Pulmonary Function Test
PFT is an important tool for investigation & monitoring the Pt with respiratory pathology...
What is PFT ?

Pulmonary function tests are a group of tests that measure how well the lungs take in and release air and how well they move gases such as oxygen from the atmosphere into the body's circulation.

Reasons for PFT
As an investigations in patient having signs & symptoms suggestive of pulmonary disease like cough, wheeze, breathlessness and abnormal chest X Ray etc.
Monitoring Pt having previously diagnosed pulmonary diseases, to know for disease progression & for evaluation of treatment such as asthma, emphysema, and other chronic lung problems and guidance for further investigations like IPF, pulmonary Vascular disease etc.
As an investigations in patient likely to have pulmonary complications / pulmonary disease like Connective tissue disease, Neuromuscular disease or occupational hazards.
As a pre operative evaluation prior to major surgeries or other invasive procedures in patients who have current lung and / or heart problems, who are smokers, or who have other conditions that might be affected by surgery or other procedures.
As a routine procedure for evaluation of lungs after lung transplantation, to evaluate lung rejection and diagnose obliterative Bronchiolitis.
In healthy individuals as part of a routine physical examination.
Reasons when PFT should not be done (Contraindications)
Pt having history of recent heart attack.
Patient having h/o effort angina.
Recent Thoraco abdominal surgery / Ophthalmic surgery as the test increases the stress at surgical site.
Patient known to have Thoracic / Abdominal aneurysm.
Patient had recent history of Pneumothorax.
Acute tuberculosis or acute respiratory infection.
Relative Contraindications
Pt taking medicines like bronchodilators (open the air ways) or pain medications may affect the ability to perform the test.
Pregnancy or gastric distention (may affect the ability to take deep breath).
Fatigue or other conditions that affect the ability to perform the test.
Before the procedure

Because pulmonary function testing is a noninvasive OPD procedure, it is safe for most individuals. It is quick and the individual needs to be able to follow clear, simple directions. Your cooperation while performing the test is crucial in order to get accurate results. Your doctor will explain the procedure and offer you the opportunity to ask any questions that you might have about the procedure. Generally, no prior preparation, such as fasting, fluid restriction, or sedation is required. However, you may be asked to avoid eating a heavy meal before the test.

If you are pregnant or suspect that you may be pregnant, you should notify your doctor.
You should tell your doctor all medications (prescription and over-the-counter) and herbal supplements that you are taking.
If you are a smoker, you will usually be asked to refrain from smoking for a period of time before the test (at least one hour prior to the test).
Your height and weight will be recorded so that your results can be accurately calculated.
You will be asked to loosen tight clothing, jewelry, or other objects that may interfere with the procedure
If you wear dentures, you will be asked to wear them during the procedure.
You will be asked to empty your bladder before the procedure to optimize comfort.
After the procedure

Generally, there is no special type of care following PFTs. You may resume your usual diet, medications, and activities unless your doctor advises you otherwise.

If you have a history of respiratory problems, you may be tired after the procedure. You will be given the opportunity to rest afterwards. Your doctor may give you additional or alternate instructions after the procedure depending upon your particular situation.

Risks of the procedure

The risk is minimal for most people. There is a small risk of collapsed lung in people with a certain type of lung disease. Complications of PFTs may include:

Faintness or light-headedness due to hyperventilation
Asthmatic episode precipitated by deep inhalation exercises
How the Test is Performed

You will be allowed to sit on the chair comfortably. You will be given a soft nose clip to wear during the procedure so that all of your breaths will go through your mouth, rather than your nose. You will be given a sterile mouthpiece that will be attached to the spirometer. With your mouth forming a tight seal around the mouthpiece, you will be instructed to perform various breathing maneuvers. The maneuvers will be done by inhaling and exhaling. Spirometry measures airflow. By measuring how much air you exhale, and how quickly, Spirometry can evaluate a broad range of lung diseases. For some of the test measurements, you can breathe normally and quietly. Other tests require forced inhalation or exhalation after a deep breath. Sometimes you will be asked to inhale the substance or a medicine to see how it changes your test results. You may be given a bronchodilator after certain tests have been performed. These tests will be repeated several minutes later after the bronchodilator has taken effect.

Lung volume measurement can be done in two ways:

The most accurate way is to sit in a sealed, clear box that looks like a telephone booth (body plethysmograph) while breathing in and out into a mouthpiece. Changes in pressure inside the box help determine the lung volume.
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 estimate the lung volume.

You will be monitored carefully during the procedure for faintness, dizziness, difficulty breathing, or any other problems.