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Respiratory > Lung function tests > Flashcards

Lung function tests Flashcards

1
Q

Contraindications for spirometry

A

Eye surgery
Thoracic/abdominal/brain/ear/ENT or vascular surgery
Lung disease - pneumothorax, haemoptysis, PE, chest infection
Ear infection
CVS disease
Aneurysms
Acute nausea, omitting, diarrhoea
Infection control
Confused/demented

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2
Q

When are pulmonary function tests used?

A

Diagnosis if respiratory symptoms
Establish progression and severity
Assess treatment response
Monitor patients on meds with lung toxicity - eg chemotherapy

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3
Q

What do pulmonary function tests measure?

A

Lung volume
Rate of airflow
Gas exchange

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4
Q

Methods/instrument examples of PFT’s

A

Peak flow rate meter
Spirometry
Diffusing capacity for carbon monoxide
Body plethysmography

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5
Q

What is peak expiratory flow rate?

A

Maximum airflow rate attained during forced expiration in L/s (PEFR)
Attained using peak flow meter

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6
Q

Normal peak flow

A

Greater than or equal to 80% of predicted average value

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7
Q

What is PEFR predicted average based on?

A

Height
Gender
Age
Ethnicity?

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8
Q

What is a peak flow meter useful for?

A

Monitoring people with asthma - give baseline when asymptomatic
When asthmatics notice a decrease in their normal peak flow they can seek medical help sooner and keep it well managed

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9
Q

What is spirometry used for?

A

Lung volumes
Airflow - volumes are measured over time
Produces graphs (FEV1 and FVC)

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10
Q

LEARN the lung volume and capacity graph

A

Page 10 of LFT lecture

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11
Q

Tidal volume define

A

Amount of air moving in and out of lungs at rest

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12
Q

Inspiratory reserve volume define

A

Additional amount of air that can be inhaled after normal inspiration (air we can breathe in above tidal volume)

These are forced and not natural

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13
Q

Expiratory reserve volume define

A

Additional amount f air that can be exhaled after normal expiration (ow much more air we can breathe out below tidal volume on graph)

These are forced and not natural

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14
Q

What is residual volume?

A

Volume of air remaining in lungs after forceful expiration

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15
Q

Inspiratory capcacity?

A

TOTAL volume of air that can be inspired after normal expiration

(tidal volume and inspiratory reserve)

ie deepest breathe in

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16
Q

What is functional residual capacity?

A

Volume of air present in lungs at the end of a passive expiration (NOT FORCED LIKE RESIDUAL VOLUME)

= expiratory reserve volume + residual volume

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17
Q

What is vital capacity?

A

Volume of air EXHALED after maximum inspiration

(inspiratory reserve + tidal + expiratory reserve)

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18
Q

Total lung capacity?

A

volume of air contained in lungs at end of maximal inspiration
(TV + inspiratory reserve volume + expiratory reserve volume + residual volume)

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19
Q

FEV1

A

Maximum volume of air that can be forcefully exhaled within 1 second after maximal inspiration

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20
Q

FVC

A

Total volume of air breathed out following maximal inhalation
Occurs over 6 seconds

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21
Q

FEV1/FVC?

A

Proportion of patients forced vital capacity that they are able to expire i first second

22
Q

Cut off value for FEV/FV

A

If <0.7 (70%) = obstructive pattern

23
Q

What happens in early COPD to FEV1 and FVC?

A

In early COPD, FVC can still be the same it just may take pt’s longer to get there so their FEV1 reduces
In late COPD, both reduce

Overall, decrease in FEV1/FVC as FEV1 reduces by a larger amount than FVC

24
Q

Two graphs in spirometry

A

Volume time plot - volume over time

Flow volume loop (shape) - rate of airflow over volume

25
Q

Volume time plot description

A

Time in seconds along bottom
Expired volume in litres along side
FEV1 is read at 1 second where graph is level with y axis
FVC is maximum volume graph line reaches

26
Q

What is the initial gradient in a volume time spirometry graph? ie draw a tangent at steepest point of graph

A

Peak expiratory flow rate (PEFR)

27
Q

Axis in flow volume loop

A

Volume across middle in litres
Flow across side in litres per second

Expiration is above volume line
Inspiration is below

28
Q

What can you read from flow volume loop?

A

PEFR - peak point of graph in expiration

Residual volume - where inspiration and expiration meet at furthest X axis point

Total lung capacity - volume after maximal inspiration (closest to 0 on flow rate)

29
Q

What does spirometry predicted values depend on?

A

Height
Age
Sex
Ethnicity

30
Q

Two examples of diseases causing obstructive spirometry pattern

A

COPD
Asthma

31
Q

What happens to FEV1 in obstructive lung disease?

A

FEV1 is REDUCED - this indicates severity

32
Q

What happens to FVC in obstructive lung disease?

A

COPD - initially normal, will decrease when severe
Asthma - FVC typically decreased (small airways close prematurely)

33
Q

KEY DIAGNOSTIC finding for spirometry suggesting obstructive pattern?

A

FEV1/FVC is LESS than 0.7

34
Q

What happens when there is air trapping in obstructive lung disease to lung volumes?

A

Increased total lung capacity and functional residual capacity - lungs will have increased residual volume as they are trapping air inside

35
Q

What happens with asthma spirometry between attacks/using inhalers?

A

Should see an improvement of FEV1 by 12% or more - spirometry should be normal between attacks

36
Q

Do people with COPD respond to inhalers?

A

To a degree yes if they have reversible airway obstruction

37
Q

Volume time graph for obstructive lung disease

A

Decreased FEV1
+/- decreased FVC

(remember if FEV1/FVC is decreasing, only FEV1 needs to decrease ella)

38
Q

Flow volume loop for obstructive lung disease

A

‘Scalloping’ or ‘coving’ of the expiration half - looks indented
This shows there is difficulty breathing out as curve it less steep

39
Q

Restrictive lung disease FEV1 an FVC

A

FEV1 - normal or decreased - decrease is proportionate to FVC
FVC is decreased

THIS causes a normal or increased FEV1/FVC as FVC is the one which is always going to be smaller (dividing by smaller number = increased number)

40
Q

What happens to total lung capacity and functional residual capacity in restrictive lung disease?

A

Always decreased - cannot inflate lungs well

41
Q

Restrictive spirometry pattern gvolume time graph

A

FVC massively reduced
FEV1 may be reduced

42
Q

Flow volume graph for restrictive lung disease

A

Wizards hat appearance - both expiration and inspiration have decreased, there is a steep sharp gradient as expiration occurs (pushes air out fast, pointy hat)
Overall size of top and bottom of graph has decreased

43
Q

Main issue in obstructive lung disease vs restrictive

A

Obstructive - Lungs find it difficult to exhale and get air out
Restrictive - lungs find it difficult to get air in

44
Q

What is DLCO?

A

Diffuse capacity of carbon monoxide - measures CO diffusion to determine how much O2 can travel from alveoli into bloodstream

45
Q

Causes of restrictive lung disease

A

Interstitial lung disease - pulmonary fibrosis eg coal miners pneumoconiosis

46
Q

When can DLCO be decreased?

A

Emphysema - decreased surface area
Alveolar inflammation - increased thickness
Pulmonary fibrosis - increased thickness

ALL affect diffusion across alveolar

47
Q

What do emphysema, alveolar inflammation and pulmonary fibrosis also show alongside decreased DLCO?

A

Abnormal spirometry or CXR

48
Q

So what does it mean if you have normal CXR with abnormal DLCO’s?

A

Something is wrong with the vascular part of membrane - blood supply is the problem eg pulmonary arterial hypertension

49
Q

So what will parenchymal lung diseases show on spirometry and DLCO?

A

Restrictive pattern of spirometry and abnormal DLCO

50
Q

Four examples of restrictive spirometry pattern causes

A

Kyphoscoliosis
Pulmonary fibrosis
Interstitial lung disease
Myasthenia gravis - or any neuromuscular disease

51
Q

Check end of lecture to see images of the graphs

A

:)

Respiratory (21 decks)

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