Pulmonary function tests (PFTs) evaluate lung function through non-invasive tests. PFTs can be done at bedside or in traditional labs and include tests of lung volumes, capacities, flows and gas exchange. Bedside PFTs include breath-holding tests to assess vital capacity, single-breath tests for functional residual capacity, cough tests for strength, blowing tests for maximum breathing capacity, and peak flow tests. PFTs help diagnose and monitor pulmonary diseases, assess disease severity and surgical risk, and track response to treatment. Common diseases detected include obstructive disorders like asthma which limit expiration and restrictive disorders like fibrosis which limit both expiration and inspiration.

1. Pulmonary function test
Dr Kavita Kadyan
Assistant professor,
DNB Anesthesiology & Critical care

2. Pulmonary function test
Bedside PFT Traditional PFT

3. BEDSIDE PFT mnemonic
0 : hold: breath hold test (Seberese)
1: single breath test (Seberese)
A: ABG
B: Blowing test (match blow)(snider)
C: Cough test (GREENE)
D: Debono test (whistle)
E: Expiratory time (forced)
F: Flow meter(peak flow meter) (wrights)

4. 0 : hold means no breathing
0 breathing: breath hold test (Seberese)
Sabrasez breath holding test:
Ask the patient to take a deep breath
inhale and exhale and then take
normal breath & hold it as long as
possible.
• >25 SEC.- NORMAL
Cardiopulmonary Reserve
• 15-25 SEC- LIMITED
• <15 SEC - VERY POOR
(breath = deep inspiration + deep
expiration + tidal volume= vital capacity)
( 1 litre start + 500ml each 5 sec VC
increase)
The length of time can crudely help to
quantify the Vital capacity
of the patient.
25- 30 SEC - 3500 ml VC
20 – 25 SEC - 3000 ml VC
15 - 20 SEC - 2500 ml VC
10 - 15 SEC - 2000 ml VC
5 - 10 SEC - 1500 ml VC
0 - 5 sec = 1000ml

5. 1: single breath test (Seberese)
After deep breath, hold it and start
counting till the next breath.
 Normal- 30-40 COUNT
 It is a measure of the FRC.
>15 : normal
<15 : dec reserve
11-15 : mild impairment
5-10 : mod impaired
<5 : severe impairment

6. B: Blowing test (match blow)(snider)
 Measures Maximum Breathing Capacity/Maximum voluntary ventilation.
 Should take 6 attempts before interpretation of test
Ask to blow a match stick from a distance of 6” (15 cms) with
 Mouth wide open
 Chin rested/supported
 No pursed lips
 No head movement
 No air movement in the room
 Mouth and match stick at the same level
(Match Blow = Maximum Breathing : MB : MB)
MATCH TEST:
DISTANCE MBC (N-150-175 L/min)
9” >150 L/MIN.
6” >60 L/MIN.
3” >40 L/MIN.

7. C: Cough test
GREENE & BEROWITZ COUGH TEST:
DEEP BREATH F/B COUGH
ABILITY TO COUGH tells ..
 STRENGTH
 EFFECTIVENESS
INADEQUATE COUGH :
FVC <20 mL/Kg
FEV1 < 15 ml/Kg
PEFR < 200 L/min.
VC ~ 3 TIMES TV FOR EFFECTIVE COUGH.
A wet productive cough / self propagated paroxysms of coughing – patient susceptible for
pulmonary Complication.

8. D: Debono test (whistle)
measures PEFR.
 Patient blows down a wide bore tube at the end of which is
a whistle, on the side is a hole with adjustable knob.
 As the patient blows down the tube, the whistle sounds only
when the rate of airflow exceeds a certain value.
 The side leak hole is gradually increased till the sound of whistling
disappears.
The last position when the whistle can be appreciated is read off the
scale and taken as the PEFR.

9. E: Expiratory time (forced)
After deep breath, exhale maximally and
forcefully & keep stethoscope over trachea
& listen.
Normal FET – 3-5 SECS.
Obstructive Lung Disease - > 6 SEC
Restrictive Lung Disease - < 3 SEC

10. F: Flow meter(peak flow meter) (wrights)
Measures PEFR
N – MALES- 450-700 L/MIN.
FEMALES- 350-500 L/MIN.
<200 L/min.–inadequate cough efficiency

11. Wright ‘s Respirometer
measures VT (tidal volume ) and minute volume of patient
Simple and rapid
Instrument- compact, light and portable.
Disadvantage: It under- reads at low flow rates and
over- reads at high flow rates.
Can be connected to endo tracheal tube or face
mask
Prior explanation to patient is needed.

13. What we get from PFTs?

14. GOALS
 To predict presence of pulmonary dysfunction
To know the functional nature of disease.
To assess the severity of disease
To assess the progression of disease
To assess the response to treatment
Medicolegal- to assess lung impairment as a result
of occupational hazard.
To identify patients at perioperative risk of
pulmonary complications

15. Evaluates
• Pulmonary function tests is a general term used to indicate a series of
maneuvers or investigations that are performed to help measure lung
functions. It evaluates one or more aspects of the respiratory system.
• Pulmonary parenchymal function/ Gas exchange (size & integrity of
the pulmonary capillary bed)
• Respiratory mechanics
• Cardiopulmonary interaction

16. • ACP GUIDELINES FOR PREOPERATIVE SPIROMETRY (modified )
Lung resection
H/o smoking, dyspnoea
Cardiac surgery
Upper abdominal surgery
Lower abdominal surgery
Uncharacterized pulmonary disease (defined as history of pulmonary
Disease or symptoms and no PFT in last 60 days)

17. Indications of PFTs
• Evaluation of signs & symptoms like breathlessness, chronic cough,
exertional dyspnoea to detect the disease.
• Evaluate the extent and assess severity of disease.
• Screening at risk patients and follow their response to therapy
• Measure the effect of drugs on pulmonary function
• To assess preoperative risk
• Monitor pulmonary drug toxicity

18. Contraindications
• History of recent thoraco-abdominal surgery
• Oral or facial pain which may be exacerbated by mouthpiece
• Stress incontinence
• Recent eye surgery (cataract)
• Thoracic, abdominal and cerebral aneurysm
• Active haemoptysis
• Nausea, vomiting
• Pneumothorax
• Dementia or confused patient,
• History of myocardial infarction within one month /Unstable angina

19. Volumes of lung

20. How to measure non-measurable lung
volumes?
Spirometry : don’t tell RV, FRC, TLC
• N2 wash out
• Helium dilution test
• Total body plethysmography

21. Spirometry

23. Helium dilution technique

24. Nitrogen washout technique

25. https://doctorlib.info/physiology/medical/143.html
Plethysmography

26. Functional residual capacity
• Functional Residual Capacity (FRC):
• Sum of RV and ERV or the volume of air in the lungs at end-expiratory tidal position.
• (30-35 ml/kg) (2300-3300ml).
• Measured with multiple-breath closed-circuit helium dilution, multiple-breath open-circuit
nitrogen washout, or body plethysmography.
• It can not be measured by spirometry.

27. Functions of FRC:
• Oxygen store
• Buffer for maintaining a steady arterial po2
• Partial inflation helps prevent atelectasis
• Minimise the work of breathing
• Minimise pulmonary vascular resistance
• Minimised v/q mismatch
- only if closing capacity is less than FRC.

28. Spirometry tells us what?
Volume time graph Flow time graph
vc

30. Flow volume loop graph: measures Forced
VITAL CAPACITY(FVC)
• PEFR( peak expiratory flow rate): large airway feature+
patient effort dependent + <200ml is abnormal+
{after maximum inspiration→ Patient maximum expires}
• Maximum flow rate during an FVC maneuvers occurs
in initial 0.1 s and the expiratory flow at this time is
termed as PEFR
• FEF-25%: the flow rate at the 25% point of the total
volume (FVC) exhaled, large-medium sized airway
• FEF50% : the flow rate at the 50% point of the total
volume (FVC) exhaled, medium to small airway.
• FEF 75% : the flow rate at the 75% point of the total
volume (FVC) exhaled, small airway (<2mm)
• Forced Expiratory Flow at 25-75% of FVC (FEF25-
75%): It is the mid-half of the FVC, which is
independent of patient’s effort and an indicator for
obstruction in the small airways
• Cant measure RV, FRC, TLC

31. Maximum Voluntary Ventilation (MVV) or
maximum breathing capacity (MBC):
• It measures the speed and efficiency of filling &
emptying of the lungs during increased respiratory
effort.
• The maximum volume of air that can be breathed
in and out of the lungs in 1 minute by maximum
voluntary effort is MVV.
• It reflects peak ventilation in physiological
demands.
• The normal value is 150 ‐175 l/min.
• Subject is asked to breathe as quickly and as deeply as possible for 12 s.
• The measured volume is extrapolated to 1min ( i.e. measured volume X 5 = MVV in 1
min).
• As a general guide, the value should correlate closely to the FEV1 x 35.
• Periods longer than 15 s should not be allowed because prolonged hyperventilation leads
to fainting due to excessive lowering of arterial PCO2 and H+.
• MVV is markedly decreased in patients with Emphysema, Airway obstruction and with
poor respiratory muscle strength.

32. Lung Capacity
• Considered abnormal if <80% of predicted value.
• Physiological factors influencing VC:
 Height
 Sex
 Age
 Posture
 Strength of respiratory muscle

33. Factors affecting VC & FRC
VC = IRV+TV+ERV
FRC= RV+ ERV
 HEIGHT :directly proportional to ht.
• Tall : more lung volume
 SEX –
• more in males : large chest size, more muscle power, more BSA.
 POSTURE-
• decreases in supine position,
• increase in erect position
 ABDOMINAL CONDITIONS–
• Obesity: decrease in lung capacities
 MUSCLE PARALYSIS/WEAKNESS : decrease
 DISEASE OF RESPIRATORY system:
• Restrictive lung disease (e.g. fibrosis, Pregnancy) decrease,
• Emphysema : increase RV, FRC
 ANAESTHESIA : position + muscle paralysis + surgical abdominal
intervention + pain
 AGE – decreases with increasing age
 FRC does NOT change with age.

34. FRC does NOT change with age.

35. • Various lung volumes and capacities will
change when comparing the standing, sitting,
and supine (lying down) positions.
• Inspiratory and expiratory volumes will be
greater when sitting or standing than lying
down.
• This is explained by gravity pulling the
abdominal contents away from the diaphragm
when upright, therefore increasing the volume
of the thoracic cavity.
• In a supine position the patient’s TV, IRV and
ERV will decrease as the abdominal organs
rest against the diaphragm limiting its
movements.
• Thus, the vital capacity will decrease
Posture

36. Posture

37. Neonates

38. Age
https://derangedphysiology.com

39. Sex

40. Weight

41. Height
individuals with tall stature tend to have greater TLC than those with short
stature

42. DIFFERENT POSTURES AFFECTING VC
• POSITION
 TRENDELENBERG
LITHOTOMY
PRONE
RT. LATERAL
LT. LATERAL
• DECREASE IN VC
 14.5%
18%
10%
12%
10%
In post operative period if VC falls below 3 times VC–
artificial respiration is needed to maintain airway clear
of secretions.

43. Muscle of respiration: weakness leads to decreases in the lung capacities

44. Exercise

45. Spirometry paper graph

46. Forced vital capacity breath: graphs
(maximum inspiration followed by maximum expiration)

47. Common problems in spirometry

48. Common problems in spirometry

49. A flow-volume loop can have a sawtooth
profile. This can occur during exhalation or
inhalation. The sawtooth pattern is usually
generated either by airflow disturbances in
the upper airway or from tremors of the
respiratory muscles. It is associated with
sleep apnea, obesity, upper airway injury
and some neurological disorders but is not a
reliable diagnostic sign of these disorders
nor does its presence or absence indicate
the severity of the disorder.

50. A rounded peak flow can be an indication of an inadequate subject effort

51. An abrupt drop in
expiratory flow
usually indicates an
early termination of
exhalation.

52. A notch in a flow-
volume loop
indicates a cough or
other pause in
exhalation. Since
the FEV1/FVC ratio is
usually between 0.70
and 0.85, if this
notch appears during
the first three-
quarters of the
exhalation then the
pause likely affects
the FEV1.

53. A side-ways hop
at the beginning
of exhalation is an
indication of a
starting hesitation
and usually
indicates the
presence of
excessive back-
extrapolation.

54. DISEASES OF LUNG
OBSTRUCTIVE DISORDERS RESTRICTIVE DISORDERS
LUNG- SHRINKED
LUNG-
OVERINFLATED
EXHALE-LIMITED
INHALE-
NORMAL
EXHALE - LIMITED
INHALE-
RESTRICTED

56. OBSTRUCTIVE DISORDERS RESTRICTIVE DISORDERS
Inspiration Normal ↓
Expiration ↓ ↓
TLC INCREASED DECREASED

58. DISEASES OF LUNG
OBSTRUCTIVE DISORDERS RESTRICTIVE DISORDERS
Inspiration Normal ↓
Expiration ↓ ↓
TLC INCREASED DECREASED
PEFR ↓
N/↑
FEV1 ↓↓ N/↓
FVC ↓ ↓
FEV1/FVC LOW NORMAL

61. Lung Volumes and Obstructive and Restrictive
Disease?

63. Obstructive disorders

65. RESTRICTIVE
“R” word elongation,
i.e. tall and narrow
Peak flow PEFR is long,
VC is narrow
OBSTRUCTIVE
“O” word widening,
i.e. small and long
Peak flow PEFR is small,
VC is long
Overall Obstructive (O) vs Restrictive (R) ?
Write word OR
Same sequence … is the flow loop,
O is towards left,
R is towards right

66. Flow-volume loops typically become more
concave both with increasing age and with
an increase in the severity of airway
obstruction. This concavity has been
variously termed “scooping” or “coving”.

67. Normal vs. Obstructive vs. Restrictive

72. Upper airway obstruction patterns
• Detect obstructive lesion in the major
airways.
Characterize the lesion:
• LOCATION : Intra-thoracic or Extra-thoracic
• BEHAVIOUR OF LESION WITH
RESPIRATION: Fixed or Variable

73. During Exhalation During Inhalation
Upper airway obstruction patterns
Intrathoracic flow limitations will appear only
during exhalation
Extrathoracic flow limitations only appear
during inhalation

74. During Exhalation During Inhalation
Upper airway obstruction patterns
Intrathoracic flow limitations will appear only
during exhalation
Extrathoracic flow limitations only appear
during inhalation

75. Airway obstruction

76. Variable extra-thoracic obstruction
• A forced inspiration causes
negative transmural pressure
inside the airway which tends
to collapse it.
• During expiration, positive
pressure in airway decreases
obstruction.
• Hence, inspiratory flow is
reduced to a greater extent
than expiratory flow.
• Bilateral and unilateral vocal
cord paralysis, Vocal cord
constriction, Chronic
neuromuscular disorders,
Airway burns and Obstructive
sleep apnoea.

77. Variable intra-thoracic obstruction
• During forced expiration,
high pleural pressure develop
causing an increased
intrathoracic pressure,
thereby decreasing airway
diameter.
• The flow volume loop shows
a greater reduction in the
expiratory phase.
• During inspiration, lower
pleural pressure around
airway tends to decrease
obstruction.
• A flattening of expiratory limb
is observed.
• eg. Tracheomalacia,
Polychondritis, Tumors of

78. Fixed obstruction
• There is a constant airflow
limitation on inspiration
and expiration
• Benign stricture of
trachea, Goiter,
Endotracheal neoplasms,
and bronchial stenosis.

79. Tracheomalacia can cause the
largest airways to collapse
during exhalation. Although
this can be said to cause an
expiratory plateau the pattern
has some differences in that
the amount of collapse tends
to increase during exhalation
making it somewhat variable

81. Some other findings of PFT
• Bd response
• DLCO

82. Bronchodilator (Bd) response on PFT
Salbutamol or levo-salbutamol 4 puffs of
100Ug, 15-20 min before

84. DL-CO {DIFFUSING CAPACITY CARBON
MONOXIDE}

85. DL-CO and diseases

86. DL-CO and diseases

87. DL-CO and diseases

92. PFT values

93. SPIROMETRY INTERPRETATION
What do the numbers mean?
FVC
• Interpretation of % predicted:
• 80-120% Normal
• 70-79% Mild reduction
• 50%-69% Moderate reduction
• <50% Severe reduction
FEV1
• Interpretation of % predicted:
• 80-120% Normal
• 70-75% Mild
• 60-69% Moderate
• 50-59% Moderately Severe
• <49-35 % Severe
• <35% Very Severe
RESULTS are expressed as % predicted of a predicted normal value of a person with the same age, sex
and height.

94. SPIROMETRY INTERPRETATION
What do the numbers mean?
FEF 25-75%
• Interpretation of % predicted:
• >79% Normal
• 60-79% Mild obstruction
• 40-59% Moderate obstruction
• <40% Severe obstruction
FEV1/FVC
• Interpretation of absolute value:
• ≥ 80 Normal
• ≤ 79 Abnormal
RESULTS are expressed as % predicted of a predicted normal value of a person with the same age, sex
and height.

95. GOLD Classification for COPD severity

96. Stepwise approach

97. Steps:
• calculate FEV1
• Calculate FVC
• Calculate FEV1/FVC
• Calculate TLC
• Calculate DLCO
• See Bd reversibility
Stepwise analysis

100. Examples