LUNG FUNCTION TESTS FOR ANAESTHETICS

1. Lung function
Tests
Dr. PARTHA PRATIM DEKA

2. Pulmonary function tests
(PFTs)
• Pulmonary function testing is a valuable
tool for evaluating the respiratory system
• comparing the measured values for
pulmonary function tests obtained on a
patient at any particular point with normal
values derived from population studies.
• The percentage of predicted normal is
used to grade the severity of the
abnormality.

3. Pulmonary Function
Tests
•Evaluates 1 or more major
aspects of the respiratory
system

4. PFTs
•Four lung components include :
The airways (large and small),
Lung parenchyma (alveoli,
interstitium),
Pulmonary vasculature, and
The bellows-pump mechanism

5. PFTs• PFTs can include:
simple screening spirometry, Flow Volume Loop
Formal lung volume measurement,
Bronchoprovocation testing
Diffusing capacity for carbon monoxide, and
Arterial blood gases. Measurement of maximal
respiratory pressures
• These studies may collectively be referred to as a
complete pulmonary function survey.

6. Spirometry
•Measurement of the pattern of air
movement into and out of the lungs
during controlled ventilatory
maneuvers.
•Often done as a maximal expiratory
maneuver

7. Importance
• Patients and physicians have inaccurate
perceptions of severity of airflow
obstruction and/or severity of lung disease
by physical exam
• Provides objective evidence in identifying
patterns of disease

8. Spirometry
 Simple, office-based
 Measures flow, volumes
 Volume vs. Time
 Can determine:
- Forced expiratory volume in one second (FEV1)
- Forced vital capacity (FVC)
- FEV1/FVC
- Forced expiratory flow 25%-75% (FEF25-75)

9. Spirometry
The most readily available most useful
pulmonary function test
It takes ten to 15 minutes
carries no risk

10. Spirometry
• Spirometry is the most commonly used lung function
screening study.
• should be the clinician's first option
• other studies being reserved for specific indications
• easily performed
• in the ambulatory setting, physician's office, emergency
department, or inpatient setting.

11. Patient care/preparations
• Two choices are available with respect to bronchodilator and
medication use prior to testing. Patients may withhold oral
and inhaled bronchodilators to establish baseline lung
function and evaluate maximum bronchodilator response, or
they may continue taking medication as prescribed. If
medications are withheld, a risk of exacerbation of bronchial
spasm exists.

12. Spirometry
• The slow vital capacity (SVC) can also be measured with
spirometers
collect data for at least 30 seconds
when airways obstruction is present, the forced vital capacity
(FVC) is reduced and
slow vital capacity (SVC) may be normal

13. Spirometry
• When the slow or forced vital capacity is within the normal
range: No significant restrictive
disorder .
No need to measure static lung volumes (residual volume and
total lung capacity).

14. Indications — Diagnosis
 Evaluation of signs and symptoms
- SOB, exertional dyspnea, chronic cough
 Screening at-risk populations
 Monitoring pulmonary drug toxicity
 Abnormal study
- CXR, EKG, ABG, hemoglobin
 Preoperative assessment

15. Indications — Diagnosis
 Evaluation of signs and symptoms
- SOB, exertional dyspnea, chronic cough
 Screening at-risk populations
 Monitoring pulmonary drug toxicity
 Abnormal study
- CXR, EKG, ABG, hemoglobin
 Preoperative assessment
Smokers > 45yo
(former & current)

16. Indications — Diagnosis
 Evaluation of signs and symptoms
- SOB, exertional dyspnea, chronic cough
 Screening at-risk populations
 Evaluation of occupational symptoms
 Monitoring pulmonary drug toxicity
 Abnormal study
- CXR, EKG, ABG, hemoglobin
 Preoperative assessment

17. Indications — Prognostic
■ Assess severity
■ Follow response to therapy
■ Determine further treatment goals
■ Referral for surgery
■ Disability

18. Contraindications for
spirometry
• Relative contraindications for spirometry include hemoptysis
of unknown origin, pneumothorax, unstable angina pectoris,
recent myocardial infarction, thoracic aneurysms, abdominal
aneurysms, cerebral aneurysms, recent eye surgery (increased
intraocular pressure during forced expiration), recent
abdominal or thoracic surgical procedures, and patients with a
history of syncope associated with forced exhalation

19. Spirometry
• Spirometry requires a voluntary maneuver in which a seated
patient inhales maximally from tidal respiration to total lung
capacity and then rapidly exhales to the fullest extent until no
further volume is exhaled at residual volume

20. Spirometry
• The maneuver may be performed in a forceful manner to
generate a forced vital capacity (FVC) or in a more relaxed
manner to generate a slow vital capacity (SVC).

21. • In normal persons, the inspiratory vital capacity, the
expiratory SVC, and expiratory FVC are essentially equal.
However, in patients with obstructive airways disease, the
expiratory SVC is generally higher than the FVC.

22. Interpretation of spirometry
results(1)
•should begin with an
assessment of test quality.
to inspect the graphic data
(the volume-time curve and
the flow-volume loop)

23. Interpretation of
spirometry results(2)
•to ascertain whether the study
meets certain well-defined
acceptability and
reproducibility standards

24. acceptable spirometry
(ATS)
• 1) minimal hesitation at the start of the forced expiration
(extrapolated volume (EV) <5% of the FVC or 0.15 L,
whichever is larger
• Time to PEF is <120 ms (optional until further information is
available)
(2) no cough in the first second of forced exhalation,
• 3) meets 1 of 3 criteria that define a valid end-of-test

25. Valid end-of-test
• (a) smooth curvilinear rise of the volume-time tracing to a
plateau of at least 1-second duration;
(b) if a test fails to exhibit an expiratory
plateau, a forced expiratory time (FET) of 15 seconds; or
(c) when the patient
cannot or should not continue forced exhalation for valid
medical reasons.

26. • If both of these criteria are not met, continue testing until:
Both of the criteria are met with analysis of additional
acceptable spirograms or
• A total of eight tests have been performed or
• Save a minimum of three best maneuvers

27. Acceptability Criteria
• Good start of test
• No coughing
• No variable flow
• No early termination
• Reproducibility

28. The volume-time tracing
• The volume-time tracing is most useful in assessing whether
the end-of-test criteria have been met

29. Spirometry

30. Flow-volume loop
•the flow-volume loop is
most valuable in evaluating
the start-of-test criteria.

31. Flow-Volume Loop
•
Ruppel GL. Manual of Pulmonary Function Testing, 8th
ed.,
Mosby 2003

32. Repeatability Criteria
• After three acceptable spirograms have been obtained, apply
the following tests. Are the two largest FVCs within
0.2 L of each other?
• Are the two largest FEV1s within 0.2 L of each other?
• If both of these criteria are met, the test session may be
concluded

33. Lung Volumes

34. Lung Volumes
• 4 Volumes
• 4 Capacities
• Sum of 2 or more
lung volumes
IRV
TV
ERV
RV
IC
FRC
VC
TLC
RV

35. Spirometry

36. Lung Factors Affecting
Spirometry
• Mechanical properties
• Resistive elements

37. Mechanical Properties
• Compliance
• Describes the stiffness of the lungs
• Change in volume over the change in pressure
• Elastic recoil
• The tendency of the lung to return to it’s resting state
• A lung that is fully stretched has more elastic recoil and thus
larger maximal flows

38. Resistive Properties
• Determined by airway caliber
• Affected by
• Lung volume
• Bronchial smooth muscles
• Airway collapsibility

39. Factors That Affect Lung Volumes
• Age
• Sex
• Height
• Weight
• Race
• Disease

40. Technique
• Have patient seated comfortably
• Closed-circuit technique
• Place nose clip on
• Have patient breathe on mouthpiece
• Have patient take a deep breath as fast as possible
• Blow out as hard as they can until you tell them to stop

41. Terminology
• Forced vital capacity (FVC):
• Total volume of air that can be
exhaled forcefully from TLC
• The majority of FVC can be
exhaled in <3 seconds in
normal people, but often is
much more prolonged in
obstructive diseases
• Measured in liters (L)

42. FVC
• Interpretation of % predicted:
• 80-120% Normal
• 70-79% Mild reduction
• 50%-69%Moderate reduction
• <50% Severe reduction
FV

43. Terminology
• Forced expiratory volume
in 1 second: (FEV1)
• Volume of air forcefully
expired from full inflation
(TLC) in the first second
• Measured in liters (L)
• Normal people can exhale
more than 75-80% of their
FVC in the first second; thus
the FEV1/FVC can be utilized
to characterize lung disease

44. FEV1
• Interpretation of % predicted:
• >75% Normal
• 60%-75%Mild obstruction
• 50-59% Moderate obstruction
• <49% Severe obstruction
FE F

45. Terminology
• Forced expiratory flow 25-
75% (FEF25-75)
• Mean forced expiratory flow
during middle half of FVC
• Measured in L/sec
• May reflect effort independent
expiration and the status of the
small airways
• Highly variable
• Depends heavily on FVC

46. FEF25-75
• Interpretation of % predicted:
• >60% Normal
• 40-60% Mild obstruction
• 20-40% Moderate obstruction
• <10% Severe obstruction

47. Flow-Volume Loop
• Illustrates maximum
expiratory and
inspiratory flow-volume
curves
• Useful to help
characterize disease
states (e.g. obstructive
vs. restrictive)
Ruppel GL. Manual of Pulmonary Function Testing, 8th
ed.,
Mosby 2003

48. Categories of Disease
• Obstructive
• Restrictive
• Mixed

49. Obstructive Disorders
• Characterized by a
limitation of expiratory
airflow
• Examples: asthma, COPD
• Decreased: FEV1, FEF25-75,
FEV1/FVC ratio (<0.8)
• Increased or Normal:
TLC

50. Spirometry in Obstructive
Disease
• Slow rise in upstroke
• May not reach plateau

51. Restrictive Lung Disease
• Characterized by diminished lung
volume due to:
• change in alteration in lung
parenchyma (interstitial lung
disease)
• disease of pleura, chest wall (e.g.
scoliosis), or neuromuscular
apparatus (e.g. muscular dystrophy)
• Decreased TLC, FVC
• Normal or increased: FEV1/FVC ratio

52. Restrictive Disease
• Rapid upstroke as in
normal spirometry
• Plateau volume is
low

53. Large Airway Obstruction
• Characterized by a
truncated inspiratory
or expiratory loop

54. Normal Spirometry

55. Obstructive Pattern
■ Decreased FEV1
■ Decreased FVC
■ Decreased FEV1/FVC
- <70% predicted
■ FEV1 used to follow severity in COPD

56. Obstructive Lung Disease —
Differential Diagnosis
 Asthma
 COPD
- chronic bronchitis
- emphysema
 Bronchiectasis
 Bronchiolitis
 Upper airway obstruction

57. Restrictive Pattern
 Decreased FEV1
 Decreased FVC
 FEV1/FVC normal or increased

58. Restrictive Lung Disease —
Differential Diagnosis
 Pleural
 Parenchymal
 Chest wall
 Neuromuscular

59. Spirometry Patterns

60. Bronchodilator Response
 Degree to which FEV1 improves with inhaled
bronchodilator
 Documents reversible airflow obstruction
 Significant response if:
- FEV1 increases by 12% and >200ml
 Request if obstructive pattern on spirometry

61. Flow Volume Loop
 “Spirogram”
 Measures forced inspiratory and expiratory flow rate
 Augments spirometry results
 Indications: evaluation of upper airway obstruction (stridor,
unexplained dyspnea)

62. Flow Volume Loop

63. Upper Airway Obstruction
 Variable intrathoracic obstruction
 Variable extrathoracic obstruction
 Fixed obstruction

64. Upper Airway Obstruction

65. Lung Volumes
 Measurement:
- helium
- nitrogen washout
- body plethsmography
 Indications:
- Diagnose restrictive component
- Differentiate chronic bronchitis from
emphysema

66. Pulmonary Function Testing
The Basics of Interpretation

67. Lung Volumes – Patterns
 Obstructive
- TLC > 120% predicted
- RV > 120% predicted
 Restrictive
- TLC < 80% predicted
- RV < 80% predicted

68. Diffusing Capacity
 Diffusing capacity of lungs for CO
 Measures ability of lungs to transport inhaled gas
from alveoli to pulmonary capillaries
 Depends on:
- alveolar—capillary membrane
- hemoglobin concentration
- cardiac output

69. Diffusing Capacity
 Decreased DLCO
(<80% predicted)
 Obstructive lung disease
 Parenchymal disease
 Pulmonary vascular disease
 Anemia
 Increased DLCO
(>120-140% predicted)
 Asthma (or normal)
 Pulmonary hemorrhage
 Polycythemia
 Left to right shunt

70. DLCO — Indications
 Differentiate asthma from emphysema
 Evaluation and severity of restrictive lung disease
 Early stages of pulmonary hypertension
 Expensive!

71. Bronchoprovocation
 Useful for diagnosis of asthma in the setting of normal
pulmonary function tests
 Common agents:
- Methacholine, Histamine, others
 Diagnostic if: ≥20% decrease in FEV1

72. Continued…
↓
SYMPTOMS
PFTs
OBSTRUCTION?
YES NO
TREAT
BRONCHOPROVOCATION
Obstruction?
TREAT
No Obstruction?
Other Diagnosis
↓
↓
↓ ↓
↓
↓ ↓

73. PFT Interpretation Strategy
 What is the clinical question?
 What is “normal”?
 Did the test meet American Thoracic Society (ATS) criteria?
 Don’t forget (or ignore) the flow volume loop!

74. Obstructive Pattern — Evaluation
 Spirometry
 FEV1, FVC: decreased
 FEV1/FVC: decreased (<70% predicted)
 FV Loop “scooped”
 Lung Volumes
 TLC, RV: increased
 Bronchodilator responsiveness

75. Restrictive Pattern –
Evaluation
 Spirometry
 FVC, FEV1: decreased
 FEV1/FVC: normal or increased
 FV Loop “witch’s hat”
 DLCO decreased
 Lung Volumes
 TLC, RV: decreased
 Muscle pressures may be important

76. PFT Patterns
 Emphysema
 FEV1/FVC <70%
 “Scooped” FV curve
 TLC increased
 Increased compliance
 DLCO decreased
 Chronic Bronchitis
 FEV1/FVC <70%
 “Scooped” FV curve
 TLC normal
 Normal compliance
 DLCO usually normal

77. PFT Patterns
 Asthma
 FEV1/FVC normal or decreased
 DLCO normal or increased
But PFTs may be normal  bronchoprovocation

78. Thank you