Resp. Misc. 5 - Overview of Lung Function Tests Flashcards
What are the 3 main categories of pulmonary function tests?
Effort dependent tests
Effort independent tests
Gas diffusion tests
What are 2 effort dependent pulmonary function tests?
Peak Expiratory Flow (peak flow metre)
Spirometry (forced expiatory volumes)
*these are the most important in clinical practice
what does the flow rate =
Volume / time
What are 5 effort independent tests?
Relaxed vital capacity (spirometry)Helium/ N2 washout stati lung volumesWhole body plethysmographyImpulse oscillometryExhaled breath nitric oxide*these are the most important in clinical practice
What are 3 gas diffusion tests?
CO transfer testsArterial blood gases (resting)SaO2 during exercise*these are the most important in clinical practice
What is the name for the following ratio:FEV1/FVC?
Forced expiratory ratio (FER)
What does RVC stand for?
Relaxed vital capacity
What is the difference between static and dynamic lung volumes?
Static = not concerned with rate at which they are inspirited or exhaledDynamic = dependent on the rate (FVC)
How many times do the airways divide?
23 times
In terms of spirometry, where is air trapping suggested?
When there is a major difference between the relaxed vital capacity and the forced vital capacity
Do people with asthma or COPD normally have a full forced vital capacity?
FVC is normally preserved in asthmatics although it is normally lowered in COPD (due to remodelling)
Is the reduced FVC in COPD patients usually proportionate to the reduced FEV1?
No meaning the ratio is still lowered where as in restrictive conditions both are reduced proportionally meaning the ratio is usually normal
if you plot the expiatory flow rate against the forced expiatory volume (from TLC to RV), what is the shape for:-normal?-volume dependent airway closure e.g. asthma, chronic bronchitis-pressure dependent airway closure e.g. emphysema
Normal = comes to a peak and decreases Volume = comes to less f a peak and decreases in a curve instead of a straight linePressure = comes to a much lesser peak and decreases suddenly
What test produces the flow-volume curve?
Spirometry (have to take gradients from some line)
What values can be extracted from the flow-volume curve?
Peak expiatory flow rate (PEFR)Forced expiatory flow rate (FEFR) at a % of FVC
What are the units of the peak expiatory flow rate?
L/min
Apart from spirometry, what other instrument can be used to measure the peak flow rate?
Simple linear peak flow meter
What is the peak expiatory flow rate?
The person’s maximum speed of expiration
PEFR in obstructive disease?Restrictive?
DecreasedNormal
FEV1 in patients with obstructive disease?Restrictive?
DecreasedDecreased
FVC in patients with obstructive disease?Restrictive?
Normal in asthmatic and decreased with COPDDecreased
FEV1/FVC ratio in obstructive?Restrictive?
Less than 75%Greater than 75%
Fev1 response to B2-agonist in asthmatics?COPD?Restrictive?
greater than 15%less than 15%No response
3 main types of triggers used in bronchial challenge testing?
ExerciseMetacholine/ histamine/ mannitol Allergens/ chemicals
What is a reaction of the airways to metacholine/ histamine/ mannitol a marker of?What is measured during this?
Airway hyper-responsiveness markerConcentration to produce 20% decrease in FEV1
Why do asthmatic patients not get wheezy in general until after exercise?
Adrenaline causing bronchodilation
What is cardiopulmonary exercise testing used to differentiate between?What does it involve?
To differentiate between cardiac and respiratory dyspnoeaMeasuring heart rate, oxygen uptake and ventilatory rate during exercise
What happens to SaO2 during exercise in interstitial lung disease?
It drops (used to monitor treatment response)
What happens to the functional residual capacity in COPD?
It increases in expense of Inspiratory capacity
What does CO diffuse across?
Alveolar capillary barrier
What is the total lung transfer for CO (TLCO)/ (interchangeable with DLCO)?
The total lung transfer for CO (corrected for alveolar volume (KCO)) - very sensitive measure of gas diffusion = implies integrity of alveolar-arterial vascular bed (anythings that impairs the bed will give a reduction in TLCO)
What can reduce TLCO? (6)
AnaemiaEmphysemainterstitial lung diseasePulmonary oedemaPEbronchiecstasis
How is airway resistance measured?
Either by whole body plethysmography or more commonly/ easily with impulse oscillometry
What does impulse oscillometry measure?
Airway resistance during quiet tidal beathing at different resonant frequencies to give total resistance and central resistance and hence peripheral airway resistance
When is impulse oscilometry particularly useful?
In patients (i.e. kids) where it is easier to breathe at tidal volume than doing forced expiatory manoeuvre
what is exhaled breath condensate?
Exhaled breath nitric oxide measured at a flow of 50ml/s
What does is exhaled breath condensate a non invasive marker of?
Eosinophilic airway inflammation in asthma
Why is exhaled breath condensate not useful in COPD?
NO suppressed by smoking
What does high levels of exhaled NO (>35ppb) reflect?
Uncontrolled asthmatic inflamation
What 2 tests are used to assess asthmatic inflammation especially when spirometry is normal?
Bronchial challengeExhaled breath condensate
