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Respiratory > Lecture 13- Pulmonary lung function tests > Flashcards

Lecture 13- Pulmonary lung function tests Flashcards

1
Q

PFTs are tests that measure

A
  • Lung volumes
  • Rate of airflow
  • Gas exchange (alveolar-vascular membrane)
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2
Q

PFTs used to

A
  • diagnose patients with resp symptoms
  • establish severity and progression of lung disease
  • assess treatment response
  • monitor patients on meds with lung toxicity
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3
Q
  • Instruments used
A
  • peak flow meter
  • spirometry
  • diffusing capacity of CO (DLCO)- provides info about alveolar-capillary membrane diffusing capacity
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4
Q

define peak expiratory flow

A

Maximum airflow rate attained during forced expiration (PEFR)

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5
Q

normal peak PEFR

A
  • Normal >80% of predicted average based on
    • Ethnicity
    • Height
    • Gender
    • Age
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6
Q

what is used to measure PEFR

A

peak flow meter

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7
Q

baseline PEFR measured when

A

when pt is asymptomatic

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8
Q
  • PEFR Useful in monitoring people with
A

asthma

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9
Q

Spirometry

A
  • Used to measure some lung volumes
  • Calculates airflow as volumes are measured over time
  • Reports those values
  • Also produces graphical representations
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10
Q

graph which can be produced by spirometry

A
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11
Q

Which values will spirometry give

A
  • Tidal volume
  • Inspiratory reserve volume
  • Expiratory reserve volume
  • Inspiratory capacity
  • Forced expiratory volume in 1 second (FEV1)
  • Forced vital capacity (FCV)
  • FEV1/FVC
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12
Q
  • Tidal volume
A
  • Breathing quietly
  • How much air you breathe in and out of the lungs
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13
Q
  • Inspiratory reserve volume
A

Extra air inspired above and beyond normal inspiration (tidal volume)

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14
Q
  • Expiratory reserve volume
A

Extra air expired above and beyond normal expiration

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15
Q
  • Residual volume
    *
A
  • Air left in lungs after expiratory reserve volume
    • Spirometry cant measure this- can only measure air that can be blown or sucked into tube
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16
Q
  • Functional reserve volume
A

= expiratory reserve volume + residual volume

  • Also cant measure this using spirometry
  • Represents the balance between lung inner elastic recoil and chest wall outer elastic recoil
  • Volume of air left when the forces are equally balanced
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17
Q
  • Inspiratory capacity
A

Amount of air I can breathe in (tidal volume) + inspiratory reserve volume

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18
Q
  • Vital capacity
A

Amount of air breathe out after maximum inspiration

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19
Q
  • Total lung capacity
A
    • Vital capacity + residual volume
      • Spirometry cant give this
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20
Q
  • Forced expiratory volume in 1 second (FEV1)
A

- maximum volume of can be forcefully expired within 1 second after maximal inspiration

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21
Q
  • Forced vital capacity (FCV)
A
  • total amount of air exhaled after maximal inspiration during entire FEV test – occurs over 6 seconds
22
Q
  • FEV1/FVC r
A
  • epresents proportion of patients forced vital capacity that they are able to expire in first second of forced expiration
    • FEV1:FVC <70% (0.7) obstructive airway disease
23
Q

volume time plot

A

shows FEV1 and FVC graphically

  • characteristic shape
  • Healthy plot
    • FEV1 = 4l
    • FVC= 5l
24
Q

Flow volume loops (spirotmetry doesn’t measure these)

A
  • Volume of air present in lungs at transition maximum inspiration expiration = total lung capacity
  • Volume of air present in lungs transition expiration to inspiration= residual volume (RV)
25
Q

example of obstructive lung disease

A

COPD and asthma

26
Q

volume time plot and flow voluem loops in obstructive diease

A

Volume time plot

  • Asthma/COPD – full line
    • FEV1 is less than normal person
    • FEV1= 1.5 in asthma/COPD / FEV1= 4 in normal peron
    • therefore FEV1/FVC ratio <70%
    • FCV will be pretty normal- jsut takes longer to get to maxinal value

Flow volume loop

  • We are looking at the shape
  • Full line = obstructive lung disease (COPD/Asthma)
    • Peak flow rate less (peak flow meter can also measure this)
      • Coving/notching on expiration
    • Peak flow rate falls quicker
    • Marked obstruction of flow during expiration
    • Not much difference on expiration
27
Q

main feature of obstrucitve lung disease

A
  • OBstrUtive
  • O= harder to breath OUT
  • B= PFTs BELOW normal value
  • U= UPPER value (numerator) reduced)
28
Q

Obstructive disease and FEV1

A

will bedecreased by more than 70%

  • how much FEV1 decreased below normal provides ifno about disease severity
29
Q

COPD and FVC

A

FVC initially normla, will decrease in severe disease

30
Q

asthma and FVC

A

FVC typically decreased- small airways close prematurely

31
Q

key diagnostic finding for obstructive lung disease

A

FEV1:FVC <0.7

32
Q

Obstructive kung disease and TLC (total lung capcity) and FRC (functional residual capacity)

A

if there is air trapping because iof small airway collapse- TLC and FRC will be increased because of increased residual volume (RV)–> air lef tin the lungs after breathing out

33
Q

how to determine if the obstructive lugn disease is asthma or COPD

A

PT given bronchodilator after baseline spirometry is taken and the values are compared

  • FEV1 12% or greater after bronchodilator – asthma
  • Not greater after bronchodilator in COPD
    • COPD is irreversible lung disease (minimal response to Beta agonists inhalers)
    • some people will have some degree of revrsibility through inhalers- most wont
34
Q

examples of restrictive lung disease

A

ILD and myasthenia gravis (chest wall weaker in MG)

35
Q

Restrictive lung disease also known as

A
  • stiff lungs
36
Q

in restictive lung disease stiff lungs means

A
  • hard to expand- hard to inspire (breathe in)
  • return to original volume very quickly (very elastic)
37
Q

why are lungs stiff in restrictive lung disease

A

inbalance between lung elastic recoil and chest elastic recoil

38
Q

volume time plot and flow volume loop for restrcitve lung disease

A

Volume time plot

  • FEV1 can be normal- will typically be reduced though
    • Amount of air that can be removed in 1s- if you have smaller amount of air in lungs- going to be less air to blow out
    • Not that they cant get it out quickly
  • FVC markedly decreased
    • Less air in lungs to begin with due to stiffness of lungs reducing the amount of air in the lungs to start with

Flow volume loop

  • Shape is the same as healthy lung
  • Total volume being moved in/out of lungs markedly decreased
39
Q

DLCO- not part of ……………….- part of PFTs

A

spirometry

40
Q

DLCO stands for

A
  • Diffusing capacity carbon monoxide
  • Determines how much oxygen travels from alveoli of lungs to bloodstream i.e. diffusion
41
Q

PFT results restrictive lung disease

A
  • normal/increased FEV/FVC ration (both may be reduced, but FVC is most markedly reduced)
  • TLC and FRC will be reduced to reduced lung capacity
42
Q

DLCO can provide info on

A
  • Can provide info about alveolar-capillary membrane
  • Can be decreased in many conditions including
43
Q

in which conditions may DLCO be reduced

A
  • Emphysema – decreased SA
  • Alveolar inflammation- increased thickness due to pus
  • Pulmonary fibrosis – increased thickness
    • These conditions would have normal spirometry or chest x-ray
44
Q

So what does an abnormal DLCO with normal chest x-ray and spirometry suggest?

A

Suggests problem with vascular part of membrane

  • Idiopathic pulmonary arterial hypertension
    • Pulmonary arterial become thickened- impaired diffusion
    • Drugs that supress appetite can cause this- don’t know why
  • Chronic thrombo-embolic disease of lungs
    • Need other tests to confirm
45
Q

volume time plot for different disease state

A
46
Q

flow volume loops in different disease states

A
47
Q

How do you differentiate different restrictive lung disease

A

By looking at the DLCO

48
Q

DLCO in myasthenia gravis (RLD)

A
  • Restrictive pattern on spirometer
  • DLCO will be normal (problem with the lung parenchyma (muscle) not the alveolar capillary barrier
49
Q
  • ILD and DLCO
A
  • Restrictive pattern on spirometry
  • Abnormal DLCO- thickening of barrier between alveoli and capillaries
50
Q

Summaery table comparing obstructive and restrictive PFTS

A

Respiratory (27 decks)

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