Flashcards in PFTs Deck (62):
What are the 5 components of the respiratory unit?
When is it appropriate to order PFTs? (5)
1. Evaluation of pts with suspected respiratory disease
2. Eval of severity of respiratory disease
4. Eval of persons at risk for pulmonary disease
5. Assessment of therapeutic response
True or false: you should never order PFTs in the acute setting
What are the three factors of respiration that are measured with PFTs?
What is the normal Tidal Volume?
What is the functional residual capacity?
Residual volume + expiratory reserve
What is the vital capacity?
TLC - residual volume (total volume that you can move)
What is inspiratory capacity?
Tidal volume + inspiratory reserve (total amount of air that you can move into your lungs, not including the residual volume)
What is the expiratory reserve volume?
Difference between the end of tidal volume expiration, and residual volume
Which lung volume cannot be measured with an inspirometer?
What is the first thing to check with a PFT result?
Name and date
What does spirometry measure? Is this a static or dynamic measure?
What do capacities measure?
What is used to determine gas exchange?
What is body plethysmography?
Static measurement of lung volumes
What is DLCO? What is it used to assess?
Diffusion capacity of the lungs for CO. Used to evaluate gas exchange capacity of the lungs
Can spirometry be used to definitively diagnose restrictive lung disease?
No, but can aid in diagnosis
What are the three major factors that may affect the accuracy of spirometry?
-Inability to follow instructions
-Poor oral seal
What is the reference population for PFTs based on? (4)
What position must the patient be in to properly evaluate PFTs?
What happens to the lungs as we age?
What is FEV1?
Change in expiratory volume in the 1st second
Where is the FEV1 on a normal time-volume curve?
max of dV/dt
What is FEV25-75?
Forced expiratory volume in the 25-75% of the curve
What part of a PFT is used to assess whether or not there is an obstruction to airflow? What value of this is characteristic of an obstruction to airflow?
Less than the 5th percentile or a value less than 0.7
What value of a PFT determines the severity of an obstruction to airflow? What values indicate mild, moderate, and severe?
Mild = greater than 70%
Mod = 50% to 69%
Severe = 35-50%
Very Severe = less than 35%
What are the obstructive pathologies to airflow? (6)
-Upper airway obstruction
-Extrinsic airway narrowing
What happens to the flow volume loop with an obstructive disease?
Earlier outflow peak, with a sudden dropoff of flow
What happens to the FVC plateau on the time-volume exhaled curve with an obstructive disease? What about the FEV1?
Lower plateau, with a lower FEV1 value
What happens to the FVC plateau on the time-volume exhaled curve with an restrictive disease? What about the FEV1?
Lower plateau, with a lower FEV1 value
Sequential FVC measurements should be within what value of each other to be considered good quality?
How can you determine that quality of the breath in a PFT (time vs volume exhaled curve)?
Morphology of the graph
What are the characteristics of the flow-volume curve pattern with restrictive lung diseases?
Lower volumes and flow rates, but normal morphology of the curve
What happens to the volume vs flow curve with an obstructive disease?
Indentation of the normal curve, with a lower PEF (flow drops off more quickly than usual after peak reached)
What happens to the time-volume expired curve with obstructive diseases?
Slow rise, reduce volume expired, prolonged time to full expiration
What is the morphology of the flow-volume loop with a large lower airway obstructive disease? Why?
Inflow is normal, but expiratory flow plateau is reduced, and prolonged
Expiration increases pressure inside the lungs, and puts pressure on a narrow airway
What is the morphology of the flow-volume loop with a fixed lower airway obstructive disease? (think concentric obstruction)
Reduced flows throughout inspiration and expiration
What is the indication for a bronchoprovocation test?
Evaluate airway hyperresponsiveness
What are the three drugs used to induce bronchospasm with a bronchoprovocation test?
What indicated a positive bronchoprovocation test?
If FEV1 decreases by more than 20% after drug administration
What is the PD20 for a bronchoprovocation test?
Dose required to lower the FEV1 by 20%
What are the three techniques to measure lung capacities?
-Nitrogen wash out
What is Boyle's law? What is the simplification that is used with body plethysmography?
(V1)(P1)(T1) = (V2)(P2)(T2)
T1=T2, thus (V1)(P1) = (V2)(P2)
What is the range of TLC that indicates a restrive lung pathology?
Less than 80% of normal
What is the range of TLC that indicates a hyperinflated lung pathology?
Greater than 120% of normal
What are some examples of the neuromuscular pathologies that can cause restrictive lung diseases?
Spinal cord injury
What are the skeletal abnormalities that can cause restrictive lung disease?
How do you determine the cause of a restrictive lung disease?
DLCO normal = respiratory unit it fine, and the restriction is outside the lungs.
If decreases, then it is affected.
What can cause abnormal DLCO? (3)
-Interstitial space process
What is the MIP? A low value indicates what?
Maximum inhalation against an occluded airway
Lower value indicates breathing problems are neuromuscular in origin
What is MEP?
Maximal exhalation against an occluded airway
What are the 8 steps of PFT interpretation?
1. Ensure demographics
3. How severe
4. Fixed or reversible
5. Large airway obstruction
6. Intra or extrathoracic
7. Restrictive process?
8. Parenchymal disease
What are the PFT values that are used to determine if there is an airway obstructive present?
What are the PFT values that are used to determine the severity of an obstruction?
FEV1 compared to reference
What are the PFT values that are used to determine if there is an airway obstruction is fixed or reversible?
Variation of FEV1 and/or FVC on prebronchodilator and post
Obstructive or restrictive pattern on time vs volume expired curve: Slow rise, reduced volume expired; prolonged time to full expiration
Obstructive or restrictive pattern on time vs volume expired curve: fast rise to plateau at reduced max volume
Reduced inflow but normal outflow on a volume-flow curve indicates what? Why?
Upper airway obstruction d/t lower pressures in the airways are occluding the upper airways
What is the treatment for paradoxical vocal cord dysfunction?
Speech pathology exercises
What does the volume-flow curve look like with a fixed obstruction? Why?
low plateau on both inspiration and expiration, since the obstruction does not change with inspiration or expiration
What does the volume-flow curve look like with neuromuscular weakness?
Lower flows and volumes throughout