Pulmonary function tests (PFTs) objectively measure lung function through tests of lung volumes, airway function, and gas exchange. Key PFTs include spirometry, which measures volumes of air inhaled and exhaled over time; tests of static lung volumes like total lung capacity and functional residual capacity; diffusing capacity tests that evaluate gas exchange; and exercise tests. PFTs are used to detect and monitor respiratory diseases, evaluate treatments, and assess surgical risk. Spirometry specifically measures volumes like forced vital capacity and forced expiratory volume in one second to evaluate airway obstruction. Interpretation compares values to predicted normals. Bedside PFTs also exist to rapidly assess lung function at the point of care

1. BY:-
Abhishek Verma J R II
PG Department of General Medicine
Rohilkhand Medical College And Hospital

2. Pulmonary Function Tests
 The term encompasses a wide variety of objective tests to
assess lung function.
 Provide objective and standardized measurements for
assessing the presence and severity of respiratory
dysfunction.
 Evaluates one or more major aspects of the respiratory
system:
 Lung volumes
 Airway function
 Gas exchange
vide valuable clinical information.

3. Includes..
 Spirometry
 Bronchial provocation tests
 Static lung volumes
 Carbon monoxide diffusing capacity
 Alveolar arterial oxygen gradient
 Exercise testing
 Bed side PFT’s

4. Indications
 Detect disease
 Evaluate extent and monitor course of disease
 Evaluate treatment
 Measure effects of exposures
 Assess risk for surgical procedures

5. 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

6. Spirometry
 Spirometry is a medical test that measures
the volume of air an individual inhales or
exhales as a function of time.
 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. Indications:
1. Symptoms and clinical signs
 Dyspnea with or without or wheezing
 Chest pain or orthopnea
 Cough for a longer time with or without phlegm production
 Cyanosis
 Decreased or unusual breath sounds
2. Abnormal chest x-ray (e.g. Hyperinflation)
3. Abnormal blood gases (hypoxemia, hypercapnia)
4. Abnormal laboratory findings (e.g. polycythemia)
5. Monitoring of known pulmonary diseases

8. Contd..
6. Assessing severity or progression of disease (e.g.
asthma, COPD)
7. To screen individuals at risk of having pulmonary
disease (eg. Smokers ,Individuals in occupations with
exposures to injurious subs.)
8. Assess prognosis (after ttt, lung transplant ...etc.)
9. Assess health status before beginning strenuous
physical activity

9. Contraindications for spirometry
1. Acute disorders affecting test performance (e.g.
vomiting, nausea, vertigo)
2. Hemoptysis of unknown origin (FVC maneuver may
aggravate underlying condition.)
3. Pneumothorax
4. Recent abdominal or thoracic surgery
5. Recent eye surgery (increases in intraocular pressure
during spirometry)
6. Recent myocardial infarction or unstable angina
7. Thoracic, abdominal, or cerebral aneurysms (risk of
rupture because of increased thoracic pressure)

12. Terminology & Interpretation
 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)
 IInterpretation of % predicted:
 Mild - 70-79% of predicted
 Moderate - 60-69% of predicted
 Moderately severe - 50-59%
 Severe - 35-49% of predicted
 Very severe - Less than 35% of predicted

13.  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
Interpretation of % predicted:
 Mild - 70-79% of predicted
 Moderate - 60-69% of predicted
 Moderately severe - 50-59%
 Severe - 35-49% of predicted
 Very severe - Less than 35% of predicted

14.  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
 Depends heavily on FVC
 Early termination artificially
increases it.
 Interpretation of % predicted:
 >60% Normal
 40-60% Mild obstruction
 20-40% Moderate
obstruction
 <10% Severe
obstruction

15. MVV
 It's the maximum volume of
air which can be respired in
1min. By deepest and fastest
breathing (test of entire
respiratory system).
 MVV = FEV1 x 35
 Reflects the status of the
respiratory muscles,
compliance of the thorax-
lung complex, and airway
resistance
 N- 150-175 L/min

16. Categories of Disease

17. Flow-Volume Loop
 Illustrates maximum
expiratory and inspiratory
flow-volume curves
 Normally:
FEF50 / FIF50 = 0.8
• Steep exp. Curve 1st (max
effort) then linear drop
(dynamic compression of
AWs)

18.  It's a curve representing the relation between flow rates
and volume during VC divided into maximum expiratory
(from TLC to RV, not effort dependant) and inspiratory
(from RV to TLC, effort dependant) flow volume curves.
 Measured by: patient must breathe several breaths in
tidal breathing  maximum inspiration to TLC 
maximum expiration to RV  maximum inspiration again.

19. Normal & abnormal FV Loops

20. Lung Volumes
Measured through various methods
 Dilutional: helium, 100% oxygen
 Body plethysmography
 Nitrogen washout

21. HELIUM DILUTION METHOD
Patient breathes in and out of a spirometer filled with 10%
helium and 90% o2, till conc. In spirometer and lung
becomes same (equilibirium).
As no helium is lost; (as it is insoluble in blood)
C1 X V1 = C2 ( V1 + V2)
V2 = V1 ( C1 – C2)
C2
V1= VOL. OF SPIROMETER
V2= FRC
C1= Conc.of He in the spirometer before equilibrium
C2 = Conc, of He in the spirometer after equilibrium

22. TOTAL BODY PLETHYSMOGRAPHY
Subject sits in an air tight box. At the end of normal exhalation
– shuttle of mouthpiece closed and pt. is asked to make resp.
efforts. As subject inhales – expands gas volume in the lung
so lung vol. increases and box pressure rises and box vol.
decreases.
BOYLE’S LAW:
PV = CONSTANT (at constant temp.)
For Box – p1v1 = p2 (v1- ∆v)
For Subject – p3 x v2 =p4 (v2 - ∆v)
P1- initial box pressure P2- final box pressure
V1- initial box vol. ∆ v- change in box vol.
P3- initial mouth pressure, p4- final mouth pressure
V2- FRC

23. DIFFERENCE BETWEEN THE TWO
METHODS
 In healthy people there is very little difference.
 Gas dilution technique measures only the communicating
gas volume.
 Thus,
 Gas trapped behind closed airways
 Gas in pneumothorax
 => are not measured by gas dilution technique, but
measured by body plethysmograph

24. N2 WASH OUT METHOD
 Following a maximal expiration (RV) or
normal expiration (FRC), Pt. inspires 100%
O2 and then expires it into spirometer ( free
of N2) → over next few minutes (usually 6-7
min.), till all the N2 is washed out of the
lungs. N2 conc. of spirometer is calculated
followed by total vol.of AIR exhaled. As air
has 80% N2 → so actual FRC/RV is
calculated.

25. TESTS FOR GAS EXCHANGE
FUNCTION
1) ALVEOLAR-ARTERIAL O2 TENSION GRADIENT:
 Sensitive indicator of detecting regional V/Q inequality
 Normal value in young adult at room air = 8 mmhg to upto
25 mmhg in 8th decade (d/t decrease in PaO2)
 Abnormal high values at room air is seen in asymptomatic
smokers & chr. Bronchitis (min. symptoms)
PAO2 = PIO2 – PaCo2
R

26. Contd..
2) DYSPNOEA DIFFENRENTIATION INDEX (DDI):
- To differentiate dyspnoea due to resp/ cardiac diseases
DDI = PEFR x PaCO2
1000
- DDI- Lower in resp. pathology

27. Contd..
3) DIFFUSING CAPACITY OF LUNG (DL): defined as
the rate at which gas enters into bld. divided by its
driving pressure
DRIVING PRESSURE: gradient b/w alveoli & end
capillary tensions.
Fick’s law of diffusion : Vgas = A x D x (P1-P2)
T
D= diffusion coeff= solubility
√MW

28. Contd..
 DL IS MEASURED BY USING CO, because:
A) High affinity for Hb which is approx. 200 times that
of O2 , so does not rapidly build up in plasma
B) Under normal condition it has low blood
concentration ≈ 0
C) Therefore, pulmonary concentration≈0

29. SINGLE BREATH TEST USING CO
 Pt inspires a dilute mixture of CO and hold the breath
for 10 secs.
 CO taken up is determined by infrared analysis:
DlCO = CO ml/min/mmhg
PACO – PcCO
 N range 20- 30 ml/min./mmhg.
 DLO2 = DLCO x 1.23

30. 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

31. TESTS FOR CARDIOPLULMONARY
INTERACTIONS
Reflects gas exchange, ventilation,
tissue O2, CO.
QUALITATIVE- history, exam, ABG,
stair climbing test
QUANTITATIVE- 6 minute walk test

32. 1) STAIR CLIMBING TEST:
 If able to climb 3 flights of stairs without stopping/dypnoea at
his/her own pace- ↓ed morbidity & mortality
 If not able to climb 2 flights – high risk
2) 6 MINUTE WALK TEST:
- Gold standard
- Cardiopulmonary reserve is measured by estimating max. O2
uptake during exercise
- Modified if pt. can’t walk – bicycle/ arm exercises
- If pt. is able to walk for >2000 feet during 6 min pd,
- VO2 max > 15 ml/kg/min
- If 1080 feet in 1 min : VO2 of 12ml/kg/min
- Simultaneously oximetry is done & if Spo2 falls >4%- high risk

33. BED SIDE PFT
1) Sabrasez breath holding test:
• Ask the patient to take a full but not too deep breath & hold it as
long as possible.
>25 SEC.-NORMAL Cardiopulmonary Reserve (CPR)
15-25 SEC- LIMITED CPR
<15 SEC- VERY POOR CPR (Contraindication for elective surgery)
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

34. BED SIDE PFT
2) Single breath count:
After deep breath, hold it and start counting till the next breath.
 N- 30-40 COUNT
 Indicates vital capacity
3) SCHNEIDER’S MATCH BLOWING TEST: MEASURES
Maximum Breathing Capacity.
Ask to blow a match stick from a distance of 6” (15 cms) with-
 Mouth wide open
 Chin rested/supported
 No purse lipping
 No head movement
 No air movement in the room
 Mouth and match at the same level

35.  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
 MODIFIED MATCH TEST:
DISTANCE MBC
9” >150 L/MIN.
6” >60 L/MIN.
3” > 40 L/MIN.

36. 4) 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.
5) FORCED EXPIRATORY TIME:
After deep breath, exhale maximally and forcefully & keep
stethoscope over trachea & listen.
N FET – 3-5 SECS.
OBS.LUNG DIS. - > 6 SEC
RES. LUNG DIS.- < 3 SEC

37. 6) WRIGHT PEAK FLOW METER: Measures PEFR (Peak
Expiratory Flow Rate)
N – MALES- 450-700 L/MIN.
FEMALES- 350-500 L/MIN.
<200 L/ MIN. – INADEQUATE COUGH
EFFICIENCY.
7) 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.

38. 9) MICROSPIROMETERS – MEASURE VC.
10) BED SIDE PULSE OXIMETRY
11) ABG.

39. THANK YOU