Body Plethysmography
BODY PLETHYSMOGRAPHY
Adrian H Kendrick BA, PhD, PgD, RPGST
Consultant Clinical Scientist
Department of Respiratory Medicine
University Hospitals, Bristol, England
DECLARATIONS

The presenter has no conflicts of interest

Where drug names are used, these relate to those
used in peer-reviewed publications quoted within
this presentation

Pictures of equipment within this presentation are
used to illustrate aspects of the presentation and
should not be represented as an endorsement by
the presenter of the equipment shown
2
OUTLINE OF TODAY
 What
do we need to measure?
 History of Body Plethysmography
 Underlying Principles


Constant Volume - Lung Volumes/Airways Resistance
Variable Volume - outline
 Technical
Issues
 Applications
Routine Applications
 Beyond Routine

 Summary
and Conclusions
3
WHAT
4
DO WE NEED TO MEASURE?
LUNG VOLUMES
5
WE CAN MEASURE
EASILY
Simple Spirometry
WHAT
6
WHAT
WE CAN MEASURE
Index
Usefulness
Vital Capacity
Useful marker for the effect of
disease and assessing outcomes
from exercise (6MWT)
Expiratory Reserve Volume
Effects of obesity on lung volumes,
particularly where BMI > 35 kg.m-2
Inspiratory Capacity
Marker of BD response where FEV1
shows no significant change –
effects of BD on hyperinflation
7
WHAT
WE CANNOT MEASURE SO EASILY
8
WHAT
WE CANNOT MEASURE
Index
Usefulness
Total Lung Capacity
Marker of effects of obstructive airways
disease and key index to confirm the
presence of a restrictive ventilatory defect
Functional Residual Capacity
Marker of hyperinflation and reflects
changes in PV relationships of chest wall
and/or lungs.
FRC/TLC ratio reflects the degree of
hyperinflation
Residual Volume
Marker of “gas trapping”.
Reflects the effects of obstructive or
restrictive disease on lung volumes.
RV/TLC ratio reflects poor gas mixing and
hence gas trapping
9
HOW
TO MEASURE
TLC
AND
RV?
Use FRC to obtain measurements  Multi-breath He dilution measurement
 Nitrogen washout
 Body plethysmography
Use TLC only
 Single-breath He/CH4 measurement (TLco) - VA
 Radiographic – CXR and/or CT
10
AIRWAYS RESISTANCE
Provides useful information on airway functions
 Can be applied to various techniques –

Bronchodilator response
 Bronchial Provocation Testing – Histamine, Manitol etc
 Pre & Post surgery for upper airway disorders


Various Techniques –
Impulse Oscillometry
 Body Plethysmography

11
BRIEF HISTORY OF BODY
PLETHYSMOGRAPHY
12
HISTORY - 1
1790 Menzies - Dissertation on Respiration
 Plunged a man into water in a hogshead up to his
chin and measured the rise and fall of the level in
the cylinder round the chin.
 With this method of body plethysmography he
determined the tidal volume
13
HISTORY - 2
1868 - Bert P: Total Body Plethysmography.
 Experiments with animals in a closed total body
plethysmographic system.
 Presented his studies to the ‘Société de Biologie’ under
the title ‘Changement de pression de l’air dans un poumon
pendent les deux temps de l’acte respiratoire’ ['Alterations
of the pulmonary air pressure during the two periods of
respiration']
 He did not do spirometric measurements together with the
plethysmography, nor did he do plethysmographic
measurements on humans.
14
MODERN BODY PLETHYSMOGRAPH - 1
Dubois et al 1956
 Most quoted couplet of papers in JCI ever!
 Forms the basis of constant-volume plethysmography
in use today for lung volume and airway resistance
measurements

15
MODERN BODY PLETHYSMOGRAPH - 2
Diagram of the apparatus for measuring lung volume.
B, body plethysmograph; S, shutter which occludes airway; L, lung; C, capacitance
manometer to record pressure changes in the plethysmograph (which are proportional to
the change in body volume); P, capacitance manometer to record pressure changes in
the mouth (which are equal to alveolar pressure when there is no airflow); O, cathode ray
oscillograph with x and y axes.
DuBois, AB, Botelho, SY, Bedell, GN, Marshall, R, Comroe (Jr), JH. A rapid plethysmographic
method for measuring thoracic gas volume: a comparison with a nitrogen washout method for
measuring functional residual capacity in normal subjects. J. Clin. Invest. 1956. 35:322-326.
16
MODERN BODY PLETHYSMOGRAPH - 3
Diagram of the apparatus for measuring airways resistance.
DuBois, AB, Botelho, SY, Comroe (Jr), JH. A new method for measuring airway resistance in man
using a body plethysmograph; values in normal subjects and in patients with respiratory disease. J.
Clin. Invest. 1956. 35:327-335.
17
18
DuBois, AB. Airway resistance. Am. J. Resp. Crit. Care Med. 2000. 162:345-346.
MEAD BODY PLETHYSMOGRAPH
19
Mead J. Volume displacement body plethysmograph for respiratory measurements in human subjects
J Appl Physiol 1960; 15: 736 - 740
BODY PLETHYSMOGRAPHS TODAY
20
ADULTS
21
CHILDREN
22
CHILDREN
23
ANIMALS
24
TYPES
25
OF
BODY PLETHYSMOGRAPH
CONSTANT VOLUME & VARIABLE VOLUME
Dubois
Mead Original
Mead Modern
26
CONSTANT VOLUME
Dubois Type
 Subject sealed inside the box
 Box volume  700 litres
 Subject breathes from within the box
 Pneumotachograph (pn) records flow
 Shutter (S) occludes airway/breathing
 Changes in mouth pressure recorded directly
 Changes in box volume recorded as changes in box
pressure

27
VARIABLE VOLUME - 1
Mead Type Box
 Patient breaths from outside the box
 Volume changes recorded with a
water-filled (Krogh-type) spirometer
 Mouth pressure recorded directly
 Flow at mouth recorded outside the
box using pneumotachograph (pn)
 Shutter (S) occludes airflow

28
VARIABLE VOLUME - 1
Mead Type Box – modern update
 Patient breaths from outside the box
 Volume changes recorded with a
wall mounted pneumotachograph
 Mouth pressure recorded directly
 Flow at mouth recorded outside the
box using pneumotachograph (pn)
 Shutter (S) occludes airflow

29
WHICH BOX –
FOR
WHAT?
Constant Volume
Variable Volume
Static Lung Volumes
 Dynamic Lung Volumes
 Airways Resistance


Static Lung Volumes
 Dynamic Lung Volumes
 Airways Resistance
 Compliance measures
 Gas compression studies
30
WHICH
IS
EASIER
TO
USE?
Constant Volume
Variable Volume
Easy to calibrate
 Simpler measures can
be made using
computerized systems


Fun to calibrate!
 More difficult to make
measurements –
limited software, better
measurements made
by hand
31
PRINCIPLES OF LUNG VOLUME
MEASUREMENTS USING A BODY
PLETHYSMOGRAPH
32
PRINCIPLES
 Based
on Boyle’s law PV = k
 Assumes temperature remains constant
 When
subject breathes in and out against a
shutter, changes in pressure and volume occur
33
BOYLES LAW
34
LUNG VOLUMES
 Boyle’s
Law: for fixed mass of gas at constant
temperature: P1V1 = P2V2
 Brief
occlusion at airway opening to seal a fixed
mass of gas in the lungs (V1) - i.e. the FRC to
be measured
 Pressure
within lungs at end expiration (P1) ~
atmospheric pressure.
 P2
and V2 represent the pressure and volume
in the lungs after a respiratory effort against the
occlusion.
35
LUNG VOLUMES
Thus PV
= (P + P).(V - V)
= V(P - P) + (P - P) V
= PV - VP + (P - P) V
Re-arranging PV = (P - P) V
VL
= (P - P)(V/P)
P is such a small fraction of P (barometric pressure)
that it can be omitted without loss of accuracy
VL
= P(V/P)
36
CONSTANT VOLUME BODY - BOX
37
THE CONSTANT VOLUME BOX
38
Specifications and Calibration
KEY FACTORS
In tidal breathing, the chamber pressure changes
are small, only a few hPa (or cmH2O).
 Disturbances may be caused by





Patient-related temperature increase within the chamber
(body heat),
Breathing-related air temperature and humidity changes
Pressure changes related to external pressure variations
To attain adequate pressure equilibration between
mouth and alveolar space, panting during the
shutter manoeuvre should be avoided
39
CONSTRUCTION
The characteristics of the body plethysmograph
chamber are key to ensure good measuring quality.
 Some of the features are:








Rigidity of the enclosure
Heat transfer characteristics of the chamber walls
Built-in equilibration vessel
BTPS compensation
Calibration unit
Adjustment of a defined leak
Type and speed of the shutter assembly
40
PATIENT SYSTEM
Bacterial Filter
Shutter
Mechanism
Pneumotachograph
41
CONSTANT VOLUME BODY - BOX
 Characteristics
of the constant volume body
box need to be accounted for
 Volume changes are recorded in terms of
pressure changes. This needs to be calibrated
 Pump air into the box - 50ml sinusoidal pump
with box sealed and record deflection
VL
= PB(V/P). Cbox = VTGV
where PB is the barometric pressure and Cbox
is the box calibration factor
42
CONSTANT VOLUME BODY - BOX
 TGV
is thoracic gas volume. This is the total
volume of compressible gas in the thorax, and
will include any compressible gas in the
stomach and abdomen
 TGV will be higher than FRC in normal
subjects due to this difference and the fact
that the shutter may not close at exactly FRC
43
BODY BOX SPECIFICATIONS
 Box
must be airtight
 All pressure transducers should be calibratable
with a known pressure
 Volume calibration with a 3 or 7 litre calibration
syringe
 Time constant for leaks tested daily
44
INTERNATIONAL
GUIDELINES
45
BODY BOX SPECIFICATIONS
Item
Specification
Mouth Pressure range
Accuracy
-2 to +2 kPa
± 0.01 kPa
Plethysmograph
Pressure range
Accuracy
At least ± 0.02 kPa
± 5 x 10-5 kPa
Volume deflection
Accuracy
-200 to +200 ml
± 0.5 ml
P and V
In phase up to 10 Hz
46
CALIBRATION
Mouth pressure is verified with a
mercury or water barometer
 Flows are verified with a rotometer
(flow-metering device) or a 3-liter
syringe
 Box pressure is calibrated by using
a sine-wave rotary pump that
simulates changes in the
inspiratory and expiratory volumes

47
BODY BOX - CALCULATIONS
Information required  Barometric pressure
 Volume of box
 Subjects mass (kg)
 Angle of deflection
 Box pressure calibration
 Mouth pressure calibration
- PB
- Vbox
-W
-
- Boxcal
- Pcal
48
EFFECTS
OF
BODY WEIGHT
When a patient sits inside the box, their body mass
displaces air from within the box
 The density of human flesh etc is 1.07 that of air
 Therefore need to adjust the volume of the air
within the box for the mass of the human

Wcorr = (Vbox - W/1.07)/Vbox

Alternatively – calibrate the box with the patient
inside it.
49
BODY BOX - CALCULATIONS
VL = PB(V/P). Cbox = TGV
TGV = (Boxcal/Pcal) x (PB-47) x Wcorr x 1.33 x Tan -1
RV = TGV - ERV
TLC = RV + IVC
or
TLC = TGV + IC
RV = TLC - EVC
50
CALCULATION
OF
TANGENT
51
52
ACCURACY
OF MEASUREMENTS
Duplicate measurements of TGV should be within
5% for a skilled operator and good coaching of the
patient
 Different operators, assessing the same patient
should get similar accuracy, but slight variations in
techniques and encouragement may reduce the
accuracy
 Computer software generated line plots MUST
always be verified by the operator and adjusted if
required.

53
CONSTANT VOLUME BOX
54
Procedure
CONTRAINDICATIONS
FOR
BOX TESTING
Preventing Patient entering the box




Mental confusion
Poor muscular co-ordination
Body cast
Wheelchair
 Claustrophobia
 Extreme Obesity


Presence of devices - continuous I.V. infusion
Conditions that interfere with pressure changes

Chest tube
 Trans-tracheal O2 catheter
 Ruptured ear drum.

Continuous O2 therapy that cannot be removed
55
http://www.artp.org.uk/en/patient/lung-function-tests/lung-volumes.cfm
56
PROCEDURE
 Seat
subject upright in box, seal door and
allow subject to temperature equilibrate within
the box (½ - 2 mins)
 Vent the box to release any pressure build up
due to thermal changes
 When equilibrium occurs, Boyle’s law applies
 Attach subject to mouthpiece, apply noseclip
and place flats of hands on sides of face and
under chin
57
PROCEDURE –
BEFORE SHUTTER CLOSES
 Situation
at end expiration, prior to any
respiratory efforts against an occlusion valve
58
PROCEDURE
 During
tidal breathing, close shutter at FRC
and ask subject to breath in and out gently
against the shutter an open glottis at a rate of
0.5 - 1 Hz (30 – 60 breaths/min)
 After 1 to 2 breaths against the shutter, open
shutter and ask subject to breathe fully out
(ERV) and then fully in (IVC) and then breathe
normally
 Release vent, seal box and repeat, obtaining
3 technically acceptable traces are obtained 59
PROCEDURE – SHUTTER OCCLUSION

During inspiratory efforts against the occlusion
As lung volume increases,
box volume decreases and
box pressure increases
As lung volume
increases, alveolar
pressure decreases
and hence pressure
at mouth decreases
P1 -ΔP
Changes in box pressure
calibrated in terms of volume
using a calibrated syringe
60
SUMMARY
OF
PROCEDURE
61
VISUAL DISPLAY
62
Body Plethysmography
Advantages
Disadvantages
• Rapid method of multiple
estimations of VTGV
• Good repeatability
• Raw and SGaw obtainable
• Measures all gas within
thorax
•
•
•
•
Expensive equipment
Few reference values
Claustrophobia
Inaccurate in severe airflow
obstruction
63
CRITERIA OF ACCEPTABILITY
Manoeuvre shows a closed loop without drift
 Tracing does not go off the screen
 Breathing is at 0.5 – 1 Hz
 Tangents should be within 10%
 At least 3 TGV values should agree within 5% and the
mean value reported

64
PRINCIPLES OF AIRWAYS
RESISTANCE MEASUREMENTS
65
AIRWAY RESISTANCE - PHYSIOLOGY
0.010
0.009
Resistance (SIUnits)
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0.000
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Airway Generation
66
AIRWAY RESISTANCE - PHYSIOLOGY
Cumulative Resistance (% of total)
100
80
60
40
20
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Airway Generation
67
AIRWAY RESISTANCE - PHYSIOLOGY
R1
R2
R3
SERIES
RTOT =
0.01
+
0.02
R1
= 0.01
R2
= 0.01
+ 0.03
= 0.06 units
PARALLEL
1/RTOT =
RTOT =
1/ 0.01 + 1/0.01 = 200
0.005 units
68
RESISTANCE
Electrical
Lungs
V P
R

I
V
Ohm’s Law
69
AIRWAYS RESISTANCE
 Resistance
to airflow in the upper airways and the
tracheobronchial tree
 Changes in airways resistance may be useful in
assessing response to interventions
 Newer techniques may be able to assess both the
upper airways and changes in the peripheral
airways during tidal breathing
70
RESISTANCE & MEASUREMENT
Pleural Space
Chest Surface
Sum
Rtotal
0.02
0.02
0.12
0.26
Forced Oscillation
Alveoli
0.05
Oesophageal balloon
2-3mm Airway
0.05
Interupter
Larynx
Glottis
Raw (large)
Raw (small)
Rti
Rth
R(SI)
Plethysmography
Mouth
71
AIRWAY RESISTANCE - BOX
 Record
airflow against
box pressure with shutter
open
 Record mouth pressure
against box pressure
with shutter closed
72
AIRWAY RESISTANCE - BOX
Shutter Closed; Box sealed
Recording of Mouth pressure versus
Box Pressure as subject breathes
against the shutter
Mouth Pressure
Airflow
Shutter Open; Box sealed
Recording of Airflow from
pneumotachograph versus
Box Pressure.
Box Pressure
Box Pressure
73
AIRWAY RESISTANCE - BOX
PBo x PAl v PAl v
x

 R Aw
V PBo x
V
Tan
k
 Rc  RAw
Tan
74
AIRWAY RESISTANCE - BOX
GAW
= 1/RAW
SGAW= GAW/TGV
75
AIRWAY RESISTANCE & LUNG VOLUME
TLC
25
RV
0.2
FRC
0.1
TLC
0.0
Airway Conductance (SI Units)
Airway Resistance (SI Units)
0.3
20
15
FRC
10
5
RV
0
0
1
2
3
4
Lung Volume (litres)
5
6
7
0
1
2
3
4
5
6
7
Lung Volume (litres)
76
PHYSIOLOGICAL MATHS!
76
77
PHYSIOLOGICAL MATHS!
r
r4
R1
= 0.75
= 0.3164
= 3.16V
P
R1
= 2.5
= 3.16
= 0.79
r
r4
R2
= 0.375
= 0.0198
= 50.57
P
R2
= 2.5
= 50.57
= 0.049
R2 ÷ R1 = 16
Flow  by 94%
77
78
DETERMINANT OF RESISTANCE
 Laminar
and Turbulent Flow
 Airway diameter/x-sectional area (A)
 Gas Density () and Viscosity ()
 Reynolds Number
79
FLOW
IN
TUBES
80
DETERMINANT
OF
RESISTANCE
< 100 – laminar flow
 Rn > 10,000 – turbulent flow
 Rn ~ 1500 – trachea
 He/O2 vs N2/O2 vs SF6/O2
 Rn
81
AIRWAY RESISTANCE MEASUREMENTS
Assessing  Reversibility of inhaled drugs
 Effect of bronchoconstrictor agents
 Large and small airway function
 Monitoring
changes in disease
82
EFFECTS
OF
DISEASE
0.6
Airway Resistance (kPa.l-1.s)
0.5
0.4
0.3
0.2
0.1
0
Normal
Mild Airflow
Obstruction
Emphysema Asthma Pre - Asthma Post
BD
- BD
83
TECHNICAL ISSUES FOR BODY
PLETHYSMOGRAPHIC
MEASUREMENTS
84
TECHNICAL
ISSUES
Shift Volume
 Inaccuracy of Measurements in AWO
 Linked and Unlinked spirometry
 Panting frequency
 Abdominal Gas Volume

85
SHIFT VOLUME
This is the change in volume within the lungs in
relation to the change in box pressure used as a
surrogate marker of changes in volume.
 As the subjects breathes against the shutter, the
lung volume changes, so the box pressure
changes.
 By calibrating the box pressure for volume change,
the actual change in volume – the shift volume can
be estimated
 The shift volume is useful in assessing the effects
of disease on resistance

86
SHIFT VOLUME
Schematic representation of specific resistance loops in a) a normal subject, b) a subject
with increased large airway resistance, c) a subject with chronic airflow obstruction d) and
87
a subject with upper airway obstruction.
INACCURACY
IN
AWO
A number of papers have demonstrated that body
plethysmography can over-estimate TGV and hence
TLC in patients with asthma and severe AWO.
 The major assumption in the technique is that Pmouth is
the same as PAlv and this is effectively true in normal
subjects and in patients with mild airflow obstruction.
 In moderate to severe airflow obstruction, there is a time
lag between Pmouth and PAlv due to the characteristics of
the airways resulting in an underestimation of PAlv and an
overestimation of TGV
 To overcome these issues, slow panting/breathing
88
against the shutter is advised

PANTING FREQUENCY
In AWO, there is a delay between alveolar pressure
and mouth pressure – out of phase with each other
 This results in an overestimation of TGV and hence
TLC
 This artefact is exacerbated when –

Airways are very narrow (Raw)
 Very compliant airways
 High panting frequency


Panting/breathing at < 1Hz allows more time for
mouth and alveolar pressures to equalize, thereby
reducing the phase differences
89
DIFFERENCES
IN
TLC
IN
CHRONIC AWO
D iff e r e n c e ( T L C m - T L C e s )
1 .6
1 .4
1 .2
1 .0
0 .8
0 .6
0 .4
0 .2
0 .0
0 .0 2
0 .0 4
0 .0 6
- 0 .2
S G aw cm H 2O
-1
sec
0 .0 8
0 .1 0
-1
Rodenstein & Stanescu Am Rev Respir Dis 1982; 126: 1040 - 1044
90
LINKED
AND
UNLINKED SPIROMETRY
TLC and RV are calculated as –
 TLC = RV + VC = FRC + IC
 RV = FRC – ERV = TLC – VC
 Does it matter if the VC manoeuvre is done immediately
after the shutter opens or using a different device?
 Purist approach – linked as FRC may change between
manoeuvres
 Acceptable alternative - unlinked

91
UNLINKED
AND
UNLINKED SPIROMETRY
Mean ± SEM
92
Williams & Bencowitz. Differences in plethysmographic lung volumes. Chest 1989; 95: 117 - 123
ABDOMINAL GAS VOLUME (AGV)
accounts for about 115 ml1
 The effects of AGV may be dependent on level
of panting. FRC appears to be the best level to
pant at2
 TGV may be lower by  900 ml if the subject
pants using diaphragm and abdominal muscles
rather than intercostal and accessory muscles3
 AGV equates to about 360 ml3
 AGV
1.
2.
3.
Bedell et al 1956
Brown et al, 1978
Habib & Engel, 1978
93
BODY
PLETHYSMOGRAPHY
VERSUS OTHER TECHNIQUES
94
AGREEMENTS
OF
METHODS
In Normal subjects  VA and TLCHe agree ~ 300 - 400 ml
 VA and TLCBox agree ~ 400 - 500 ml
 TLCBox and TLCHe agree ~ 300 – 400 ml
 Similar
results observed in patients with mild airflow
obstruction and in restrictive ventilatory defects
95
AGREEMENTS
 Moderate
 Note:
OF
METHODS
to severe airflow obstruction
TLCBox > TLCHe > VA
if TLCBox > VA by 3+ litres
then emphysematous bulla may be present
96
WHY
DIFFERENCES IN
TLC
MEASURES

97
DIFFERENCES
IN
TLC & VA
TLCHe - VA
6
T L C p le t h - V A
4
3
TLCx
x
- V A ( lit r e s )
5
2
1
0
0
20
40
60
80
F E V 1 % p r e d ic t e d
Data from T Goddard, ERS 2011 with permission
100
120
140
98
GAS DILUTION – NORMAL/RESTRICTIVE
Model 1
1min
75%
2min
20%
5 min
5%
In 1 minutes, 75% of the lung volume will be measured
In 5 minutes, 100% of the lung volume will be measured
99
GAS DILUTION – SEVERE AWO
Model 2
5min
20min
65%
25%
30min
10%
In 5 minutes, 65% of the lung volume will be estimated
In 10 minutes, 80% of the lung volume will be measured
100
BODY BOX – ANY
Model 3
1min
75%
PATIENT!
+ Xml
2min
20%
+ Xml
5 min
5min
20min
5%
65%
25%
30min
10%
In 15 seconds all the lung volume will be estimated
101
INTERPRETATION
102
OF
RESULTS
ATS/ERS INTERPRETATION STRATEGY
103
ATS/ERS INTERPRETATION STRATEGY
Uses Standardized Residuals for each index to
assess the Lower Limit of Normal (LLN)
 Based on physiologically and statistically sound
approach to interpretation of lung function
 ATS/ERS guidelines do not state which test of lung
volumes – Body plethysmography, Helium Dilution
or Nitrogen washout should be used within the
interpretation strategy.

104
Interpretation of Results
• In patients with obstructive diseases
– airway closure occurs at an abnormally high lung volume
  FRC (functional residual capacity)
  RV (residual volume)
• Patients with reduced lung compliance (e.g., diffuse
interstitial fibrosis)
– stiffness of the lungs + recoil of the lungs to a smaller resting
volume
  FRC
  RV
105
CLINICAL APPLICATIONS &INTERPRETATION
 FRC

Gas trapping due to intrathoracic airway obstruction

Cystic lung disease
 FRC

Abnormal alveolar development

Reduced recoil of chest-wall

Decreased lung compliance

Atelectasis
106
OBSTRUCTIVE LUNG DISEASE
107
EMPHYSEMA: PRESSURE-VOLUME CURVES
108
LUNG VOLUME REDUCTION SURGERY
109
LUNG VOLUME REDUCTION SURGERY
Current guidelines recommend the use of Body
Plethysmography for the measurement of lung volumes
 Measures all lung volume within the chest, not just that
which is accessible through gas dilution techniques

110
RESULTS
OF
LVRS
111
Gerald M. O’Brien; Satoshi Furukawa; Anne Marie Kuzma; Francis Cordova; Gerard J. Criner. CHEST 1999; 115:75–84
RESIDUAL
VOLUME
(RV)
Normally it accounts for about 25% of TLC.
 Limited by chest wall compression
RV increased
 in airway narrowing with air trapping (Asthma)
 in loss of elastic recoil (Emphysema).
RV decreased
 Increased elastic recoil (pulmonary fibrosis)

112
TIDAL
VOLUME
(TV)
Equates to about 7ml/kg
 400-700 ml
TV increased
 Severe AWO + reduced breathing frequency
TV decreased
 in severe RLD, + increase in breathing frequency

113
TOTAL LUNG CAPACITY (TLC)
It is the total volume of air within the lung after
maximum inspiration.
 TLC is limited by lung compliance
TLC Increased
 in airway narrowing with air trapping (Asthma)
 in loss of elastic recoil (emphysema).
TLC Decreased
 in ILD, muscle weakness, Obesity etc

114
EXPIRATORY RESERVE VOLUME
ERV reduced
 Obesity (BMI > 35 kg.m-2)
 ILD
115
INSPIRATORY


CAPACITY
(IC)
It is the maximal volume of air inspired from resting
expiratory level
Useful marker of de-hyperinflation after BD’s
116
FUNCTIONAL RESIDUAL CAPACITY (FRC)
It is the volume of air remaining in the lungs at the end
of resting (normal) expiration.
 Balance of chest wall and lung compliances
FRC Increased (>+1.65 SR) in
 Emphysema (decreased elastic recoil)
 Asthma
 Bronchiolar obstruction (air trapping)
FRC decreased (< 1.65 SR) in
 intrinsic ILD
 by upward movement of diaphragm (obesity, painful
thoracic or abdominal wound)

117
VITAL CAPACITY

volume of gas measured on complete expiration
after complete inspiration without effort
Decreased in
 Obstructive Lung Disease
 ILD, Muscle weakness, Obesity etc
Note
If VC < 15 ml/kg and VT < 5ml/kg, patient needs
ABG’s and overnight oximetry as this indicates likely
need for non-invasive ventilation
118
FEV1
FVC
FEV1/FVC
RV
TLC
RV/TLC
VC
FRC
FRC/TLC
FEV1/TLC
AWO
RLD (Lung)
RLD (non-Lung)

 or N
N or 

N or 



N or 
N or 


N or 
N



N

N





N or 
N

N or 
N
119
INTERPRETATION OF AIRWAYS
RESISTANCE
120
INDICATION
FOR
R
AW MEASUREMENT
Further evaluation of airflow limitation beyond spirometry
 Determining the response to B.D.
 Determination of bronchial hyper-reactivity

The commonly used limit for bronchial provocation is a 15 or
20% decrease in FEV1 relative to control baseline FEV1.
 The comparable limit for sRtot is 100%, for Rtot 50% increase
and for sGtot 40% decrease from baseline, respectively.

Difference between types of obstructive lung disease
having similar spirometry pattern.
 Following the course of the disease and response to
treatment.

121
ASSESSMENT
OF
RAW DATA
122
PARAMETER
OF AIRWAY RESISTANCE
sReff (specific effective airway resistance) which reflects
the larger central airways
 sRtot (specific total airway resistance) which reflects the
smaller peripheral airways
 The parameter of sR0.5 reflects the behavior of larger ,
more proximal airways with much less sensitivity to
peripheral airways.

123
APPLICATION
OF
RAW
124
DEFINITION OF ABNORMAL LUNG FUNCTION
USING RAW ETC
Threshold to abnormality for Rtot and Reff in
adults: 0.3 kPa/(L/s)
 Predicted values for Rtot and Reff in children:
normal if below 150% of predicted
Bronchial hyper-responsiveness
Povocation:
+PD/C 50 in Raw equivalent to -PD/C 20 in FEV1
+PD/C 100 in sRaw equivalent -PD/C 20 in FEV1
-PD/C 40 in sGaw equivalent -PD/C 20 in FEV1
Dilatation:
>25 % response to bronchodilator (children 2-5 yrs

125
126
AIRWAYS OBSTRUCTION
127
RESTRICTIVE LUNG DISEASE
128
EXTRATHORACIC AIRFLOW PROBLEM
129
AIRWAY COLLAPSE
130
BEYOND
131
THE
ROUTINE
OBESITY
AND
LUNG VOLUMES
Small differences in TLC and VC over range of BMI’s
132
OBESITY
AND
LUNG VOLUMES
Big differences in FRC and especially ERV over range of BMI’s
133
OBESITY
AND
LUNG VOLUMES
134
135
BRONCHODILATOR RESPONSE
Where FEV1 does not significantly improve, patients
often state they feel symptomatically better
 Changes have occurred in the degree of hyperinflation,
so work of breathing is reduced.
 Raw decreases
 FRC decreases
 RV decreases
 IC increases
 Demonstrated for 2-agonists, combination drugs and
anticholinergic drugs
 Relate changes in static lung volumes and Raw pre and
136
post treatment to symptomatic improvement (VAS score)
and to 6MWT

137
138
GAS COMPRESSION
139
TRACHEAL STENTING
Assess airway function by use of airways resistance
measurements before and after stenting and to follow
progress of patient over time
 Raw is more comfortable for the patient to perform
 Stent should  Raw as radius of airway is greater.
 FEV1 should also increase and shape of F-V curve
should be more normalized

140
PNEUMOTHORAX
AND
PLEURAL EFFUSION
Possible to make measurements of He dilution and
TGV from body plethysmograph to demonstrate
differences between total volume of the chest and
actual accessible lung volume
 TLCpleth – TLCHe equates to difference in accessible
gas exchange volume.

141
SUMMARY
Body plethysmography provides a more accurate
reflection of the true size of the lungs at RV, FRC and
TLC than gas dilution techniques, especially in AWO.
 Airways resistance provides a useful measure of airway
dysfunction and can be used in relation to dynamic lung
volumes to further assess airway dysfunction
 Body plethysmography is recommended in the
assessment of patients undergoing LVRS and may be
used to assess other disorders including spinal cord
injury etc.
 Body plethysmography can be used beyond the simple
142
static lung volume measurements

CONTACT & CONSULTANCY

[email protected]
143
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