Spirometry Flashcards
What does a spirometer measure, produce and what can this be used to calculate?
Records the volume of air that is breathed in & out ->
Generates tracings of air flow (pneumotachographs/ spirograms)->
Used to calculate: vital capacity, tidal volume, Flow rate of air movement
Reasons for pulmonary function tests
- Diagnosis - tests are rarely diagnostic alone, used together with history & examination
- patient assessment (most usual reason) e.g. serial changes, response to therapy, assessment for compensation, pre-surgical assessment
- research purposes e.g. epidemiology, study of growth & development, investigation of disease processes
What’s a vitalograph?
Make of a spirometer which records the volume expired during a vital capacity breath
Use a volume X time graph to calculate the following: vital capacity, tidal volume, expiratory reserve, residual volume, function residual capacity, inspiratory reserve volume, total lung capacity
Vital capacity - highest inspiration reached from normal expiratory reached
Tidal volume - normal inspiration reached from normal expiratory reached
Expiratory reserve - from normal expiratory reached to lowest expiratory reached
Residual volume - volume below lowest expiratory point reached
Functional residual capacity - residual volume + expiratory reserve
Check slide 6
IRV - volume from normal inspiration to max inspiration
Total lung capacity - highest inspiration to O volume (VC + RV)
Check slide 10
Draw out the shape of a normal flow X volume graph and label inspiration and expiration.
How do you calculate vital capacity total lung capacity and peak expiratory flow? Explain the shape of the expiratory curve.
Slide 6
&
Slide 21 - upward deflection air leaving large airways quickly, downward deflection small airways
Draw out a normal volume X time graph, now draw it to show obstructive and restrictive disease. Explain how FEV1 and FVC are calculated and what the ratios would be for each disease type. Give an example of each disease type.
Slide 6
Obstructive - FVC not markedly reduced, FEV1 markedly reduced. FEV1/ FVC ratio <70% (reduced speed at which air breathed out) e.g. asthma, COPD
Slide 18
Restrictive - FVC markedly reduced, FEV1 normal or even greater so FEV1/ FVC ratio _>70% e.g. lung fibrosis ( lungs stiff so cannot expand adequately but speed at which air breathed out is normal)
Slide 19
How would you calculate the following lung capacities from a volume x time graph: inspiratory, inspirational, functional residual capacity?
Inspiratory capacity: VT + IRV
Inspirational: VT + IRV
Functional residual capacity: ERV + RV
What is FEV1 , FVC and peak expiratory flow? Show how you would calculate them form a volume X time graph
forced expiratory Volume exhaled in the first second
Forced volume capacity - max amount of air that the patient can forcibly exhale after taking a max inhalation
Peak expiratory flow - max speed of airflow as the patient exhales
See slide 14
How does deflection change if you do an expired volume X time graph?
E.g. patient inspires to vital capacity and then only rapid forced expiration measured
Expiration shown as upward deflection (different to normal)
What do you see in an asthmatic flow- volume loop? compare this to someone with COPD.
Scalloping (bend) in downward expiratory deflection as air moves out of small airways and they contract abnormally slide 22
Will become linear with bronchodilators
COPD - more obvious scalloping (no/ less change with bronchodilators)
What would a flow- volume loop look like in the following: fixed extra- thoracic obstruction, cough, restrictive lung disease, supper airway obstruction?, vocal cord dysfunction?
FETO - flattened exp, prevents large airways effectively letting air exhale
Cough- wobbly baseline exp
Restrictive - narrowed exp
Upper airway obstruction
variable - shallower, wavey insp
Fixed- shallower insp, shallower exp
VCD - crazy insp v Wobley
