Pulmonary Function Tests

Question 1

what is demonstrated with the maximal effort flow volume loop?

Answer 1

the maximal flow that can be attained at each lung volume

Question 2

when is maximal flow greater? why?

Answer 2

at greater lung volume because airways are distended and have less resistance to flow`

Question 3

why is the maximal expiratory flow volume curve often used as a diagnostic tool?

Answer 3

because it does not require the use of an esophageal balloon and the test does not require as much patient cooperation because it is effort independent

Question 4

what types of diseases can be recognized with the MEFV curve?

Answer 4

obstructive and restrictive diseases

Question 5

how is the MEFV curve recorded?

Answer 5

with a spirometer that measures air flow and expired volume during a breathing cycle. the patient inspires fully and expires with maximal force to residual volume

Question 6

how can an IVPF curve be converted to a MEFV curve?

Answer 6

by taking points off the flow pressure plateaus at each lung volume and replotting maximal flow vs volume expired

Question 7

what happens to the MEFV curve when lung elastic recoil pressure is low or if the airway dimensions are restricted?

Answer 7

the maximal expiratory flow rate will be low

Question 8

what is responsible for the MEFV curve?

Answer 8

dynamic compression

Question 9

in the flow volume loop, why are the inspiratory and expiratory curves not symmetric?

Answer 9

because dynamic compression is only a factor during expiration

Question 10

what does a concave down portion of the expiratory curve in the flow volume loop indicate?

Answer 10

increased compliance resulting in increased dynamic compression

Question 11

what is the FEV1?

Answer 11

the portion of the vital capacity that can be expired in 1 second (usually 80%)

Question 12

why could looking at the inspiratory portion of the maximal effort flow-volume loop be helpful?

Answer 12

because greater assymmetry of the two portions may point you in the direction of certain diseases

Question 13

what is normal vital capacity?

Answer 13

4.75 L

Question 14

when does peak expiratory flow occur in the maximal effort flow-volume loop?

Answer 14

at about 75% of vital capacity

Question 15

what is FVC?

Answer 15

forced vital capacity

Question 16

what are two examples of obstructive diseases and how do they impact the MEFV loop?

Answer 16

emphysema and bronchitis.

may cause the expiration part of the loop to become concave (moreso with emphysema) but keep vital capacity the same

Question 17

what is an example of restrictive disease and how does it impact the MEFV loop?

Answer 17

fibrosis of the lung and it decreases vital capacity and narrows the loop without having much impact on the shape otherwise

Question 18

what would a change in overall size of the MEFV loop indicate?

Answer 18

a smaller lung

Question 19

what does a plateau of the MEFV with a decrease in maximum flow indicate?

Answer 19

a respiratory muscle disease or a lack of effort on the part of the patient

Question 20

which lab finding on the MEFV curve is independent of effort?

Answer 20

concavity in the expiratory portion of the loop.