Pulmonary Function Tests + Respiratory Mechanics

Question 1

What do predicted pulmonary test values depend on?

Answer 1

age, height, and sex

Question 2

What is FVC?

Answer 2

forced vital capacity (amount you can forcefully exhale after forceful inhalation)

Question 3

If an FEV1/FVC ratio is normal, but FVC is low, what is indicated?
What else is needed to confirm this diagnosis?

Answer 3

restrictive pattern

low total lung capacity would confirm restrictive disease

Question 4

What measurement will air trapping increase?

In what diseases does this happen?

Answer 4

residual volume

in severe obstructive disease

Question 5

What happens in obstructive disease w/ pseudorestriction?

Answer 5

air trapping occurs –> RV increases so much it encroaches on the amount of air you can exhale –> FVC is lowered
will see low FEV1/FVC ration w/ low FVC, but NORMAL TLC

Question 6

What is FEV1?

Answer 6

forced expiratory volume in 1 second

Question 7

What are the indications for pulmonary function testing?

Answer 7

evaluate symptoms and signs of lung disease
assess progression of a disease
monitor effectiveness of therapy
evaluate preoperative pts
screen ppl at risk (smokers, etc)
monitor for side effects of other drugs

Question 8

What is diffusing capacity decreased by?

Answer 8

anemia/conditions that min ability of blood to accept O2
decrease in surface area of alveolar-capillary membrane
conditions that increase membrane thickness

Question 9

What is measurement of residual volume and TLC useful for?

Answer 9

for pts with obstructive disease - can demonstrate air trapping and hyperinflation

Question 10

What is diffusing capacity?

Answer 10

measure of the ability of the lungs to transfer gas

Question 11

What does a low FEV1/FVC ratio indicate?

Answer 11

obstructive pattern

Question 12

When are pulmonary function tests NOT indicated?

Answer 12

pts without symptoms

results can be confusing w/ heart disease

Question 13

If FEV1/FVC ratio is low, but FVC is normal, what is indicated?

Answer 13

pure obstructive disease

Question 14

Is asthma considered an obstructive or restrictive disease?

Answer 14

obstructive

Question 15

If FEV1/FVC ratio is low and FVC is low, what is indicated?

Answer 15

mixed obstructive and restrictive disase

must have low TLC to confirm

Question 16

What does a normal FEV1/FVC ratio indicate?

Answer 16

normal or restrictive pattern

Question 17

What can spirometry NOT measure?

Answer 17

residual volume or total lung capacity

Question 18

What generally characterizes restrictive lung disease?

Answer 18

can’t fully expand lungs w/ inspiration

Question 19

What generally characterizes obstructive disease?

Answer 19

can’t fully exhale

Question 20

What is compliance?

Answer 20

slope of the volume - pressure curve = stretchability of lungs
(deltaV/deltaP)

Question 21

Where is compliance of lungs the highest?

Answer 21

in the normal breathing range

Question 22

What is compliance of the lungs the lowest?

Answer 22

at very low volumes and very high volumes

Question 23

What is hysteresis?

What do we think its due to?

Answer 23

the difference between inspiration and expiration curves
We think it’s because surfactant is in little droplets –> grow during inspiration and blob back up in expiration but in a different pattern

Question 24

What is the difference in the saline and air volume-pressure curves due to?

Answer 24

presence of surfactant = surface tension exists

remember that saline curve is steeper bc no surface tension

Question 25

What is the slight hysteresis from saline-filled curve due to?

Answer 25

resistance of the tissue sliding over one another

Question 26

What is minimal volume?

Answer 26

What the lungs will shrink down to without the ribcage

Question 27

Why is RV > minimal volume?

Answer 27

because of rib cage - pulls lungs out more than they would like to be alone

Question 28

If you have a pneumothorax, what happens to the lungs and ribcage?

Answer 28

lungs will shrink down to mv

ribs will pop out without pleural pressure holding them in

Question 29

At what point do the elastic recoil of the lungs and the rib cage exactly counter each other?

Answer 29

FRC = functional residual capacity

Question 30

What changes the radius of the airway?

When might this happen?

Answer 30

bronchial smooth muscle –> decreasing radius increases Resistance of airway
would see this in alveolar dead space

Question 31

In a normal person, how much of the FVC is exhaled in the first second of forced expiration?

Answer 31

70-80%

Question 32

What is interdepence?

Answer 32

shared walls of alveoli and airways prevent their collapse because the recoils oppose each other

Question 33

What could reduce interdependence?

Answer 33

emphesema/COPD –> lose some walls –> lose interdependence and other alveoli also collapse

Question 34

In the work of breathing, what is the largest amount of work/ largest shaded area on graph?

Answer 34

work done to stretch the lungs - opposing compliance

Question 35

What is the smaller amount of work done/smaller shaded area on the work of breathing graph?

Answer 35

work done to overcome airway resistance

Question 36

When does expiration have to become active?

Answer 36

when passive recoil isn’t enough –> work done to deflate overcomes the work put into stretching the lungs