Pulmonary Function Tests

Question 1

What are the three major components that PFTs are testing for?

Answer 1

1) Lung Volumes
2) Airflow
3) Gas exchange

Question 2

What are some examples of obstructive pulmonary diseases?

Answer 2

Asthma

COPD

Bronchiolitis/Bronchiectasis

Question 3

What are some examples of restrictive pulmonary diseases?

Answer 3

Pulmonary edema

Interstitial Lung Disease

Neuromuscular weakness

Pleural disease

Obesity

Question 4

A spirometer is used to give a spirogram which provides data on lung volumes and capacities. What is the difference between volumes and capacities?

Answer 4

Volumes can be measured (or at least estimated)

Capacities are the sums of at least 2 different volumes.

Question 5

What is the tidal volume?

Is inspiration or expiration active when producing tidal volume?

Answer 5

Tidal volume=Volume of normal, even inspirations at rest

Inspiration is active (requires effort), Expiration is passive

Question 6

What is the ERV?

Can it be expired?

Answer 6

The ERV is the expiratory reserve volume.

It is the volume remaining in the lungs after a tidal expiration, and it can be exhaled when effort is put into expiration.

Question 7

What’s the IRV?

Answer 7

Inspiratory Reserve volume.

It’s the volume of gas that can be inhaled above that inhaled with a normal tidal inspiration.

Question 8

T or F?

The ERV requires effort but the IRV does not require effort.

Answer 8

False

Both ERV and IRV require effort.

Just remember that for TIDAL volume, inspiration requires effort but expiration is passive.

Question 9

What is the Residual Volume?

T or F?

Residual Volume can either be measured or estimated.

Answer 9

Residual volume is the volume of gas remaining in the lung after a maximal expiration.

T or F answer: False

Residual Volume can ONLY be estimated.

Question 10

What is the FRC?

What is it the sum of?

Answer 10

The FRC is the Functional Residual Capacity.

It’s the volume of gas remaining after a tidal expiration.

It’s the sum of the ERV and the RV.

*System is in equilibrium here. It’s the volume at which elastic recoil is at balance with desire of chest wall to spring out.

Question 11

What’s the IC?

What is it the sum of?

Answer 11

IC=Inspiratory Capacity.

It’s the volume of gas that can be maximally inspired from the FRC (functional residual capacity).

Sum of IRV and Tidal Volume

*requires effort

Question 12

What is the VC?

What is it the sum of?

Answer 12

VC=Vital Capacity

It’s the volume of gas that can be maximally inspired from RV.

Sum of IRV, Tidal volume, and ERV

*requires effort

Question 13

What is the TLC? (Not the TV show)

What is it the sum of?

Answer 13

TLC=Total Lung Capacity

It’s the total gas volume of the lung.

Sum of IRV, Tidal Volume, ERV, and RV

*Requires effort

**RV is only estimated.

Question 14

What does Airflow test?

What is considered an acceptable test and a reproducible test?

Answer 14

Airflow tests the measurement of expiratory airflow (flow=volume/time)

Acceptable test: 6 second expiratory time, curve plateaus for 1 second

Reproducible test: 3 FEV₁ maneuvers w/in 200 ml of eachother

Question 15

What is FEV₁, FVC, and what should the FVC₁/FVC ratio be?

Answer 15

FEV₁=forced expiratory volume in 1 second

FVC=Vital capacity

FEV₁/FVC ratio should be about 75% or 0.75 (0.7-0.8)

This means that in the first second of maximal expiration you should get rid of 75% of the vital capacity.

Question 16

What is the hallmark of a reduced FEC₁/FVC ratio?

Answer 16

An obstructive lung disease

Question 17

Upon spirometry (airflow), a patient demonstrates an elevated FEC₁/FVC ratio. You turn to your attending and proudly diagnose the patient with a restrictive lung disease. What would you expect the attending to say?

A) Excellent job, you get the rest of the day off!

B) You fool, an elevated ratio is indicative of an obstructive lung disease!

C) Nice try suck up. You can’t diagnose a restrictive disease on spirometry!

Answer 17

C.

Airflow can be normal or decreased in restrictive diseases, but the ratios are often elevated. You need to do other tests to diagnose restrictive disease.

Question 18

How do the flow volume loops for expiration and inspiration differ?

Answer 18

The inspiration loop is symmetrical. The expiration loop increases at a sharper angle than it decreases. This is because the latter 2/3 of expiration are effort independent. So your effort pays off for the first 1/3 (sharper angle), but after that you have no control for the 2nd 2/3rds (shallower angle).

Question 19

You observe a left shift, “coving”, and a lower total airflow in the pressure volume loop of a patient.

What type of disease do you expect?

Answer 19

Obstructive.

Those are the hallmark signs of obstructive lung disease for P/V loops.

Question 20

You observe a right shift, lower total airflow, and “supranormal airflows” in a P/V loop.

What should you suspect?

Answer 20

Restrictive lung disease.

Restrictive = Right Shift

Question 21

Match the following P/V abnormalities with cause:

1) Abnormal inspiration and expiration
2. Abnormal expiration
3. Abnormal inspiration

Causes:

a) Variable intrathoracic obstruction
b) Variable extrathoracic obstruction
c) Fixed obstruction (intra or extrathoracic)

Answer 21

1) Abnormal inspiration and expiration=c.fixed obstruction
2) Abnormal expiration=a. variable intrathoracic obstruction
3) Abnormal inspiration=b. variable extrathoracic obstruction

Question 22

T or F?

Helium dilution method is more accurate for people with obstructive lung diseases than the plethysmography (body box).

Answer 22

False.

The body box is better because it doesn’t require diffusion of gas.

Question 23

How do you determine if a lung volume is hyperinflated or decreased/restricted?

Answer 23

Look at the FRC (TLC)

Normal=80-120% TLC

Hyperinflated=>120% TLC (or RV>140%)

*If only RV is inflated, it means there is air trapping

Decreased/Restricted=<80% TLC

Question 24

List the 4 factors that impact the diffusion capacity (DLCO): (think of the equation from previous lectures)

Answer 24

1) Surface area
2) Membrane thickness
3) Diffusion gradient of gas
4) Presence of hemoglobin

Question 25

Generally, how is the DLCO (diffusion capacity) measured?

Answer 25

A mixture using CO is used in the patient. They inhale the mixture then hold their breath for 10 seconds. You then measure how much CO remains (meaning it didn’t diffuse or bind), and use that to determine the DLCO.

Question 26

Which 4 diseases/conditions INCREASE DLCO?

Answer 26

1) Polycythemia
2) Interstitial Edema
3) Asthma
4) Alveolar hemorrhage

Question 27

Which 5 diseases/conditions DECREASE DLCO?

Answer 27

1) Emphysema
2) Pulmonary vascular disease
3) Interstitial lung disease
4) Anemia
5) Pulmonary edema or pneumonia

Question 28

How can you test for respiratory muscle strength?

Hint-2 test.

Answer 28

PiMax=inspiration against a closed valve

PeMax=Expiration against a closed valve (Valsalva)

Question 29

What is the formula for compliance?

How does compliance relate to transpulmonary pressure?

Answer 29

Compliance=deltaV/deltaP

(change in volume over change in pressure)

As transpulmonary pressure increases, compliance increases (and vise versa)

Question 30

List 2 conditions that cause increased compliance and 2 conditions that cause decreased compliance

Answer 30

Increased compliance:

1) Emphysema
2) Asthma (acute)

Decreased compliance:

1) Obesity/Decreased strength/chest wall abnormalities
2) Pulmonary fibrosis

Question 31

A young man comes into your office who thinks he has asthma. What 3 tests could you perform, and what results would indicate he indeed has asthma (a reversible obstructive disease)

Answer 31

Perform airway responsiveness test

1) Bronchodilator challenge with albuterol: looking for >12% change in FEV₁ or FVC and 200cc increase in volume
2) Methacholine challenge: Looking for 20% decrease in FEV₁ or FVC and PC₂₀<8mg/ml
3) Exercise Test: Run on treadmill w/ cold air, look for 20% decrease in FEV₁ or FVC.