PFT's

1. Pulmonary Function Testing
Craig S. Glazer, MD, MSPH
Pulmonary and Critical Care

2. What Are PFTs?
• Series of maneuvers designed to
measure lung size and function
• Elements of the test:
– Spirometry – dynamic flows and volumes
– Static lung volumes
– Gas transfer

3. Uses of PFTs
• Diagnosis
– Patterns of abnormalities
• Obstruction – COPD, asthma, bronchiectasis,
bronchiolitis
• Restriction – ILD, pleural disease, neuromuscular
disease, thoracic cage abnormalities
– Identify subtle physiologic abnormalities
• Isolated low DLCO – pulmonary hypertension,
emphysema, early ILD
• Prognosis
– Measure of disease severity – COPD
– Assess risk – neuromuscular disease
• Assess treatment response

4. What does the test measure?
• Flow and volume during maximal inspiration
and forced expiration - spirometry
• Total lung volumes
• Surface area of gas exchange
• Respiratory muscle function
• Cardiopulmonary function during exercise

5. Definition of volumes
time
volume

6. Definition of volumes
time
volume
Tidal volume
Vital capacity (VC)

7. Definition of volumes
time
volume Total lung capacity
(TLC)
Reserve volume
(RV)

8. Pulmonary Function Testing:
Spirometry
• Simplest measurement:
– Measure how fast/how long you can blow
• Maneuver:
– Deep breath (to TLC)
– Forced exhalation (to RV)
– Measure volume and time
– Calculate flow
TLC
RV

9. Pulmonary Function Testing:
Spirometry
TLC
RV

10. A given patient
can never get out
of the envelope of
the flow-volume
loop
•WHY?
Dynamic airway
collapse
Pulmonary Function Testing:
Spirometry
TLC RV

11. Dynamic ventilatory mechanics:
dynamic airway compression
Alveolus
Palv= 0
outside
PB= 0
End-expiration:
(No air flow)
Negative pleural pressure
(- 5 cmH2O)

12. Dynamic ventilatory mechanics:
dynamic airway compression
Alveolus
Palv= - 3 cmH2O
Pleural pressure more negative
(- 8 cmH2O)
Inspiration:
outside
PB= 0

13. Dynamic ventilatory mechanics:
dynamic airway compression
Alveolus
Palv= - 3 cmH2O
Inspiration:
Air flow down pressure gradient
outside
PB= 0
Pleural pressure more negative
(- 8 cmH2O)

14. Dynamic ventilatory mechanics:
dynamic airway compression
Alveolus
Palv= +30 cmH2O
Forced expiration:
outside
PB= 0
Positive pleural pressure
(+ 25 cmH2O)

15. Dynamic ventilatory mechanics:
dynamic airway compression
Alveolus
Palv= +30 cmH2O
Forced expiration:
Air flow down pressure gradient
outside
PB= 0
Positive pleural pressure
(+ 25 cmH2O)

16. Dynamic ventilatory mechanics:
dynamic airway compression
Alveolus
Palv= +30 cmH2O
Forced expiration:
30 29 28 27 26 ...
outside
PB= 0
Positive pleural pressure
(+ 25 cmH2O)

17. Dynamic ventilatory mechanics:
dynamic airway compression
Forced expiration:
30 29 28 27 26 … 25
outside
PB= 0
Positive pleural pressure
(+ 25 cmH2O)
Alveolus
Palv= +30 cmH2O

18. Dynamic ventilatory mechanics:
dynamic airway compression
Forced expiration:
Equal pressure point
Closing volume

19. Dynamic ventilatory mechanics:
dynamic airway compression
• Distal movement of equal pressure
point exaggerated with:
– Increased airway resistance
• Asthma, etc.
– Reduced lung elastic recoil
• Emphysema
• Aging

20. Pulmonary Function Testing
Spirometry

21. Spirometry Interpretation: Step 1
Is the test of adequate quality?
1. Reproducibilty Criteria
2. Acceptability Criteria

22. Spirometry Interpretation:
Acceptability Criteria
• Flow Volume Loop
– Good Start
– No artifacts
• Volume Time Curve
– 6 seconds exhalation
• Or plateau
TLC RV

23. Spirometry Interpretation:
Acceptability Criteria

24. Algorithm for Spirometry
Interpretation
1. Assess test quality
2. Is there obstruction?
1. Is there a bronchodilator response?
3. Is there evidence for restriction?

25. Algorithm for Spirometry Interpretation
FEV1/FVC ratio < lower limits of normal (LLN)?
Obstruction
Yes
Bronchodilator response?
Obstruction
No response to BD
No
Obstruction
With significant response to BD
Yes
Adapted from www.clevelandclinicmeded.com/diseasemanagement/pulmonary/pft/pft.htm
Grade severity by the FEV1

26. What is the Lower Limit of Normal?
5%
1.645 SD

27. Algorithm for Spirometry Interpretation
FEV1/FVC ratio < lower limits of normal (LLN)?
Obstruction
Yes
Bronchodilator response?
Obstruction
No response to BD
No
Obstruction
With significant response to BD
Yes
Adapted from www.clevelandclinicmeded.com/diseasemanagement/pulmonary/pft/pft.htm
Grade severity by the FEV1
No

28. Algorithm for Spirometry Interpretation
FEV1/FVC ratio < lower limits of normal (LLN)?
Normal
No
Suggests Restriction
Ye
s
Adapted from www.clevelandclinicmeded.com/diseasemanagement/pulmonary/pft/pft.htm
Is FVC < LLN?
No

29. Algorithm for Spirometry Interpretation
FEV1/FVC ratio < lower limits of normal (LLN)?
Possible Mixed
Process
Yes
Obstruction
Yes
Bronchodilator response?
Obstruction
No response to BD
No
Obstruction
With significant response to BD
Yes
Is FVC < LLN?
Isolated Obstruction
No

30. Severity of impairment as determined
by spirometry:
Normal > LLN
Mild 70-80% predicted
Moderate 60-69%
Moderate-Severe 50-59%
Severe 34-49%
Very Severe < 34%

31. Case #1
• Obstructive or Restrictive
Process?
Obstructive
• What is the severity?
– moderate
• 45 y/o man complaining of
cough and dyspnea for
months. Smoked 10 pack-
yrs

32. Case #1 Spirometry
• Bronchodilator response:
– Spirometry repeated after inhaled beta-agonists
– “Significant” with a 12% and a 200ml
improvement in FEV-1 or FVC
BD response = obstructive defect but doesn’t equal
asthma
No response does not mean adequate Rx

33. Case #1 Spirometry with BD
challenge
Pre-BD
%
Pred
Post-
BD
%
Pred
%
Chang
e
FEV1 1.33 60% 1.89 80% 42%
FVC 2.61 95% 2.97 108% 14%
FEV1
/FVC
50% 64%

34. Case #2
• 64 y/o man referred for
shortness of breath on
exertion
Suggests restrictive process
- good start
- smooth contour
- effort/reproducibility

35. Spirometry interpretation
• Obstruction:
– Diagnosis: FEV1/FVC < LLN
– Severity: degree of reduction in FEV1
• Restriction:
– Defined as TLC <80%
– “can be inferred” if
• FEV1/FVC normal or increased and
• FVC < LLN
If FEV1/FVC is reduced,
can’t diagnose restriction
based on FVC

37. Static lung volumes
TLC
VC
RV
TV
TLC
VC
RV
TV
TLC VC
RV
TV
Normal ObstructiveRestrictive

38. How to measure static lung
volumes
• Gas dilution techniques:
Introduce known
amount of a gas
TLC
VC
RV

39. Static lung volumes
• Gas dilution techniques:
Give it time to
diffuse throughout
the lung TLC
VC
RV

40. Static lung volumes
• Gas dilution techniques:
Measure concentration
of the gas in the
exhaled sample
TLC
VC
RV

41. Static lung volumes
• Gas dilution techniques:
– Easy to do
– Extra equipment cheap
– Only measures volume of
areas in free communication
with the mouth
TLC
VC
RVbulla

42. Static lung volumes
• Body plethysmography
Patient makes panting
movements against a
closed mouth shutter

43. Static lung volumes
• Body plethysmography
Measure pressure at
the mouth and in the box
Use Boyle’s law to
calculate the
intra-thoracic volume

44. Case #2
• 64 y/o man referred for
shortness of breath on
exertion
Restrictive process

45. CO
RBC
Capillary
CO CO + Hb
Hb.CO
Alveolus
Measuring gas transfer

46. CO
RBC
Capillary
CO CO + Hb
Hb.CO
Alveolus
Amount of CO taken
up is proportional to
surface area available
for gas exchange

47. Gas transfer
alveolus
capillary
CO
Introduce known
(and small) amount of
carbon monoxide
• Concept:
– measuring the area
available for gas
exchange

48. Gas transfer
alveolus
capillary
CO
Introduce known
(and small) amount of
carbon monoxide
Most will get into
blood and bind Hb

49. Gas transfer
Introduce known
(and small) amount of
carbon monoxide
Most will get into
Blood and bind Hb
Measure amount of
exhaled CO
alveolus
CO
capillary

50. Gas transfer
• Reduced DLCO • Increased DLCO

51. Gas transfer
• Reduced DLCO
– Fewer alveoli
•
•
– Fewer working alveoli
•
•
– Not enough blood
•
•
• Increased DLCO

52. Gas transfer
• Reduced DLCO
– Fewer alveoli
• Lobectomy
• Pleural effusion
– Fewer working alveoli
• Emphysema
• IPF
– Not enough blood
• Anemia
• Vasculitis
• Pulmonary Hypertension
• Increased DLCO

53. Gas transfer
• Reduced DLCO
– Fewer alveoli
• Lobectomy
• Pleural effusion
– Fewer working alveoli
• Emphysema
• IPF
– Not enough blood
• Anemia
• Vasculitis
• Pulmonary
Hypertension
• Increased DLCO
– Too much blood
– Faster transit of blood

54. Gas transfer
• Reduced DLCO
– Fewer alveoli
• Lobectomy
• Pleural effusion
– Fewer working alveoli
• Emphysema
• IPF
– Not enough blood
• Anemia
• Vasculitis
• Pulmonary
Hypertension
• Increased DLCO
– Too much blood
• Polycythemia
• Alveolar hemorrhage
– Faster transit of blood
• High cardiac output
• L -> R shunt

55. Case #3
• 62 y/o woman referred for
shortness of breath
Obstructive Defect
- very severe
????
- good start
- smooth contour
- effort/reproducibility

56. Case #3
• 62 y/o woman referred for
shortness of breath
Severe obstruction
Hyperexpansion and air-trapping
Moderately reduced DLCO
- good start
- smooth contour
- effort/reproducibility

57. Case #4
• 53 y/o woman with chest
tightness
• FVC 5.08 103%pred
FEV-1 2.66 74%pred
FEV-1/FVC 52% 72%
Uninterpretable study
0 1 2 3 4 5 6 7
time

58. Case #5:
• 32 y/o LVN with poorly-controlled
asthma on chronic steroids.
• Admitted to Zale-Lipshy University
Hospital with a diagnosis of status
asthmaticus.
• Physical exam: Retractions, audible
wheezing, and respiratory distress.

61. “Asthma attack” No attack

62. Vocal Cord Dysfunction:
• Mimicker of asthma
• Predominantly seen in women
• Conversion disorder
– History of physical or sexual abuse
– Pre-existing psychiatric illness
• Diagnosis:
– Flow-volume loops
– Direct laryngoscopy
• Treatment:
– Heli-Ox
– Speech therapy and psychotherapy
– ?Self-hypnosis and bio-feedback self-regulation
training

63. Vocal Cord Paralysis
• Most common cause of
extra-thoracic airflow
obstruction
• Due to trauma or a
laryngeal or intrathoracic
tumor
• Speech might be
preserved
• Acute treatment with Heli-
Ox or emergency
tracheostomy

64. Diseases of the larynx and trachea:
The Flow-Volume loop
St. John RC. Journal of General Internal Medicine 1993; 8:564-572
and Cherniack RM. Pulmonary Function Testing 1992, 209-230.

65. Case #6
• 38 y/o man with a
“wheeze”
FVC 3.66 103%pred
FEV-1 2.30 83%pred
FEV-1/FVC 63% 78%
Fixed large airway obstruction

66. Tracheal lesions:
Post-intubation stenosis