Title: Pulmonary Function Testing
1Pulmonary Function Testing
- Modified from
- Esmeralda E. Morales, MD
- 2004 (about 27 slides)
2Objectives
- State the reasons pulmonary function tests (PFTs)
are performed. - Describe the technique and basic interpretation
of spirometry. - State the difference between obstructive and
restrictive lung disease.
3What are PFTs?
- The term encompasses a wide variety of objective
methods to assess lung function. - Examples include
- Spirometry
- Lung volumes by helium dilution or body
plethysmography - Diffusing capacity
- Bronchial challenge testing
- Exercise tests
4Why are these tests performed?
- Help diagnose disease
- May help guide management of a disease process
eg, bronchodilators - Can help monitor progression of disease and
effectiveness of treatment - Aid in pre-operative assessment of certain
patients
5Where would I perform PFTs?
- At home--peak flow meter
- On hospital wards ICUs
- Doctors office
- PFT laboratory in the hospital
- (In order of increasing level of sophistication)
6Spirometry
- Spirometry is a medical test that measures the
volume of air an individual inhales or exhales as
a function of time. (ATS, 1994)
7Spirometer Types
- Volume-displacement spirometers
- Flow-sensing spirometers
8Lung Volumes and Capacities
- 4 volumes 4 capacities
- 2 or more volumes comprise a capacity
9Lung Volumes
- Tidal Volume (TV) volume of air inhaled or
exhaled with each breath during quiet breathing
(500 ml) - Inspiratory Reserve Volume (IRV) maximum volume
of air inhaled from the end-inspiratory tidal
position - Expiratory Reserve Volume (ERV) maximum volume
of air that can be exhaled from resting
end-expiratory tidal position
10Lung Volumes
- Residual Volume (RV)
- Volume of air remaining in lungs after maximium
exhalation - Indirectly measured (FRC-ERV) not by spirometry
11Lung Capacities
- Total Lung Capacity (TLC) Sum of all volume
compartments or volume of air in lungs after
maximum inspiration ( 6.0 L) - Vital Capacity (VC) TLC minus RV or maximum
volume of air exhaled from maximal inspiratory
level ( 4.8L) - Inspiratory Capacity (IC) Sum of IRV and TV or
the maximum volume of air that can be inhaled
from the end-expiratory tidal position
12Lung Capacities (cont.)
- Functional Residual Capacity (FRC)
- Sum of RV and ERV or the volume of air in the
lungs at end-expiratory tidal position - Can be measured with multiple-breath
closed-circuit helium dilution (not by
spirometry) - RV 1.2L
13A spirometer can be used to measure
- FVC and its derivatives (such as FEV1, FEF
25-75) - Peak expiratory flow rate
- IC, IRV, and ERV
- Pre and post bronchodilator studies
14Forced Expiratory Vital Capacity
- The volume exhaled after a subject inhales
maximally then exhales as fast and hard as
possible. -
15Normal values depend on
- Height
- Age
- Gender
- Ethnicity
16Measurements Obtained from the FVC Curve
- FEV1---the volume exhaled during the first second
of the FVC maneuver - FEF 25-75---the mean expiratory flow during the
middle half of the FVC maneuver reflects flow
through the small (lt2 mm in diameter) airways - FEV1/FVC---the ratio of FEV1 to FVC X 100
(expressed as a percent) an important value
because a reduction of this ratio from expected
values is specific for obstructive rather than
restrictive diseases
17Obstruction vs Restriction
Airway obstruction
Chest wall restriction
Alveolar restriction
18Spirometry Interpretation Obstructive vs
Restrictive
- Obstructive Disorders
- Characterized by low FEV1/VC
- Examples
- Cystic Fibrosis
- Bronchitis
- Asthma
- Bronchiectasis
- Emphysema
- C-babe
- Restrictive Disorders
- Characterized by low VC reduced lung volumes
- Examples
- Interstitial Fibrosis
- Scoliosis
- Obesity
19Spirometry Interpretation Obstructive vs
Restrictive
- Obstructive Disorders
- FEV1 ?
- FEV1/FVC ?
- TLC nl or ?
- Restrictive Disorders
- FVC ?
- FEV1/FVC nl to ?
- TLC ?
20Spirometry Interpretation What do the numbers
mean?
- FVC
- Interpretation of predicted
- 80-120 Normal
- 70-79 Mild reduction
- 50-69 Moderate reduction
- lt50 Severe reduction
- FEV1
- Interpretation of predicted
- gt75 Normal
- 60-75 Mild obstruction
- 50-59 Moderate obstruction
- lt49 Severe obstruction
21Spirometry Interpretation
- FEV1/FVC
- Interpretation of absolute value
- 80 or higher Normal
- 79 or lower Obstruction
22What about lung volumes and obstructive and
restrictive disease?
(From Ruppel, 2003)
23Helium Dilution Lung Volume
6.0 L
Unknown volume
0 He
5 He
24Spirometry Pre and Post Bronchodilator
- Measure FEV1
- Administer a bronchodilator.
- Measure FEV1 again a minimum of 15 minutes later
- Calculate percent change
- Reversibility indicated by 15 or greater change.
25Case 1
26Case 2
27The wind God (one of the gods of RC)