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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
Q

What is TLC primarily determined by?

A
  • Elastic recoil
  • More recoil, smaller than normal
  • Less recoil, larger lungs
26
Q

What is residual volume?

A
  • 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
Q

What is FRC?

A
  • 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
Q

What does low TLC mean?

A
  • Lungs expansion is being restricted
29
Q

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

A
  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
Q

What is kyphoscoliosis?

A
  • Deformity of spine characterized by abnormal curvature of vertebral column in two planes
  • Seen in old ladies who have to hunch over
31
Q

How can liver failure lead to restrictive lung disease?

A
  • Leads to ascites expanding abdomen to press up against diaphragm and lungs
  • Pleural effusions can do the same
  • Same with obesity
32
Q

What can mild obesity cause?

A
  • Decrease in FRC

- Morbid results in decreased TLC

33
Q

How does NM disease cause reduced TLC?

A
  • Do not have muscle strength to inhale a full TLC

- Also takes strength to blow out so RV ends up high

34
Q

How to test for diffusion defect?

A
  • Assess alveolar capillary surface area available for gas exchange
  • Alveolar capillary contact necessary for exchange
35
Q

How to measure diffusion capacity?

A
  • 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
Q

What should diffusion measurement (DLCO) be corrected for?

A
  • Hg content of ptn

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

37
Q

What is DL/Va?

A
  • Correction for decreased lung volume

- Could be from lung resection eg

38
Q

What does abnormal DLCO mean?

A
  1. Loss of alveoli
    a. Emphysema
    b. ILD
  2. Loss of capillary perfusion
    a. pulm htn
  3. Anemia (if you dont correct)
39
Q

What is first though in low DLCO?

A
  • Loss of alveoli

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

40
Q

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

A
  • Asthma

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

41
Q

What does high TLC indicate?

A

Loss of elastic recoil: emphysema

42
Q

Classic triad of COPD/emphysema?

A
  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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