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Physiology > lung function testing > Flashcards

lung function testing Flashcards

1
Q

what are the devices used for lung function testing?

A

peak flow meter
vitalograph
spirometer

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2
Q

peak flow meter

A

measures peak expiratory flow rate

rapid exhaled puff from full inspiration

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3
Q

normal peak flow range

A

500-600L/min

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4
Q

vitalograph

A

sustained forced expiration from full inspiration

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5
Q

what does vitalograph measure?

A

measures volumes exhaled
FVC
FEV1
cannot measure residual volume

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6
Q

what is the slope on a vitalograph?

A

PEFR - measured by peak flow meter

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7
Q

normal vitalograph

A

FEV1/FVC greater than 0.75/ 75%

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8
Q

spirometer

A

measures continuous trace

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9
Q

work of breathing

A

2 factors to overcome = resistance and compliance

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10
Q

resistance

A

ease with which gas flows through conducting airways

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11
Q

compliance

A

expandability of lungs and chest wall

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12
Q

increasing resistance

A

obstructive disease

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13
Q

what happens to vitalograph in obstructive disease?

A

same volume but takes longer to reach, gentler initial slope and plateaus later . FVC is same FEV1 decreases and ratio of FEV1:FVC decreases

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14
Q

decreases compliance

A

restrictive disease

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15
Q

what happens in obstructive disease?

A

increasing resistance

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16
Q

what happens in restrictive disease?

A

decreasing compliance

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17
Q

what happens to vitalograph in restrictive disease?

A

lungs cannot expand normally because of restriction . FVC decreases, FEV1 decreases and the ratio stays the same . the line is the same shape as the normal line but lower

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18
Q

what causes variation in lung function test results?

A

gender
height
age

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19
Q

example of obstructive diseases

A

asthma

COPD

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20
Q

example of restrictive diseases?

A

pulmonary fibrosis

sarcoidosis

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21
Q

what does a spirometer measure?

A

IRV
VC
Vt
ERV

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22
Q

what does a spirometer calculate for the height/ gender/ age of the person but is unable to measure?

A

FRC
RV
TLC

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23
Q

what is Vt

A

tidal volume

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24
Q

what is IRV

A

inspiratory reserve volume - how much more can be breathed in on top of tidal volume

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25
Q

what is ERV

A

expiratory reserve volume - how much can be breathed out on top of tidal volume

26
Q

what is RV

A

residual volume

27
Q

what is TLC

A

total lung capacity

28
Q

what is VC

A

vital capacity

29
Q

what is FRC

A

functional residual capacity

30
Q

what are capacities

A

the sum of 2 or more volumes

31
Q

mixed obstructive and restrictive disease

A

reduced FEV1
reduced FVC
reduced ratio
COPD produces a similar trace for different reasons
gentler initial slope, plateaus later and is lower

32
Q

COPD

A

lungs are hyperinflated at end of expiration and limits inspiratory reserve so IRV decreases

33
Q

FRC

A

quantity of gas in the lungs at the end of a normal expiration
results from the balance of forces acting inwards (lung elastic) and outwards (diaphragm and intercostal muscle tone)

34
Q

FRC in COPD

A

elastin in the lung is normally broken down by proteases but there are protease inhibitors that limit this . In COPD the balance is disturbed causing elastin destruction and hyperinflation (raised FRC) and alveolar destruction

35
Q

what protease breaks down elastin

A

elastase

36
Q

e.g. of protease inhibitor

A

alpha 1 anti-trypsin

37
Q

alveolar destruction

A

causes coalescence into large air spaces - bullae

38
Q

severe COPD

A

hyperinflation limits inspiration and airway closure limits expiration

39
Q

hyperinflation

A

due to breakdown of elastin there is nothing limiting the chest wall pulling the lungs outwards

40
Q

vitalograph trace for COPD

A

similar to mixed obstructive and restrictive disease

41
Q

reality of COPD vitalograph

A

stops after a second as most COPD patients are unable to sustain expiration for much longer

42
Q

sign of COPD on chest x–ray

A

hyperinflation, normally able to see 10 ribs max but can see more (11 or 12)

43
Q

what are the methods used to measure RV or FRC?

A

helium dilution

body plethysmohraphy

44
Q

helium dilution

A

known quantity of He is distributed throughout the lungs

FRC calculated from final concentration

45
Q

body plethysmography

A

inspiratory effort against a closed shutter produces measureable pressure and volume changes in box and lungs
FRC derived using boyles law

46
Q

what is wheeze?

A

from lower airway obstruction at level of bronchioles
heard on expiration
inside thoracic cavity

47
Q

what is stridor?

A

from upper airway obstruction
situated outside thoracic cavity
normally heard on inspiration

48
Q

what causes wheeze?

A

inflammation or smooth muscle spasm
greater expiratory effort increases positive intrapleural pressure, compressing small intrathoracic airways and limiting expiratory flow

49
Q

what happens in inspiration in relation to wheeze?

A

negative intrapleural pressure generated helps increase bronchiolar diameter, improving air flow

50
Q

what causes stridor?

A

tumours, infection, swelling, vocal cord palsy or foreign bodies
greater inspiratory effort creates a more negative pressure in thorx, which further narrows the obstructed part of the airway

51
Q

what happens in expiration in relation to stridor?

A

the greater positive pressure generated within the airways helps increase upper airway diameter, improving air flow

52
Q

how long does ventilation take?

A

0.75 seconds

53
Q

how long does full oxygenation take?

A

0.25 seconds

54
Q

difference in time for ventilation and fully oxygenation

A

allows a reserve in healthy lungs for exercise

55
Q

impaired diffusion

A

there may not be time for full oxygenation, especially during exercise

56
Q

how is diffusion capacity measured?

A

transfer factor - TLco

57
Q

how does TLco work?

A

carbon monoxide used, CO binds to haemoglobin, keeping plasma partial pressure at 0
single vital capacity inhaled with 0.3% CO and 10% He
breath held in for 10 seconds then exhaled and gases measured

58
Q

what is the purpose of He in transfer factor measurement?

A

to calculate initial volume and partial pressure of CO

59
Q

what happens to CO in TLco?

A

known starting volume and partial pressure of CO, CO readily binds to haemoglobin and then the final volume and partial pressure of CO is measured. The reduction in volume of CO enables rate of transfer to be calculated

60
Q

what is TLco measured in?

A

mL/kPa/min

Physiology (46 decks)

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