PFT known as pulmonary function test is used to assess pulmonary function of the patient with any type of obstructive and restrictive disease.

1. PULMONARY FUNCTION TEST
Dr. Anand Patel
M.P.T. Cardio-Respiratory
Assistant professor

2. INTRODUCTION
• Pulmonary function tests or lung function tests are useful in assessing
the functional status of the respiratory system both in physiological
and pathological conditions.
• MEASURE:
(1) Dynamic flow rates of gases through the airways,
(2) Lung volumes and capacities, and
(3) The ability of the lungs to diffuse gases
• Identify the presence and type of pulmonary impairments and the degree of
pulmonary disease present.

3. INDICATIONS
• To identify and quantify changes in pulmonary function
• To evaluate need and quantify therapeutic effectiveness
• To perform epidemiologic surveillance for pulmonary disease
• To assess patients for risk for postoperative pulmonary complications
• To determine pulmonary disability

4. Contraindications
• acute, unstable cardiopulmonary problems, such as
• hemoptysis,
• pneumothorax,
• myocardial infarction,
• pulmonary embolism, and
• patients with acute chest or abdominal pain should not be tested.
• Patients who have nausea and who have recently vomited
• Recent cataract removal surgery

5. Lung Volumes and Capacities
• 4 lung volumes and 4 lung capacities
Tidal volume (VT),
Inspiratory reserve volume
(IRV),
Expiratory reserve volume
(ERV),
Residual volume
Total lung capacity
Inspiratory capacity
Vital capacity
Functional Residual Capacity

6. LUNG VOLUMES
• TIDAL VOLUME: Tidal volume (TV) is the volume of air breathed in
and out of lungs in a single normal quiet respiration. Tidal volume
signifies the normal depth of breathing.
• Normal value: 500ml
• INSPIRATORY RESERVE VOLUME: Inspiratory reserve volume (IRV) is
an additional volume of air that can be inspired forcefully after the
end of normal inspiration.
• Normal value: 3,300 ml

7. • EXPIRATORY RESERVE VOLUME: Expiratory reserve volume is the
additional volume of air that can be expired out forcefully, after
normal expiration.
• Normal value: 1000 ml
• RESIDUAL VOLUME: Residual volume (RV) is the volume of air
remaining in lungs even after forced expiration. Normally, lungs
cannot be emptied completely even by forceful expiration. Some
quantity of air always remains in the lungs even after the forced
expiration.
• Normal value: 1200ml

8. LUNG CAPACITIES
• INSPIRATORY CAPACITY: Inspiratory capacity (IC) is the maximum
volume of air that is inspired after normal expiration. It includes tidal
volume and inspiratory reserve volume.
• IC = TV + IRV
500 + 3,300 = 3,800 mL
• VITAL CAPACITY: Vital capacity (VC) is the maximum volume of air that
can be expelled out forcefully after a deep inspiration. VC includes
inspiratory reserve volume, tidal volume and expiratory reserve
volume.
• VC = IRV + TV + ERV
• = 3,300 + 500 + 1,000 = 4,800 mL

9. • FUNCTIONAL RESIDUAL CAPACITY: Functional residual capacity (FRC)
is the volume of air remaining in lungs after normal expiration.
Functional residual capacity includes expiratory reserve volume and
residual volume.
• FRC = ERV + RV = 1,000 + 1,200 = 2,200 mL
• TOTAL LUNG CAPACITY:
• Total lung capacity (TLC) is the volume of air present in lungs after a deep
inspiration. It includes all the volumes.
• TLC = IRV + TV + ERV + RV
• = 3,300 + 500 + 1,000 + 1,200 = 6,000 mL

12. PFT
• INCLUDES:
• SPIROMETRY
• LUNG VOLUMES AND CAPACITIES
• GAS TRANSFER

13. SPIROMETRY
• SPIROMETRY: Measures of breathing
• Spiro means breathing
• Metry means measurement
• Spirometry is a method of assessing lung function by measuring the
total volumes of air the patient can expel from the lungs after a
maximal inhalation.
• It measure how much and how quickly air can be expelled following
deep breath
• Spirometry is an effort-dependent test that requires careful patient
instruction, understanding, coordination, and cooperation

15. • Measures:
• Forced vital capacity (FVC)
• Forced expiratory volume in one second. (FEV1)
• FEF25-75 - Forced Expiratory Flow between 25% to 75% of forced vital capacity
• peak expiratory flow rate (PEFR)
• Fev1/FVC

16. Forced vital capacity
• Volume of air that can be maximally and forcibly expelled from the
lung after a deep inhalation.
• Depends on:
• Lung elasticity
• Size of airways
• Resistance to flow along these airways

18. Fev1/FVC
• Expressed as percentage
• In normal adult, the ratio ranges from 75%-85%.
• Childrens may have higher flow.
• Obstructive condition: Decreased
• Restrictive condition: Normal or Increase

19. PEFR
• Maximum rate at which air can be expired after a deep inspiration.
• Normal values: 400L/min
• Measured by peak flow meter
• Pefr reduced in obstructive disease more than restrictive disease.

20. Before the test- avoid
• Alcohol – 4hours
• Large meal -2 hours
• Smoking – 1hr
• Vigorous exercise- 30 minutes
• Wear loose, comfortable clothing
• Avoid use of bronchodilators

21. Prior to test
• Gain verbal consent
• Check for contraindication
• Gain accurate height and weight
• Patient should sit comfortable and upright
• Technique in detail should be explained

22. Spirometry maneuver
• A few normal tidal respiration
• Then deep inspiration
• Breath holding,
• Very forced and fast expiration as hard as patient can
• Then deep, quick and full inspiration.
• Repeat atleast 3 times.
• Take the best readings.

23. Forced vital capacity
• Possible causes of a decrease in FVC:
• 1. The problem may be with the lung itself. There may have been a
resectional surgical procedure or areas of collapse. Various other
conditions can render the lung less expandable, such as fibrosis,
congestive heart failure, and thickened pleura. Obstructive lung
diseases may reduce the FVC by limiting deflation of the lung.
• 2. The problem may be in the pleural cavity, such as an enlarged
heart, pleural fluid, or a tumor encroaching on the lung.

24. • 3. Another possibility is restriction of the chest wall. The lung cannot
inflate and deflate normally if the motion of the chest wall (which
includes its abdominal components) is restricted.
• 4. Inflation and deflation of the system require normal function of the
respiratory muscles, primarily the diaphragm, the intercostal muscles,
and the abdominal muscles.

26. FEV1
• Fev1 is the volume of air exhaled in the first second of the FVC test.
• Normal value depends on patient age, size, sex and race.
• When flow rates are slowed by airway obstruction, as in emphysema,
the FEV1 is decreased by an amount that reflects the severity of the
disease.
• The FVC may also be reduced, although usually to a lesser degree.

27. FEV1 /FVC
• The FEV1 /FVC ratio is generally expressed as a percentage.
• The amount exhaled during the first second is a fairly constant
fraction of the FVC, irrespective of lung size.
• In the normal adult, the ratio ranges from 75% to 85%, but it
decreases somewhat with aging.
• Children have high flows for their size, and thus, their ratios are
higher, up to 90%.

28. • Significance:
• It aids in quickly identifying persons with airway obstruction
• The ratio is valuable for identifying the cause of a low FEV
• In pulmonary restriction, the FEV1 and FVC are decreased
proportionally; hence, the ratio is in the normal range, as in the case
of fibrosis.

29. • How to determine whether airway obstruction or a restrictive:
• A low FEV1 with a normal ratio usually indicates a restrictive process
• A low FEV1 and a decreased ratio signify a predominantly obstructive process.

32. MAXIMAL VOLUNTARY VENTILATION
• The test for maximal voluntary ventilation (MVV) is an athletic event.
• The subject is instructed to breathe as hard and fast as possible for 10
to 15 seconds.
• The result is extrapolated to 60 seconds and reported in liters per
minute.
• A low MVV can occur in obstructive disease, in restrictive disease, in
neuromuscular disease, in heart disease, in a patient who does not
try or who does not understand, or in a frail patient

34. MAXIMAL INSPIRATORY FLOW
• With spirometer systems that measure both expiratory and
inspiratory flows, the maximal inspiratory flow (MIF) can be
measured.
• The subject exhales maximally (the FVC test) and then immediately
inhales as rapidly and completely as possible, producing an
inspiratory curve.
• The combined expiratory and inspiratory FV curves form the FV loop.
• Increased airway resistance decreases both maximal expiratory flow
and MIF

38. Reversibility
• Based on the initial results of baseline spirometry, additional testing
of pulmonary mechanics is often desirable.
• If the baseline test indicates airway obstruction, determining the
reversibility of the obstruction is indicated.
• RTs also use the concept of reversibility when evaluating routine
therapy by performing spirometry before and after therapy.
• In the laboratory, the FVC maneuver is often repeated after the
patient has received a bronchodilator administered by small volume
nebulizer or metered dose inhaler.

39. • Reversibility of the airway obstruction indicates effective therapy.
• Although improvement in other measurements of pulmonary
function is sometimes used, reversibility is defined as a 15% or
greater improvement in FEV1 and at least a 200-ml increase in FEV1.
• % Improvement = PostFEV1 – PreFEV1/ PreFEV1 * 100

40. Bronchoprovocation
• When the patient’s history suggests episodic symptoms of
hyperreactive airways and airway obstruction, such as seasonal or
exercise-induced wheezing, and the results of baseline spirometry are
normal, performing a bronchial provocation may be indicated.
• Bronchial provocation testing uses an agent to stimulate a
hyperreactive airway response and to create airway obstruction.
• The procedure usually begins with the patient inhaling a normal
saline aerosol and then repeating the FVC maneuver.
• Some very sensitive patients exhibit hyperreactive airways with saline
alone; a positive response to saline is defined as a decrease in FEV1 of
10% or greater.

41. • The methacholine provocation protocol systematically exposes the patient
to increasing dosages of methacholine. Usually starting with a low dose of
0.03 mg/ml, patients inhale methacholine aerosol and then repeat the FVC
maneuver.
• A positive response to methacholine is defined as a decrease in FEV1 of
20% or greater.
• If a positive response does not occur, the methacholine dose is doubled to
0.06 mg/ml, and the FVC maneuver is repeated.
• The process of “double-dosing” and performing FVC maneuvers continues
until there is a positive response or until the full dose, 16 mg/ml, is given.
• If a positive response occurs, treatment with a fast-acting bronchodilator is
indicated, and sometimes administering O2 is helpful

42. Static lung volume
• The three most commonly used methods of measuring the FRC are
• Nitrogen washout,
• Inert gas dilution, and
• Plethysmography.

43. Helium Dilution
• The helium dilution technique for measuring lung volumes uses a closed,
rebreathing circuit.
• This technique is based on the assumptions that the patient has no He in
his or her lungs, and that an equilibration of He can occur between the
spirometer and the lungs.
• First, volume (V1) and concentration (C1) of He are measured at the
beginning of the test.
• Next, the valve is turned to connect the patient to the breathing circuit,
usually at the resting expiratory level of the FRC.
• The patient is connected to the He-air mixture, and the concentration of
He is diluted slowly by the patient’s lung volume.

44. • The patient is connected to the He-air mixture, and the concentration
of He is diluted slowly by the patient’s lung volume.
• Wearing nose clips, the patient breathes normally in the closed
circuit.
• Exhaled CO2 is absorbed with soda lime, and O2 is added at a rate
equal to the patient’s O2 consumption.
• A constant volume is maintained to ensure accurate He concentration
measurements.
• The patient rebreathes the gas in the system until equilibrium of He
concentration is established.

45. • In healthy patients and patients with a small FRC, equilibration occurs
in 2 to 5 minutes.
• Patients with obstructive lung disease may require 20 minutes to
equilibrate because of slow gas mixing in the lungs.

47. Nitrogen Washout Method
• The nitrogen washout technique uses a nonrebreathing or open
circuit.
• The technique is based on the assumptions that the N concentration
in the lungs is 78% and in equilibrium with the atmosphere, that the
patient inhales 100% O2, and that the O2 replaces all of the N in the
lungs.
• Similar to the He dilution technique, the patient is connected to the
system at FRC.
• The patient’s exhaled gas is monitored, and its volume and N
percentage are measured.

49. Plethysmography
• The principle of plethysmography is based on Boyle’s law, which
states that the product of the pressure (P) and volume (V) of a gas is
constant under constant temperature conditions.
• The whole-body plethysmograph consists of a sealed chamber in
which the patient sits.
• Pressure transducers (electronic manometers) measure pressure at
the mouth and in the chamber.
• The plethysmographic method measures essentially all the gas in the
lung, including that in poorly ventilated areas.

51. Diffusing Capacity
• The third major category of pulmonary function testing is measuring
the ability of the lungs to transfer gases across the alveolar-capillary
membrane.
• Vgas = DL× − ( P1-p2 )
• Vgas = Amount of the gas transferred into the lungs
• P1 = Partial pressure of the gas in the alveolus
• P2 = Partial pressure of the gas in the pulmonary capillary

52. • Carbon monoxide (CO) is the gas normally used to measure the DL.
• The diffusing capacity of the lung for carbon monoxide (DLCO) is expressed
in ml/min/mm Hg under standard temperature and pressure and dry
conditions.
• CO is used as the transfer gas because CO is similar to O2 in important
ways.
• CO and O2 have similar molecular weights and solubility coefficients.
Similar to O2, CO also chemically combines with hemoglobin (Hb).
• CO has a very high affinity for Hb and diffuses rapidly into the pulmonary
blood, keeping the pulmonary capillary partial pressure of CO near zero.

53. An average normal value is 20 to 30 mL/min/mm Hg; that is, 20 to 30
mL CO is transferred per minute per mm Hg difference in the driving
pressure of CO, namely, the difference between the partial pressure of
CO in alveolar air and blood.
The normal values depend on age, sex , and size.

54. Causes of Increased Dlco
• 1. Supine position: Rarely is the Dlco measured while the subject is supine,
but this position produces a higher value because of increased perfusion
and blood volume of the upper lobes.
• 2. Exercise: It is difficult to hold one’s breath for 10 seconds during exercise.
When this is done just after exercise, however, Dlco is increased because of
increased pulmonary blood volumes.
• 3. Asthma: Some patients with asthma, especially when symptom-free,
have an increased Dlco, possibly because of more uniform distribution of
pulmonary blood flow.
• 4. Obesity: The Dlco can be increased in obese persons, especially those
who are massively obese. This increase is thought to be due to an
increased pulmonary blood volume.