Resp. function tests Flashcards
What limitations/ problems may arise when completing respiratory function tests
- Need to understand orders
- Max effort
- Mouthpiece leak
- Ability to carry out orders
What is normal resp rate
<25
What is plotted in spirometry
Volume/ time
What is the FEV1/ VC if there is an obstructive defect
<75%
What is an obstructive defect typical in
Asthma, COPD, upper airway obstructions
What is the FEV1/ VC ratio in a restrictive defect
> 75%
What is restrictive defect typical in
Lung fibrosis, reduced chest wall movement and muscle disease
When is peak flow typically reduced
Large airway obstruction
Upper airway obstruction
Asthma
What diseases effect peak flow less
COPD
Small airway disease
When is peak flow lowest
Morning
What pattern is seen on peak flow charts with asthma
Saw tooth pattern
What changes in peak flow must be observed with asthma to determine diagnosis
- > 20% dirunal variation for 3 days a week for 2 weeks
With what kind of training may peak flow increase
Inspiratory muscle training
What changes in FEV1 must be seen after use of bronchodilators to determine obsuctive disease is reversible
Increase by >15% or 200ml
A 15% increase in FEV1 is adequate to suggest reversibility after….
a) 400mg salbutamol via spacer
b) 2.5mg by nebuliser
c) 30mg/day of steroids for 14 days
What may be the problem if there is reduced inspiratory limb flow with normal expiratory flow
Extra-thoracic obsutrction
What may be the problem if there is reduction in both inspiratory and expiratory flow
Intra-thoracic obsutrction such as a goitre
How do you measure vital capacity
Spirometry
How can you measure total lung capacity
- Inspiration of gas mixture including helium
- Rebreathing
- Dilution of helium and decrease in concentration * vital capacity= TLC
Where do oxygen and co2 diffuse
Oxygen diffuses into circulation
CO2 diffuses out of the lungs
How can you calculate alveolar volume and gas transfer
- Single large breath of air with CO and helium
- Calculate total CO transfer and per l of lung volume
What does TLCO stand for and how do you calculate it
Transfer factor for CO
=kco*va
What can cause decreased TLCO (4)
- Anaemia
- Decreased perfusion
- Decreased ventilation
- V/Q mismatch
What can cause increased TLCO (3)
Increased CO
Polycythaemia
Alveolar haemorrhage
