11.23: Pulmonary Function Test

Question 1

What info do PFTs provide?

Answer 1

1. Flow rate: Obstructive disease
2. Volume: Restrictive disease
3. Gas exchange: PVD

Question 2

What to ask about dyspnea?

Answer 2

1. When
2. At rest or at what activity
3. Risk factor
4. Other symptoms

Question 3

3 types of extra breath sounds?

Answer 3

1. Crackles
2. Wheezes
3. Others

Question 4

What question do PFTs answer?

Answer 4

• Is there pulmonary symptom for your SOB?

Question 5

3 components of PFT and what do they examine?

Answer 5

1. Spirometry: obstruction
2. Lung volume determination: restriction
3. Diffusion capacity: diffusion defects

Question 6

What has biggest impact on expected PFT?

Answer 6

• Height and age
• Sex and race have some impact as well
• Peak function is met at 25yo
• **Weight is not factored in

Question 7

What is a “normal” PFT result?

Answer 7

• Within +/- 20% of expected value

Question 8

What is spirometry?

Answer 8

• Patient takes in full breath and blows out as hard as can
• Volume and rate of exhale vs. time is measure
• Portrayed in flow volume loop

Question 9

When is flow rate highest?

Answer 9

• At max lung volume

Question 10

What occurs in obstructive disease?

Answer 10

Less air exhaled per unit time and expected for any given lung volume

Question 11

When is less are exhaled per time?

Answer 11

Obstructive disease

Question 12

What is value that matters in spirometry? What is normal?

Answer 12

• Ration of FEV1/FVC
• **Normal >.7
• If less, there is evidence of obstruction

Question 13

Why is flow highest at high lung volume?

Answer 13

Both recoil and airway diameter are largest at this point

Question 14

What is on top and bottom of flow / volume loop?

Answer 14

Bottom: Inspiration
Top: Expiration
***Flow is on x axis: TLC left, residual, right

Question 15

What is scooped FV loop characteristic of?

Answer 15

• Obstruction

- Lower flow at any volume than expected

Question 16

Do you need to look at FV loop to see if ptn has obstruction?

Answer 16

• NO!

- Just look at the FEV/FVC rate

Question 17

What is considered reversibility of obstruction?

Answer 17

BOTH:

1. Increase in 200cc
2. Increase in FEV1 of 12% from baseline

Question 18

How do you determine how bad obstruction is?

Answer 18

Look at the FEV1 % predicted

Question 19

Does failure to respond to bronchodilator in lab mean you dont give broncho dilator?

Answer 19

NO!!!!

- It can still be beneficial in long term

Question 20

What is methacholine?

Answer 20

• Given to patient in lab to provoke asthma symptoms during spirometry test

Question 21

Do you need PFT to diagnose asthma?

Answer 21

NO, usually clinical diagnosis

Question 22

What happens in small airway obstruction?

Answer 22

• **ASTHMA or EMPHYSEMA
• Gradually worsening of obstruction
• Obstruction worsens as lung volume decreases due to decreased tethering of bronchioles

Question 23

What happens in upper airway obstruction?

Answer 23

• Airflow / obstruction is fixed since even at high lung volumes since bronchioles do not depend on tethering to remain open

Question 24

How is restrictive lung disease tested for?

Answer 24

• Measurement of TLC needed
• Can be done via 2 ways:
  1. Body box plethysmography: cant be done in Dr. office needs to be done in lab
  2. Helium dilution

Question 25

What is TLC primarily determined by?

Answer 25

- Elastic recoil - More recoil, smaller than normal - Less recoil, larger lungs

Question 26

What is residual volume?

Answer 26

- Amount of gas trapped in lungs by airway closure - Cannot blow out even as max exhalation - Increases with gas trapping diseases such as emphysema

Question 27

What is FRC?

Answer 27

- Lung volume when not breathing in or out at end of normal tidal breath - No pressure applied: balance of recoil chest that wants to get big and lungs that want to get small

Question 28

What does low TLC mean?

Answer 28

- Lungs expansion is being restricted

Question 29

3 categories of disease that can lead to restrictive lung disease?

Answer 29

1. Interstitial lung disease: increased lung elastic recoil due to things trapped in interstitium making lungs stiff 2. Chest wall disease: Lungs normal but can't expand chest wall

Question 30

What is kyphoscoliosis?

Answer 30

- Deformity of spine characterized by abnormal curvature of vertebral column in two planes - Seen in old ladies who have to hunch over

Question 31

How can liver failure lead to restrictive lung disease?

Answer 31

- Leads to ascites expanding abdomen to press up against diaphragm and lungs - Pleural effusions can do the same - Same with obesity

Question 32

What can mild obesity cause?

Answer 32

- Decrease in FRC | - Morbid results in decreased TLC

Question 33

How does NM disease cause reduced TLC?

Answer 33

- Do not have muscle strength to inhale a full TLC | - Also takes strength to blow out so RV ends up high

Question 34

How to test for diffusion defect?

Answer 34

- Assess alveolar capillary surface area available for gas exchange - Alveolar capillary contact necessary for exchange

Question 35

How to measure diffusion capacity?

Answer 35

- Known volume of CO inhaled, measure how much is exhaled | - The difference is what has diffused across so this is used to calculate the diffusion capacity

Question 36

What should diffusion measurement (DLCO) be corrected for?

Answer 36

- Hg content of ptn | - If there is not Hg to bind (anemia) the diffusion will be lower

Question 37

What is DL/Va?

Answer 37

- Correction for decreased lung volume | - Could be from lung resection eg

Question 38

What does abnormal DLCO mean?

Answer 38

1. Loss of alveoli a. Emphysema b. ILD 2. Loss of capillary perfusion a. pulm htn 3. Anemia (if you dont correct)

Question 39

What is first though in low DLCO?

Answer 39

- Loss of alveoli | - If no evidence of rest/obstructive disease cause is likely pulm htn

Question 40

What to expect if patient complains of SOB and pulm function test is normal?

Answer 40

- Asthma | - Do methacholine challenge test and see if FEV1 drops and gets better with bronchodilator

Question 41

What does high TLC indicate?

Answer 41

Loss of elastic recoil: emphysema

Question 42

Classic triad of COPD/emphysema?

Answer 42

1. Obstruction w/o dilator response 2. Lack of restriction 3. Hyper inflation/increased TLC/gas trapping 4. Decreased DLCO