Pulmonary function tests Flashcards
What can a volume- time curve show us?
FEV1 - read up from x at 1 sec
FVC- highest observed y value
Peak expiratory flow rate- for the steepest part: (change in y/ change in x) x 60
What can a flow- volume loop show us?
FEV1- given
FVC-highest x value on curve
Peak expiratory flow rate- peak y value x 60
How is a flow-volume loop produced?
- Patient wears nose clip
- Patient wraps lips around mouthpiece and completes at least 1 tidal breath
- Patient inhales steadily in to total lung capacity
- Patient exhales as hard as possible until residual volume is reached
- Patient immediately inhales to total lung capacity
What is an obstructive disease?
Airway disease- inflamed and easily collapsible
Obstructs you from emptying your lungs
Airway trapping due to mucus plugs and airway collapse
FVC will be the same- can get normal amount of air out just takes longer
FEV1 is reduced- can’t get air out quick enough
FEV1/FVC ratio is normal or lower
E.g. Bronchitis, Emphysema, COPD, Asthma
What is a restrictive disease?
Extra-airway disease
Restrict the ability for lungs to fill
Stiffening of lungs from fibrotic tissue replacing healthy tissue means they can’t expand adequately for normal breath in
Reduced FVC
If airways unaffected then normal FEV1, can be lower
FEV1/FVC ratio is normal or increased
Flow volume loop becomes narrower
E.g. pulmonary fibrosis, pulmonary oedema
What is asthma?
Airway inflammation
Leads to accumulation of pro-inflammatory mediators which obstruct the lumen
Increased airway responsiveness to stimuli
Symptoms: dyspnoea, wheezing, coughing
Pathology: mucus plug, basement membrane thickens, smooth muscle hypertrophy
What is COPD?
Loss of elastic
Chronic bronchitis
Breakdown of alveolar walls leads to impaired gas exchange- this is emphysema
Symptoms include a characteristic wheeze
What is cystic fibrosis?
CFTR mutation in chloride channels
Viscous, mucous secretions
Bronchoconstriction
