Pulmonary function Test Flashcards
What are PFTs used for?
permit an accurate and reproducible assessment of the functional state of the respiratory system and allow quantification of the severity of disease.
What are the types of PFTs?
Lung volume
Flow rates
Diffusing capacity
Maximal inspiratory and expiratory pressures
What does lung volume measure?
measure the maximum volume of the lungs as well as sub-compartments thereof.
What does flow rate measure?
measure the maximal flow of gas out of (and sometimes into) the lung.
What does diffsing capacity measure?
measures the transfer of gas from the alveolar space into the capillary blood stream
What does maximal insiratory and expiratory
measure the applied strength of the respiratory muscles.
What is used to measure Lung volumes?
Spirometer
What are the lung volumes measured and capacities?
tidal volume (TV) inspiratory Reserve Volume (IRV) Expiratory reserve volume (ERV) Residual volume (RV) Vital capacity (VC) inspiratory capacity (IC Functional residual capacity (FRC) Total lung capacity (TLC)
What is tidal volume (TV)?
Volume of air inspired and expired during normal quiet breathing
What is inspiratory reserve volume (IRV)?
The maximum amount of air that can be inhaled after a normal tidal volume inspiration
What is expiratory reserve volume?
Maximum amount of air that can be exhaled from the resting expiratory level
What is residual volume?
Volume of air remaining in the lungs at the end of maximum expiration
What is Vital capacity? what is it equal to?
Volume of air that can be exhaled from the lungs after a maximum inspiration
VC = IRV + TV + ERV
What is inspiratory capacity? what is it equal to?
Maximum amount of air that can be inhaled from the end of a tidal volume
IC = IRV + TV
What is functional residual capacity? what is it equal to?
Volume of air remaining in the lungs at the end of a TV expiration
The elastic force of the chest wall is exactly balanced by the elastic force of the lungs
FRC = ERV + RV
What is total lung capacity? What is it equal to?
Volume of air in the lungs after a maximum inspiration
TLC = IRV + TV + ERV + RV TLC = IC + FRC TLC = VC + RV
What is FRC?
the volume of air present in the lungs at the end of passive expiration.
How is FRC measured?
Helium dilution
Helium is insoluble gas, and the amount of helium is the same before and after equilibrium.
C1 x V1 = C2 x (V1 + V2)
FRC V2 = V1(C1 – C2) / C2
What is diffusing capacity (DL)?
the pulmonary function tests that is done to determine the overall ability of the lung to transport gas into and out of the blood.
What test is done for restrictive and obstructive lung disease?
Measurement of the single-breath diffusing capacity for carbon monoxide (DLCO)
How is DLCO measured?
DLCO= Vgas/(PACO- PaCO)
What is the signifigance of DLCO?
Normals vary by as much as 30%
•
Decreased in restrictive diseases (generally)
-Alveolar fibrosis
•
Decreased by space occupying tumors and
after lung resection
•
Decreased in loss of lung tissue
-EmphysemaWhat are expiratory flow useful in measuring?
Which curves are generated?
Obstructive lung diseases
volume time and flow volume loops are generated
Which terms are found in expiratory flow measurements?
Force vital capacity (FVC)
Forced expiratory volume in 1 second: (FEV1)
Forced expiratory flow 25-75% (FEF25-75)
What are forced vital capacity?
Total volume of air that can be exhaled forcefully from TLC
How long does it takes to exhale FVC in normal people and obstructive lung disease?
The majority of FVC can be exhaled in <3 seconds in normal people, but often is much more prolonged in obstructive diseases
What is forced expiratory volume in 1 second (FEV1)?
Volume of air forcefully expired from full inflation (TLC) in the first second
How can FEV1/FVC be utilzed?
Normal people can exhale more than 75-80% of their FVC in the first second; thus the FEV1/FVC can be utilized to characterize lung disease
What is FEF25-75?
What does it depends on?
Mean forced expiratory flow during middle half of FVC
depends heavily on FVC
What are the terminology found in flow volume loops?
Peak expiratory flow (PEF)
Max inspiratory force (MIF)
Max Expiratory force (MEF)
What is Peak expiratory flow?
This measures how quickly you can exhale.
What does Maximum inspiratory force (MIF), maximum expiratory force (MEF) measure?
This measurement reflects inspiratory and expiratory muscle power.
