Phys: Test 3: Lecture 11. Intro To Pulmonary Function Test

Front 1

List the main types of pulmonary function test.

Back 1

• Ventilatory capacity
o Forced expiration
o Lung volumes
o FRC measurement
• Detection of hypoxemia
o Blood gasses
o V/Q scan
o Ventilation inequality
o Diffusion capacity

Front 2

Explain how obstructive and restrictive disease differ in terms of the typical lung volumes
and airway resistance found in each.

Back 2

• Obstructive
o Characterized by:: Increased airway resistance
o Large lung volumes (have to try and increase radial traction)
o Ex: Emphysema
• Restrictive
o Characterized by: Small lung volumes
o Normal/decreased airway resistance
 There is more lung parenchyma giving it more radial traction
o Ex: fibrosis

Front 3

Define Forced Expiratory Volume (FEV) and Forced Vital Capacity (FVC). Explain how
these can be measured using a spirometer.

Back 3

o Take maximal expiration
o Breath out as rapidly and as much as possible
• FEV1
o Volume of air expired after the first second of expiration
• Forced vital capacity
o Total volume exhaled

Front 4

Describe how FEV, FVC and the FEV/FVC ratio typically change in obstructive and
restrictive disease.

Back 4

• Obstructive disease
o FEV is reduced
o FVC is also reduced
• Restrictive disease
o Also get a reduction in FEV and FVC

Front 5

Name the parameter which is most useful in differentiating between
obstructive and restrictive disease.

Back 5

• You have to look at the RATIO in order to differentiate between the two diseases
o FEV1/FVC
 In Obstructive disease
• Decreased
 Restrictive
• Normal or increased

Front 6

Obstructive, Normal, Restrictive FEV1/FVC values?

Back 6

less than .8
.8
greater than or equal to .8

Front 7

List the factors that determine FEV

Back 7

• Lung volume
o More lung volume, there is more there to push out in the 1st second
• Airway resistance
o Affects how quickly you can push out the air
o If it is increased, you can push less out per second
• Airway collapse
o Forced expiration will cause Ppl to be positive making PTA to be positive, compressing the airway

Front 8

Describe which factors are involved in reducing FEV in
obstructive and restrictive disease.

Back 8

• Obstructive disease
o Due to increased airway resistance
• Restrictive
o Due to low lung volume
o So can push out less air per second

Front 9

. Describe the factors that are involved in reducing FVC in obstructive and restrictive disease.

Back 9

• Obstructive
o Earlier airway collapse (note you will get airway collapse in restrictive, but it happens earlier in obstructive)
 Air gets trapped
• Restrictive
o Due to lowered total lung capacity (TLC)
o Less maximum volume to begin with

Front 10

Define the Forced Expiratory Flow (FEF25-75%) rate. Describe what the FEF represents

Back 10

• Rate of airflow in the middle portion of expiration=FEF
o Divide the volume over time (volume to move from 25%-75% of expiration)
• Useful in identifying increased airway resistance

Front 11

how does FEF typically change in obstructive and restrictive disease

Back 11

• Obstructive
o FEF is reduced
 Much slower flow rate of air over that portion
• Restrictive
o FEF is increased
 Due to increased radial traction (decreasing the resistance)

Front 12

How does obstructive disease look different on a flow-volume curve?

Back 12

lower flow rate, and it has a dip in it

Front 13

How does restrictive disease look different on a flow-volume curve?

Back 13

looks like the normal curve but smaller; has high flow rate for low lung volume

Front 14

Explain what additional information can be obtained from plotting a flow-volume curve using
absolute lung volumes.

Back 14

• Volume inspired and expired
• Tidal volume

Front 15

Name the lung capacity that is necessary for the conversion of volumes measured with a
simple spirometer into absolute lung volumes. . Describe one way in which this lung capacity
can be measured, and list an alternative method.

Back 15

• You have to have FRC
• One method to measure it is helium dilution
o Breath in helium
 O2 will dilute the helium
• The more volume in lungs the more dilution of helium
o Once equilibrated you measure the volume of helium to see the dilution, then you can put it the following equation
 Note that helium is used because it is insoluble in the blood

V2= ( V1 (C1-C2) ) / C2

Front 16

List the tests that can be used to assess the presence and causes of hypoxemia.

Back 16

• Blood gas measurement
• Ventilation-perfusion inequality
• Diffusion capacity

Front 17

Explain how a V/Q scan can reveal ventilation-perfusion inequality.

Back 17

• Inject radioactive substance into blood and lung
o See the radiation in the lung and blood and see if there is reduced radiation in one or the other (tells you if V or Q is affected)

Front 18

Explain why carbon monoxide can be used to measure diffusion capacity (DLCO). Explain
why interpretation of DLCO is complex in lung disease.

Back 18

• Look at the rate of diffusion of CO into the blood
o See how fast it disappears from the alveolar gas
 Will be dependent on the partial pressure difference
• We use CO b/c the CO PP will not rise in the capillary (due to binding to Hb, and removal from capillary)
o DL=VdotCO/PACO
 VdotCO=rate of disappearance of CO from alveolar gas during a 10sec breath hold
• Problem with this
o If there is regional inequality of ventilation (aka part of the lung is not well ventilated) then DLCO will be reduced (b/c CO doesn’t get to the alveoli)
 Thus the diffusion rate will be decreased

Front 19

explain how a single breath of pure O2 can be used to assess the extent of inequality of
ventilation.

Back 19

• Measure nitrogen concentration following a single breath of O2
• With pure Oxygen will dilute the N2 already in the lung
o The extent of dilution will tell you how well the O2 is getting into the alveoli
• Equal ventilation
• Inequality
o O2 will get into 1 part of the lung very well, but not into the obstructed airway (so no dilution there)
 First part of exhale, all O2 from dead space
• Then you see diluted N2
o Finally you will see the less diluted N2 from the obstructed airway (because it is harder to get it out, it comes out later)

Front 20

If you have obstructive disease with decreased DLCO (diffusion capacity) what do you have?

Back 20

Emphysema

Front 21

if you have obstructive disease with a normal DLCO what do you have?

Back 21

asthma or chronic bronchitis

Front 22

if you have restrictive disease with lowered DLCO what do you have?

Back 22

interstitial fibrosis

Front 23

if you have restrictive disease with normal DLCO what do you have?

Back 23

chest wall abnormality or neuromuscular problem