Pulmonary function tests (PFTs) measure how well the lungs work by assessing lung volumes, capacity, flow rates, and gas exchange. PFTs can detect obstructive or restrictive lung diseases and monitor treatment effectiveness. Common PFTs include spirometry, lung volume tests, diffusion tests, oximetry, and exercise tests. Spirometry measures airflow and lung size while breathing normally and forcefully. Lung volume tests directly measure lung capacity. Diffusion tests assess how well oxygen transfers to blood. Together, PFTs provide information on lung function and help diagnose and monitor respiratory conditions.
2. Pulmonary function tests , or PFTs
Pulmonary function tests or PFTs, measure how well the lungs works. For some of
the test measurements, the patient can breathe normally and quietly. Other tests
require forces inhalation or exhalation after a deep breathe. Sometimes they will
be asked to inhaled a different gas or a medicine to see how it changes test
results.
3. PFTs can be used in a variety of settings
and generally ordered to :
Look for evidence of respiratory disease when patients presents with respirator
symptoms (e .g dyspnea, cyanosis, wheezing , etc.)
Assess for any progression of lung disease.
Monitor the efficacy of a given treatment.
Evaluate patients pre- operatives.
Monitor for potentially toxic side effects of certain drugs (e.g. amiodarone, an
antiarrhythmic drug)
4. 1. Spirometry :- . •Measure the rate of air flow and estimates lung size.
For this test, patient will breathe multiple times, with regular and
maximal effort, through a tube that is connected to a computer. Some
people feel lightheaded or tired from the required breathing effort.
Data obtained from spirometry
The most commonly used measures include the forced vital capacity (
FVC) , the forced expiration volume in one second (FEV1), and the ratio
of the two (Fev1/FVC), which should be about 80% in normal patients
Different pulmonary tests
5. An FEV 1 / FVC <80% suggests obstructive lung disease , while restrictive lung
disease typically has normal or increased FEV1/ FVC .
Other useful data from spirometry include measures of flow , eg peak inspiration
flow ( PIF) and peak expiratory flow ( PEF )
6.
7.
8.
9. 2. Lung volumes tests :- are the most accurate way to measure how much air the
lungs can hold .
Lung volume measurements can be done in two ways : -
1. The most accurate way is called body plethysmography . Patient sit in a clear
airtight box that looks like a phone booth. The technologist asks you to breathe in
and out of mouthpiece . Changes in pressure inside the box help determine the
lung volume .
2. Lung volume can also be measured when you breathe nitrogen or helium gas
through a tube for a certain period of time. The concentration of the gas in a
chamber attached to the tube is measured to be estimate the Lung volume.
10. 3.Lung diffusion capacity assesses how well oxygen gets into the blood from the
air you breathe. Patient breathes a harmless gas, called a tracer gas, for a vary
short time , often for only one breathe. The concentration of the gas in the air you
breathe out is measured. The difference in the amount of gas inhaled and exhaled
measures how effectively gas travels from the lungs into the blood. This test
provides an estimate how well the lungs move oxygen from the air into the
bloodstream.
11. 4. Oximetry :- the measuring of the percentage of oxygen-
saturated hemoglobin in the blood by means of an oximeter.
Readings below 90 percent may be indicative of impaired lung
function or infection. In noninvasive pulse oximetry , a small device
placed on a fingertip or earlobe uses light waves to measure the
oxygen saturation in arterial blood.For this test, a probe will be
placed on the finger or another skin surface such as the ear. It
causes no pain and has few or no risks.
5. Arterial blood gas :-directly measure the levels of gases, such
as oxygen and carbon dioxide, in your blood. Arterial blood gas
tests are usually performed in a hospital, but may be done in a
doctor’s office. For this test, blood will be taken from an artery,
usually in the wrist.
12. Fractional exhaled nitric oxide tests measure how much nitric oxide is in
the air that you exhale. For this test, client will breathe out into a tube that
is connected to the portable device. It requires steady but not intense
breathing. It has few or no risks.
Other tests may be needed to assess lung function including:
6. Diffusing Capacity of Carbon monoxide (DLCo) Oxygen. Diffusing
capacity is a measure of the ability of the lungs to transfer gas into the
blood. Diffusion of gas to blood in the lungs is the most efficient when
there is a high surface area for transfer, and when the blood is able to
accept the gas being transferred. The diffusing capacity is helpful
primarily in distinguishing between types of obstructive lung disease. For
example, the diffusing capacity will generally be normal or increased
in asthma, while it will be decreased in emphysema.
13. 7. Bronchodilator Test. A bronchial challenge test measures how sensitive
the airways in your lungs are. It’s used to help make a diagnosis in people
who may have asthma. The bronchial challenge test is sometimes called an
airway provocation test. It involves breathing in gradually increasing doses
of a medication that can irritates the airways and cause them to get
narrower. People with sensitive lungs will be affected by a much lower dose
of this medication than people with healthy lungs. The test is done carefully
to make sure it is safe. One of the defining characteristics of asthma is an
increase in the responsiveness of the airways to a number of stimuli. If lung
function is normal but the patient experiences intermittent episodes of
cough, dyspnea, or wheezing, the demonstration of bronchial hyper-
responsiveness may be useful in establishing a diagnosis of
asthma, exercise-induce asthma or eucapnic voluntary hyperpnea.
14. 8.Cardiorespiratory Exercise Test Lung problems can make it
harder to do day-to-day activities. Exercise capacity tests can be
used to measure what people are able to do. If someone’s
exercise capacity is reduced, the tests may help to explain why.
Exercise capacity tests are also sometimes used to tell
anaesthetic teams how fit a person is (important when assessing
people for major surgery). Walking tests can measure how
effective pulmonary rehabilitation has been and whether client
needs oxygen when you are walking (called an ambulatory
oxygen assessment).
15. 9. Respiratory muscle function test :- Respiratory muscle tests
measure how much pressure the breathing muscles can generate when
patient breathes in or out. Maximal inspiratory and expiratory pressures
(MIP/MEPs) are measured by having the patient perform maximal
inspiratory and expiratory efforts against a closed valve and measuring
the static pressures that are generated.
16. Pattern of Respiratory diseases
•Obstructive pattern :-Decreased FEV1, normal or
decreased FVC, and decreased FEV1/FVC
•Classically, these are the patients with asthma, chronic
bronchitis, or emphysema
• PFTs can help further distinguish between the
above three:
• Bronchodilator responsiveness - an increase in
the FEV1 by 12% following bronchodilator use
suggests asthma
• Bronchial provocation - inducing asthmatic
obstruction of reactive lower airways by
administering methacholine, histamine, or
adenosine monophosphate
• DLCO ( Diffusing capacity for carbon monoxide
)will be decreased in patients with
emphysema, and can be normal or increased
17. Lower airway obstruction vs. upper airway obstruction
Lower airway obstruction typically displays impaired expiratory capacity ,while upper
airway obstruction has impaired inspiratory capacity, which can be evident on the flow
volume loop (seen as flattening of the inspiratory arm)
Restrictive pattern
Decreased TLC, FEV1, and FVC with a normal FEV1/FVC, and a low DLCO
Typically these are patients with interstitial lung disease, severe skeletal abnormalities,
or diaphragmatic paralysis
The flow volume loop is generally normal in appearance, but has low lung volumes
18. Radiology
• Pulmonary function tests (PFTs) provide important
quantitative information about lung function and can be
used to elucidate pathologic conditions responsible for
respiratory symptoms, assess the severity and course
of disease, and evaluate the patient for suitability and
timing for lung transplantation . PFTs may provide the
radiologist with clues to the diagnosis and grading of a
wide variety of pulmonary diseases
19. Indication
Investigation of a patient with sign/symptoms that shows respiratory problems. e.g. wheezing, coughing, crackles and abnormal chest xray e.t.c.
Monitoring of patients with respiratory condition for disease progression and response to treatment.
Evaluation of degree of cardio-respiratory disability
Preoperative evaluation for patient that will undergo thoracic and abdominal surgery
Montoring of patients at risk of pulmonary complications
Routine assessment for individual with high exposure to pulmonary toxic agent e.g abestos, dust and fumes
Diagnose lung disease.
Monitor the effect of chronic diseases like asthma, chronic obstructive lung disease, or cystic fibrosis.
Detect early changes in lung function.
Identify narrowing in the airways.
Evaluate airway bronchodilator reactivity.
Show if environmental factors have harmed the lungs
lung cancer
Infections
Thickening or hardening of your connective tissues (scleroderma)
Weakness of the muscles in the wall of the chest
20. • Contraindications
Myocardial Infarction in the last month
Unstable Angina
Recent thoracic and abdominal surgeries
Recent Opthalmic surgery
Active Hemoptysis ( rapid rate of bleeding )
Pneumothorax leaking of gas between lungs and chest wall
