Interpretation of Lung Function Flashcards Preview

Year 3 - CR > Interpretation of Lung Function > Flashcards

Flashcards in Interpretation of Lung Function Deck (32)
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1
Q

What are the values of lung function dependent on

A
  • Age
  • height
  • sex
  • BMI
  • ethinic origin
2
Q

What are the 4 main lung function tests

A
  • Spirometry
  • PEF
  • Lung volume
  • Gas exchange
3
Q

What does spirometry measure

A

Spirometry measures the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled

4
Q

What are the two measurements that spirometry measures

A
  • forced vital capacity (FVC)

- Forced expiratory volume in one second (FEV1)

5
Q

what is forced expiratory volume in one second

A

This is the amount of air you can blow out within one second.
- With normal lungs and airways you can normally blow out most of the air from your lungs within one second.

6
Q

What is forced vital capacity

A

The total amount of air that you blow out in one breath.

7
Q

what is the ratio in spriometry

A

FEV1 divided by FVC (FEV1/FVC).
- Of the total amount of air that you can blow out in one breath, this is the proportion that you can blow out in one second.

8
Q

spirometry is more

A

reproducible than PEF

9
Q

What airways does spirometry mostly detect changes in

A
  • Mostly detects changes in the smaller airways
10
Q

What is PEF

A
  • Maximal rate that a person can exhale during a short maximal expiratory effort after a full inspriation
11
Q

What is PEF useful for detecting

A
  • detecting changes or trends in a patients asthama control
12
Q

What type of airways does PEF detect changes in

A
  • detects changes mostly in the larger airways
13
Q

PEF has significant

A

testing variability

14
Q

what is the differences in spirometry in obstructive and restrictive lung disorders

A

Obestructive

  • FEV1 is lowered by a greater proprotion than the FVC
  • FVC is lowered
  • FEV1/FVC is lowered

restrictive

  • FEV1 is lowered
  • FVC is lowered
  • FEV1/FVC is raised or normal
15
Q

What is the normal FEV1/FVC ratio

A

when the ratio is 0.7 or 70% or above

16
Q

If the FEV1/FVC falls below 0.7 what type of lung disease is this

A

Obstructive

17
Q

Name some obstructive disorders

A
  • asthma
  • COPD
  • endobronchial tumour
  • foreign body
18
Q

Name some restrictive disorders

A
PAINT 
P- pleural 
A - alveolar 
I - interstitial 
N - neuromuscular 
T - thoracic cage
19
Q

define tidal volume

A
  • volume of air breathed in and out in each breath at rest
20
Q

How do you wokr out inspriatory capaicty

A

IRV + TV

21
Q

How do you work out vital capacity

A

IRV + TV + ERV

22
Q

How do you work out total lung capacity

A

IRV + TV + ERV + RV

23
Q

How do you work out functional residual capacity

A

ERV + RV

24
Q

Why can you not measure residual volume on spirometry

A
  • RV cannot be expired
  • Since RV is the volume left in the lungs after a maximal expiration, it cannot be measured by simple spirometry. Similarly, the capacities containing RV (i.e. FRC & TLC) cannot be measured directly with a spirometer
25
Q

How do you measure residual volume

A
  • use a tracer gas (helium) which mixed with the air in the lung but does not diffuse out the lung
  • the volume is then determined by the amount that this tracer gas is diluted as it mixes with the air in the lungs
26
Q

How do you measure oxygen transfer

A

O2 transfer is measured indirectly using CO

- CO has a higher affinity than oxygen

27
Q

What happens to the flow volume loop in obstruction

A
  • loop moves to the left
28
Q

What happens to the flow volume loop in restrictive

A
  • loop moves to the right
29
Q

What happens to the flow volume loop in extrathroacic tracheal obstruction

A
  • inspriatory loop is flattend but the expriatory loop is normal
30
Q

What happens to the flow volume loop in intrathroacic large airway obstruction

A
  • expiratory loop is flattend but the inspiratory loop is normal
31
Q

anything between

A

80-120% is given as normal in lung function tests

- excpet the FEV1/FVC ratio in which the normal value is 0.7

32
Q

Why do you measure alveolar volume

A
  • measures CO transfer or KCO