What are PFTs indicated for?
The diagnosis, severity assessment, prognostic, and treatment evaluation in patients with pulmonary disorders and/or symptoms
Measures FVC, FEV1, FEF, PEFR
Static lung volume testing.
Measurement of TLC, FRC, and RV
Diffusion capacity (DLCO sb)
Indirect information about the adequacy of O2 transfer; measures rate at which carbon monoxide is taken up by hemoglobin in the pulmonary capillaries.
Easily performed, excellent screening tool, reflects airway function, measures volumes with forced expiration after maximal inspiration.
Assesses response to bronchodilators
Generates flow-volume loops (provides pictorial view of airway function)
What is FEV1?
Forced Expiratory Volume in 1 second
What is FVC?
Forced Expiratory Vital Capacity - Total volume exhaled during a maximal forced expiratory effort - Restrictive = >88%; Lower number indicates obstructive disease
What is FEV1/FVC%? Normal values?
Percentage of the FVC expired in 1 second - normal is greater than 70%
What is FEV6?
Forced expiratory volume in 6 seconds - lung normally empty in 6 seconds.
What are some obstructive lung diseases?
COPD - Emphysema; chronic bronchitis; bronchiectasis
Upper Airway Obstruction - Tumor; Goiter
What does an obstructive pattern volume look like?
Concave shaped curve
Will COPD show reversibility in obstructive PFT tests?
Will have none or minimal reversibility after bronchodilator use.
Will asthma show reversibility in obstructive PFT tests?
Yes, will see reversibility after bronchodilator administration
What are some restrictive pulmonary diseases?
Idiopathic pulmonary fibrosis
Amyotrophic lateral sclerosis
*Indicates decreased ability of lungs to expand*
What does a restrictive pattern look like on a volume curve?
Increased or steep slope
This indicates decreased ventilation
What occurs to FVC in obstructive disease?
What occurs to FVC in restrictive disease?
What occurs to FEV1 in obstructive disease?
What occurs to FEV1 in restrictive disease?
What occurs to FEV1/FVC % in obstructive disease?
Normal to decreased
What occurs to FEV1/FVC% in restrictive disease?
Normal to increased
What occurs to FEF in obstructive disease?
What occurs to FEF in restrictive disease?
Normal to decreased
What occurs to the slope of the curve in obstructive disease?
What occurs to the slope of the curve in restrictive disease?
What PFTs test lung volumes and ventilation?
Functional Residual Capacity (FRC)
Total Lung Capacity (TLC)
Residual Volume (RV)
Minute Ventilation, alveolar ventilation, dead space
Distribution of ventilation
What is Static Lung Volumes?
Crude estimation of number of alveoli
Reflects the size of the lungs and bellows function
Represents passive lung volume; FRC
What is Residual Volume (RV)?
Volume of air remaining in the lung after a maximal exhalation
What is Total Lung Capacity (TLC)?
Volume of gas in the lungs at maximal inflation
What is Volume Capacity (VC)?
Total volume of air during maximal inspiration and expiration (Volume Capacity)
What occurs to TLC in obstructive disease?
normal to increased
What occurs to TLC in restrictive disease?
What occurs to RV in obstructive disease?
What occurs to RV in restrictive disease?
What occurs to RV/TLC % in obstructive disease?
What occurs to RV/TLC% in restrictive disease?
How do you test Diffusing Capacity? What is a normal range?
Patient inhales, holds breath for 10 seconds and then exhales. Exhaled air is evaluated.
Average/Normal = 20-30ml/min/mmHg
Dependent upon age, gender, size
What does diffusion capacity measure?
Gas transfer capacity from the alveoli to the blood
Reflects alveolar-capillary surface area
Thickness of basement membrane
Pressure gradient for the gas to diffuse
What changes affect diffusion capacity?
Capillary blood volume
What causes increased diffusion capacity?
Usually not a concern
Intra-vascular hemorrhage (goodpasture's syndrome)
Left-right intracardiac shunts
What causes decreased diffusion capacity?
Decreased area for diffusion caused by Emphysema, lung/lobe resection, bronchial obstruction, multiple pulmonary emboli, anemia
Misc causes: high carbon monoxide (smoking), pregnancy, VQ mismatch
Increased thickness of alveolar-capillary membrane: Idiopathic pulmonary fibrosis, sarcoidosis, asbestosis, hypersensitivity pneumonitis, eosinophilic granuloma, CHF, Collagen vascular disease, Drug induced alveolitis or fibrosis
What do ABGs indicate?
Assesses adequacy of ventilation to remove CO2 and add O2
Assesses need for supplemental ventilation and/or oxygen
Reflects hemoglobin saturation
Allows calculation of A:a gradient
What are the steps of interpreting PFTs?
Examine the expiratory flow volumes
Examine the response to bronchodilators
Examine the Diffusion Capacity
Examine other tests that may be available (ABGs, etc) and use to confirm PFT results