2. Pulmonary Function Tests

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

4. ERV/IRV Expiratory/Inspiratory reserve volume
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 Vt
TLC

8. Residual Volume VC Vt
TLC
Residual Volume RV

9. Functional Residual CapacityIC Vt
TLC
FRC RV

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

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

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

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

14. FEV1 & FVC Forced expiratory volume in 1 second Forced vital capacity
young trained athletes: 4.0 L
Forced vital capacity
young trained athletes: 5.0 L
FEV1/FVC = 80%
FEV1
FVC

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

16. TLC RV
ERV IC
TLC VC Vt VC
FRC RV RV
Normal

17. Vital capacity is reduced in both obstructive and restrictive diseasesVC VC VC RV RV RV
Obstructive
Normal
Restrictive

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

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

20. RV RV TLC TLC Vt Vt VC FRC VC FRC
Be careful before citing “restrictive deficits” in people with obstructive lung disease
TLC
TLC Vt Vt VC
FRC VC RV
FRC RV
Emphysema
Normal

21. FLOW-VOLUME CURVE in respiratory patients Obstructive disease
FEV1 + FVC cst
 FEV1/FVC
Obstructive disease
 resistance to airflow
e.g., COPD, asthma
FVC +  FEV1
 FEV1/FVC= cst
Restrictive disease
 expansion of the lung
e.g., interstitial fibrosis
FVC +   FEV1
  FEV1/FVC

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

23. Plethysmography (body box)
Measuring TLC
To measure TLC or FRC, which include RV, spirometry is insufficient
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.
The final dilution of the gas used to calculate the volume of air in the thorax.
It is sensitive to errors
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 doesn’t readily diffuse across the alveolar capillary membrane .

25. C1=N/Vbox
C2=N/(Vbox+FRC)

26. Gas Dilution
C1V1 = C2V2
C1V1 C2
V2=V1 + FRC

27. Lung Volumes / Gas Distribution
Body Plethysmography (BP)
Measurement of FRC by body plethysmograph is based on an application of Boyle’s law
P1V1 = P2V2 or
V1 = P2V2 P1

28. 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.

29. Plethysmography (Body Box)
Boyle’s Law :
P1V1= 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.

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

31. Plungx Vlung=P’lungx V’lung
Plethysmography- measures total thoracic gas volume, but is more cumbersome. Uses Boyle’s law to calculate RV.
Pbox x Vbox=
P’box x V’box
V’box =Vbox+∆V
P’box =Pbox+∆P
Plung
Vlung
Plungx Vlung=P’lungx V’lung
V’lung = Vlung +∆V
P’lung =Plung+∆P
Pbox x Vbox

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
Changes in box pressure calibrated in terms of volume using a calibrated syringe
P1 -ΔP

35. Lung Volumes / Gas Distribution
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 VTG)
ATS is recommending term be dropped and changed to “plethysmographic lung volume” (VL, pleth), and “FRC by body plethysmography” or TGV at FRC (FRCpleth)

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 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.
transparent box that resembles a telephone booth

37. Lung Volumes / Gas Distribution
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)

38. Lung Volumes / Gas Distribution
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)

39. Lung Volumes / Gas Distribution
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 FRCpleth values should agree within 5% and the mean reported

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

44. Lung Volumes / Gas Distribution
Body Plethysmograph
Two types
Constant-volume, variable-pressure
“Pressure Plethysmograph”
Flow or variable-volume
“Flow Plethysmograph”
Both 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 pressure

45. Lung Volumes / Gas Distribution
Body 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 volumes

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
gas trapping due to intrathoracic airway obstruction
cystic lung disease
 FRC
abnormal alveolar development
reduced recoil of chest- wall
decreased lung compliance
atelectasis

48. What do the results mean: Algorhithim for PFT's Assessing severity of restrictive defects
Without 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 measured
Gold standard to define restrictive ventilatory defect
Only order “Full PFTs” if you suspect restrictive or interstitial lung disease (expensive!)

49. What do the results mean: Algorhithim for PFT's
Is the FEM adequate? y e s n o
Is the FEV1/FVC lower than predicted?
Interpretation may be limited by falsely low FVC y e s n o
This is the definition of obstruction
Mild FEV1 >70%
Moderate FEV %
Mod severe FEV %
Severe FEV1 <50%
Very severe FEV1 <40%
Is FVC reduced? y e s n o
Restriction may be present; Need TLC to definitively diagnose restriction
Normal pulmonary mechanics
Restriction
Spirometry:
Lung volumes:
Severity is determined
Severity determined by
by the reduction in VC
the reduction in TLC
Mild
70-80%
Mild
65-80%
Moderate
60-70%
Moderate
50-65%
Severe
<60%
Severe
<50%

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

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

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

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. 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. 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…

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

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. 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. Lung volumes & capacities

63. Obstructive Lung Disease
Lung Volume in
Obstructive Lung Disease

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.
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)

65. 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

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. Restrictive Lung Disease
Lung Volume in
Restrictive Lung Disease

68. 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

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
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 .

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

71. 3. In combined obstructive and restrictive disease (e,g
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. FEV1 FVC FEV1/FVC RV TLC RV/TLC VC FRC 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

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

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

76. Interpretation: Severe intrathoracic airway obstruction, slightly reversible overinflation after ß2-agonist inhalation 20 5

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

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

79. The infant plethysmograph

80. Infant plethysmography

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