1. Pulmonary Function Testing
Sandra B. Weibel MD
Thomas Jefferson University

2. Objectives
To review the basic principles of performing lung function studies and the physiology
To understand the calibrations and to be able to assess that lung function studies are performed according to standards
To understand basic interpretation

3. Indications Differential diagnosis of dyspnea
Provides objective assessment of symptoms versus severity
Determine fitness for surgery
To guide therapy
To follow the course of a disease

5. Physiologic classification of disease
Obstructive Impairment- Airway limitation due to the resistive properties of the respiratory system
Restrictive Impairment- Loss of volume capacity of the lung due to loss of air space units or inability to expand the respiratory system

6. Obstructive Processes
L ocal obstruction
A sthma
C hronic bronchitis (COPD)
E mphysema

7. Restrictive Processes
P leural disease
A lveolar filling processes
I nterstial lung disease
N euromuscular diseases
T horacic cage abnormailites

8. Spirometry
Most widely performed study and is important in initial screening of patients
Easily and quickly performed in many settings

9. Types of spirometers
Types include flow (pneumotach) or volume (water seal, rolling and diaphragm)
Water seal device previoisly most commonly used in pulmonary function labs of the volume
Collect exhaled gas and act as a reservoir for inhaled gas
Composed of a mouthpiece, bell system and a pen on a rotating drum

12. Volume Displacement Spirometer

13. Flow Spirometry

14. Calibration of spirometer
Warmed up and temperature controlled Barometric pressure and temperature recorded
Volume calibration with 3L syringe (within 3%)
Flow spirometer tested at 3 flow rates between 2 and 12L

15. Quality Control

17. Prior to testing

18. Performing the maneuver
It is a forced expiratory maneuver and the patient must be sitting upright in a chair with lips around a mouthpiece
After a maximal inspiration, a forced and rapid expiration is made
Quality of the maneuver needs to be assessed noting that the patient started at zero, had a maximal initial efffort and lasted 6 seconds.

21. Measurements
FVC
FEV1
FEV1/FVC
Also FEF25-75 and TET

22. FVC Measurement

23. FEV1 Measurement

24. Flow volume

25. Interpretation First need to assess the quality of the maneuvers
Choice of reference values
Use of LLN
Compare to previous tests
Race adjustments

26. Interpretation Restrictive Lung Obstruction FVC AND FEV1 decreased
FEV1/FVC normal
FEV1 main distinguishing feature
Obstruction
FEV1 decreased
FVC Normal
FEV1/FVC are low

27. Pitfalls in Interpretation
Predicted need to fit your population
Non Caucasians have lower lung volumes and this may need to be addressed
Prior to interpretation the test needs to be assessed to see if it meets standards
Machines need to be calibrated daily to ensure accuracy

28. Effort

30. Poor effort

33. Interpretation The patient’s data is compared to predicted
Predicted values are obtained after studying populations of normal nonsmokers and then regression equations developed
Regressions are based on sex, height, and age.

34. Predicted Values

35. Decline in PFTS

36. References Many different ones used in past Knudson Crapo etc
Current recommendation is NHANES III
This studied over 7000 individuals
Included Caucasians, blacks and Mexican Americans

42. Interpretaion Normal is > 80% of predicted Mild impairment 65-79%
Moderate %
Severe < 50%

43. Interpretations

44. Flow Volume Loops
Inspiratory loops can also be obtained to evaluate for the presence of large airway obstruction
Theory changes in pressure outside and inside the thoracic cage will cause changes in airway diameter
These airway changes can cause a limitation to airflow if large enough

45. Extrathoracic Obstruction

46. Intrathoracic Obstruction

47. Fixed Obstruction

48. Large Airway Obstruction

50. Bronchodilator Response

51. Bronchodilator testing
No short acting agents for 4 hrs
No long acting beta agonists for 12 hrs
No theo for 12 hrs
No smoking for 1 hr
Beta agonist given recommended 4 puffs and wait minutes later

55. Performance of the Maneuver

56. Peak Flow Measurements
Convenient portable device for measuring peak expiratory flow in l/min
May be less reliable than spirometry but easy to use and inexpensive
Useful to follow the course of asthma and to possibly look and work exposure
Technique

57. Lung Volumes May be measured by multiple methods
Is important to understand what volumes the lung is composed of
The total volume of the lung is TLC
The subdivisions include ERV, IRV, TV,and RV
Capacities are composed of 2 or more volumes.

59. Helium Dilution Technique
Uses an inert gas, helium and by a closed circuit technique, allow it to come to equilibrium and FRC is measured
May underestimate lung volumes in bullous lung disease

62. Lung volume measurements
FRC is directly measured as well as SVC
Other volumes and capacities can be calculated
Lung volume measurements are important to confirm RLD
TLC and RV the usual volumes assessed

63. Nitrogen Washout
Determine FRC by multiple breath open circuit nitrogen washout
Involves having nitrogen in patients lung being washed out by inhaling 100% O2 for several minutes.
Widely used, easy to perform but may underestimate bullous lung disease

64. Nitrogen Washout
Performed by having the patient breath comfortably for several minutes and then turn in to 100% O2 at FRC.
Monitor N2 concentrations and test ends when falls below 1%
Easy to see leaks

65. Nitrogen Washout Concept is C1V1= C2V2
C1 = Nitrogen concentration at the start of the test
V1 = FRC volume
C2 =N2 concentration in exhaled volume
V2 = Total exhaled volume during O2 breathing period
Nitrogen is measured by photoelectric principle

66. Body Plethsymography Is a sealed box with a fixed volume
Uses Boyle’s Law that changes in pressure are brought about by changes in volume for the person seated in the box
P1V1= P2V2

68. Body Plethysmograph

69. Lung volume measurements
FRC is directly measured as well as SVC
Other volumes and capacities can be calculated
Lung volume measurements are important to confirm RLD
TLC and RV the usual volumes assessed

70. Interpretation RLD OLD TLC is reduced in all
Predicted values and interpret same as FVC and FEV1
OLD
TLC can be increased and is then called hyperinflation (120%)
RV can be increased in asthma and COPD indicating air trapping

72. Diffusing Capacity
Provides information about the transfer of gas between the alveoli and the pulmonary capillary bed
It is the only noninvasive test of gas exchange
Performed by a single breath technique and uses CO as the inert gas

74. Diffusing Capacity
Diffusion of a gas is dependent of the area, the concentrations, the thickness of the membrane and the diffusing properties of the gas
Diffusion is the rate at which a gas is transferred across the alveolar capillary membrane, the plasma, the RBC and ultimately combined with Hgb

75. Diffusing Capacity
CO is typically used because it is freely diffusable
It usually is not present in significant amounts in the blood except in some heavy smokers
Helium or methane is also used to measure volume
A single maximal inspiration is taken and held for 10 sec

77. Diffusing Capacity Normal result is >80%
Can be reduced in interstitial diseases such as sarcoid or asbestosis
Can be reduced also in emphysema or pulmonary vascular diseases
False low measurements in anemia or lung resection and elevated in alveolar hemm

78. Summary Spirometry- Most commonly performed and useful screening test.
Lung volumes- Can be measured several different ways. Are used to evaluate for restrictive disease and will also show air trapping
Diffusing Capacity - Transfer of gas across the alveolar membrane

80. Selecting Tests Who should get what test Who cannot get certain tests
Which method of lung volume testing
Inpatients

81. Case 1
A 25 year old female comes to your office complaining of chest tightness and shortness of breath with running.
Exam is normal
What tests would you order?

82. Spirometry Pre Post FVC 2.64 90% FEV1 1.83 79% FEV1/FVC 69 TET 5.0
FEFmax 4.85 L/S
Post %
% (18%)
FEV1/FVC 71
TET 5.5
FEFmax 5.02 L/S

83. Case 2
A 58 year old male presents to office complaining of dyspnea on exertion over the last 6 months. He has a dry cough but no other complaints. He has smoked 1ppd for 35 years and works in construction.

84. PFTS FVC 1.43 48% FEV1 1.30 57% FEV1/FVC 91 TLC 3.05 63% RV1.53 68%
Dsb %
Dsb(adj) %
VA %
D/VA %
Hsb 11.4

85. Causes of Hypoxemia Hypoventilation Elevated altitude Shunt
V/Q mismatch
Impairment of diffusion

86. Hypoxemia
Daltons Law In a gaseous mixture the partial pressure of each gas in the mixture is independent of the other gases and the total pressure of the mixture is equal to sum of all the gases and must equal barometric pressure
PB=PA=PN2+PH2O+ PO2 +PCO2

87. Alveolar Oxygen

88. Hypoxemia
Nitrogen concentration is fixed and minimal variation in water vapor pressure
PA (alveolar pressure) is mainly determined by PCO2 and PO2 and there is an inverse relationship
pAO2 = (PB- PH2O) x FiO2 - PaCO2/R
From this can calculate PA-a gradient
Normal 10-20

89. V/Q Mismatch

90. Hypoxemia
Calculate A-a gradient if normal than hypoventilation or altitude
If >20 then V/Q mismatch, shunt or diffusion
Shunt does not respond to O2