Pulmonary function tests

1. PRE-OPERATIVE PULMONARY
EVALUATION IN
CARDIOTHORACIC SURGERY

2. The living thorax is a dynamic theatre
of fluid and air movement played upon
by a myriad of interacting muscles.

3. WHAT IS ‘PULMONARY
FUNCTION TEST’?

4. PULMONARY FUNCTION
TESTS
Group of physiological studies for
assessing presence and severity of
lung diseases

5. LUNG FUNCTION TESTS
• SPIROMETRY
• Arterial Blood gas studies
• Diffusion capacity
• Exercise tests

6. LUNG FUNCTION TESTS
• Lung volumes
• Bronchial challenge
• Tests of small airways
• Compliance study
• VD / V T (dead space ventilation)
• QS / QT (shunt fraction)

7. WHAT IS SPIROMETRY?

8. SPIROMETRY : DYNAMIC
LUNG VOLUMES
• Measures volume of air a person
inhales/exhales as a function of
time and flow
• Essentially it measures airflow and
lung volume during forced
expiratory manoeuvre from full
inspiration (the FVC test)

9. SPIROMETRY
• When to do?
• How to do?
• How to interpret?

10. INDICATIONS OF SPIROMETRY
• Diagnostic
Abnormal chest symptoms, signs, lab tests
Effect of disease
Preoperative risk assessment
Screening of subjects (smokers, occupation)
• Monitoring
• Disability Impairment Evaluation
• Public Health
• Derive Reference Equations

11. HOW TO PERFORM SPIROMETRY?

12. • Record the type and dosage of all medications.
• Avoid smoking 24 hrs before test ( esp DLco )
• No alcohol within 4 hrs.
• No vigorous exercise in last 2 hours.
• Avoid tight clothings.
PERFORMING SPIROMETRY: PRETEST

13. Short acting β agonists 4-8 hours.
Sustained action β agonists 12 hours.
Short acting anticholinergics 24 hours.
Long acting anticholinergics 48 hours.
WITHHOLDING BRONCHODIALATORS

14. Case Age Height Weight FEV1 predicted FVC predicted
Laxmi 30 yrs 160 cm 45 kg 2.67 3.08
Rani 35 yrs 160 cm 45 kg 2.44 2.82
Difference of 5 years can change the predicted
values by 200-400 ml
RECORD THE AGE ACCURATELY

15. Patient Age Height Weight Predicted FEV1 Predicted FVC
Ramdas 35 yrs 160 cm 62 kg 3.04 3.45
Sankar 35yrs 165cm 62 kg 3.39 3.83
Difference of 5 cm can change the predicted
values by 200-400 ml
MEASURE THE HEIGHT ACCURATELY

17. • Sitting position.
• Get a good seal around the mouthpiece.
• Inhale maximally.
• Blow out as hard and as fast as possible.
• Continue to exhale till can blow no more
(at least 6 seconds).
• At least 3 acceptable effort; select the best.
• No more than 8 blows at one time.
TEST TECHNIQUE

19. • Salbutamol MDI (200 μg) or 2.5 mg nebulised
solution.
• Spirometry after 15-30 minutes.
• Improvement in FEV1 by 12% or more and
200 ml of more than prebronchodialator
value.
• Do not use FEV1/FVC to assess
bronchodialator response.
• Postbronchodialator FEV1 used to grade COPD
severity.
• In chronic asthma there may be only partial
reversibility of the airflow obstruction
REVERSIBILITY TEST

20. HOW TO INTERPRET SPIROMETRY?

21. • Free from artifacts : cough, glottic closure in early
expiration.
• No hesitation or false start.
• Acceptable exhalation
at least 6 seconds.
plateau in volume curve i.e , no detectable
change in volume for over 1 seconds
• Best determined by examining the graphic forms.
ACCEPTABLE EFFORT

22. UNACCEPTABLE PATTERNS

23. • Three acceptable maneuvers.
• Two largest FVC within 200 ml from
each other.
• Two largest FEV1 within 200 ml from
each other.
REPRODUCIBLE DATA

24. Absolute values.
Graphic forms.
SPIROMETRIC MEASUREMENT

25. • FEV1.
• FVC.
• FEV1/FVC (FEV1%)
SPIROMETRY : ABSOLUTE VALUES

26. • Volume of air expired in the first second
of force expiration measured in litres.
• Normally it is 70-80% FVC.
• Indicates severity of obstructive airway
disease.
FEV1

27. • Largest volume of air that can be
delivered by a forced maximal
expiration after full inspiration. (i.e,
volume of air expired from TLC to RV)
• Measured in liters.
FORCED VITAL CAPACITY (FVC)

28. • Also known as Forced Expiratory Ratio
(FER) or FEV1%.
• Normal value is 0.7-0.8.
• Reduction of FEV1/FVC (less than 70%) is
a cardinal feature of airflow obstruction.
FEV1/FVC

29. SLOW VITAL CAPACITY (SVC)
• Maximum volume of air
that can be exhaled slowly
after slow maximum
inhalation.
• Normally SVC and FVC
identical
• In airway obstruction
FVC<SVC
• Difference between SVC
and FVC- Air trapping

30. SPIROMETRY : OTHER INDICES
• FEF25%
Amount of air forcibly expelled in the first
25% of the FVC test
• FEF75%
Amount of air expelled from the lungs
during the first (75%) of the FVC test.
• FEF25%-75%
Amount of air expelled from the lungs
during the middle half of the FVC test.

31. • Diseases affecting primarily small (peripheral)
airways can be extensive yet not affect FEV1(e.g.
early COPD, interstitial granulomatous disorders).
• Small airways status is reflected by the FEF25-75%
• Some patients have normal spirometry with the
exception of a reduced FEF25-75%, this is
suggestive of possible small airways dysfunction
and potentially early obstruction.
SMALL AIRWAYS OBSTRUCTION

32. • Volume vs Time : spirogram or timed
vitalograph.
• Flow rate vs volume : flow volume
curve/ loop.
SPIROMETRY : GRAPHIC FORMS

33. •Shows amount air expired from the lungs as a
function of time.
•Approximately 80% of the total volume is 1st
second (FEV1) and curve reaches plateau by 6
seconds .
VOLUME-TIME GRAPH (SPIROGRAM)

34. •Flow ( volume/time) is plotted against
volume to display a continuous loop.
•Poor technique may be more obvious in
flow volume loops.
FLOW-VOLUME CURVE

35. DIFFERENTIATING OBSTRUCTIVE AND
RESTRICTIVE DISORDERS

36. COMMON OBSTRUCTIVE DISORDERS
• Asthma
• COPD
• Asthma COPD Overlap Syndrome (ACOS)
• Bronchiectasis

37. •FEV1/FVC % -less than 70% with normal FVC.
•Reduced FVC in severe obstruction.
OBSTRUCTIVE PATTERN : VOLUME
TIME GRAPH

38. •Reduced peak flow.
•Reduced mid expiratory flow; concave loop.
•Airway collapse , closure in emphysema . ( dogleg
appearence)
•Concavity of flow volume loop may be the first sign of
airflow obstruction.
•Reduced peak flow.
•Reduced mid expiratory flow; concave loop.
•Airway collapse , closure in emphysema . ( dogleg appearance )
•Concavity of flow volume loop may be the first sign of airflow
obstruction.
OBSTRUCTIVE PATTERN : FLOW-
VOLUME LOOP

39. • Peak expiratory flow reduced
so maximum height of the
loop is reduced
• Airflow reduces rapidly with
the reduction in the lung
volumes because the airways
narrow and the loop become
concave
ASTHMA

40. Airways may collapse during
forced expiration because of
destruction of the supporting
lung tissue causing very reduced
flow at low lung volume and a
characteristic (dog-leg)
appearance to the flow volume
curve.
EMPHYSEMA

41. Postbronchodialator FEV1
Stage I Mild FEV1 > 80%
Stage II Moderately 50% <FEV1 >80%
Stage III Severe 30% < FEV1 >50%
Stage IV Very severe FEV1< 30% or FEV1 < 50% +
Chronic respiratory failure
PaO2 < 60 mm Hg with or without PaCO2 > 50 mm Hg :
air at sea level.
SPIROMETRIC CLASSIFICATION OF
COPD (GOLD)

42. COMMON RESTRICTIVE DISORDERS
• Lung-DPLD, Fibrosis, Thickened
pleura, Atelectasis, Resection
• Pleural cavity-effusion, tumour
• Muscle-Neuromuscular diseases,
Old polio, Paralyzed diaphragm
• Chest wall-Obesity, Kyphoscoliosis,
Scleroderma, Ascites

43. Low FVC with normal or raised FEV1/FVCV
RESTRICTIVE PATTERN : VOLUME
TIME GRAPH

44. •Tall narrow peak.
•Steep expiratory phase.
•Physicians ordering PFT predicted obstructive pattern in
83% of the time but only in 50% for restrictive patterns.
•Poor technique ( low FVC ) may produce a restrictive
pattern.
•Tall narrow peak.
•Steep expiratory phase.
•Physicians ordering PFT predicted obstructive pattern in
83% of the time but only in 50% for restrictive patterns.
•Poor technique ( low FVC ) may produce a restrictive
pattern.
RESTRICTIVE PATTERN : FLOW-
VOLUME LOOP

45. Stage FVC% predicted normal
Normal > 80%
Mild 60-80%
Moderate 40-60%
Severe < 40%
SPIROMETRIC STAGING OF
RESTRICTIVE DISORDER

46. FLOW-VOLUME LOOP IN PROXIMAL
AIRWAY DISORDERS
(LOOK AT THE INSPIRATORY PART OF
FLOW VOLUME LOOP)

47. FLOW- VOLUME LOOP: FIXED
OBSTRUCTION
• Post intubation stenosis
• Goiter
• Endotracheal neoplasms
• Bronchial stenosis
Maximum airflow is limited to a
similar extent in both inspiration
and expiration

48. FLOW- VOLUME LOOP: VARIABLE
EXTRATHORACIC OBSTRUCTION
• Bilateral and unilateral vocal cord
paralysis
• Vocal cord constriction
• Reduced pharyngeal cross-sectional
area
• Airway burns
The obstruction worsens in inspiration
because the negative pressure narrows
the trachea and inspiratory flow is
reduced to a greater extent than
expiratory flow

49. FLOW- VOLUME LOOP: VARIABLE
INTRATHORACIC OBSTRUCTION
• Tracheomalacia
• Polychondritis
• Tumors of the lower trachea or
main bronchus.
The narrowing is maximal in
expiration because of increased
intrathoracic pressure compressing
the airway.

50. • Patient breathes as hard and as rapidly as possible for 12
sec. Total volume noted
• MVV is reduced in both obstructive and restrictive lung
disease. In both cases it is proportional to FEV1(FEV1X
40 approximates MVV).
• Useful as test of consistency of patient performance,
and is very dependent on patient effort and
cooperation
MAXIMUM VOLUNTARY VENTILATION

51. • Myocardial infarction in last 1 month
• Significant hemoptysis.
• Pneumothorax.
• Recent eye ,thoracic, abdominal surgery.
• Aneurysm ( cerebral , abdominal, thoracic.)
• Pregnancy.
• Caution if recent seizure , syncope, angina
• Children below 7 years.
• Chest or abdominal pain of any cause.
CONTRAINDICATIONS OF
SPIROMETRY

52. LIMITATIONS OF SPIROMETRY
• Depends on patient’s effort. Suboptimal
results common.
Cannot measure FRC
and TLC for which
Helium dilution or Body
plethysmography is
required.

53. Acceptable and Reproducible
FEV1/FVC
Reduced
FVC
Normal
FVC
Normal
Obstruction
Reduced
Mixed defect/severe Obstruction normal Reduced
Normal RestrictionBDR
COPD ASTHMA
negative positive
INTERPRETING SPIROMETRY

54. CASE ILLUSTRATIONS

55. 18 year female with recurrent wheezing

56. Mild Obstructive Defect with good
response to
bronchodilator
Asthma
DIAGNOSIS

57. A 66 year female with cough
%PredRefMeans
852.582.2FVC
971.851.79FEV1
7281FEV1/FVC
822.231.82FEF 25-75
1095.25.67PEF

58. Normal Spirometry

59. 60 year male smoker with cough and dyspnea

60. • Flow volume loop suggestive of obstructive
disease
• Spirometry showed Severe Obstructive defect
with no response to bronchodilator
• Decreased FVC could be because of Air-trapping
or could be combined obstructive and restrictive
defect to confirm need to do Lung Volume
COPD
DIAGNOSIS

61. A 38 year female with wheezing
%PredRefMeas
1033.543.66FVC
832.772.30FEV1
7863FEV1/FVC
514.202.15FEF25-75
386.252.39PEF

62. Small airways obstruction
DIAGNOSIS

63. PRE-OPERATIVE PFTs IN
CARDIOTHORACIC
SURGERIES

64. PREOPERATIVE PFTs IN
CARDIOTHORACIC SURGERIES
• WHY?
• FOR WHOM?
• WHAT TESTS?

65. A CASE ILLUSTRATION
17th March 2014 17th June 2014
50 yr old non-smoker male presented with Right sided
pyo-pneumothorax with BPF with history of ATD intake
for PTB in 2010. ICTD inserted on 28th March 2015 and
posted for Decortication on 5th May 2015.

66. A CASE ILLUSTRATION
2nd May 2015
• Patient had to undergo
Pneumonectomy during
exploratory thoracotomy.
• Patient could not be
extubated and succumbed on
4th post operative day
following pneumonectomy.

67. LUNG FUNCTION AND
ANAESTHESIA
• Marked alteration of respiratory drive
• Diminished response to hypoxia, hypercarbia
• Alteration of diaphragmatic movement
• Reduction of FRC
• Increased closing capacity
• Poor cough reflex
• Impaired mucociliary clearance

68. FRC decreased-
If CC exceeds FRC : atelectasis , V/Q mismatch, persistent hypoxia
30% after upper abdominal surgery.
35% after Thoracotomy.
10-15% after lower abdominal surgery.
< 1% after extremity surgery.
LUNG VOLUMES AFTER SURGERY

69. PATHOPHYSIOLOGICAL
CONSEQUENCES
• V/Q mismatch
• Atelectasis
• Increased dead space
• Pneumonia
• Respiratory failure
• Prolonged ventilation

70. • Thoracic resection 25%
• Upper abdominal surgery 5-10%
• Head and neck surgery 3.5%
• Lower abdominal surgery < 5%
• Non thoracoabdominal surgery <1%
POSTOPERATIVE PULMONARY
COMPLICATIONS

71. SUBJECTS AT RISK
• Smoker
• COPD
• Advanced age
• Obesity
• Malnutirtion
• Antecedant respiratory infection
• Sleep apnea syndrome

72. COPD & POST-OP
COMPLICATIONS
• COPD is the strongest and consistent risk
factor for PPC
• PPC 4%, 10%, 23% with no; mild-
moderate; severe COPD.
• Except for lung resection, no cutoff PFT
value that prohibits surgery /anesthesia.
• Intensive preoperative respiratory
therapy decreases PPC by 50% in COPD

73. INDICATIONS OF PREOPERATIVE
SPIROMETRY
• LUNG RESECTION
• COPD
• Smoker >20 pack years
• Unexplained cough, dyspnea
Spirometry not routinely indicated before all
surgeries

74. WHY PREOPERATIVE PFT?
• RISK BENEFIT ASSESSMENT
• Too risky : abandon surgery at the
moment
• Minimise risk by intensive pre and peri-
operative respiratory therapy to allow
acceptable safe surgery.

75. PRE-OPERATIVE OPTIMISATION
• Smoking cessastion
• Optimise airway function to best possible level
Aerosolised bronchodilators
Steroids
Antibiotics
• Deep breathing exercise
• Incentive spirometry

76. Quit 8 weeks before surgery produce
statistically significant reduction of PPCs.
SMOKING CESSATION

77. • Preoperative corticosteroids has low complication
rate of postoperative infection.
• In severe COPD /symptomatic asthma start
Hydrocortisone at least 12 hrs before surgery.
• Taper to 20-40 mg Prednisolone in 5-7 days.
CORTICOSTEROIDS & PPC

78. • Aim : to increase FRC ;recruit diaphragm.
• Starting before surgery makes them more
effective.
• Deep breathing exercise .simple inexpensive.
• Incentive spirometry; gives visual feedback.
• CPAP ; If no patient cooperation.
MAXIMAL INSPIRATORY
MANEUVERS

79. CARDIAC SURGERY AND PFT
• Spirometry if history of lung disease
• ABG if a case of COPD
• PaCO2 > 45 mm of Hg predicts
increased mortality
• Elective CABG after optimisation of
lung disease

80. LUNG RESECTION AND PFT
• Routine PFT is indicated in all cases
prepared for lung resection
• Potentially resectable lung carcinoma
are the commonest subjects

81. LUNG RESECTIONAL SURGERIES
• Segmentectomy
• Lobectomy (commonest)
• Pneumonectomy

82. WHY PFT FOR ALL CASES?
• To find out if loss of resected lung tissue
tolerable
• 90% lung cancer patients have COPD.
20% severe dysfunction
• With advanced peri-operative care more
sick patients are offered aggressive
surgical therapies.

83. PHILOSOPHY OF LUNG
RESECTION
• Pneumonectomy may have to be
performed owing to unsuspected,
extensive disease found on exploratory
thoractomy.
• Even if lobectomy / wedge resection is
planned for an anatomically resectable
lung cancer evaluate for
penumonectomy.

84. LUNG COMPLICATIONS OF
THORACIC SURGERY
• Fall of chest wall compliance
• Increased work of breathing
• Pulmonary bruising
• Fluids and blood clots in the pleura

85. PFT AND LUNG RESECTION
PNEUMONECTOMY LOBECTOMY SEGMENTECTOMY
FEV1 <2 L <1 L <0.6 L
MVV < 55% < 40% < 35%
FEV1 > 2L or >60% predicted after optimisation
of medical therapy is regarded as cut-off point
for pneumonectomy.

86. PREOPERATIVE ABG
• Lung resection with preexisting lung disease .
• Lung resection without significant lung disease.
• COPD with high risk surgery.
• Hypercarbia : not absolute contraindication ,
more vigilance in postoperative period.

87. PFTs FOR LUNG RESECTION
• STEP I : Spirometry, DLCO
• STEP II : Split Lung Function
• STEP III : Cardiopulmonary Exercise Test

88. DLCO
• Low concentration of CO inhaled and expired gas
is analyzed for CO
Diffusing capacity is reduced when:
• Alveolar walls are destroyed and pulmonary
capillaries are obliterated by emphysema
• Alveolar-capillary membrane is thickened by
oedema, consolidation, or fibrosis

89. PREDICTED POST
OPERATIVE FEV1
• PPO FEV1= Preoperative FEV1 X No. Of remaining segments
18
• Preop FEV1 = 2L
• Rt lower lobectomy ( 5 segments)
• Predicted post-op FEV1 = 2 X 18-5 = 1.4
18
• Predicted Post-op FEV1 <0.8 L or 40% predicted : prohibitive
risk for lung resection

90. SPLIT LUNG FUNCTION TESTS
• To calculate anticipated pulmonary reserve after
resection
• Spirometry and quantitative perfusion lung scan
• Eg. Post-pneumonectomy predicted FEV1
=Preop FEV1 X (% perfusion to remaining lung)

91. PERFUSION LUNG SCAN
(99m Tc labelled)
• Tumour : Rt main bronchus
• PNEUMONECTOMY
• 40% Right Lung
• 60% Left Lung
• FEV1 =1.5L
• Estimated Post-op FEV1 = 60 X 1.5 L = 900ml
100

92. PERFUSION LUNG SCAN
(99m Tc labelled)
• Tumour Rt upper lobe requiring LOBECTOMY
• Estimated FEV1 loss
= 3 X 40 X 1.5 L = 0.18 L
10 100
• PPO FEV1 = (1.5-0.18) L = 1.32 L

93. EXERCISE TESTS
• 6 minute walk
• Stair climbing
• VO2 max by cardiopulmonary
exercise testing

94. EXERCISE TESTS
• VO2 max <10 ml/kg/min : unacceptable for
surgery
• VO2 max >20 ml/kg/min : low risk
• Stair climb <2 flights : high mortality for
pneumonectomy
• 6MWD <100m. Post test desaturation:
unacceptable for pneumonectomy

95. ALGORITHM FOR LUNG
RESECTION
STEP
III
• VO2 max >
15ml/kg/min
STEP II
• PPO FEV1> 40%
STEP I
• FEV1 > 2L
• DLCO > 60%
OFFER
SURGERY
<60%
<40%

96. MESSAGE
PULMONARY
EVALUATION
ANAESTHESIOLO
GIST
PULMONOLOGIST, PHYSICAL
MEDICINE, NURSING PERSONEL
PHYSICIAN

97. CONCLUSION
• Cornerstone is good history and physical
examination.
• Clinical evaluation often as informative as
PFT.
• Normal PFT is no guarantee to complication
free postoperative course.
• Normal PFT is not substitute to diligent
postoperative respiratory care.