Pulmonary function tests evaluate lung function through measurements of lung volumes, capacities, flows, and gas exchange. Spirometry is the most common pulmonary function test and measures volumes of air inhaled and exhaled over time through the use of a spirometer. Key spirometry metrics include forced vital capacity, forced expiratory volume in 1 second, and peak expiratory flow rate. Arterial blood gases analyze blood pH, oxygen, and carbon dioxide levels to assess lung function and respiratory disease. Together, pulmonary function tests provide diagnostic and monitoring tools for conditions like asthma, COPD, and lung impairments.

1. PULMONARY FUNCTION TEST
Prepared By:
Sharmin Susiwala

2. DEFINITION:
• Pulmonary Function Testing (PFT) is a complete
evaluation of the respiratory system including patient
history, physical examinations, chest x-ray
examinations, arterial blood gas analysis, and tests of
pulmonary function.
• The primary purpose of pulmonary function testing is
to identify the severity of pulmonary impairment.
• Pulmonary function testing has diagnostic and
therapeutic roles and helps clinicians answer some
general questions about patients with lung disease.

3. INDICATIONS:
• Pulmonary function testing is a diagnostic and management tool used for
a variety of reasons.
• Pediatric neuromuscular disorders
• Neuromuscular disorders such as Duchenne muscular Dystrophy.
• Musculoskeletal deformities such as kyphoscoliosis contribute to
restrictive lung disease.
• Pulmonary function testing in patients with neuromuscular disorders
helps to evaluate the respiratory status of patients at the time of
diagnosis, monitor their progress and course, evaluate them for possible
surgery, and gives an overall idea of the prognosis.
• Other indications
• Chronic dyspnea
• Asthma
• Chronic obstructive pulmonary disease
• Restrictive lung disease
• Preoperative testing
• Impairment or disability

4. MEASUREMENTS:
• There are four lung volumes and four lung capacities.
• A lung capacity consists of two or more lung volumes.
• The lung volumes are:
1. Tidal volume (VT)
2. Inspiratory reserve volume (IRV)
3. Expiratory reserve volume (ERV)
4. Residual volume (RV).
• The four lung capacities are:
1. Total lung capacity (TLC)
2. Inspiratory capacity (IC)
3. Functional residual capacity (FRC)
4. Vital capacity (VC).

6. 1. Tidal volume: It is the volume of air moved into or
out of the lungs during quiet breathing. Value: 500
ml
2. Inspiratory reserve volume: It is the maximal
volume that can be inhaled from the end-inspiratory
level(after the inspiration of a normal
tidal volume). Value: 3100 ml
3. Expiratory reserve volume: It is the maximal
volume of air that can be exhaled from the end-expiratory
position(after the expiration of a normal
tidal volume). Value: 1200 ml
4. Residual volume: It is the volume of air remaining
in the lungs after a maximal exhalation. Value:
1200 ml

7. 1. Total lung capacity: It is the volume in the lungs at
maximal inflation or maximum amount of air that
can fill the lungs. Value: 6000 ml (TLC = TV + IRV +
ERV + RV).
2. Vital capacity: It is the total amount of air that can
be expired after fully inhaling. Value: 4800 ml (VC
= TV + IRV + ERV = approximately 80 percent TLC).
The value varies according to age and body size.
3. Inspiratory capacity: It is the maximum amount of
air that can be inspired. Value: 3600 ml (IC = TV +
IRV).
4. Functional residual capacity: It is the amount of
air remaining in the lungs after a normal
expiration. Value: 2400 ml (FRC = RV + ERV)

8. SPIROMETRY

11. • Spirometry (meaning the measuring of breath) is the most
common of the pulmonary function tests (PFTs),
measuring lung function, specifically the amount (volume)
and/or speed (flow) of air that can be inhaled and exhaled.
• Indications:
• Spirometry is indicated for the following reasons:
 to diagnose or manage asthma
 to detect respiratory disease in patients presenting with symptoms of
breathlessness, and to distinguish respiratory from cardiac disease as the
cause
 to measure bronchial responsiveness in patients suspected of having
asthma
 to diagnose and differentiate between obstructive lung
disease and restrictive lung disease
 to follow the natural history of disease in respiratory conditions
 to assess of impairment from occupational asthma
 to identify those at risk from pulmonary barotrauma while scuba diving
 to conduct pre-operative risk assessment before anaesthesia
or cardiothoracic surgery
 to measure response to treatment of conditions which spirometry detects

12. • Spirometer
• The spirometry test is performed
using a device called a spirometer,
which comes in several different
varieties. Most spirometers display
the following graphs, called
spirograms:
• a volume-time curve, showing
volume (liters) along the Y-axis and
time (seconds) along the X-axis
• a flow-volume loop, which
graphically depicts the rate of
airflow on the Y-axis and the total
volume inspired or expired on the
X-axis.
flow-volume loop

13. • Parameters
• The most common parameters measured in spirometry
are
1. Vital capacity (VC),
2. Forced vital capacity (FVC),
3. Forced expiratory volume (FEV) at timed intervals of
0.5, 1.0 (FEV1), 2.0, and 3.0 seconds,
4. Forced expiratory flow 25–75% (FEF 25–75) and
5. Maximal voluntary ventilation (MVV),[5] also known as
Maximum breathing capacity.
* Functional residual capacity (FRC) cannot be measured
via spirometry, but it can be measured with
a plethysmograph or dilution tests (for example, helium
dilution test)

14. • Forced vital capacity (FVC)
• Forced vital capacity (FVC) is the volume of air that can forcibly be blown
out after full inspiration, measured in liters.
• FVC is the most basic maneuver in spirometry tests.
• Forced expiratory volume in 1 second (FEV1)
• FEV1 is the volume of air that can forcibly be blown out in one second, after
full inspiration.
• Average values for FEV1 in healthy people depend mainly on sex and age.
• Values of between 80% and 120% of the average value are considered
normal.
• FEV1/FVC ratio (FEV1%)
• FEV1/FVC (FEV1%) is the ratio of FEV1 to FVC.
• In healthy adults this should be approximately 75–80%.
• Forced expiratory flow (FEF)
• Forced expiratory flow (FEF) is the flow (or speed) of air coming out of the
lung during the middle portion of a forced expiration.
• It can be given at discrete times, generally defined by what fraction remains
of the forced vital capacity (FVC).
• The usual intervals are 25%, 50% and 75% (FEF25, FEF50 and FEF75), or 25%
and 50% of FVC.

16. • Forced inspiratory flow 25–75% or 25–50%
• Forced inspiratory flow 25–75% or 25–50% (FIF 25–75% or 25–50%) is similar to FEF
25–75% or 25–50% except the measurement is taken during inspiration.
• Peak expiratory flow (PEF)
• Peak expiratory flow (PEF) is the maximal flow (or speed) achieved during the
maximally forced expiration initiated at full inspiration, measured in liters per
minute.
• Maximum voluntary ventilation (MVV)
• Maximum voluntary ventilation (MVV) is a measure of the maximum amount of air
that can be inhaled and exhaled within one minute.
• For the comfort of the patient this is done over a 15 second time period before
being extrapolated to a value for one minute expressed as liters/minute.
• Average values for males and females are 140–180 and 80–120 liters per minute
respectively.
Measurement
Approximate value
Male Female
Forced vital
capacity (FVC)
4.8 L 3.7 L
Tidal volume (Vt) 500 mL 390 mL
Total lung
6.0 L 4.7 L
capacity (TLC)

17. Incentive Spirometer

18. Peak expiratory flow
• The peak expiratory flow (PEF),
also called peak expiratory flow
rate (PEFR) is a person's
maximum speed of expiration,
as measured with a peak flow
meter, a small, hand-held
device used to monitor a
person's ability to breathe out
air.
• It measures the airflow through
the bronchi and thus the degree
of obstruction in the airways

19. • Measurement
• The highest of three readings is used as the recorded value of the Peak
Expiratory Flow Rate.
• Peak flow readings are often classified into 3 zones of measurement
according to the American Lung Association; green, yellow, and red. Doctors
and health practitioners can develop an asthma management plan based on
the green-yellow-red zones.
Zone Reading Description
Green Zone
80 to 100 percent of the usual
or normal peak flow readings
are clear.
indicates that the asthma is
under good control.
Yellow Zone
50 to 79 percent of the usual
or normal peak flow readings
Indicates caution. It may mean
respiratory airways are
narrowing and additional
medication may be required.
Red Zone
Less than 50 percent of the
usual or normal peak flow
readings
Indicates a medical emergency
Severe airway narrowing may
be occurring and immediate
action needs to be taken.

21. Arterial Blood Gases
• An arterial blood gas (ABG) test measures the acidity (pH) and the levels of oxygen and
carbon dioxide in the blood from an artery.
• This test is used to check how well your lungs are able to move oxygen into the blood and
remove carbon dioxide from the blood.
• As blood passes through your lungs, oxygen moves into the blood while carbon dioxide
moves out of the blood into the lungs.
• An ABG test uses blood drawn from an artery, where the oxygen and carbon dioxide levels
can be measured before they enter body tissues.
• An ABG measures:
1. Partial pressure of oxygen (PaO2). This measures the pressure of oxygen dissolved in the
blood and how well oxygen is able to move from the airspace of the lungs into the blood.
2. Partial pressure of carbon dioxide (PaCO2). This measures how much carbon dioxide is
dissolved in the blood and how well carbon dioxide is able to move out of the body.
3. pH. The pH measures hydrogen ions (H+) in blood. The pH of blood is usually between 7.35
and 7.45. A pH of less than 7.0 is called acid and a pH greater than 7.0 is called basic
(alkaline). So blood is slightly basic.
4. Bicarbonate (HCO3). Bicarbonate is a chemical (buffer) that keeps the pH of blood from
becoming too acidic or too basic.
5. Oxygen content (O2CT) and oxygen saturation (O2Sat) values. O2 content measures the
amount of oxygen in the blood. Oxygen saturation measures how much of
the hemoglobin in the red blood cells is carrying oxygen (O2).

22. • Importance:
• An arterial blood gas (ABG) test is done to:
• Check for severe breathing problems and lung diseases,
such as asthma, cystic fibrosis, or chronic obstructive
pulmonary disease (COPD).
• See how well treatment for lung diseases is working.
• Find out if you need extra oxygen or help with
breathing (mechanical ventilation).
• Find out if you are receiving the right amount of oxygen
when you are using oxygen in the hospital.
• Measure the acid-base level in the blood of people who
have heart failure, kidney failure,
uncontrolled diabetes, sleep disorders, severe
infections, or after a drug overdose.

23. • Measurements
• A sample of blood from an artery is usually taken from the inside of the
wrist (radial artery), but it can also be taken from an artery in the groin
(femoral artery) or on the inside of the arm above the elbow crease
(brachial artery).
• Pulse oximetry plus transcutaneous carbon dioxide measurement is an
alternative method of obtaining measurement.
• Results
• An arterial blood gas (ABG) test measures the acidity (pH) and levels of
oxygen and carbon dioxide in the blood.
• Normal
Partial pressure of oxygen
(PaO2):
Greater than 80 mm
Hg (greater than 10.6 kPa)
Partial pressure of carbon
dioxide (PaCO2):
35-45 mm Hg (4.6-5.9 kPa)
pH: 7.35-7.45
Bicarbonate (HCO3): 23-30 mEq/L (23-30 mmol/L)
Oxygen content (O2CT):
15-22 mL per 100 mL of
blood (6.6-9.7 mmol/L)
Oxygen saturation (O2Sat): 95%-100% (0.95-1.00)