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MHD VI: Pulm > 11.23: Pulmonary Function Test > Flashcards

11.23: Pulmonary Function Test Flashcards

1
Q

What info do PFTs provide?

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

What to ask about dyspnea?

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

3 types of extra breath sounds?

A
  1. Crackles
  2. Wheezes
  3. Others
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4
Q

What question do PFTs answer?

A
  • Is there pulmonary symptom for your SOB?
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5
Q

3 components of PFT and what do they examine?

A
  1. Spirometry: obstruction
  2. Lung volume determination: restriction
  3. Diffusion capacity: diffusion defects
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6
Q

What has biggest impact on expected PFT?

A
  • Height and age
  • Sex and race have some impact as well
  • Peak function is met at 25yo
  • **Weight is not factored in
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7
Q

What is a “normal” PFT result?

A
  • Within +/- 20% of expected value
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8
Q

What is spirometry?

A
  • 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
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9
Q

When is flow rate highest?

A
  • At max lung volume
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10
Q

What occurs in obstructive disease?

A

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

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11
Q

When is less are exhaled per time?

A

Obstructive disease

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12
Q

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

A
  • Ration of FEV1/FVC
  • **Normal >.7
  • If less, there is evidence of obstruction
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13
Q

Why is flow highest at high lung volume?

A

Both recoil and airway diameter are largest at this point

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14
Q

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

A

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

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15
Q

What is scooped FV loop characteristic of?

A
  • Obstruction

- Lower flow at any volume than expected

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16
Q

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

A
  • NO!

- Just look at the FEV/FVC rate

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17
Q

What is considered reversibility of obstruction?

A

BOTH:

  1. Increase in 200cc
  2. Increase in FEV1 of 12% from baseline
18
Q

How do you determine how bad obstruction is?

A

Look at the FEV1 % predicted

19
Q

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

A

NO!!!!

- It can still be beneficial in long term

20
Q

What is methacholine?

A
  • Given to patient in lab to provoke asthma symptoms during spirometry test
21
Q

Do you need PFT to diagnose asthma?

A

NO, usually clinical diagnosis

22
Q

What happens in small airway obstruction?

A
  • **ASTHMA or EMPHYSEMA
  • Gradually worsening of obstruction
  • Obstruction worsens as lung volume decreases due to decreased tethering of bronchioles
23
Q

What happens in upper airway obstruction?

A
  • Airflow / obstruction is fixed since even at high lung volumes since bronchioles do not depend on tethering to remain open
24
Q

How is restrictive lung disease tested for?

A
  • 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
25
What is TLC primarily determined by?
- Elastic recoil - More recoil, smaller than normal - Less recoil, larger lungs
26
What is residual volume?
- Amount of gas trapped in lungs by airway closure - Cannot blow out even as max exhalation - Increases with gas trapping diseases such as emphysema
27
What is FRC?
- 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
28
What does low TLC mean?
- Lungs expansion is being restricted
29
3 categories of disease that can lead to restrictive lung disease?
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
30
What is kyphoscoliosis?
- Deformity of spine characterized by abnormal curvature of vertebral column in two planes - Seen in old ladies who have to hunch over
31
How can liver failure lead to restrictive lung disease?
- Leads to ascites expanding abdomen to press up against diaphragm and lungs - Pleural effusions can do the same - Same with obesity
32
What can mild obesity cause?
- Decrease in FRC | - Morbid results in decreased TLC
33
How does NM disease cause reduced TLC?
- Do not have muscle strength to inhale a full TLC | - Also takes strength to blow out so RV ends up high
34
How to test for diffusion defect?
- Assess alveolar capillary surface area available for gas exchange - Alveolar capillary contact necessary for exchange
35
How to measure diffusion capacity?
- 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
36
What should diffusion measurement (DLCO) be corrected for?
- Hg content of ptn | - If there is not Hg to bind (anemia) the diffusion will be lower
37
What is DL/Va?
- Correction for decreased lung volume | - Could be from lung resection eg
38
What does abnormal DLCO mean?
1. Loss of alveoli a. Emphysema b. ILD 2. Loss of capillary perfusion a. pulm htn 3. Anemia (if you dont correct)
39
What is first though in low DLCO?
- Loss of alveoli | - If no evidence of rest/obstructive disease cause is likely pulm htn
40
What to expect if patient complains of SOB and pulm function test is normal?
- Asthma | - Do methacholine challenge test and see if FEV1 drops and gets better with bronchodilator
41
What does high TLC indicate?
Loss of elastic recoil: emphysema
42
Classic triad of COPD/emphysema?
1. Obstruction w/o dilator response 2. Lack of restriction 3. Hyper inflation/increased TLC/gas trapping 4. Decreased DLCO

MHD VI: Pulm (20 decks)

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