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Pulmonary Function Tests Spirometer A device that measures the volume of gas entering or leaving the mouthA device that measures the volume of gas entering.

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Presentation on theme: "Pulmonary Function Tests Spirometer A device that measures the volume of gas entering or leaving the mouthA device that measures the volume of gas entering."— Presentation transcript:

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2 Pulmonary Function Tests

3 Spirometer A device that measures the volume of gas entering or leaving the mouthA device that measures the volume of gas entering or leaving the mouth A spirometer measures changes in lung volumeA spirometer measures changes in lung volume A spirometer measures subdivisions of vital capacityA spirometer measures subdivisions of vital capacity A spirometer does NOT measure RVA spirometer does NOT measure RV

4 Vt Tidal volume VC Vital Capacity ERV/IRV Expiratory/Inspiratory reserve volume 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

5 RESPIRATORY MANOEUVRE Maximal breath in Maximal breath out

6 Tidal Volume Vt Total Lung Capacity

7 Vital Capacity VC TLC Vt

8 Residual Volume RV VC TLC Vt Residual Volume

9 Functional Residual Capacity RV Vt TLC FRC IC

10 TLC=VC + RV RV VC TLC Vt Residual Volume

11 Subdivisions of Lung Volume RV ERV IRV Vt VC TLC FRC IC TLC

12 Tidal volume Dead space ? Total lung capacity Vital capacity Tidal volume Inspiratory reserve volume Expiratory reserve volume LUNG VOLUMES ? Residual Volume

13 Capacities Total Lung CapacityTotal Lung Capacity –TLC = IC + FRC –TLC = RV + ERV + VT + IRV Functional Residual Capacity –FRC = RV + IRV Vital Capacity –VC = ERV + VT + IRV –VC= ERV + IC

14 FEV 1 & FVC Forced expiratory volume in 1 second – young trained athletes: 4.0 L Forced vital capacity – young trained athletes: 5.0 L FEV 1 /FVC = 80% FEV 1 FVC

15 By calculation: RV = TLC - VC by spirometry by body plethysmography or helium dilution TLC FRC = TLC - IC

16 VC FRC RV TLC VtVtVtVt Normal RV ERV IC RV VC TLC

17 RV VC RV VC RV VC NormalObstructiveRestrictive Vital capacity is reduced in both obstructive and restrictive diseases

18 By definition means a reduced total lung capacity Reduced vital capacity can suggest restriction Restrictive lung disease V t VC FRC RV TLC

19 Why measure residual volume? Look at two people with identical vital capacity VC FRC RV TLC VtVt VtVt VC FRC RV TLC

20 Be careful before citing restrictive deficits in people with obstructive lung disease VC FRC RV TLC VtVt VtVt VC FRC RV TLC Emphysema Normal

21 in respiratory patients FLOW-VOLUME CURVE FVC + FEV 1 FEV 1 /FVC FEV 1 + FVC cst FEV 1 /FVC Obstructive disease – resistance to airflow – e.g., COPD, asthma FVC + FEV 1 FEV 1 /FVC= cst Restrictive disease – expansion of the lung – e.g., interstitial fibrosis

22 Indication for lung volume test : Low FVC :Low FVC : -? Restrictive -? Restrictive -? Obstructive with hyperinflation and air trapping -? Obstructive with hyperinflation and air trapping -? Mixed pattern -? Mixed pattern -? Equivocal spirometry findings (FEV1&FVC at -? Equivocal spirometry findings (FEV1&FVC at lower limit of normal) lower limit of normal)

23 Measuring TLC To measure TLC or FRC, which include RV, spirometry is insufficientTo measure TLC or FRC, which include RV, spirometry is insufficient Techniques:Techniques: –Gas dilution –Plethysmography (body box)

24 Gas dilution tests: Lung volume can be measured when a person breathes nitrogen or helium gas through a tube for a specified period of time. Lung volume can be measured when a person breathes nitrogen or helium gas through a tube for a specified period of time. The final dilution of the gas used to calculate the volume of air in the thorax. The final dilution of the gas used to calculate the volume of air in the thorax. It is sensitive to errors It is sensitive to errors Leakage of gas Leakage of gas Failure to measure the volume of gas in lung bullae.because helium may not mix with all parts of the lung. Helium doesnt readily diffuse across the alveolar capillary membrane. Failure to measure the volume of gas in lung bullae.because helium may not mix with all parts of the lung. Helium doesnt readily diffuse across the alveolar capillary membrane.

25 C 1 =N/V box C 2 =N/(V box +FRC)

26 Gas Dilution C1V1C1V1 C2C2 C2C2 C2C2 V2=V1 + FRC C 1 V 1 = C 2 V 2

27 Body Plethysmography (BP)Body Plethysmography (BP) –Measurement of FRC by body plethysmograph is based on an application of Boyles law P 1 V 1 = P 2 V 2 or V 1 = P 2 V 2 V 1 = P 2 V 2 P 1 P 1 Lung Volumes / Gas Distribution 27

28 Boyles Law: for fixed mass of gas at constant temperature: P 1 V 1 = P 2 V 2Boyles Law: for fixed mass of gas at constant temperature: P 1 V 1 = P 2 V 2 Brief occlusion at airway opening to seal a fixed mass of gas in the lungs (V 1 ) - i.e the FRC to be measuredBrief occlusion at airway opening to seal a fixed mass of gas in the lungs (V 1 ) - i.e the FRC to be measured Pressure within lungs at end expiration (P 1 ) ~ atmospheric pressure.Pressure within lungs at end expiration (P 1 ) ~ atmospheric pressure. P 2 and V 2 represent the pressure and volume in the lungs after a respiratory effort against the occlusion.P 2 and V 2 represent the pressure and volume in the lungs after a respiratory effort against the occlusion.

29 Plethysmography (Body Box) Boyles Law : Boyles Law : P 1 V 1 = kP 1 V 1 = k Closed container whose volume can be adjusted so that the pressure in the container increases in proportion to the fractional decrease in container volume.Closed container whose volume can be adjusted so that the pressure in the container increases in proportion to the fractional decrease in container volume.

30 Plethysmograph Pm Pbox No flow at the mouth so that Pm = palv Pbox Vbox is the volume of the box (known) Vth is the volume of the thorax (unknown) Vth Vbox

31 P lung x V lung =P lung x V lung V lung = V lung +V P lung =P lung +P P box x V box = P box x V box V box =V box +V P box =P box +P P lung P box x V box V lung Plethysmography- measures total thoracic gas volume, but is more cumbersome. Uses Boyles law to calculate RV.

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33 Plethysmography: Situation at end expiration, prior to any respiratory efforts against an occlusion valve

34 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 P 1 - Δ P Changes in box pressure calibrated in terms of volume using a calibrated syringe

35 Body Plethysmography (BP)Body Plethysmography (BP) –Unlike gas dilution tests, BP includes both air in communication with open airways as well as air trapped within noncommunicating thoracic compartments –In patients with air trapping, plethysmography lung volumes are usually larger those measured with gas dilution methods –Volume measured is referred to as thoracic gas volume (TGV or V TG ) –ATS is recommending term be dropped and changed toplethysmographic lung volume (VL, pleth), and FRC by body plethysmography or TGV at FRC (FRCpleth ) Lung Volumes / Gas Distribution 35

36 Body plethysmography The patient sits inside a fully enclosed rigid box and breath through mouthpiece connected through a shutter to the internal volume of the box The patient sits inside a fully enclosed rigid box and breath through mouthpiece connected through a shutter to the internal volume of the box The subject makes respiratory efforts against the closed shutter (like panting), causing their chest volume to expand and decompressing the air in their lungs. The subject makes respiratory efforts against the closed shutter (like panting), causing their chest volume to expand and decompressing the air in their lungs. while breathing in and out again into a mouthpiece. The volume of all gas within the thorax can be measured by Changes in pressure inside the box and allow determination of the lung volume. while breathing in and out again into a mouthpiece. The volume of all gas within the thorax can be measured by Changes in pressure inside the box and allow determination of the lung volume.

37 Lung Volumes / Gas Distribution Body Plethysmography (BP)Body Plethysmography (BP) Procedure Patient is required to support cheeks with both hands and pant with an open glottis at a rate of Hz (30 – 60 breaths/min) BP shutter is suddenly closed at end-expiration prior to inspiration Panting is continued for several breaths against closed shutter (no air flow) 37

38 Lung Volumes / Gas Distribution Body Plethysmography (BP)Body Plethysmography (BP) Procedure The thoracic-pulmonary volume changes during panting, produce air volume changes within the BP cabinet Decreases in cabinet volume are an equal inverse response to thoracic volume increase (As thoracic volumes increase with panting inspiration, BP cabinet volume decreases and visa versa) 38

39 Lung Volumes / Gas Distribution Body Plethysmography (BP)Body Plethysmography (BP) Criteria of Acceptability Panting maneuver shows a closed loop without drift Tracing does not go off the screen Panting is 0.5 – 1 Hz Tangents should be within 10% At least 3 FRC pleth values should agree within 5% and the mean reported 39

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41 The history of clinical whole body plethysmography Verzar, Du Bois, Mead etc Verzar, Du Bois, Mead etc 1972, 2005 Matthys Historische Entwicklung der klinischen Ganzkörperplethysmographie1972, 2005 Matthys Historische Entwicklung der klinischen Ganzkörperplethysmographie Atemw.u.Lungenkrkh. 31/4, Atemw.u.Lungenkrkh. 31/4, l 1790 Menzies Dissertation on Respiration l 1881/2 Gad und Pflüger, Residualvolumen

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44 Lung Volumes / Gas Distribution Body PlethysmographBody Plethysmograph –Two types Constant-volume, variable-pressureConstant-volume, variable-pressure Pressure PlethysmographPressure Plethysmograph Flow or variable-volumeFlow or variable-volume Flow PlethysmographFlow Plethysmograph Both measure thoracic gas volumes and airway resistance and it derivativesBoth measure thoracic gas volumes and airway resistance and it derivatives Both use a pneumotachometer to measure flow and a mouth transducer with a shutter to measure alveolar pressureBoth use a pneumotachometer to measure flow and a mouth transducer with a shutter to measure alveolar pressure 44

45 Lung Volumes / Gas Distribution Body BoxBody Box –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 simulates inspiratory/expiratory volumessimulates inspiratory/expiratory volumes 45

46 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

47 Clinical Applications and Interpretations FRC FRC gas trapping due to intrathoracic airway obstructiongas trapping due to intrathoracic airway obstruction cystic lung diseasecystic lung disease FRC FRC abnormal alveolar developmentabnormal alveolar development reduced recoil of chest- wallreduced recoil of chest- wall decreased lung compliancedecreased lung compliance atelectasisatelectasis 47

48 What do the results mean: Algorhithim for PFT's Assessing severity of restrictive defects Without TLC measurement, base severity on the FVCWithout TLC measurement, base severity on the FVC –80% is considered normal –70-80% is considered mild –60-70% is considered moderate – 60% is considered severe When TLC is measuredWhen TLC is measured –Gold standard to define restrictive ventilatory defect –Only order Full PFTs if you suspect restrictive or interstitial lung disease (expensive!)

49 yes no yes no yes no What do the results mean: Algorhithim for PFT's Is the FEM adequate? Is the FEV1/FVC lower than predicted? Interpretation may be limited by falsely low FVC This is the definition of obstruction MildFEV1 >70% ModerateFEV % Mod severeFEV % SevereFEV1 <50% Very severeFEV1 <40% Is FVC reduced? Restriction may be present; Need TLC to definitively diagnose restriction Lung volumes: Severity determined by the reduction in TLC Mild65-80% Moderate50-65% Severe<50% Spirometry: Severity is determined by the reduction in VC Mild70-80% Moderate60-70% Severe<60% Normal pulmonary mechanics Restriction

50 What can PFTs tell you about the patient Normal or abnormalNormal or abnormal What diseases can you diagnose?What diseases can you diagnose? –Only asthma is defined by its PFTs Estimation of impairment, or severity of diseaseEstimation of impairment, or severity of disease Response to therapyResponse to therapy Occupational surveillanceOccupational surveillance

51 What PFTs cannot tell you Does the degree of abnormality explain the patients symptoms?Does the degree of abnormality explain the patients symptoms? Normality does not exclude the presence of diseaseNormality does not exclude the presence of disease Abnormal test may not reflect loss of lung functionAbnormal test may not reflect loss of lung function

52 52 By this technique we will be able to know Residual volume (RV) Residual volume (RV) Tidal volume (TV) Tidal volume (TV) Total Lung Capacity (TLC) Total Lung Capacity (TLC) Expiratory reserve volume (ERV) Expiratory reserve volume (ERV) Inspiratory Reserve Volume (IRV) Inspiratory Reserve Volume (IRV) Inspiratory capacity (IC) Inspiratory capacity (IC) Functional residual capacity (FRC) Functional residual capacity (FRC) Vital Capacity (VC) Vital Capacity (VC)

53 53 Residual volume (RV) It is the volume of air remaining in the lungs at the end of maximal expiration. Normally it accounts for about 25% of TLC. - RV increased in airway narrowing with air trapping (Asthma) or in loss of elastic recoil (emphysema). - RV decreased in Increased elastic recoil (pulmonary fibrosis)

54 54 Tidal volume (TV) It is the volume of air inspired or expired with each breath during normal breathing ( 7ml/kg) ml TV decreased in severe RLD

55 55 Total Lung Capacity (TLC) It is the total volume of air within the lung after maximum inspiration. (the maximum volume of air that the lung can contain). TLC = FVC + RV OR TLC = RV + ERV + TV + IRV TLC Increased in airway narrowing with air trapping (Asthma) or in loss of elastic recoil (emphysema). TLC Decreased in RLD, increased recoil (Pulmonary fibrosis), muscle weakness, Obesity… Total Lung Capacity (TLC) It is the total volume of air within the lung after maximum inspiration. (the maximum volume of air that the lung can contain). TLC = FVC + RV OR TLC = RV + ERV + TV + IRV TLC Increased in airway narrowing with air trapping (Asthma) or in loss of elastic recoil (emphysema). TLC Decreased in RLD, increased recoil (Pulmonary fibrosis), muscle weakness, Obesity…

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57 57 Expiratory reserve volume (ERV): It is the maximal volume of air exhaled from the resting end-expiratory level. ( volume expired by active expiration after passive expiration. ERV: From TV to RV ERV decreased in RLD

58 58 Inspiratory Reserve Volume (IRV): It is the maximal volume of air inspired with effort in excess of tidal volume IRV: From TV to TLC Inspiratory Reserve Volume (IRV): It is the maximal volume of air inspired with effort in excess of tidal volume IRV: From TV to TLC

59 59 Inspiratory capacity (IC): It is the maximal volume of air inspired from resting expiratory level IC= IRV+TV.

60 60 Functional Residual Capacity (FRC) It is the volume of air remaining in the lungs at the end of resting (normal) expiration. FRC = RV + ERV. -FRC Increased (>120% of predicted) in Emphysema (decreased elastic recoil), Asthma, bronchiolar obstruction (air trapping) -FRC decreased in intrinsic ILD or by upward movement of diaphragm (obesity,painful thoracic or abdominal wound)

61 61 Vital Capacity: volume of gas measured on complete expiration after complete inspiration without effort VC= TLC – RV or VC= IRV+TV+ERV decreased in OLD and RLD ( VC < 15 ml/kg (and VT < 5ml/kg) indicates likely need for mechanical ventilation

62 62 Lung volumes & capacities

63 63 Lung Volume in Obstructive Lung Disease

64 64 Obstructive Lung Disease Narrowing and closure of airways during expiration tends to lead to gas trapping within the lungs and hyperinflation of the chest. 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 Air trapping increase in RV Hyperinflation increases TLC Hyperinflation increases TLC RV tends to have a greater percentage increase than TLC RV tends to have a greater percentage increase than TLC RV/TLC ratio is therefore increased (nl 20-35%) RV/TLC ratio is therefore increased (nl 20-35%) Gas trapping may occur without hyperinflation (increase in RV & normal TLC) Gas trapping may occur without hyperinflation (increase in RV & normal TLC)

65 65 Gas trapping and airway closure at low lung volume cause the patient to breath at high lung volume so FRC (RV+ERV) increased 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 This will prevent airway closure and improve ventilation-perfusion relationship It will reduce mechanical advantage of respiratory muscles and increases the work of breathing It will reduce mechanical advantage of respiratory muscles and increases the work of breathing

66 66 Obstructive Lung Disease cont. RV increased TLC Nl/increased RV/TLC increases FRC increased VC decreased *Air trapping :Normal TLC with increase RV/TLC *Hyperinflation: Increase in both TLC and RV/TLCl/

67 67 Lung Volume in Restrictive Lung Disease

68 68 Reduction in TLC is a cardinal feature 1. In Intrinsic RLD (Interstitial Lung Disease) TLC will decrease TLC will decrease RV will decrease because of increased elastic recoil (stiffness) of the lung and loss of the alveoli. 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. Breathing take place at low FRC because of the increased effort needed to expand the lung. RV/TLC normal RV/TLC normal

69 69 2. In extrinsic RLD (chest wall disease :kyphoscoliosis or neuromuscular disease:ALS,MG) TLC is reduced either because of mechanical limitation to chest wall expantion or because of respiratory muscle weakness TLC is reduced either because of mechanical limitation to chest wall expantion or because of respiratory muscle weakness RV is Normal because Lung tissue and elastic recoil is normal RV is Normal because Lung tissue and elastic recoil is normal So RV/TLC ratio will be high So RV/TLC ratio will be high Breathing take place at low FRC because of the increased effort needed to expand the lung. Breathing take place at low FRC because of the increased effort needed to expand the lung.

70 70 Restrictive Lung Disease: 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

71 71 3. In combined obstructive and restrictive disease (e,g.sarcoidosis,COPD+IPF) Obstructive pattern on spirometry and Reduced lung volume 4. 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

72 72 RLD Extrinsic RLD Interinsic Obstructive Lung dis. FEV1 FVC FEV1/FVC RV TLC RV/TLC VC FRC

73 Interpretation: no significant differences of the measured data from the normal reference values 73

74 Interpretation: Cough with light obstructive ventilatory defect and relative overinflation 74

75 Interpretation: severe effort dependant intrathoracic airway obstruction with overinflation and trapped air 75

76 Interpretation: Severe intrathoracic airway obstruction, slightly reversible overinflation after ß2-agonist inhalation 76

77 Interpretation: Mixed restrictive and obstrucive ventilatory defect with relative overinflation 77

78 Interpretation: Carbacholtest positive, overinflation with good reversibility after ß2-agonist inhalation 78

79 The infant plethysmograph 79

80 Infant plethysmography 80

81 Plethysmography: Closed system: changes in thoracic volume are inversely proportional to changes in box volume. 81

82 82


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