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Cardiorespiratory CC > Resp Function Tests > Flashcards

Resp Function Tests Flashcards

1
Q

Spirometry Aim

A

Diagnostic tool to assess lung disease, quantify lung impairment, monitor the effects of occupational/environmental exposure + determine effects of medications

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2
Q

Spirometry Description

A

Measure expired + inspired air
Volume, time and flow
Measure FEV1 and VC

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3
Q

Hering-Breuer Reflex

A

Reflex triggered to prevent over-inflation of the lung

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4
Q

Obstructive defect

A

FEV1 more reduced than VC
FEV1/VC <75%
Asthma
COPD

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5
Q

Restrictive defect

A

FEV1 reduced no more than VC
FEV1/VC ratio >75% and may be 100%
VC reduced

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6
Q

Peak flow measurement

A

Only valid if done at TLC and with max effort

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7
Q

Peak flow reduction

A

Large airway obstruction
Upper airway obstruction
Asthma

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8
Q

Peak flow less affected in

A

COPD

Small airway disease

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9
Q

Interpreting Spirometry data

A

In adults, age, height, sex + race main determinants

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10
Q

Reduced inspiratory limb flow with normal expiratory flow

flow vol loop

A

Extra-thoracic obstruction

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11
Q

Equal reduction in both flows

flow vol loop

A

Intrathoracic obstruction

e.g. retrosternal goitre

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12
Q

Obstructive Flow vol loop

A

Shifts to left
Scoop in top bit, and smaller top bit
Same bottom bit

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13
Q

Restrictive flow vol loop

A

Shifts to right

Exact same shape as normal but smaller

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14
Q

FEV1/FVC ratio

A

Ratio of Forced Expiratory volume in 1 sec + forced vital capacity

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15
Q

FEV1/FVC ratio incorrect in

A

Asian communities

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16
Q

Total lung capacity measurement

A

Inspiration of gas mixture which includes helium, with rebreathing and VC manoeuvre for mixing
Dilution of helium + decrease in concentration x VC gives TLC

17
Q

Alveolar volume + gas transfer calculation

A

Single large breath of air + CO + helium

Hold breath for 10 seconds

18
Q

TLCO equation

A

KCO x Ca

19
Q

Decreased TLCO

A

Decrease perfusion
Decrease ventilation
V/Q mismatch
Anaemia

20
Q

Increased TLCO

A

Increased CO
Polycythaemia
Alveolar haemorrhage

21
Q

The Fick principle

A

the volume of gas per unit time which diffuses across a tissue sheet is proportional to:

  • proportional to area of sheet
  • inversely proportional to thickness
  • proportional to difference in pressure on 2 sides
  • dependent upon permeability coefficient for that gas
22
Q

Fick equation

A

Volume/time = area/thickness x pressure (P2-P1) x diffusion constant

23
Q

Diffusion constant

A

Dependent on solubility + molecular weight of gas

More soluble, easier to pass

24
Q

Graham’s law

A

Rate of diffusion of a gas is inversely proportional to the square root of molecular weight
Bigger things diffuse more slowly

25
Q

Gas transfer reduced with

A

Reduced SA
Increased thickness of membrane
Reduced O2 conc.
Inadequate time

26
Q

DLCO/TLCO

A

Measures how efficient lungs are at exchanging gases

Ability of lungs to transfer gas from inhaled air to RBCs

27
Q

Haemoglobin binding

A

CO>O2 (200-250x)

28
Q

DLCO

A

Lung SA available for gas exchange (Va) x rate of capillary blood CO uptake (Kco)

29
Q

DLCO/TLCO

A

Quantity of CO transferred per min from alveolar gas to red blood cells (mL/min/mmHg)

30
Q

DLCO/TLCO normal

A

> 75%

31
Q

Increased DLCO

A

Exercise
Supine
Pulmonary haemorrhage
Polycythemia
Obesity
Left to right shunt- atrial septal defect
Muller manoeuvre- inspiration against closed mouth + nose after expiration

32
Q

Decrease DLCO

A 
Post exercise
Standing
Valsava manoeuvre 
Lung resection
Pulmonary emphysema
Interstitial lung disease
33
Q

ILD

A

Decreased DLCO due to decreased Kco (fibrosis of interstitium)
Useful for early ILD detection

Cardiorespiratory CC (34 decks)

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