Pulmonary function tests (PFTs) evaluate lung function through tests of lung volumes, gas flow rates, and gas exchange. Spirometry measures volumes like forced vital capacity (FVC) and flows like forced expiratory volume in 1 second (FEV1). Flow-volume loops graphically represent forced inspiration and expiration, identifying obstructive or restrictive lung diseases. PFTs classify pulmonary diseases as obstructive, restrictive, or combined based on the test results.

1. PFT
By: Dr. Rekha Marbate

2. Content
• Introduction
• Method of pulmonary function test
• Normal values
• Interpretation

3. Introduction
• Pulmonary function tests (PFTs) provide the clinician with information
about the integrity of the airways, the function of the respiratory
musculature, and the condition of the lung tissues themselves.
• A thorough evaluation of pulmonary function involves several tests that
measure lung volumes and capacities, gas flow rates, gas diffusion, and
gas distribution.
• Based on the results of PFTs, pulmonary diseases may be classified into
three basic categories: obstructive, restrictive, or combined.

5. Spirometry
• Spirometers may be of the traditional manual water-seal type,
or they may be electronic computerized devices (e.g.,
pneumotachometer).
• In either case, a spirogram of the lung volumes is typically
produced to facilitate interpretation of the measurements .

6. Procedure:
• Subject position: Upright sitting
• Instruments: Nose clip, computerized spirometer device with
mouthpiece.
• Procedure: The patient should breathe normally into the
spirometer (or other appropriate instrument) through a tight-
fitting mouthpiece

7. Instruction:
• Step 1: Breath in deeply and hold
• Step2: nose clip applied to avoid expiration
• Step3: Hold mouth-piece tightly in mouth and expired
forcefully as fast and long as possible .
• Step 4: once further expiration end, remove mouthpiece.

9. Test for lung volume and capacities
• IRV- inspiratory reserve volume[ 3300ml]
• TV- tidal volume[ 500ml]
• ERV- expiratory reserve volume [1000ml];
• RV- residual volume[ 1200ml];
• TLC- Total lung capacity [IRV+TV+ERV+RV=6000ml];
• IC- inspiratory capacity [ IRV+TV=3800ml] ;
• FRC- functional residual capacity [ ERV+RV=2200ml];
• VC- vital capacity[ TV+IRV+ERV= 4800ml]

10. Test for gas flow rate
• Tests that measure airflow rates during forced breathing
maneuvers provide important information relating to the
actual function of the lungs, the degree of impairment, and
often the general location (large airways, small airways, etc.)

11. Basic measures of airflow rates:
• Forced vital capacity (FVC) is the maximum volume of gas
the patient can exhale as forcefully and as quickly as
possible.
• Forced expiratory volume in 1 second (FEV1) is the volume
of air that is exhaled during the first second of the FVC and
reflects the airflow in the large airways.

12. • Forced midexpiratory flow (FEF25-75), previously called the
maximal midexpiratory flow rate, is volume of air exhaled
over the middle half of the FVC, divided by the time required
to exhale it.
• Maximum voluntary ventilation (MVV) is the maximal volume
of gas a patient can move during 1 minute
• Peak expiratory flow (PEF) is the maximum flow that occurs
at any point in time during the FVC

14. Flow-Volume Loop
• The flow-volume loop or curve is a way of graphically
representing the events that occur during forced inspiration
and expiration.
• The flowv olume procedure simply records flow against
volume on an X-Y recorder.
• Following a period of normal, quiet breathing, the patient is
instructed to perform a maximal inspiratory maneuver, to hold
the breath for 1 to 2 seconds, to do an FVC maneuver, and
then to do another maximal inspiratory maneuver.

15. A normal expiratory
and inspiratory flow
volume loop.

16. • A characteristic flow-
volume loop as seen in a
patient with severe
chronic airflow limitation
caused by smoking.
• Notice the deeply scooped
out appearance of the
expiratory limb of the
curve, reflecting the
pronounced flow limitation
occurring at low lung
volumes (predicted flow-
volume loop in the red
line).

17. C. A characteristic flow volume loop in a patient with severe lung restriction from pulmonary fibrosis. Notice
the patient’s relatively small lung volumes. Compared with predicted values, flow rates are relatively
increased in relation to lung volume (predicted flowvolume loop in the red line).
D, A characteristic flowvolume loop in a patient with a fixed tracheal stenosis

18. This Photo by Unknown author is licensed under CC BY-NC-ND.