2. INTRODUCTION
-It is a group of procedures that measures the function of
the lungs.
-Pulmonary function tests can provide valuable information
about the important individual processes that support gas
exchange.
CATEGORIES OF PFT
There are 3 categories of PFT measuring
i. Dynamic flow rates of gases through airways.
ii. Lung volumes and capacities.
iii. The ability of the lungs to diffuse gases.
3. PURPOSE OF PFT
- To identify and quantify the changes in pulmonary function
due to any disease.
- Evaluate effectiveness of therapy.
- Perform epidemiological surveillance for pulmonary disease.
- Assess patients for risk of postoperative complications.
- Determine pulmonary disability.
4. PATHOPHYSIOLOGY
*Pulmonary disease are divided into two major categories:
-Obstructive pulmonary disease. Eg. COPD
-Restrictive pulmonary disease. Eg. Asthma
-Some pulmonary disease can cause both obstructive and
restrictive pulmonary disease.
*Comparison of obstructive & restrictive pulmonary disease
5. Fig. Obstructive Pulmonary Disease
* Obstructive pulmonary disease
- The primary problem in obstructive pulmonary disease is
an increased airway resistance (Raw).
- In simple terms difficulty in expiration.
6. Fig. Restrictive Pulmonary Disease
* Restrictive pulmonary disease
- The primary problem in restrictive pulmonary disease is
reduced lung compliance, lung volume or both.
- In simple terms difficulty in inspiration.
7. PULMONARY FUNCTION TEST EQUIPMENT
• Two general types of measuring devices exist, those that:
- Measure volume
- Measure flow
• Volume-measuring devices - spirometers
• Flow-measuring devices - pneumotachometers
• Every measuring device has capacity, accuracy, error,
resolution, precision, linearity, & output
8. SPIROMETRY
*It is the measurement of air entering and leaving lungs
which includes measurement of several values of forced
airflow and volume during inspiration and expiration.
• Tests of pulmonary mechanics:
-Forced vital capacity (FVC)
-Forced expiratory volume in 1 second (FEV1)
-Other forced expiratory flow measurements
-Maximum voluntary ventilation
• These measurements assess ability of lungs to move large
volumes of air quickly through airways
9. PURPOSE/IMPORTANCE OF SPIROMETRY
• The purpose of spirometry is to assess the ability of the
lungs to move large volumes of air quickly through the
airways to identify airway obstruction.
• Measuring flow rates is a surrogate for measuring airway
resistance.
• To a lesser extent spirometry can also identify and quantify
a restrictive type of pulmonary disease.
10. TYPES OF SPIROMETRY
-Computerized spirometer
-Incentive spirometer
-Tilt compensated spirometer
-Windmill type spirometer
-Tank type spirometer
12. INDICATIONS OF SPIROMETRY
It should be especially indicated for persons with complaint
of shortness of breath.
-Asthma evaluation
-COPD diagnosis
-Screening for occupational lung disease
-Pre-operative evaluation
-Chronic cough
-Unexplained dyspnoea
-Smoking cessation
-Nonspecific
13. CONTRAINDICATIONS OF SPIROMETRY
It should not be indicated for persons with,
-Haemoptysis of unknown origin
-Pneumothorax
-Unstable angina pectoris
-Recent myocardial infarction
-Thoracic aneurysms, abdominal aneurysms, cerebral
aneurysms.
-Recent eye surgery ( intraocular pressure during forced
expiration)
-History of syncope associated with forced expiration
-Patient with active Tuberculosis should not be tested
14. PRECAUTIONS TO BE TAKEN FOR SPIROMETRY
-Persons with high blood pressure
-Semi-comatic patients
-Patients with age of 80yrs or more
-The subject should be healthy (free from asthma)
-No air leaks in the apparatus (or else will give inaccurate
readings)
-The mouth piece should be sterilized
-The water chamber should not be overfilled (or it may
enter air tubes)
15. TERMINATION CRITERIA FOR SPIROMETRY
-Feeling of giddiness
-Gasping
-Dyspnoea
-Hesitation or false starts
-Coughs
-Variable efforts
-Glottis closure
-Air leaks
-Early termination before a plateau (6s) reached
-Laughing
16. TECHNIQUES OF PFT
*Spirometry
*Helium dilution method
- Based on fact that known amount of helium will be diluted by
size of patient’s RV
*Nitrogen washout method
- Based on fact that 79% of RV is nitrogen
- Volume of nitrogen exhaled Ă· 0.79 = RV
*Whole body plethysmography
- Boyle’s law
Unknown lung gas vol = Gas pressure of the box
Known box gas vol Gas pressure of the lungs
20. PARAMETERS OF PFT
-Forced vital capacity (FVC)
-Slow vital capacity (SVC)
-Maximal voluntary ventilation (MVV)
*Forced vital capacity
-Most common test of pulmonary mechanics
-Many measurements are made while patient is performing
FVC maneuver
-FVC is an effort-dependent maneuver requiring careful
patient instruction & cooperation
-To ensure validity, each patient must perform at least 3
acceptable FVC maneuvers
23. *Slow vital capacity
-Slow Vital Capacity is a spirometry test that displays the
volume of gas measured on a low complete expiration
after a maximal inspiration without forced or rapid effort.
-Ensure that at least four consecutive tidal breaths are
stable before beginning SVC.
-SVC’s should agree within 5% or 150ml.
-SVC’s can be performed as inspiratory, expiratory or mixed
IC/ERV efforts.
25. *Maximal voluntary ventilation
-Effort-dependent test: the patient should be instructed
to breathe as rapidly and as deeply as possible for at
least 12 seconds.
-The patient’s breathing is measured on a spirogram or
electronically for the specific number of seconds (t) and
the volume (V) breathed when the MVV is converted to
liters per minute.
• Results reflect:
-Patient effort
-Function of respiratory muscles
-Ability of chest wall to expand
-Patency of airways
26. *Maximal voluntary ventilation (cont.)
-Normal MVV for males is 160 to 180 L/min & slightly lower in
females
-MVV is reduced in patients with moderate to severe
obstructive lung disease
-MVV may be normal or slightly reduced in patients with
restrictive disease
-Undernourished patients may have reduced MVV
27. LUNG VOLUMES AND CAPACITIES
There are four lung volumes and four lung capacities. A lung
capacity consists of two or more lung volumes.
*Lung Volumes *Lung Capacities
- Tidal volume - Total lung capacity
- Inspiratory reserve volume - Inspiratory capacity
- Expiratory reserve volume - Functional residual capacity
- Residual volume - Vital capacity
29. FLOW VOLUME LOOP
-The flow-volume loop is a plot of inspiratory and
expiratory flow (on the Y-axis) against volume (on the X-
axis) during the performance of maximally forced
inspiratory and expiratory maneuvers
-The normal expiratory portion of the flow-volume curve is
characterized by a rapid rise to the peak flow rate
followed by a nearly linear fall in flow as the patient
exhales toward RV.
-The inspiratory curve, in contrast, is a relatively
symmetrical, saddle-shaped curve.
*NOTE – Answer is given above for the question how flow
volume loop is produced?
32. REVERSIBILITY TEST
-If obstruction is present, reversibility must be evaluated
-Done by performing spirometry before & after therapy
-Bronchodilator is administered by small-volume nebulizer
or MDI
-Reversibility indicates effective therapy
-Reversibility is defined as 15% or greater improvement in
FEV1 & at least 200-ml increase in FEV1
33. PFT REPORT INTERPRETATION
-FEV1/FVC ratio is good place to start with; reduced
(<70%) with obstructive lung disease
-If TLC less than 80% of predicted normal & FEV1/FVC is
normal - restrictive disease is present
*If DLCO is <80% of normal - diffusion defect is present
-Reduced surface area = emphysema
-Thickened AC membrane = pulmonary fibrosis
35. CONCLUSION
-Pulmonary function tests are an important tool in the
assessment of patients with suspected or known respiratory
disease.
-They are also important in the evaluation of patients prior to
major surgery.
-Interpretation of the tests, which requires knowledge of normal
values and appearance of flow volume curves, must be
combined with the patient’s clinical history and presentation.
REFERENCE:
-Egan’s Fundamentals of respiratory care
-PDF-Slow Vital Capacity - UTMB.edu
-Pubmed-www.ncbi.nlm.nih.gov/pmc/articles/PMC3229853/
-www.uptodate.com/contents/flow-volume-loops
-Article- Spirometry in the evaluation of pulmonary function