This document discusses pulmonary function tests (PFTs), including their goals, uses, limitations, procedures, and interpretations. PFTs are used to assess lung function before surgeries and characterize any pulmonary dysfunction. Key information obtained from PFTs includes measurements of forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), their ratio (FEV1/FVC), and peak expiratory flow rate. Interpretations of these values can indicate restrictive or obstructive lung disease. The document outlines how PFTs are performed using portable devices or clinic spirometers and flow-volume loops.

1. by: Dr ZIKRULLAH

2. • Pulmonary function tests have been used traditionally in
the preoperative assessment before any major surgery.
• GOALS OF PFT
– Determination of any significant impairment of lung
function.
– Degree and severity of impairment
– Characterize any pulmonary dysfunction physiologically
as obstructive or restrictive

3. – Identify the site of airway obstruction
– Evaluate the risk of procedures on lung
– To assess prognosis and response to bronchodilator
therapy
– Evaluate airway hyper-reactivity .

4.  To identify patients at increased risk of morbidity and
mortality, undergoing pulmonary resection
 To wean patient from ventilator in icu.
 Medicolegal- to assess lung impairment as a result of
occupational hazard.
 Epidemiological surveys- to assess the hazards to
document incidence of disease

5.  Patients with chronic pulmonary disease.
 Smoker.
 Patients with dyspnoea on exertion ( noncardiac).
 Patients with chest wall and spinal deformities.
 Morbidly obese patients.
 Age > 70 years.
 Patients undergoing upper abdominal surgeries.
 Patients undergoing thoracic surgeries.
 Presence of respiratory symptoms such as cough
and wheeze.
Patients requiring PFT

6. Limitations of tests:
 The maneuver is highly dependent on patient cooperation and
effort, and is normally repeated at least three times to ensure
reproducibility.
 Since results are dependent on patient cooperation, FEV1 and
FVC can only be underestimated.
 Spirometry can only be used:
 On children old enough to comprehend and follow the
instructions given (typically about 4-5 years old), and
 Only on patients who are able to understand and follow
instructions - thus, this test is not suitable for patients who are
unconscious, heavily sedated, or have limitations that would
interfere with vigorous respiratory efforts.

7.  Where are PFTs done?
 In the clinic
 At the bedside.
 PFTs done at the bedside are called bedside PFTs.
 PFTs done in the clinic are done using various types of
spirometers.

8.  Various types of bedside PFTs performed are as
follows:
1. Snider’s match blowing test
2. Forced expiratory time
3. Seberese’s single breath count
4. Seberese’s breath holding test
5. Cough test
6. Debono’s whistle test
7. Wright’s peak flow meter
8. Spirometry with pocket sized spirometer

9. 1. Snider’s Match Blowing test
 Mouth wide open
 Match held at 6 inches or 15 cm distance
 Chin supported
 No head tilting
• No head movement
• No air movement in the room
 Match stick and mouth at the same level

10.  Can not blow out a match
 MBC < 60 L/min
 FEV1 < 1.6L
 Able to blow out a match
 MBC > 60 L/min
 FEV1 > 1.6L

11.  Modified Snider’s test
 3 inches MBC > 40 L/min
 6 inches MBC > 60 L/min
 9 inches MBC > 150 L/min
 2. FORCED EXPIRATORY TIME
After deep breath, exhale maximally and forcefully & keep
stethoscope over trachea & listen.
 NORMAL FET : 3-5 SECS.
 FET < 3 Sec (Restrictive lung )
 FET > 6 sec (Obstructive lung )

12. 3. SEBERESE’S SINGLE BREATH COUNT
 Patients is asked to take a deep breath followed by counting
1,2,3……….. till the time he cannot hold breath .
 Normal - 30-40 Counts
 Indicates vital capacity
 Shows trend of deteriorating or improving pulmonary
function in pre op & post op patients

13. 4. SEBARESE ‘S BREATH HOLDING TEST
 Subject is asked to take a normal tidal inspiration and hold
breath
 (N) ≥ 40 Sec
< 15 Sec is a C/I for elective surgery
25- 30 SEC - 3500 ml VC
20 – 25 SEC - 3000 ml VC normal value of
15 - 20 SEC - 2500 ml VC VC = 3100- 4800 ml
10 - 15 SEC - 2000 ml VC or
5 - 10 SEC - 1500 ml VC 60- 70ml/kg

14. 5. COUGH TEST
DEEP BREATH F/BY COUGH
 ABILITY TO COUGH
 STRENGTH
 EFFECTIVENESS
INADEQUATE COUGH IF:
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 paraoxysms of
coughing – patient susceptible for pulmonary
Complication.

15. 6. DEBONO WHISTLE BLOWING TEST:
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 subject blows → whistle blows, leak hole is
gradually increased till the intensity of whistle
disappears.
At the last position at which the whistle can be blown
the PEFR can be read off the scale.

16. DEBONO’S WHISTLE

17. 7. WRIGHT’S PEAK FLOW
METER.
 : Measures PEFR (Peak Expiratory
Flow Rate)
 Values < 200 L/ min in surgical
candidates suggest impaired
cough efficiency
 (N) Males – 450 – 700 L/min
 Females – 300 – 500 L/min
Zones
Green – Good control
Yellow – Caution
required
Red - Emergency

18. 8. SPIROMETRY WITH POCKET SIZED
SPIROMETERS
• VC & FEV1 Can be readily performed

19. What is spirometry ??
Spirometry is a measure of airflow and lung volumes
during a forced expiratory maneuver from full inspiration.
How to do it ??
- Stand or sit up straight (The patient places a clip over the
nose )
- Inhale maximally
- Get a good seal around mouthpiece of the spirometer
Blow out as hard AND as fast as possible and count for at
least 6 seconds.
- Record the best of three trial

20. PORTABLE SPIROMETERS

21. PFT DONE USING SPIROMETERS
 There are 2 primary kind of spirometers:
1. Primary volume measuring spirometers (PVM)
2. Primary flow measuring spirometers (PFM)
 Procedure:
 Generally, the patient is asked to take the deepest
breath they can, and then exhale into the sensor as hard
as possible, for as long as possible.
 It is sometimes directly followed by a rapid inhalation
(inspiration), in particular when assessing possible
upper airway obstruction.

22.  Sometimes, the test will be preceded by a period of quiet
breathing in and out from the sensor (tidal volume), or
the rapid breath in (forced inspiratory part) will come
before the forced exhalation.
 During the test, soft nose clips may be used to prevent air
escaping through the nose.
 Filter mouthpieces may be used to prevent the spread of
microorganisms, particularly for inspiratory maneuvers.

23. Primary volume measuring spirometers
 A volume-time curve is generated, showing volume (liters)
along the Y-axis and time (seconds) along the X-axis
 Flow is measured indirectly:
 Flow = volume (lit.)/ time(sec)
 They work by displacing or collecting volume of air in a
chamber of some kind.
 Examples:
 Water sealed spirometers
 Dry seal spirometers
 Bellows spirometers
 Rotor spirometer.

24.  Four volumes
 Four capacities

26.  Forced Vital Capacity (FVC):
 It is the maximum volume of gas that can be expired, when the
subject tries to expire as forcefully and rapidly as possible
after a maximal inspiration to total lung capacity.
 Most common PFT measured
 It assesses deep breathing and effective cough
 Values <15 ml/kg– increased post-op pulmonary complication
 FEV1 (forced expiratory volume in 1 sec)
 This is the amount of air that you can forcibly blow out in one
second, measured in liters.
 Along with FVC it is considered one of the primary indicators
of lung function.

27.  Volume Time Graph (spirogram)
The volume is plotted against the time, it displays the
expiration.

28.  FEV1/FVC:
 This is the ratio of FEV1 to FVC.
 In healthy adults this should be approximately 75–80%.
This value is critically important in the diagnosis of
obstructive and restrictive diseases

29.  FEF 25-75% (forced expiratory flow
25–75%)
 This is the average flow of air coming
out of the lung during the middle
portion of the expiration.
 Earliest indicator to get deranged in
obstructive airway disease.
 Unlike FEV1 which is dependent on
patient’s efforts, it is independent of
patients efforts.
 It represents flow through the small (<2
mm) airways.
 N ormal value is 100 +/- 25% of
predicted
 Approx 4.7L/sec

30. RESTRICTIVE Vs OBSTRUCTIVE
VALUE RESTRICTIVE OBSTRUCTIVE
DEFINITION Proportional decrease in all
lung volumes
Small airway obstruction to
expiratory flow
FVC N or slightly increased
FEV1 N or slightly
FEV1 / FVC NORMAL
FEF 25-75% NORMAL
FRC N or increased (gas trapping)
TLC
Mid VC flow NORMAL
N or increased (gas trapping)

31. 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:
 >75% Normal
 60%-75% Mild obstruction
 50-59% Moderate
obstruction
 <49% Severe obstruction

32.  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 or higher
Normal
 79 or lower
Abnormal

33. Primary Flow Measuring Spirometers
 A flow-volume loop is generated, which graphically depicts
the rate of airflow on the Y-axis and the total volume
inspired or expired on the X-axis.
 PFMs measure flow directly by using a pneumotachometer.
 Volume = flow rate (l/sec)*time (sec)
 3 primary types of pneumotachometer
 Differential pressure pneumotachometer
 Thermal anemometers
 Ultrasonic sensor spirometers

34.  Flow volume loop showing
successful FVC maneuver.
• Positive values
represent expiration,
negative values
represent inspiration.
.

35.  The contour of the loop assists in the diagnosis
and localization of airway obstruction as different
lung disorders produce distinct ,easily recognized
pattern.

37.  ASTHMA :- 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
 FVC may be
 FEV1/FVC <50%
 RV is markedly increased (400%)

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

39. Flow volume loop in Restrictive lung disease :
 Full lung expansion is prevented by fibrotic tissue in
the lung parenchyma and the FVC is reduced.
 Both FEV1 and FVC may be reduced because the lungs are
small and stiff ,but the peak expiratory flow may be
preserved or even higher than predicted leads to
tall,narrow and steep flow volume loop in expiratory
phase.

40. Fixed obstruction
1. Post intubation stenosis
2. Goiter
3. Endotracheal neoplasms
4. Bronchial stenosis
Maximum airflow is limited to a similar extent in both
inspiration and expiration

41. Variable extrathoracic obstruction:
 1. Bilateral and unilateral vocal cord paralysis
 2. Vocal cord constriction
 3. Chronic neuromuscular disorders
 4. Airway burns
 • Forced inspiration‐ negative transmural
pressure inside airway tends to collapse it
 • Expiration – positive pressure in airway
decreases obstruction
 • inspiratory flow is reduced to a greater extent
than expiratory flow

43. variable intrathoracic obstruction
1.Tracheomalacia
2. Polychondritis
3. Tumors of the lower trachea or main bronchus.
 During forced expiration – high pleural
pressure – increased intrathoracic pressure ‐
decreases 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

46. CONTRAINDICATIONS
 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
 History of syncope associated with forced exhalation

47. THANKS