Lecture 55 -- PFTs (obstruction vs restriction)

Question 1

What can be measured by Spirometry ?

what is not measured by spirometry?

Answer 1

○ FVC = Vital Capacity = IRV + TV + ERV
○ Resting Tidal Volume
○ FEV 1
○ FEV 1/ FVC

does not measure: TLC, FRC, RV

Question 2

what defines obstruction disease of lower airways?

Answer 2

○ Flattened Volume time curve
○ Scooped out expiratory limb of flow
○ Low FEV1/FVC
○ Low FEV1

Question 3

How is severity of Obstruction measured?

Answer 3

Compare to predicted value of FEV1

§ Normal -- >  or equal to 80% of predicted value 
§ Mild -- 65 to 80 % of predicted 
§ Moderate -- 50 to 65%  Severe -- < 50%

Question 4

How do you determine if obstruction is reversible ?

Answer 4

Bronchodilator Responsiveness
○ Give patient Albuterol and repeat PFTs
§ If FEV1 or FVC improve by 200 mL or 12% improvement above the baseline

Question 5

How is restrictive lower airway disease defined?

what is the defining characteristic that is not seen on spirometry?

Answer 5

Low FVC on T/V graph
narrow expiratory arm on F/V graph
normal or high FEV1/FVC

Not seen on spirometry – low TLC

Question 6

how is severity of restrictive airway disease determined?

Answer 6

§ Compared FVC to the predicted values

not FEV 1; which is for obstruction

Question 7

what is a fixed upper airway obstruction? what does the FV graph look like

Answer 7

• Intra or Extra Thoracic upper airway lesion, but cannot determine the location bc the lesion is fixed; will not change size in the response to pressure changes

both inspiratory and expiratory limbs are blunted

Question 8

• Variable Intra Upper Airway Obstruction

• describe it?
• what does the graph look like

Answer 8

• Tracheal mass – moves with breathing
  
  • Mass moves out of the way on inspiration due to negative pressure
  • Mass occludes on exhalation due to positive pressure
  • Blunted expiratory limb; normal inspiratory limb

Question 9

• Variable Extrathroacic Upper Airway Obstruction

Answer 9

• Above the thoracic inlet (vocal cords)
  
  • Abnormal inhalation due to obstruction with the vocal cords (floppy vocal cords obstruction with negative pressure?)

Normal expiatory; stenting open positive pressure