Spirometry

Question 1

standard spirometry indices?

Answer 1

FEV1 (forced expiratory volume in 1 sec)
FVC (total volume of air which can be forcibly expelled in one breath)
FEV1/FVC (fraction of total air exhaled which can be exhaled in 1 sec)

Question 2

additional indices?

Answer 2

VC (full relaxed breath volume, not done under force)
FEV6 (forced volume in 6 secs)
MEFR (mid-expiratory flow rate)

Question 3

normal spirometry trace (volume/time)

Answer 3

sharp upward slope, then plateaus
volume at 1sec = FEV1
volume at 6secs = FVC

Question 4

normal FEV1/FVC?

Answer 4

> 0.7 (70%)

remember to combine with history (eg you would expect a fit young person to be fair bit >0.7

Question 5

3 obstructive diseases?

Answer 5

asthma
COPD
bronchiectasis

Question 6

obstructive disease mainly affects inhalation or exhalation?

Answer 6

exhalation

Question 7

obstructive spirometry trace?

Answer 7

shallower curve (not a sharp upward curve as cant expel lot of air quickly)
some cases reach a normal FVC eventually, some dont

Question 8

FEV1, FVC and FEV1/FVC in obstructive disease?

Answer 8

FEV1 = redcued
FVC = can be normal or slightly reduced
FEV1/FVC = reduced

Question 9

how is COPD diagnosed in most cases?

Answer 9

clinical

symptoms and history

Question 10

diagnostic test for COPD? (not usually needed)

Answer 10

post-bronchodilator FEV1/FVC
measure FEV1/FVC 15 mins after 400mcg salbutamol or equivalent
(has to be after bronchodilator to distinguish from asthma as asthma would basically resolve after bronchodilator)

Question 11

examples of restrictive disease?

Answer 11

anything causing fibrosis (ILD, sarcoid, idiopathic pulmonary fibrosis etc)
obesity
neuromuscular problems
scoliosis

Question 12

FEV1, FVC and FEV1/FVC in restrictive disease?

Answer 12

FEV1 = normal or mildly reduced
FVC = <80% predicted
FEV1/FVC = normal (both reduced same amount)

Question 13

spirometry trace in restrictive disease?

Answer 13

same sharp upward curve but it stops short and plateaus at a lower volume
(so can expel at normal rate, just not as much overall)

Question 14

what is a flow volume curve?

Answer 14

shows flow rate against volume rather than volume against time
exhalation on top and inhalation in bottom
shows peak flow

Question 15

obstructive flow volume curve?

Answer 15

same sharp upstroke but stops short of normal peak flow rate
scooped out downstroke as airways start to close while exhaling (will close more quickly in more severe disease causing steeper drop off and bigger scoop out)

Question 16

restrictive flow volume curve?

Answer 16

basically normal flow rate but doesnt last as long (less overall volume)

Question 17

what is gas transfer?

Answer 17

measurement of ability of oxygen to be absorbed at alveolar level

Question 18

gas transfer values?

Answer 18

DLCO (diffusion capacity of lung for carbon monoxide)

KCO = corrected DLCO for measured alveolar volume

Question 19

how is DLCO measured?

Answer 19

breathe in a known amount of CO then check how much is breathed out, if a lot breathed back out then not good transfer

Question 20

how is COPD mainly graded?

Answer 20

ABCD
A = few symptoms or exacerbations
B = more symptoms, few exacerbations
C = few symptoms, more exacerbations
D = more symptoms and exacerbations