Pulm: PFTs Flashcards
What three tests make up the basic PFTs?
Airflow Spirometry
Lung Volumes
DLCO
FEF 25-75%
Forced Expiratory Flow 25-75%
SVC
Slow vital capacity
IC
inspiratory capacity
IRV
Inspiratory Reserve Volume
FRC
Functional Residual Capacity
How many times must spirometry be performed and for what reason
3x, it is an operator dependent test
In what position should spirometry be performed?
sitting
What is the test procedure for spirometry?
- relax, breath normally
- deep breath in
- Forceful exhalation of all air
- Deep Breath In
This measurement is most useful for measuring obstruction…
FEV1
This measure is the total volume of air with maximal effort
FVC
This measure defines the severity of obstruction and assists in differentiating obstructive and restrictive lung disease
FEV-1/ FVC Ratio
What measure of FEV-1/FVC is considered an obstructive pattern?
< 0.7
This measures the airflow movement during the middle half of forced expiration.
It is nonspecific for small airway obstruction, but may indicate early disease.
FEF 25-75%
If this test is positive it:
Aides in Dx
Provides Tx options
Improves Compliance
Bronchodilator/Reversibility testing
What indicates reversibility with bronchodilator testing?
FEV1 increased by 12% and 200ml
What is the protocol for bronchodilator/reversibility testing?
- Use neb or inhaler, monitor technique
- 2-4 puffs, hold in lungs 5-10 seconds
- spirometry after 15 minutes
- Repeat 3-8 rounds
What indicates a positive bronchoprovication/methacholine challenge test?
FEV-1 decreased by 20%
What is the protocol for the bronchoprovocation/methacholine challenge test?
- administer dilute methacholine solution via neb.
- spirometry at 30 and 90s
- increase concentration
Does bronchoprovocation need to be monitored? Methacholine is a part of what drug class that makes this so?
Yes
M agonist causes bronchoconstriction
What must be achieved when assessing the quality of the curves in spirometry? (4)
- volume-time curve plateu
- expiration lasting > 6s
- two best efforts w/in 0.2:L
- flow-volume loop free of artifact
Inspiratory flow > Expiratory flow indicates…
obstructive disease
Inspiratory flow > Expiratory flow indicates…
restrictive lung disease
Volume of air within the lung after maximal inhalation…
TLC
Volume of air we breathe out following maximal inhalation
VC
The volume of air remaining in the lungs after maximal exhalation
RV
Formula for TLC…
TLC = VC + RV
This test:
Measures ability of lungs to transfer gas and saturate Hb
Uses CO as surrogate for O2 transfer
DLCO
What can lead to a false reduction in the DLCO?
anemia
How is DLCO measured?
measurement of helium/CO during exhalation
DLCO test is administered and the following result achieved:
-Little CO collected during exhalation
How should these results be interpreted?
Healthy lungs (CO exchanged for CO2 in the alveoli, so little CO remains in lungs)
DLCO test is administered and the following result is achieved:
-higher CO levels collected during exhalation
How should these results be interpreted?
Diseased lungs
less CO can diffuse, so more remains in the lungs
This PFT profile indicates obstructive or restrictive disease?
TLC: Increased FVC: Normal RV: Increased FEV-1: Decreased FEV-1/FVC: Decreased
Obstructive
This PFT profile indicates obstructive or restrictive disease?
TLC: Decreased FVC: Decreased RV: Decreased FEV-1: Decreased FEV-1/FVC: Normal/Increased
Restrictive
Obstructive or restrictive?
Airway narrowing –> limited airflow with expiration
Reduced airflow with high lung volumes
Normal inspiration
Obstructive
Obstructive or restrictive?
Reduced lung expansion –> Reduced lung volume
Inspiration and expiration will appear normal, but flow and volume significantly reduced
Restrictive
FEV-1/FVC Decreased…
obstructive
FEV-1/FVC increased/normal
Restrictive
The following conditions are considered obstructive or restrictive?
Asthma Asthmatic bronchitis bronchitis COPD CF Emphysema Upper Airway Obstruction
Obstructive
The following conditions are considered obstructive or restrictive?
Pulm. Fibrosis ILD Thoracic deformity pleural effusion tumor neuromuscular disease obesity
Restrictive
5 Steps to PFT Interpretation:
- examine flow-volume curve
- examine FEV-1 value
- Examine FEV-1/FVC ratio
- Examine bronchodilator response
- Examine DLCO
3 things to look for on flow-volume curve…
- normal appearing?
- scooped out? (obstructive pattern)
- increased/peaked slope? (restrictive)
On the flow-volume curve, you notice a scooped out appearance. What does this indicate?
Obstructive Lung Disease
On the flow-volume curve, you notice the slope is increased with a peak appearance. What does this indicate?
Restrictive lung disease
What 3 things should you look for when examining FEV-1 and lung volumes?
- Normal? r/o obstruction/restriction
- Decrease by 15-20% from predicted value? Obstruction
- TLC increased 15-20%? Obstruction
What 3 things should be examined when looking at the FEV-1/FVC Ratio
- Ratio 70% or less? Obstructive
- Ratio 70%-LLN.
- Normal/increased? restrictive
A normal FEV-1 and lung volumes rules out…
obstruction and restriction
A decreased FEV-1 and lung volume by 15-20% of predicted value indicates…
obstruction
A TLC increased by 15-20% indicates…
obstruction
An FEV-1/FVC ratio 70% or less indicates…
obstruction
If FEV-1/FVC ratio is between 70%-LLN, what should you consider?
Mild obstruction
Refer to FEV-1 and FEF 25-75% for asthma consideration
If FEV-1/FVC is normal to increased, what should you consider?
restrictive disorder
When examining bronchodilator response, the FEV-1 increased by 12%. What does this suggest?
hyperreactive, reversible airways
What should you look for on DLCO?
normal, increased or decreased?
