Lung function tests Flashcards
what are lung funtion tests?
- Pulmonary function tests are non-invasve that allow us to evaluate monitor and manage
- can measure lung air flow, volumes and rates
- lung volumes and capacities
what are the two most common PFTs
- PEFR -> use a peak flow meter
- Spirometery
what is a peak flow meter
- maximal expiration
- blow out as hard as you can
what is residual volume
after full expiration, you still have some air left in your lungs
what is residual volume
after full expiration, you still have some air left in your lungs
label this graph
label this diagram
what does vital capacity rely on
- it may be reduced due to to lungs not being fully filled in inspiration
- lungs not fully emptied on expiration
- could be both
- ## can be due to lungs being stiff eg, pulmonary lung fibrosis as a form of interstitial lung disease
what is forced vital capacity
- during expiration small airways are compressed
- there is a point when no more air can be driven out the alveoli
- ## if expiratory flow is compromised much earlier in expiration then this produces an obstructuve deficit -> Chronic obstructuve lung disease
what does it mean if FVC>0.7
and FVC<0.7
- FVC<0.7 =obstructive
- FVC>0.7 = restrictive
what are some features of obstructive defect
- FVC nearly normal in early days but may decrease if there is ari trapping
- FEV1 is reduced
- FEV1/FEV < 0.7
- seen in asthma, COPD, bronchiastasis
what are some features of a restrictive defect
- TLC is reduced
- FVC is reduced
- FEV1 is reduced proportionately
- FEV1/FVC is normal
- lung fibrosis, interstitual lung disease, myasthenia gravis
mild obstructive flow chart
moderate obstructive flow chart
restrictive flow limitation
- vital capacity is reduced
- FEV1 is reduced
- there is an elevated FEV1 ratio due to reduced complications
in which situaton does a bronchodialator help
significant improvement in asthma than in COPD
label this
what is tidal volume
- amount of air moving in and out of the lungs
what is inspiratory reserve volume
- additional amount of air that can be inhaled after normal inspiration (how much more air we breathe in after tidal volume)
what is expiratory reserve volume
additional amount if air we can expel
what is inspiratory capacity?
tidal volume + inspiratory reserve volume
what is functional residual capacity
expiratory reserve volume + residual volume
vital capacity equation
volume exhaled after max inspiration - sum of inspiratory volume + tidal volume + expiratory reserve volume
DLCO test
- diffusing capacity carbon monoxide
- lets us determinate how much oxygen travels from alevoili of lungs to blood eg diffusion
- can be decreased due o:
- emphysema - reduced surface area
- alveolar inflammation - increased thickness
- pulmonary fibrosis - increased thickness
how do you differentate different restrictive lung diseases
- parenchymal lung disease -> restructive pattern and abnormal DLCO
- chest wall abnormalities - normal DLCO
- neuromuscular (myasthenia gravis) normal DLCO
