2. Lung volumes andLung volumes and
capacitiescapacities
BYBY
Dr/HALA SALAHDr/HALA SALAH
PhysiologyPhysiology ofof ProfProf..
3. Determination of lung volumes isDetermination of lung volumes is
used toused to::
11--assess the efficiency of the respiratory systemassess the efficiency of the respiratory system..
22--diagnose respiratory diseasesdiagnose respiratory diseases..
Most of these volumes can be measured
using a simple spirometer
6. It is the volume of air inspired orIt is the volume of air inspired or
expired each breath during normalexpired each breath during normal
quiet breathing. It is about 500 mlquiet breathing. It is about 500 ml..
Tidal volume (Tidal volume (VTVT((
8. Inspiratory reserve volume (IRVInspiratory reserve volume (IRV((
It is maximal
volume of air
which can be
inspired after a
normal
inspiration. It is
about 3000 ml.
9. Expiratory reserve volume (ERVExpiratory reserve volume (ERV((
It is the maximalIt is the maximal
volume of airvolume of air
which can bewhich can be
expired after aexpired after a
normalnormal
expiration. It isexpiration. It is
about 1100 mlabout 1100 ml..
10. Residual volume (RVResidual volume (RV((
It is the volume ofIt is the volume of
air remaining inair remaining in
the lungs afterthe lungs after
maximalmaximal
expirationexpiration..
It is about 1200It is about 1200
mlml..
11. Tidal volume
Dead space
Tidal volume
Inspiratory reserve
volume
Expiratory reserve
volume
LUNG VOLUMESLUNG VOLUMES
Residual
Volume
14. Inspiratory capacity (ICInspiratory capacity (IC((
It is the maximalIt is the maximal
volume of air thatvolume of air that
can be inspiredcan be inspired
from the restingfrom the resting
expiratoryexpiratory
volumevolume..
15.
16. Functional residual capacity (FRCFunctional residual capacity (FRC((
It is the volume of air which remains in the lungIt is the volume of air which remains in the lung
at the resting expiratory level (after normalat the resting expiratory level (after normal
expirationexpiration(.(.
FRC = RV + ERVFRC = RV + ERV
==12001200++11001100
23002300mlml
17.
18. Vital capacity (VCVital capacity (VC((
It is the maximum volumeIt is the maximum volume
of air that can beof air that can be
expelled from lung by aexpelled from lung by a
maximal expirationmaximal expiration
after a maximalafter a maximal
inspirationinspiration..
VC = IRV + TV + ERVVC = IRV + TV + ERV
30003000++500500++11001100==46004600
It is a good index forIt is a good index for
pulmonary efficiencypulmonary efficiency..
19. Total lung capacity (TLCTotal lung capacity (TLC((
It the volume of air contained in the lung atIt the volume of air contained in the lung at
the end of maximal inspirationthe end of maximal inspiration..
TLC = IRV + TV + ERV + RVTLC = IRV + TV + ERV + RV
==30003000++500500++11001100++12001200==58005800
mlml..
20.
21. Tidal volume
Dead space
Tidal volume
Inspiratory reserve
volume
Expiratory reserve
volume
LUNG VOLUMESLUNG VOLUMES
Residual
Volume
FRC
IC
VC
T LC
22. Lung volumes and capacities areLung volumes and capacities are
Decreased inDecreased in
The recumbent position than in standingThe recumbent position than in standing..
Women than in men by about 20-25%Women than in men by about 20-25%..
Small and athenic personsSmall and athenic persons..
Old ageOld age..
Increased inIncreased in::
Larger and athletic personsLarger and athletic persons..
23. All lung volume and capacities areAll lung volume and capacities are measuredmeasured
directly by spirometerdirectly by spirometer exceptexcept::
Functional Residual capacityFunctional Residual capacity FRCFRC..
Total lung capacityTotal lung capacity TLCTLC..
Residual volumeResidual volume RVRV..
Because the air in the residual volume of the lung cannot beBecause the air in the residual volume of the lung cannot be
expired into the spirometer and this volume constitutesexpired into the spirometer and this volume constitutes
part of FRC, TLCpart of FRC, TLC..
24. Lung volumes measured by spirometerLung volumes measured by spirometer
For the others parameters additional measurements needed
• Values obtained by simple spirometry
27. Determination of RV and FRCDetermination of RV and FRC
They are measured indirectly usingThey are measured indirectly using
helium dilution methodhelium dilution method
28. Why HeliumWhy Helium??
11--Its low solubility in respiratory membraneIts low solubility in respiratory membrane
so it does not diffuse into the pulmonaryso it does not diffuse into the pulmonary
capillary bloodcapillary blood..
22--It is an inert gas not utilized by the tissuesIt is an inert gas not utilized by the tissues..
33--The total amount of helium does notThe total amount of helium does not
change during the testchange during the test..
29.
30. • Helium dilution
Spirometer of known volume (Vs)and He
Conc .(C1) connected to the patient.
At end of normal expiration.
-Closed circuit
- After several minutes of breathing.
-C1XV1=C2X(Vs+VL)
-C2= final He conc,VL=FRC.
At beginning After several minutes
Unknown lung volume can be calculated
[He] initial · Vs = [He] final · (Vs + VL)
Determination of RV and FRCDetermination of RV and FRC
31. Clinical significance of FRCClinical significance of FRC
FRC maintainsFRC maintains gas exchangegas exchange with blood in betweenwith blood in between
breathsbreaths..
The large volume of FRC prevents marked rise inThe large volume of FRC prevents marked rise in
alveolar pressure of oxygen during inspiration and itsalveolar pressure of oxygen during inspiration and its
drop during expiration i.e. it providesdrop during expiration i.e. it provides stability ofstability of
oxygen pressure in the alveolar air and arterial bloodoxygen pressure in the alveolar air and arterial blood..
Normally the residual volume should beNormally the residual volume should be less thanless than 30%30%
of the total lung capacity. It exceeds that level inof the total lung capacity. It exceeds that level in
some pathological conditions e.g.some pathological conditions e.g. Bronchial asthmaBronchial asthma
((RV/TLC>30RV/TLC>30%%(.(.
32. Minute Respiratory VolumeMinute Respiratory Volume
It isIt is the total amount of air that moves into thethe total amount of air that moves into the
respiratory passages each minute inspired orrespiratory passages each minute inspired or
expired (total ventilationexpired (total ventilation((
it equals = Tidal volume X Respiratory Rateit equals = Tidal volume X Respiratory Rate
==500500X 12 breath / minuteX 12 breath / minute
==60006000cc/min = 6 L / mincc/min = 6 L / min
35. Maximal Voluntary VentilationMaximal Voluntary Ventilation
(MVV(MVV))
It is the maximal volume of air that can be breathed per minuteIt is the maximal volume of air that can be breathed per minute
using the fastest rate and the deepest respiratory effortusing the fastest rate and the deepest respiratory effort
possiblepossible..
The subject breathes as fast and as deep as possible for 15
seconds only
-To avoid fatigue of the respiratory muscles.
-To avoid wash out of CO2.
Normal MVV = 80-160 L/min for male,
=60-120L /min for females,
average 100 L/minute.
It is a better index for:
1-respiratory efficiency.
2-physical fitness.
36. Breathing reserve (BRBreathing reserve (BR))
It is the difference between MVV and minuteIt is the difference between MVV and minute
Respiratory volumeRespiratory volume
BR = MVV – MRVBR = MVV – MRV
100100––66==9494L/minL/min..
It is a good test for the functional reserve of the respiratory
system and the higher is the BR, the better the state of
physical fitness.
37. Dyspneic indexDyspneic index
It is the ratio between BR and MVV and it isIt is the ratio between BR and MVV and it is
usually about 90%. If it is decreased below 60%usually about 90%. If it is decreased below 60%
dyspnea (difficulty in breathing) occurs ondyspnea (difficulty in breathing) occurs on
slightest effect and the person is consideredslightest effect and the person is considered
physically unfitphysically unfit..
39. Factors affecting the vital capacityFactors affecting the vital capacity
PosturePosture..
Movement of diaphragm.
Strength of Respiratory MusclesStrength of Respiratory Muscles..
Thoracic wall expansibilityThoracic wall expansibility..
Resistance to air flowResistance to air flow..
Lung elasticityLung elasticity..
Restrictive lung diseaseRestrictive lung disease..
42. Timed vital capacityTimed vital capacity
It is the volume of expired air at the end of theIt is the volume of expired air at the end of the
first, second or third second, when measuringfirst, second or third second, when measuring
vital capacityvital capacity..
also called forced expiratory volume (FEV(.
43. TIMED VITAL CAPACITY (FVCTIMED VITAL CAPACITY (FVC))
Importance of the timed VCImportance of the timed VC
The timed vital capacity is a useful test toThe timed vital capacity is a useful test to
differentiate betweendifferentiate between obstructiveobstructive lunglung
diseases (COPD( asdiseases (COPD( as emphysemaemphysema andand
chronic bronchitischronic bronchitis andand restrictiverestrictive lunglung
diseases as interstitial lungdiseases as interstitial lung fibrosisfibrosis..
44. How to measure FVCHow to measure FVC??
The patient is asked to
inspire as deep as
possible and expires as
deep and as rapid as he
can into the spirometer
that measures not only
the volume expired but
also the time taken in
expiration. Normally
the FVC takes place in
4 seconds.
46. Normally FEVNormally FEV11 (which is the fraction of the(which is the fraction of the
forced vital capacity which can be expired byforced vital capacity which can be expired by
the end of the first second using the maximalthe end of the first second using the maximal
expiratory effort( is about 80-83% of FVC.expiratory effort( is about 80-83% of FVC.
FEVFEV22 about 90-93% of FVC, andFEVabout 90-93% of FVC, andFEV33 equalsequals
97% of FVC97% of FVC..
48. FEVFEV11 & FVC& FVC
• Forced expiratory volume
in 1 second (FEV1) in
young trained athletes: 4 L
•FVC in young trained
athletes: 5 L
• FEV1/FVC %=
80%-83%
FEV1
FVC
FVC
49. In obstructive lung diseases, the air wayIn obstructive lung diseases, the air way
resistance is greatly increased, the vitalresistance is greatly increased, the vital
capacity is reduced and FEVcapacity is reduced and FEV11 is markedlyis markedly
reduced FEV1/FVC is less thanreduced FEV1/FVC is less than 80%80%. While in. While in
restrictive lung disease FEVrestrictive lung disease FEV11/FVC is normal or/FVC is normal or
even increasedeven increased 90%90% due to proportionatedue to proportionate
decrease in both FEV1 and FVCdecrease in both FEV1 and FVC..
50. Spirometry Interpretation: Obstructive vs. RestrictiveSpirometry Interpretation: Obstructive vs. Restrictive
diseasesdiseases
Obstructive DisordersObstructive Disorders
FEV1/FVCFEV1/FVC↓↓
Restrictive DisordersRestrictive Disorders
FEV1/FVC normal orFEV1/FVC normal or↑↑
59. Dead spaceDead space
It is the volume of air which does notIt is the volume of air which does not
undergo gas exchange with pulmonaryundergo gas exchange with pulmonary
capillariescapillaries..
Types of dead spaceTypes of dead space::
Anatomical dead spaceAnatomical dead space..
Alveolar dead spaceAlveolar dead space..
Physiological dead spacePhysiological dead space..
60. Dead Space Ventilation [VDS[
Includes ventilation of both:
1.the anatomic dead space: the portion of the
breath that enters and leaves the conducting
zones of the airways (nose→ terminal
bronchioles(
2.the alveolar dead space: air that reaches the
alveoli but does not participate in gas exchange
Alveolar DS + Anatomic DS= Physiologic DS
61. Measurement of dead spaceMeasurement of dead space
By using Bohr's equation (physiological DSBy using Bohr's equation (physiological DS(:(:
DS =TVDS =TV XX
PCO2 in alveolar air – PCO2 in expired air
PCO2 in alveolar air
PCO2 in arterial blood 40mmHg
PCO2 in expired air 28mmHg
T.V 500ml
=500X
40
2840 −
63. Measurement of Anatomic Dead Space.
[ Fowler’s Method[
The Fowler’s method is based of the
principle that the last bit of air you breath
in, you breath out first & it represents gas
in the anatomic dead space (conducting
airways(.
The remaining expired gas represents a
mixture of gas in the alveoli and anatomic
dead space.
66. Procedure
•maximal expiration to RV
•maximal inspiration to TLC of 100% O2
•maximal expiration to RV performed slowly
•measure the [N2[ during expiration.
Phase I
first bit of gas expired from TLC, 0% N2:pure anatomic dead space
gas
Phase II
transition phase, mixture of 100% O2 in anatomic DS & alveolar
gas
Phase III “alveolar plateau”, gas from alveoli(40 %N2(
VDS measured as the volume expired between beginning of
expiration & mid point determined geometrically
67. Functions of the dead spaceFunctions of the dead space:-:-
Conduction of air to and from the alveoliConduction of air to and from the alveoli..
Conditioning of inspired airConditioning of inspired air..
Filtration of inspired airFiltration of inspired air..
Initiation of sneezing and cough reflexesInitiation of sneezing and cough reflexes..
Secretion of immunoglobulin (antibodiesSecretion of immunoglobulin (antibodies(.(.
Perception of smell sensationPerception of smell sensation..
Production of sound (phonationProduction of sound (phonation
69. Ventilation: Minute(MRV),
Alveolar(VA )& Dead Space(VDS(
MRV=VT X breathing frequency=
500ml X12= 6.0 L/min.
VA =VA X breathing frequency=
(VT-VDS)XR.R=
(500-350(X12=
350ml X12= 4.2 L/min
70. Dyspneic indexDyspneic index
It is the ratio between BR and MVV and it isIt is the ratio between BR and MVV and it is
usually about 90%. If it is decreased below 60%usually about 90%. If it is decreased below 60%
dyspnea (difficulty in breathing) occurs ondyspnea (difficulty in breathing) occurs on
slightest effect and the person is consideredslightest effect and the person is considered
physically unfitphysically unfit..
Editor's Notes
After several minutes of breathing, the helium concentrations in the spirometer and lung become the same. From the law of conservation of matter, we know that the total amount of helium beforehand after is the same. Therefore we can set the fractional concentration times the volume before equal to the fractional concentration times the volume, because of the conservation law of matter.
We solve for the volume after (the volume of the lung and spirometer), subtract out the volume of the spirometer, and we get the volume of the lung.
Helium poorly soluble in water and thus diffuses very poorly across the alveolar wall. Subjects breath a gas that cannot escape from the lungs
