacities are
made up of two
or more Volumes
Note that Residual Volume, and
hence any Capacity including it,
cannot be measured by spirometry
alone.
75. Lung Volume
By calculation:
RV = TLC - VC
by spirometry
by body
plethysmography
TLC or helium dilution
FRC = TLC - IC
76. Measuring vital capacity and
its subcomponents.
Use a spirometer.
TLC
VC
RV
IC
FRC
IRV
ERV
RV
Can Use
Spiromenter
Can’t Use a Spirometer
TV
77. Vt Tidal volume
VC Vital Capacity
ERV/IRV
These are all measured easily with
spirometers
FRC Functional residual capacity
RV residual volume
TLC Total lung capacity (RV + VC)
Measuring these requires more
specialized equipment
95. Specific changes in lung volumes also occur during
pregnancy. Functional residual capacity drops 18–
20%,due to the compression of the diaphragm by the
uterus.
The compression also causes a decreased total lung
capacity (TLC) by 5% and decreased expiratory
reserve volume by 20%.
Tidal volume increases by 30–40%, from 0.5 to 0.7
litres,and minute ventilation by 30–40% giving an
increase in pulmonary ventilation. This is necessary to
meet the increased oxygen requirement of the body,
95
96. Lung Volumes
– The most significant volumes for evaluating
the effects of pulmonary disorders are
1. VC
2. FRC
3. RV
4. TLC
99. PFT Reports
o When performing PFT’s three values are reported:
o Actual – what the patient performed
o Predicted – what the patient should have
performed based on Age, Height, Sex, Weight,
and Ethnicity
o % Predicted – a comparison of the actual value to
the predicted value
100. PFT Reports
Example
Actual Predicted %Predicted
VC 4.0 5.0 80%
101. The simple rule for static lung volumes is that they
increase in obstructive disorders and decrease in
restrictive disorders.
TLC , RV and RV/ TLC ratio are the most important
in interpreting lung volume studies.
IC and IRV are not discussed as they have little
diagnostic role.
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102. Lung Volume Changes
Restrictive patterns
Demonstrate reductions in ALL lung volumes
Obstructive patterns
Demonstrate increases in only some lung volumes
Exception:
VC may be normal or even decreased
103. Vital capacity is reduced in both
obstructive and restrictive diseases
VC
RV
VC
RV
VC
RV
Obstructive Normal Restrictive
104. Lung Capacity and Disease
IRV
TV
ERV
RV
VC
FRC
Normal
IRV
TV
ERV
RV
VC
FRC
Restrictive
IRV
TV
ERV
RV
VC
FRC
Obstructive
125
100
75
50
25
0
% Normal TLC
111. SPIROMETRY
Vital Capacity
The vital capacity (VC) is the volume of gas
measured from a slow, complete expiration after
a maximal inspiration, without a forced effort.
112. SPIROMETRY
Forced Vital Capacity (FVC)
The maximum volume of gas that can be
expired when the patient exhales as forcefully
and rapidly as possible after maximal
inspiration (sitting or standing)
113. The slow vital capacity (SVC)
Also called the vital capacity (VC) – is similar to
the FVC, but the exhalation is slow rather than
being as rapid as possible as in the FVC.
In a normal subject, the SVC usually equals the
FVC, while in patients with an obstructive lung
disorder, the SVC is usually larger than the FVC.
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114. The slow vital capacity (SVC)
The reason for this is that,in obstructive lung
disorders, the airways tend to collapse and close
prematurely because of the increased positive
intrathoracic pressure during a forceful
expiration.
This increased pressure leads to air trapping.
Accordingly, a significantly higher SVC
compared with FVC suggests air-trapping .
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115. FVC and SVC are compared with each other in a normal subject
( a ) and in a patient with an obstructive disorder ( b ). In case of airway
obstruction, SVC is larger than FVC, indicating air trapping
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5
116. SPIROMETRY
FVC: Significance and Pathophysiology
– FVC equals VC in healthy individuals
– FVC is often lower in patients with obstructive
disease
117. SPIROMETRY
FVC: Significance and Pathophysiology
– Healthy adults can exhale their FVC within
4 – 6 seconds
– Patients with severe obstruction (e.g.,
emphysema) may require 20 seconds,
however, exhalation times >15 seconds will
rarely change clinical decisions
118. SPIROMETRY
FVC: Significance and Pathophysiology
– FVC is also decreased in restrictive lung
disease
Pulmonary fibrosis
– dusts/toxins/drugs/radiation
Congestion of pulmonary blood flow
– pneumonia/pulmonary hypertension/PE
Space occupying lesions
– tumors/pleural effusion
119. SPIROMETRY
FVC: Significance and Pathophysiology
– FVC is also decreased in restrictive lung
disease
Neuromuscular disorders, e.g,
– myasthenia gravis, Guillain-Barre
Chest deformities, e.g,
– scoliosis/kyphoscoliosis
Obesity or pregnancy
120. SPIROMETRY
VC: Significance/Pathophysiology
– If the VC is less than 80% of predicted:
FVC can reveal if caused by obstruction
121. SPIROMETRY
VC: Significance/Pathophysiology
– If the VC is less than 80% of predicted:
– Lung volume testing can reveal if caused by
restriction
122. The inspiratory vital capacity (IVC) is the VC
measured during inspiration rather than
expiration.
The IVC should equal the expiratory VC. If it does
not, poor effort or an air leak could be
responsible.
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123. The IVC may be larger than the expiratory VC in
patients with significant airway obstruction,
In this case the increased negative intrathoracic
pressure opens the airways facilitating inspiration,
as opposed to the narrowing of airways during
exhalation as the intrathoracic pressure becomes
positive. Narrowed airways reduce airflow and
hence the amount of exhaled air.
12
3
124. Functional residual capacity
Is the volume of air that remains in the lungs at the
end of a tidal exhalation, i.e., when the respiratory
muscles are at rest.
This means that at FRC, the resting negative
intrathoracic pressure produced by the chest wall
(rib cage and diaphragm) wanting to expand is
balanced by the elastic recoil force of the lungs,
which naturally want to contract.
125. Factors influencing FRC, inward (red) from lung
elasticity, outward (blue) from the muscular action of
the diaphragm and intercostals
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126. Therefore, when the elastic recoil of the lungs
decreases as in emphysema, the FRC increases
(hyperinflation), while when the elastic recoil
increases as in pulmonary fibrosis, the FRC
decreases.
The FRC is the sum of the expiratory reserve
volume (ERV) and the RV and is ∼ 50% of TLC.
12
6
127. FRC measured using body plethysmography
is sometimes referred to as the thoracic gas
volume (TGV or V TG )
Indeed, FRC is the volume measured by all
the volume measuring techniques and RV is
then determined by subtracting ERV .
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128. FRC has important functions:
– Aids the mixed venous blood oxygenation during
expiration and before the next inspiration.
– Decreases the energy required to reinflate the lungs
during inspiration.
If, for example, each time the patient exhales, the lungs
want to go to the fully collapsed position, a tremendous
force will be needed to reinflate them. Such effort would
soon result in exhaustion and respiratory failure.
12
8
129. Clinical Significance Of FRC
A high FRC (as in emphysema) means that when
the patient is not breathing in, the lungs contain
more air than normal.
Breathing at that high lung volume helps prevent
collapse of the airways and air trapping in
emphysematous lungs, but at the same time,
increases the effort of breathing. This can be very
uncomfortable and can lead to dyspnea.
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9
130. The increased effort noticed when breathing at high
lung volumes is caused by two consequences of a
high lung volume.
1. The breathing muscles are shortened and become at
a mechanical disadvantage. As a result, more
muscular activity is required to produce the pressure
gradient that leads to airflow and tidal volume.
2. the lungs are less compliant as lung volume
increases above FRC (more elastic recoil) and so
more force is required to produce airflow.
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0
132. When patients with emphysema exercise, their
respiratory rate increases and the expiratory time
decreases.
The reduced expiratory time impairs lung emptying
and leads to air trapping.
The air trapping results in a progressive increase in
the FRC with each respiratory cycle.
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2
133. This process continues until the FRC approaches the
TLC, at which point, the patient cannot continue
exercising.
This phenomenon is called dynamic hyperinflation
and is characteristic of patients with emphysema
and is responsible for much of their exercise
limitation .
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3
134. 13
4
Dynamic hyperinflation in patients with emphysema during exercise.
Note that V T increases with exercise. Note also that the expiratory
phase decreases progressively with continued exercise indicating
progressive air trapping .
135. Breathing at a low FRC, as in pulmonary fibrosis
and obesity, can also increase the work of
breathing.
In restrictive lung disorder, the lung compliance
is reduced, which means that more effort is
needed to inflate the lungs.
13
5
136. Increase in FRC
Increase is pathologic
> 120% means air trapping
1. Emphysema
2. Asthma
137. TLC
TLC < 80% of predicted value = Restriction.
TLC > 120% of predicted value = Hyperinflation.
13
7
138. RV and TLC Determination
– Determination of RV and TLC are based
on the FRC from indirect spirometry and
volumes measured during direct
spirometry
RV = FRC – ERV or RV = (FRC+IC) - VC
TLC = FRC + IC or TLC = (FRC – ERV) + VC
139. Determining RV
Measure FRC by He dilution
Measure IC from spirometer tracing
FRC + IC = TLC
Measure VC from spirometer tracing
RV = TLC - VC
Correct data to BTPS
Express as percent predicted value
140. The rest of the lung volumes can then be
measured by simple spirometry, using the SVC
rather than the FVC.
The TLC can then be calculated by adding RV to
VC or functional residual capacity (FRC) to
inspiratory capacity (IC)
Therefore, spirometry is an essential part of any
14 lung volume study.
0
141. Residual volume (RV)
Is the volume of air that remains in the lungs at
the end of a maximal exhalation.
An abnormal increase in RV is called air trapping
The techniques used to measure lung volumes
are primarily designed to measure the residual
volume, as this volume cannot be exhaled to be
measured.
14
1
142. Increase in RV
Acute asthma attack
Chronic air trapping (Emphysema)
RV and FRC increase together, generally
As RV increases:
More ventilation is done in order to obtain gas
exchange
VT, respiratory rate increase
Work of breathing is increased
Hypoxemia, carbon dioxide retention
144. Total Lung Capacity and Residual
Volume
In obstructive lung diseases, the narrowing and
closure of airways during expiration tends to lead to
“gas trapping” and “hyperinflation” of the chest.
Gas trapping leads to an increase in RV while
hyperinflation increases the TLC.
145. Total Lung Capacity and Residual
Although both values increase, the RV tends to have
a greater percentage increase than TLC.
The RV/TLC ratio is therefore also increased.
Sometimes gas trapping occurs (raised RV) without
hyperinflation.
Volume
146. In restrictive disorders the cardinal feature is a
reduction in TLC.
Be cautious about diagnosing a restrictive disorder
if the TLC is normal –a high FEV1/FVC ratio with a
normal TLC is more likely to be due to poorly
performed spirometry than to true restriction
In fibrotic lung disease the RV also falls because of
increased elastic recoil.
147. Total Lung Capacity and Residual
Volume
Chest wall disease (such as neuromuscular disease
or kyphoscoliosis) can also cause a restrictive
pattern in which the TLC is reduced.
Nevertheless, the lung tissue (and therefore the
elastic recoil) is normal and the RV tends to be
preserved , leading to a high RV/TLC ratio.
148. RV/TLC Ratio
– The RV/TLC ratio also known as RV/TLC% and
is expressed as a percentage
RV/TLC% = RV x 100
TLC
– In normal, young, healthy adults, the RV/TLC%
ranges between 20% and 35%
149. RV/TLC ratio
Describes the percentage of total lung volume that
must be ventilated by tidal breathing
20-35% in healthy adults
RV/TLC : RV veya TLC
RV/TLC : TLC Hyperinflation
TLC normal Air trapping
150. TLC and RV/TLC Ratio
– RV/TLC% >35% + Normal TLC =
AIR TRAPPING
– RV/TLC% >35% + >Normal TLC =
HYPERINFLATION
151.
152. Causes of abnormal lung
volumes
TLC increased in:
1. COPD, mainly emphysema
2. Acromegaly patients may have a high TLC, which can
be differentiated from emphysema by RV/TLC ratio
(normal in acromegaly and high in emphysema )
3. TLC may be high in normal subjects with big lungs,
15 e.g., swimmers
2
153. TLC is usually normal in bronchial asthma,
as lung elastic recoil is normal
TLC Decreased in restrictive disorders
15
3
154. RV
Increased (air trapping) in obstructive disorders:
1. COPD
2. Bronchial asthma, although the TLC is normal,
but the RV is high because of air trapping
Decreased in parenchymal restriction
15
4
155. RV/TLC ratio
Normal in parenchymal restriction
Increased Mainly in obstructive disorders
Can be increased in chest wall restriction
(because of normal RV and low TLC)
15
5
156. ERV
Decreased in
1. Restrictive disorders, similar to TLC
2. Obstructive disorders (because of the increased
RV due to air trapping)
3. An isolated reduction in ERV is characteristic for
obesity
15
6
157. FRC
Increased (hyperinflation)
1. in Obstructive disorders, mainly emphysema
due to loss of lung elastic recoil
2. FRC increases slightly with aging
Decreased in
1. Restrictive disorders, mainly lung fibrosis
2. Obesity
3. Supine position (abdominal organs push the
15 diaphragm against the lungs)
7
158. Disease Patterns
Additional information acquired by lung volume
study compared with spirometry
1. Differentiates the subtypes of obstructive disorders
2. Confirms the diagnosis of a restrictive disorder and
separates its subtypes
3. Separates restrictive from obstructive disorders
4. Helps in detecting combined, obstructive, and
restrictive disorders
15
8
159. Lung Volume Changes
Restrictive patterns
Demonstrate reductions in ALL lung volumes
Obstructive patterns
Demonstrate increases in only some lung volumes
Exception:
VC may be normal or even decreased
160. Obstructive Pattern
1. Significance/Pathophysiology
Increase FRC is considered pathologic
FRC values >120% of predicted
represent air trapping
─ Emphysematous changes
─ Obstruction caused by asthma or chronic
bronchitis
161. Obstructive Pattern
2. Significance/Pathophysiology
Increased RV often results in a equivalent
decrease in VC
Increased RV is characteristic of:
– Emphysema
– Bronchial obstruction
RV and FRC usually increase together
162. Obstructive Pattern
3. Significance/Pathophysiology
As RV becomes larger, increased ventilation
is needed to adequately exchange O2
and CO2
Requires increased VT and/or respiratory
rate
Work of breathing is increased
Often display hypoxemia or CO2 retention
163. RV
TLC
FRC
Obstruction
TLC
TLC
FRC FRC
RV RV
RV
Normal Air trapping Hyperinflation
164. Obstructive Diseases
RV is always increased
VC is decreased, TLC remains normal (Air
trapping)
VC is normal, TLC is increased
(Hyperinflation)
165. Two types of obstructive
patterns
•Increases in RV with a
proportional reduction in VC;
TLC remains constant
(normally 80-120% of
Predicted)
Air Trapping
166. Two types of
obstructive patterns
•RV increases with little or
no change in VC; TLC
increased proportional to RV
(TLC >120% of predicted)
Hyperinflation
167. 1) Differentiate subtypes of obstructive
disorders
Generally, obstructive disorders (emphysema and
asthma) result in increased RV (air trapping) due to
airway narrowing
While TLC is increased only in emphysema due to loss
of elastic recoil.
Bronchial asthma, however, has normal elastic recoil
16 and, therefore, normal TLC.
7
168. The RV/TLC ratio is increased in both emphysema
and bronchial asthma.
The RV/TLC ratio can be used also to differentiate
an obstructive from a nonobstructive increase in
TLC, such as acromegaly (the RV/TLC ratio is
normal).
16
8
169. If lung volumes are measured pre- and
postbronchodilator use, much can be learned
from looking at the behavior of TLC and RV
before and after the use of bronchodilators.
TLC and RV may be shown to decrease following
bronchodilators, even in the absence of a
significant response in FEV 1 and FVC.
16
9
170. Furthermore, IC may increase as FRC may decrease
more than TLC in response to bronchodilators.
In this case, an increase in IC gives patients with
emphysema more room or time to breathe before
they develop dynamic hyperinflation to the point of
stopping exercise.
These volume changes indicate that the
bronchodilators are clinically useful to such patients
even though there is no change in FEV
171. COPD is a Complex Disease
Progressive Loss of Lung Function
Reduced Quality of Life
Exacerbations
Mortality
Broncho-constriction
Inflammation
Structural
Changes
Airflow
Limitation &
Hyperinflation
172. Lung Vollumes iin Obstructiive Diisease
TLC
VT
VT
RV
RV
FRC
Normall COPD
IC
IC
TLC
FRC
Volume
173. Clinical Course of COPD
COPD
Expiratory Flow Limitation
Air Trapping
Hyperinflation
Breathlessness
Inactivity
Deconditioning
Reduced Exercise
Capacity
Poor Health-Related Quality of Life
EXACERBATIONS
Disability Disease progression Death
175. Effects of Exercise on Hyperinflation
Normal
ERV IRV
VT
IC
RV
Progression
Years - Decades
Static
Hyperinflation
Air Trapping
at Rest
Rest
Dynamic
Hyperinflation
Air Trapping
During Exercise
Seconds - Minutes
Exercise
176. Expiratory flow-limitation and lung hyperinflation that are only partially
reversible to bronchodilator therapy are pathophysiological hallmarks of COPD
177. Unlike asthmatic patients who experience dyspnea
when acute bronchospasm occurs, patients with
COPD most commonly experience dyspnea due to
increased respiratory demands, such as occurs with
exertion.
Given that airflow obstruction is the primary concern
in COPD, it follows that short-acting and long-acting
bronchodilators form the cornerstone of
17 pharmacologic management.
7
178. Restrictive Pattern
Significance/Pathophysiology
FRC, RV and TLC typically decreased
Usually lung volumes are decreased equally
When TLC is <80% a restrictive process is
present
RV/TLC is relatively normal
179. Restrictive Diseases
FRC, RV, TLC are decreased
Volumes are generally equally reduced
RV/TLC normal
181. 2)Confirm the diagnosis of a restrictive disorder and
differentiate its subtypes
– A decreased TLC is essential to make the
diagnosis of a restrictive disorder with
confidence.
18
1
182. The RV and RV/TLC ratio, however, may be
used to differentiate the subtypes of
restriction:
(A) In a parenchymal restriction (lung fibrosis),
where there is increased elastic recoil and loss of
air space, the RV and TLC are reduced with a
normal RV/TLC ratio (both RV and TLC decrease
proportionately).
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2
183. (B) In chest wall restriction (NMD, musculoskeletal
disease, paralyzed diaphragms, and obesity),
where the lung parenchyma is normal, the RV is
usually normal (or increased) with an increased
RV/TLC ratio (remember that TLC is low).
In NMD, RV may be increased because the ERV
can be very low due to weakness of the expiratory
muscles.
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184. (C) The diffusing capacity for carbon monoxide
(DL CO ) is a more reliable way of differentiation
between parenchymal and chest wall restriction
Maximal voluntary ventilation (MVV) and
maximal respiratory pressures are measures to
help differentiate the different types of chest wall
restriction.
18
4
185. Diffusing Capacity
Single Breath Method (DLcosb)
(Modified Krogh Technique)
– DLco measures the transfer of a CARBON
MONOXIDE (CO) across the alveolocapillary
membranes to measure the diffusion capacity
of the lungs.
186. Carbon Monoxide Diffusing Capacity
(DLCO)
Known concentration of CO is inhaled in
single breath and held. CO binds avidly to
hemoglobin and uptake is measured. Not
truly diffusion-limited and not true “capacity”
Better term is
“Transfer Factor”
187. Diffusing Capacity
DLcosb
– CO combines with Hb 210 times more readily
than O2
– DLco is expressed as:
ml of CO/minute/mm Hg (STPD)
STPD (0 C, 760 mm Hg, Dry)
192. 192
Interpreting the PFT Report
If DLCO is <80% of normal, a diffusion defect
is present.
– Reduced surface area = emphysema
– Thickened AC membrane = pulmonary
fibrosis
193. 193
Diffusing Capacity
Results reported in ml/min/mm Hg.
Results may be low in both obstructive and
restrictive lung disease.
Emphysema and pulmonary fibrosis are two
common causes of a reduced DLCO.
194. Diffusing Capacity
DLcosb
Significance and Pathology
– In patients with COPD, DLco less than
50% of predicted is accompanied by O2
desaturation during exercise
– Low resting DLco (<50% - 60% of predicted) may
indicate the need for assessment of oxygenation
during exercise
195. DLCO — Indications
● Differentiate asthma from emphysema
● Evaluation and severity of restrictive lung
disease
● Early stages of pulmonary hypertension
● Expensive!
196. 19
6
Degree of severity of the reduction
in diffusing capacity of CO
197. – Obstructive and restrictive disorders are
sometimes hard to separate based on
spirometry alone. Lung volumes may
provide additional clues
19
7
3)Separates obstructive from restrictive
disorders
198. For obstructive diseases, measurement of the
residual volume and total lung capacity can
demonstrate air trapping and hyperinflation.
For restrictive diseases, the total lung capacity
is needed to confirm true restriction and better
quantitate the degree of restriction.
19
8
199. 3)Separates obstructive from restrictive
disorders
As an example, when the FEV 1 and FVC are at
the lower limit of the normal range, with a normal
FEV 1 /FVC ratio, a lung volume study may be of
value:
(A) If the TLC and RV are high, then an obstructive
disorder is the most likely (RV/TLC ratio is usually
high).
19
9
200. (B) If the TLC is normal and RV is mildly increased,
then a mild bronchial asthma and air trapping
could be responsible (RV/TLC ratio is high).
In this case, the airway obstruction is not severe
enough to cause significant drop in FEV 1 and the
ratio.
A bronchodilator study may show a significant
20 response.
0
201. (c) If the TLC is low, then a restrictive defect is likely to
be the cause, provided that FVC is below the 5th
percentile (a normal FVC rules out restriction ).
Before you make such a conclusion, have a quick
look at the FV curve and the rest of the PFT values.
If all the values are decreased proportionately with
a normal FV curve, then consider in your report a
normal person with relatively small lungs (racial
20 variations).
1
202. (D) If the TLC and RV are normal, then the
study is most likely normal.
20
2
203. Detection of combined disorders
– Combined disorders are hard to diagnose based on
spirometry alone.
– Spirometry coupled with a lung volume study is very
useful:
(a) An obstructive disorder should be clear in spirometry, with
low FEV 1 /FVC ratio.
(b) If this airflow obstruction is seen with a reduced TLC, then the
reduced TLC suggests an additional restrictive disorder.
(c) The RV could be low, normal, or high as airway obstruction
may result in air trapping and increased RV.
20
3
204. – Combined defects can be seen in conditions
such as sarcoidosis or coexisting COPD and lung
fibrosis.
– Keep in mind that an obstructive disorder (such as
emphysema) with pulmonary resection
(lobectomy or pneumonectomy) can give a
similar pattern.
20
4
205. A mixed pattern of restrictive and obstructive
disorders may be indicated by an obstructive
pattern on spirometry or flow volume loop
combined with reduced lung volumes.
Lung volumes are also useful when there are
equivocal findings on spirometry . For example if
the FEV1 and FVC are at the lower limit of normal,
the findings of the raised TLC or RV supports a
diagnosis of obstruction.
211. Pulmonary Function Testing
Volumes and Capacities
Total Lung
Capacity
(TLC),
Functional
Residual
Capacity
(FRC), &
Residual
Volume (RV)
For normal
and disease
states.
212. Doing the right thing sometimes is
the hardest thing to do.
219. APPROACH TO LUNG VOLUME STUDY
Examine TLC, RV, and RV/TLC ratio (these are
the most important lung volume variables):
They usually change in the same direction, i.e.,
the direction of obstruction or restriction.
The following are the possibilities:
21 (A) Normal, when all are normal.
9
220. (B) High volumes, suggesting obstruction;
remember:
↑ TLC usually indicates hyperinflation
(hyperinflation is more accurately defined by ↑
FRC).
↑ RV indicates air trapping.
↑ RV/TLC ratio reflects the degree of air
trapping.
22
0
221. (C) Low in restrictive disorders (↓TLC is essential to
make a confident diagnosis of restriction)
– TLC should be used to grade severity, if
available;
Examine the rest of the lung volumes (FRC, ERV,
IC) They usually follow the TLC and RV, so they
are high in obstructive and low in restrictive
disorders.
22
1
222. ● Special situations :
– Isolated reduction in ERV indicates obesity,
check the patient's weight.
– When the lung volumes are incompatible
with spirometry, consider combined
disorders.
223. In combined obstructive and restrictive
disease (e,g. sarcoidosis ,COPD+IPF)
Obstructive pattern on spirometry and Reduced lung
volume
In equivocal spirometry result :
e,g.when FEV1,FVC at lower limit of normal
If TLC or RV raised the diagnosis is obstructive lung
disease
225. • Obstructive Lung Disease
• Narrowing and closure of
airways during expiration
tends to lead to gas trapping
within the lungs and
hyperinflation of the chest.
• Air trapping → increase in
RV
• Hyperinflation → increases
TLC
• RV tends to have a greater
percentage increase than
TLC
• RV/TLC ratio is therefore
increased (nl 20-35%)
• Gas trapping may occur
without hyperinflation
(increase in RV & normal TLC)
226. Obstructive Lung Disease
(cont.)
• Gas trapping and airway
closure at low lung volume
cause the patient to breath at
high lung volume so FRC
(RV+ERV) increased
• This will prevent airway
closure and improve
ventilation-perfusion
relationship
• It will reduce mechanical
advantage of respiratory
muscles and increases the
work of breathing
227. Obstructive Lung
Disease (cont.)
RV increased
TLC N/increased
RV/TLC increases
FRC increased
VC decreased
*Air trapping :Normal TLC with
increase RV/TLC
*Hyperinflation: Increase in
both TLC and RV/TLC
228. Obstructive Lung
Disease (cont.)
RV increased
TLC N/increased
RV/TLC increases
FRC increased
VC decreased
*Air trapping :Normal TLC with
increase RV/TLC
*Hyperinflation: Increase in
both TLC and RV/TLC
231. Restrictive lung disease:
Reduction in TLC is a
cardinal feature
1. In Intrinsic RLD (Interstitial
Lung Disease)
• TLC will decrease
• RV will decrease because of
increased elastic recoil
(stiffness) of the lung and loss
of the alveoli.
• Breathing take place at low
FRC because of the
increased effort needed to
expand the lung .
• RV/TLC normal
232. 2. In extrinsic RLD (chest wall
disease :kyphoscoliosis or
neuromuscular disease)
• TLC is reduced either
because of mechanical
limitation to chest wall
expansion or because of
respiratory muscle
weakness
• RV is Normal because
Lung tissue and elastic
recoil is normal
So RV/TLC ratio will be high
• Breathing take place at
low FRC because of the
increased effort needed to
expand the lung .
233. RLD Intrinsic & severe chest
wall dis (pleural and skeletal)
TLC decreased
RV decreased
RV/TLC normal
FRC decreased
VC decreased
Extrinsic RLD
TLC decreased
RV normal
RV/TLC High
VC decreased
FRC decreased
235. Which of the following is NOT a normal occurance
with increasing age?
A. Vital capacity of the lung decreases.
B. Residual volume increases.
C. Functional residual capacity increases.
D. Inspiratory capacity decreases.
E. Expiratory reserve volume increases
23
5
Quiz Practice
236. Which of the following is NOT a normal occurance
with increasing age?
A. Vital capacity of the lung decreases.
B. Residual volume increases.
C. Functional residual capacity increases.
D. Inspiratory capacity decreases.
E. Expiratory reserve volume increases
23
6 Correct Answer: E
237. Tidal Volume (TV):
– Total volume of air breathed in and out over 1
minute
– Volume of air breathed in and out in a single
(quiet) breath
– Maximum volume of air breathed in over and
above normal inspiration
– Maximum volume of air breathed out over and
above normal expiration
23
7
Quiz Practice
238. Quiz Practice
Which of the following concerning average lung
volumes and capacities of a person at rest is TRUE?
A. TLC >VC > TV >FRC
B. TLC >FRC > VC >TV
C. TLC> VC > FRC >TV
D. TLC >FRC > TV >VC
23
8
239. Which of the following concerning average lung
volumes and capacities of a person at rest is TRUE?
A. TLC >VC > TV >FRC
B. TLC >FRC > VC >TV
C. TLC> VC > FRC >TV
D. TLC >FRC > TV >VC
23
9
Correct Answer: C
240. A patient presents with decreased vital
capacity and total lung volume. What is the
most probable diagnosis?
A. Bronchiectasis
B. Sarcoidosis
C. Cystic fibrosis
D. Asthma
24
0
Quiz Practice
241. A patient presents with decreased vital
capacity and total lung volume. What is the
most probable diagnosis?
A. Bronchiectasis
B. Sarcoidosis
C. Cystic fibrosis
D. Asthma
Answer : B. Sarcoidosis
24
1
242. Quiz Practice
In a normal healthy individual with a total
lung capacity of 6 litres:
a) The tidal volume at rest is about 1 litre.
b) The functional residual capacity would be
about 2 litres.
c) The expiratory reserve volume at rest would be
about 2 litres.
d) The FEV1 would be equivalent to about 1.5 litres
243. In a normal healthy individual with a total
lung capacity of 6 litres:
a) The tidal volume at rest is about 1 litre.
b) The functional residual capacity would be
about 2 litres.
c) The expiratory reserve volume at rest would be
about 2 litres.
d) The FEV1 would be equivalent to about 1.5 litres
244. Quiz Practice
Inspiratory reserve volume (IRV):
– Maximum volume of air breathed out over and
above normal expiration
– Maximum volume of air breathed in by a
maximum inspiration and maximum expiration out
– Volume of air breathed in and out in a single
(quiet) breath
– Maximum volume of air breathed in over and
above normal inspiration
24
4
245. Which of the following combine to make up
Functional Residual Capacity (FRC)?
- Tidal Volume (TV)
- Vital Capacity (VC)
- Inspiratory Reserve Volume (IRV)
- Expiratory Reserve Volume (ERV)
24
5
Quiz Practice
246. Which of the following combine to make up
Functional Residual Capacity (FRC)?
- Tidal Volume (TV)
- Vital Capacity (VC)
- Inspiratory Reserve Volume (IRV)
- Expiratory Reserve Volume (ERV)
Correct answer: Expiratory Reserve Volume (ERV)
24
6
247. Minute Volume is measured by:
– TV X RR
– TV
– IRV+TV+ERV
– VC
24
7
Quiz Practice
248. All the lung volumes can be measured by
spirometry except
A) Tidal volumes.
B) Inspiratory reserve volume.
C) Expiratory reserve volume.
D) Residual volume
24
8
Quiz Practice
249. Residual volume
– Volume of air remaining in lungs at end of
normal expiration (ERV + RV)
– Vital capacity plus residual volume
– Volume of air remaining in the lungs at the end
of maximum expiration
– Maximum volume of air breathed in by a
maximum inspiration and maximum expiration
out
24
9
Quiz Practice
250. Quiz Practice
The sum of the four primary lung volumes
(tidal volume, inspiratory reserve volume,
expiratory reserve volume, and residual
volume) equals
A) the functional residual capacity (FRC).
B) the vital capacity (VC).
C) the total lung capacity (TLC).
D) the maximum ventilatory volume (MVV).
251. One can determine the total lung capacity
(TLC) by
A) helium dilution.
B) nitrogen washout.
C) body plethysmography.
D) all of the above
25
1
Quiz Practice
252. Quiz Practice
The amount of air moved in and out with
each breath is called the __________.
A) vital capacity
B) tidal volume
C) residual volume
D) dead space
E) ventilation rate
253. Quiz Practice
Which of the following best describes the
Forced Vital Capacity (FVC) maneuver?
a. The volume of gas measured from a slow,
complete exhalation after a maximal inspiration,
without a forced effort
b. The volume of gas measured from a slow,
complete exhalation after a rapid maximal
inspiration
c. The volume of gas measured after 3 seconds of a
rapid, complete exhalation
d. The maximum volume of gas that can be expired
when the patient exhales as forcefully and rapidly
as possible after maximal inspiration
254. Quiz Practice
Even after the most forceful exhalation, a
certain volume of air remains in the lungs.
This volume is called the ________________.
A) tidal volume
B) expiratory reserve volume
C) vital capacity
D) residual volume
255. Even after the most forceful exhalation, a
certain volume of air remains in the lungs.
This volume is called the ________________.
A) tidal volume
B) expiratory reserve volume
C) vital capacity
D) residual volume
256. Quiz Practice
The maximum amount of air a person can
exhale after taking the deepest breath
possible is the _________________.
A) total lung capacity
B) inspiratory reserve volume
C) vital capacity
D) expiratory reserve volume
25
6
257. 25
7
Quiz Practice
The amount of air inspired or expired in a
normal inhalation or exhalation is called
__________ and has a volume of about
____________ mL.
A) tidal volume, 4600
B) vital capacity, 4600
C) residual volume, 1200
D) tidal volume, 500
258. The amount of air inspired or expired in a
normal inhalation or exhalation is called
__________ and has a volume of about
____________ mL.
A) tidal volume, 4600
B) vital capacity, 4600
C) residual volume, 1200
D) tidal volume, 500
259. Quiz Practice
The maximum amount of air in the lungs from a
rapid, complete exhalation after a rapid
maximal inspiration is called ______________
and has a volume of about _____________mL.
A) vital capacity, 4600
B) total lung capacity, 5800
C) inspiratory reserve volume, 3000
25 D) inspiratory capacity, 3500
9
260. The maximum amount of air in the lungs from a
rapid, complete exhalation after a rapid
maximal inspiration is called ______________
and has a volume of about _____________mL.
A) vital capacity, 4600
B) total lung capacity, 5800
C) inspiratory reserve volume, 3000
26 D) inspiratory capacity, 3500
0
261. Quiz Practice
Vital capacity is defined as which of the
following?
a. The volume of gas measured from a slow,
complete exhalation after a maximal
inspiration, without a forced effort
b. The volume of gas measured from a rapid,
complete exhalation after a rapid maximal
inspiration
c. The volume of gas measured after 3 seconds
of a slow, complete exhalation
d. The total volume of gas within the lungs after a
maximal inhalation
262. Quiz Practice
Vital capacity is defined as which of the
following?
a. The volume of gas measured from a slow,
complete exhalation after a maximal
inspiration, without a forced effort
b. The volume of gas measured from a rapid,
complete exhalation after a rapid maximal
inspiration
c. The volume of gas measured after 3 seconds
of a slow, complete exhalation
d. The total volume of gas within the lungs after a
maximal inhalation
263. Quiz Practice
In which of the following diseases is air-trapping
likely to occur?
A. Acute exacerbation of asthma
B. Sarcoidosis
C. Asbestosis
D. Emphysema
E. B & C
F. A & D
264. Quiz Practice
Which of the following statements are true regarding the
acceptability criteria for vital capacity measurement?
I. End-expiratory volume varies by less than 100 ml
for three preceding eatbrhs
II. Volume plateau observed at maximal inspiration
and expiration
III. Three acceptable vital capacity maneuvers should
be obtained; volume within 150 ml
IV. Vital capacity should be within 150 ml of forced
vital capacity in healthy individuals
a. I, II, and IV
b. II, III, and IV
c. III and IV
d. I, II, III, IV
265. Quiz Practice
All of the following are true regarding
the acceptability criteria of an FVC
maneuver EXCEPT?
a. Maximal effort, no cough or glottic closure during
the first second; no leaks of obstruction of the
mouthpiece
b. Good start of test; back extrapolated volume less
than 5% of the FVC or 150 ml
c. Tracing shows a minimum of 3 seconds of
exhalation
d. Three acceptable spirograms obtained; two
largest FVC values within 150 ml; two largest FEV1
values within 150 ml
