Lung volumes and capacities

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  • 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
  • Lung volumes and capacities

    1. 1. Lung volumes andLung volumes and capacitiescapacities BYBY Dr/HALA SALAHDr/HALA SALAH PhysiologyPhysiology ofof ProfProf..
    2. 2. 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
    3. 3. THE SPIROMETERTHE SPIROMETER • Old version – spirometer bell – kymograph pen • New version
    4. 4. LUNG VOLUMES
    5. 5. 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((
    6. 6. Tidal volumeTidal volume
    7. 7. 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.
    8. 8. 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..
    9. 9. 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..
    10. 10. Tidal volume Dead space Tidal volume Inspiratory reserve volume Expiratory reserve volume LUNG VOLUMESLUNG VOLUMES Residual Volume
    11. 11. LUNG CAPACITIES
    12. 12. PULMONARY CAPACITIESPULMONARY CAPACITIES A capacity is two volumes or more addedA capacity is two volumes or more added togethertogether..
    13. 13. 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..
    14. 14. 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
    15. 15. 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..
    16. 16. 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..
    17. 17. Tidal volume Dead space Tidal volume Inspiratory reserve volume Expiratory reserve volume LUNG VOLUMESLUNG VOLUMES Residual Volume FRC IC VC T LC
    18. 18. 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..
    19. 19. 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..
    20. 20. Lung volumes measured by spirometerLung volumes measured by spirometer  For the others parameters additional measurements needed • Values obtained by simple spirometry
    21. 21. Factors affecting lung volumes andFactors affecting lung volumes and capacitiescapacities
    22. 22. %%Predicted ValuePredicted Value Observed value/predicted value x100%Observed value/predicted value x100%
    23. 23. Determination of RV and FRCDetermination of RV and FRC They are measured indirectly usingThey are measured indirectly using helium dilution methodhelium dilution method
    24. 24. 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..
    25. 25. • 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
    26. 26. 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%%(.(.
    27. 27. 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
    28. 28. Minute Respiratory Volume Minute Ventilation= VT X breathing frequency =500ml X12 b/min =6000ml/min =6L/min
    29. 29. Maximal voluntary ventilationMaximal voluntary ventilation
    30. 30. 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.
    31. 31. 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.
    32. 32. 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..
    33. 33. THANK YOU
    34. 34. 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..
    35. 35. Vital Capacity Based on Age & Gender Male Female VC(ml) Age (Years)
    36. 36. 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(.
    37. 37. 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..
    38. 38. 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.
    39. 39. SpirometrySpirometry
    40. 40. 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..
    41. 41. Timed vital capacityTimed vital capacity
    42. 42. 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
    43. 43. 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..
    44. 44. 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↑↑
    45. 45. Restrictive lung diseasesRestrictive lung diseases
    46. 46. Lung Capacity and DiseaseLung Capacity and Disease Normal RV ERV TV IRV FRC VC Restrictive RV ERV TV IRV FRC VC Obstructive RV ERV TV IRV FRC VC 125 100 75 50 25 0 %NormalTLC
    47. 47. Alveolar dead spaceAlveolar dead space
    48. 48. 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..
    49. 49. 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
    50. 50. 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 −
    51. 51. Nitrogen-meter methodNitrogen-meter method Fowler’s Method )Anatomic DS(
    52. 52. 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.
    53. 53. Nitrogen-meter methodNitrogen-meter method
    54. 54. 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
    55. 55. 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
    56. 56. Alveolar Ventilation Alveolar ventilation the portion of breathing that reaches the alveoli &participates in gas exchange
    57. 57. 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
    58. 58. 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..

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