PFTs measure lung function through objective methods like spirometry, lung volumes, diffusing capacity, and exercise tests. They are useful for diagnosing pulmonary diseases, monitoring disease progression and treatment effectiveness, and assessing surgical risk. Spirometry specifically measures volumes of air inhaled and exhaled over time through tests like FVC, FEV1, and FEF25-75. Flow-volume loops can help characterize obstructive, restrictive, and mixed lung diseases. Bronchodilator tests assess reversibility of airway obstruction.

1. PULMONARY FUNCTION
TESTS

2. What exactly are PFTs?
⚫The term encompasses a wide variety of objective
methods to assess lung function. (the primary function is
gas exchange).
⚫Examples include:
⚫Spirometry
⚫Lung volumes by helium dilution or body plethysmography
⚫Blood gases
⚫Exercise tests
⚫Diffusing capacity
⚫Bronchial challenge testing
⚫Pulse oximetry

3. ADVANTAGES OF PFT -
⚫Add to diagnosis of disease (pulmonary and cardiac).
⚫May help guide management of a disease process.
⚫Can help monitor progression of disease and
effectiveness of treatment.
⚫Aids in pre-operative assessment of patients.

4. INDICATIONS-
⚫Diagnostic
⚫To evaluate symptoms, signs, or abnormal laboratory tests
⚫Symptoms: dyspnea, wheezing, orthopnea, cough, phlegm production,
⚫chest pain
⚫Signs: diminished breath sounds, overinflation, expiratory slowing,
⚫cyanosis, chest deformity, unexplained crackles
⚫Abnormal laboratory tests: hypoxemia, hypercapnia, polycythemia,
⚫abnormal chest radiographs
⚫To measure the effect of disease on pulmonary function
⚫To screen individuals at risk of having pulmonary diseases
⚫Smokers
⚫Individuals in occupations with exposures to injurious substances
⚫Some routine physical examinations
⚫To assess preoperative risk
⚫To assess prognosis (lung transplant, etc.)
⚫To assess health status before enrollment in strenuous physical activity
programs

5. ⚫Monitoring
⚫To assess therapeutic interventions
⚫ -bronchodilator therapy
⚫ -Steroid treatment for asthma, interstitial lung
disease, etc.
⚫ -Management of congestive heart failure
⚫ -Other (antibiotics in cystic fibrosis, etc.)
⚫To describe the course of diseases affecting lung function
⚫-Pulmonary diseases
⚫ Obstructive airways diseases
⚫ Interstitial lung diseases
⚫-Cardiac diseases
⚫ Congestive heart failure
⚫-Neuromuscular diseases
⚫ Guillain-Barre Syndrome
⚫To monitor persons in occupations with exposure to injurious agents
⚫To monitor for adverse reactions to drugs with known pulmonary toxicity

6. INDICATIONS (contd-)
⚫Disability/Impairment Evaluations
⚫ To assess patients as part of a rehabilitation program
⚫ -Medical
⚫ -Industrial
⚫ -Vocational
⚫To assess risks as part of an insurance evaluation
⚫Public Health
⚫ Epidemiologic surveys
⚫ -Comparison of health status of populations living in different
⚫ environments
⚫ -Validation of subjective complaints in
occupational/environmental
⚫ settings
⚫Derivation of reference equations
(From ATS, 1994)

7. Spirometry
⚫“Spirometry is a medical test that measures the
volume of air an individual inhales or exhales as a
function of time. (ATS, 1994)”

8. Brief History
⚫John Hutchinson (1811-1861)—inventor of the
spirometer and originator of the term vital
capacity (VC).
⚫Original spirometer consisted of a calibrated bell
turned upside down in water.
⚫Observed that VC was directly related to height
and inversely related to age.
⚫Observations based on living and deceased
subjects.

9. Silhouette of Hutchinson
Performing Spirometry

10. Lung Volumes and Capacities

11. Lung Volumes
⚫Tidal Volume (TV): volume of
air inhaled or exhaled with each
breath during quiet breathing
⚫Inspiratory Reserve Volume
(IRV): maximum volume of air
inhaled from the end-
inspiratory tidal position
⚫Expiratory Reserve Volume
(ERV): maximum volume of air
that can be exhaled from resting
end-expiratory tidal position

12. Lung Volumes
⚫Residual Volume (RV):
⚫Volume of air
remaining in lungs after
maximium exhalation
⚫Indirectly measured
(FRC-ERV) not by
spirometry

13. Lung Capacities
⚫Total Lung Capacity (TLC): Sum
of all volume compartments or
volume of air in lungs after
maximum inspiration
⚫Vital Capacity (VC): TLC minus
RV or maximum volume of air
exhaled from maximal inspiratory
level
⚫Inspiratory Capacity (IC): Sum
of IRV and TV or the maximum
volume of air that can be inhaled
from the end-expiratory tidal
position

14. Lung Capacities (cont.)
⚫Functional Residual
Capacity (FRC):
⚫Sum of RV and ERV or the
volume of air in the lungs at
end-expiratory tidal position
⚫Measured with multiple-
breath closed-circuit helium
dilution, multiple-breath
open-circuit nitrogen
washout, or body
plethysmography (not by
spirometry)

15. What information does a
spirometer yield?
⚫A spirometer can be used to measure the
following:
⚫FVC and its derivatives (such as FEV1, FEF 25-75%)
⚫Forced inspiratory vital capacity (FIVC)
⚫Peak expiratory flow rate
⚫Maximum voluntary ventilation (MVV)
⚫Slow VC
⚫IC, IRV, and ERV
⚫Pre and post bronchodilator studies

16. Lung Factors Affecting Spirometry
⚫Mechanical properties
⚫Resistive elements

17. 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

18. Resistive Properties
⚫Determined by airway caliber
⚫Affected by
⚫Lung volume
⚫Bronchial smooth muscles
⚫Airway collapsibility

19. Factors That Affect Lung Volumes
⚫Age
⚫Sex
⚫Height
⚫Weight
⚫Race
⚫Disease

20. 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

21. WATER SEALED SPIROMETRY

22. 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)

23. FVC
⚫Interpretation of % predicted:
⚫> 80% Normal
⚫70-79% Mild reduction
⚫50%-69% Moderate reduction
⚫<50% Severe reduction
FVC

24. 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

25. FEV1
⚫Interpretation of % predicted:
⚫>80% Normal
⚫60%-80% Mild obstruction
⚫40-60% Moderate obstruction
⚫<40% Severe obstruction
FEV1 FVC

26. CLINICAL RANGE FOR FEV1
⚫CLINICAL RANGE PATIENT
GROUP
3 to 4.5L normal adult
1.5 to 2.5L mild to moderate
obstruction
<1L handicaped
0.8 disability
0.5 severe emphysema

27. FVC AND FEV1 IN DISEASED STATE
⚫DISEASED STATE FVC FEV1 FEV1/FVC
⚫Airway obstruction normal decreased decreased
Asthma, bronchitis
⚫Stiff lung
Pneumonia,pulmonary decreased decreased normal
Oedema, pulmonary
Fibrosis
⚫Respiratory muscle decreased decreased normal
Weakness
MG, myopathies

28. 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

29. FEF25-75
⚫Interpretation of % predicted:
⚫>79% Normal
⚫60-79% Mild obstruction
⚫40-59% Moderate obstruction
⚫<40% Severe obstruction

30. PEAK EXPIRATORY FLOW RATE
⚫It is the maximum flow generated in the first fraction
of second during a forced expiratory manoeuvre
⚫The major contribution to the peak flow is from
large central airways
⚫Peak flows is useful for monitoring than diagnosing
airflow obstruction

31. MAXIMUM VOLUNTARY
VENTILATION
⚫Is the largest volume of gas that can be breathed in
one minute by voluntary effort for 10 to 15 seconds
and the results are extraplotted to 1 minute
⚫Healthy adults – 170l/min
⚫Is decreased in obstructive lung disease
⚫A poor performance suggests that patient may have
pulmonary problems postoperatively due to muscle
weakness

32. Acceptability Criteria
⚫Good start of test
⚫No coughing
⚫No variable flow
⚫No early termination
⚫Reproducibility

33. PHYSIOLOGICAL DETERMINANTS
OF MAXIMUM FLOW RATE
⚫Degree of effort of driving pressure generated by
muscle contraction
⚫Elastic recoil pressure of lung
⚫Airway resistance

34. DEGREE OF EFFORT
⚫The expiratory effort is maximum at high lung
volumes near TLC and decreases as the lung vulume
decreases
⚫Whereas the inspiratory effort is maximum at low
lung volume near RV and diminishes at higher lung
volume

35. ELASTIC RECOIL PRESSURE OF
LUNG
⚫At all lung volumes from RV to TLC the lung has
tendancy to recoil inward
⚫The lung pressure is greatest at TLC(25 to 30 cm of
H2O) and lowest at RV
⚫The PL is opposed by outward recoil pressure of
chest wall(PCW)
⚫The recoil pressure of the respiratory system is
algebric sum of PL + PCW
⚫PL and PCW are equal and opposite at some point, ie
FRC and it is respiratory normal resting volume

36. ⚫Is determined by size of airways
⚫Because airways are largest at high lung volumes and
smallest at RV ,so airway resistance is greatest at RV
and least at TLC
AIRWAY RESISTANCE

37. AIRWAY RESISTANCE
Relationship between lung volume and airways resistance. Total lung capacity is at
right; residual volume is at left. Solid line = normal lung; dashed line =
abnormal (emphysematous) lung.
R
V
FR
C
TLC

38. EQUAL PRESSURE POINT CONCEPTOF EXPIRATORY FLOW
LIMITATIONS
Schematic diagram illustrating
dynamic compression of airways
and the equal pressure point
hypothesis during a forced
expiration. Left: Passive (eupneic)
expiration. Intrapleural pressure is
–8 cm H2O, alveolar elastic recoil
pressure is +10 cm H2O, and
alveolar pressure is +2 cm H2O.
Right: Forced expiration at the
same lung volume. Intrapleural
pressure is +25 cm H2O, alveolar
elastic recoil pressure is +10 cm
H2O, and alveolar pressure is +35
cm H2O.

39. 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

40. Categories of Disease
⚫Obstructive
⚫Restrictive
⚫Mixed

41. 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

42. Spirometry in Obstructive Disease
⚫Slow rise in upstroke
⚫May not reach
plateau

43. 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

44. Restrictive Disease
⚫Rapid upstroke as
in normal
spirometry
⚫Plateau volume is
low

45. Large Airway Obstruction
⚫Characterized by a
truncated
inspiratory or
expiratory loop

46. FLOW-VOLUME LOOPS IN DIFFERENT TYPES OF
AIRWAY OBSTRUCTION
Inspiratory and expiratory
flow-volume curves
representing the patterns
in: A: Fixed intra- or
extrathoracic
obstruction. B: Variable
extrathoracic
obstruction. C: Variable
intrathoracic
obstruction. TLC = total
lung capacity; RV =
residual volume; Paw =
airway pressure; Patm =
atmospheric pressure;
Ppl = intrapleural
pressure.

47. FIXED OBSTRUCTION
⚫As in benigin strictures
resulting from
trachostomy or tracheal
intubation, a tumor or
mass like goitre
⚫The air flow is limited to
similar extent in both
inspiration and expiration
as breathing occurs
through fixed external
resistance
⚫Both inspiratory and
expiratory phases on the
loop show plateaus

48. VARIABLE EXTRATHORACIC
OBSTRUCTION
⚫As in vocal cord paralysis,
pharangeal weakness,
neuromuscular disorder
⚫The obstruction worsens
during inspiration because
the negative pressure
narrows the trachea and
inspiratory flow is reduced
to greater extent than
expiratory flow

49. VARIABLE INTRATHORACIC
OBSTRUCTION
⚫As occurs in tumors of
trachea and major bronchi
⚫The obstruction is maximal
during expiration because of
increase intrathoracic pressure
compressing airway
⚫The narrowing is minimal in
inspiration because
intrathoracic pressure is lower
than airway pressure
⚫The flow-volume loop shows
a greater decrease in the
expiratory loop

50. Bronchodilator Test
Indications:
⚫Establish reversibility of airway obstruction.
⚫Evaluation of effect of bronchodilator for patients
with obstructive disease.
⚫Help plan long-term bronchodilator therapy.

51. Bronchodilator Test
Avoidance before test
⚫Inhaled sympathomimetics
6 hours
⚫Short-acting oral methylxanthines
12 hours
⚫Long-acting oral methylxanthines
24 hours

52. Bronchodilator Test
⚫Positive bronchodilator response:
Increase of FVC or FEV1 ≥ 12% or
Increase of FVC or FEV1 ≥ 0.2 L from baseline
⚫Significant bronchodilator response:
Increase of FVC or FEV1 12-24%
⚫Marked bronchodilator response:
Increase of FVC or FEV1 ≥ 25%

53. Bronchial Provocative Test
Indications:
1. History of wheezing with normal pulmonary
function tests
2. Chronic cough
3. Exercise tolerance
4. Unexplained dyspnea
5. Identifying specific provocative factors
6. Study the pathophysiology of acute reversible
bronchospasm

54. Bronchial Provocative Test
Avoidance before test
⚫Sympathomimetic drugs ≥6 hours
⚫Methylxanthines ≥12 hours
⚫Sustained-release methylxanthines ≥48 hours
⚫Cromolym sodium 48 hours
⚫Corticosteroids 12 hours
⚫Significant exercise ≥2 hours
⚫Exposure to cold air ≥2 hours
⚫Smoking ≥6 hours
⚫Ingestion of coffee, cola, or chocolate drinks
≥6 hours

55. Bronchial Provocative Test% f
SGAW
⚫Bronchial challenge with methacholine, exercise,
allergic materials, SO2, cigarette smoke.
⚫Positive bronchoprovocative response:
Decrease of FEV1 ≥ 20%
Decrease of PEFR ≥ 20%

56. Distribution of Ventilation
Single-breath nitrogen test:
⚫A full inhalation of 100% O2 form RV.
⚫Phase I: Air in trachea and upper airway.
⚫Phase II: Alveolar gas begins washing out the dead
space O2.
⚫Phase III: Alveolar gas.
⚫Phase IV: Expired air from the apical region with
higher percentage of N2.

57. Distribution of Ventilation
Single-breath nitrogen test:
⚫Normal slope of phase III: 1.0-2.5%N2/L.
⚫Phase IV: The onset of airway closure in the
dependent regions, called “closing volume”. It
expressed as a fraction of vital capacity in
percent(CV/VC%), showed final 15% vital capacity in
normal individual

58. Distribution of Ventilation

59. Distribution of Ventilation

60. Gas exchange in the lungs

61. Diffusing Capacity

62. Diffusing Capacity
⚫A single-breath(SB) method(SBDLCO).
⚫A He-CO-O2 mixed gas(0.3% CO, 10% He, 20% O2,
69.7% N2).
⚫A 10 seconds breath-holding, and should be a
minimum of 5 seconds.
⚫The vital capacity should exceed 1.5 L for results to
be acceptable.

63. Diffusing Capacity

64. Pulmonary Function Test
Interpretation of gas transfer
DLCO(Diffusing capacity)
Severity
Normal 81-140%
Mild 61-80%
Moderate 41-60%
Severe <41%

65. Diffusing Capacity
⚫It estimates the patient’s ability to absorb alveolar
gases.
⚫Reduced DLCO:
Disorders of the pulmonary parenchyma, vascular
abnormalities, reductions in effective alveolar
units, and anemia.
⚫Elevated DLCO:
Left-to-right intracardiac shunt, polycythemia, and
post-exercise physiology.

66. Diffusing Capacity
Causes of a decreased diffusing capacity

67. ABG
⚫Results: pH / PCO2 / PO2 / bicarbonate / base excess
⚫Usually obtained from radial, brachial, femoral,
axillary, or dorsalis pedis artery
⚫Drawn in heparinized syringe
⚫Must be measured within 15 minutes or glycolysis
will occur with lactic acid production, decreased pH,
and increased PCO2
⚫Sample can be stored on ice for 1 to 2 hours
⚫Heparin may significantly lower PCO2 by dilution,
esp. in children when small samples taken

68. ABG normal values
⚫pH: 7.35 – 7.45
⚫PCO2: 35 – 45 mmHg
⚫PO2: 75 – 105 mmHg
⚫Bicarbonate: 20 – 26 mmoles/L
⚫Base excess: -3 to +3 mmoles/L

69. pH
⚫Acidemia = blood pH < 7.35
⚫Alkalemia = blood pH > 7.45
⚫Acidosis = a process which causes acid to accumulate
⚫Alkalosis = a process which causes alkali
accumulation
⚫Altered pH 🡪 next determine if respiratory (CO2) or
metabolic (HCO3
-)
⚫Buffers: substance that can absorb or donate H+
⚫Bicarb(HCO3
-), Hb, serum proteins, phosphate(HPO4
-)

70. PaCO2
⚫Hypercapnia – increased CO2
⚫Hypocapnia – decreased CO2
⚫*Rule: an increase of PCO2 by 10 mmHg causes a
decrease in pH by 0.08, likewise, a decrease of PCO2
by 10 mmHg will increase pH by 0.08
⚫So an acute increase in CO2 to 60 should cause a drop
in pH to 7.24

71. Bicarbonate
⚫A calculated value from:
[H+] = 24 * (PaCO2/[HCO3
-])
⚫Values alter due to acidosis/alkalosis
⚫Base excess is calculated directly using PaCO2, pH,
and bicarbonate values
⚫Rule: a decrease in bicarb. by 10 mmoles decreases
the pH by 0.15, likewise, an increase in bicarb. By 10
mmoles increases pH by 0.15
⚫A bicarb. of 13 would result in a pH of 7.25
⚫Total body bicarb. deficit = (base deficit * wt in Kg *
0.4), in mEq/L, usually replace ½ of deficit

72. Respiratory Acidosis
⚫Low pH & High PaCO2
⚫Acute and chronic causes:
⚫Hypoventilation with hypercarbia
⚫CNS depression – trauma, drugs
⚫Decreased FRC – obesity
⚫Upper or lower airway obstruction
⚫COPD, asthma, pulmonary fibrosis
⚫After 1-2 days renal compensation occurs
⚫H+ excreted by kidney and HCO3
- reabsorbed into
blood to partially correct pH

73. Respiratory Alkalosis
⚫High pH & Low PaCO2
⚫Hyperventilation with hypocarbia
⚫Causes: hypoxic respiration, CNS Dz, encephalitis,
anxiety, narcotic withdrawl, pregnancy, early septic
shock, hypermetabolic states, artificial ventilation
⚫Renal compensation will occur causing increased
excretion of HCO3
- and decreased secretion of H+
which partially corrects pH

74. LUNG FUNCTION OBSTRUCTIVE
DISORDER
RSTRICTIVE
DISORDER
FEV1 ↓↓ ↓
FVC ↓↓ ↓↓
FEV1/FVC ↓ Normal or ↓
FRC ↑ ↓
TLC ↑ ↓
PEFR ↓ ↓
MBC ↓ ↓↓
FEF25-75 ↓ ↓
AIRWAY RESISTANCE ↑ ↓
RV/TLC ↑ ↓
COMPLIANCE Dynamic ↓ Static ↓

75. BED SIDE PFTs
⚫Breathing holding tests of sabrasez : vital capacity is
checked
⚫Sniders test
⚫Auscultation over trachea

76. REFERENCES
⚫MILLER 6TH
⚫McGRAW-HILLS-POCKET GUIDE TO LUNG
FUNCTION TESTS

77. Thank
you