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lung function testing Flashcards

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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
what is ERV
expiratory reserve volume - how much can be breathed out on top of tidal volume
26
what is RV
residual volume
27
what is TLC
total lung capacity
28
what is VC
vital capacity
29
what is FRC
functional residual capacity
30
what are capacities
the sum of 2 or more volumes
31
mixed obstructive and restrictive disease
reduced FEV1 reduced FVC reduced ratio COPD produces a similar trace for different reasons gentler initial slope, plateaus later and is lower
32
COPD
lungs are hyperinflated at end of expiration and limits inspiratory reserve so IRV decreases
33
FRC
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
FRC in COPD
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
what protease breaks down elastin
elastase
36
e.g. of protease inhibitor
alpha 1 anti-trypsin
37
alveolar destruction
causes coalescence into large air spaces - bullae
38
severe COPD
hyperinflation limits inspiration and airway closure limits expiration
39
hyperinflation
due to breakdown of elastin there is nothing limiting the chest wall pulling the lungs outwards
40
vitalograph trace for COPD
similar to mixed obstructive and restrictive disease
41
reality of COPD vitalograph
stops after a second as most COPD patients are unable to sustain expiration for much longer
42
sign of COPD on chest x--ray
hyperinflation, normally able to see 10 ribs max but can see more (11 or 12)
43
what are the methods used to measure RV or FRC?
helium dilution | body plethysmohraphy
44
helium dilution
known quantity of He is distributed throughout the lungs | FRC calculated from final concentration
45
body plethysmography
inspiratory effort against a closed shutter produces measureable pressure and volume changes in box and lungs FRC derived using boyles law
46
what is wheeze?
from lower airway obstruction at level of bronchioles heard on expiration inside thoracic cavity
47
what is stridor?
from upper airway obstruction situated outside thoracic cavity normally heard on inspiration
48
what causes wheeze?
inflammation or smooth muscle spasm greater expiratory effort increases positive intrapleural pressure, compressing small intrathoracic airways and limiting expiratory flow
49
what happens in inspiration in relation to wheeze?
negative intrapleural pressure generated helps increase bronchiolar diameter, improving air flow
50
what causes stridor?
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
what happens in expiration in relation to stridor?
the greater positive pressure generated within the airways helps increase upper airway diameter, improving air flow
52
how long does ventilation take?
0.75 seconds
53
how long does full oxygenation take?
0.25 seconds
54
difference in time for ventilation and fully oxygenation
allows a reserve in healthy lungs for exercise
55
impaired diffusion
there may not be time for full oxygenation, especially during exercise
56
how is diffusion capacity measured?
transfer factor - TLco
57
how does TLco work?
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
what is the purpose of He in transfer factor measurement?
to calculate initial volume and partial pressure of CO
59
what happens to CO in TLco?
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
what is TLco measured in?
mL/kPa/min

Physiology (46 decks)

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