Interpretation of Lung Function Testing Flashcards
Reasons for lung function tests
Spirometry
PEF
Lung volume
Gas Exchange
What are values dependent upon?
Age Sex Height BMI Ethnicity
What doe spirometry measure?
Volume and/or speed/flow of air that can be inhaled and exhaled
Most common used measurements in spirometry
FEV1
FVC
FEV1/FVC
Define FEV1
Forced Expiratory Volume in one 1 second
Amount of ait you can blow out within 1 second
Normal lungs and airways mean you can blow out most of air from lungs
Define FVC
Total amount of air you can blow out in one breath
Define FEV1/FVC
Of the total amount of air than you can blow out in 1 breath, this is the proportion that you can blow out in 1 second
Why is spirometry better than PEF?
More reproducible
Detects changes in smaller airways vs. larger in PEF
PEF more variable
What is PEF?
Maximal rate that a person can exhale during maximum short expiratory effort after full inspiration
What is PEF useful for?
Detecting change or trends in asthma control
Obstructive Spirometry Result
FEV1 reduced
FVC same
FEV1/FVC reduced
Restrictive Spirometry Result
FEV1 reduced
FVC Reduced
FEV1/FVC normal or increased
Obstructive Diseases
Asthma
COPD
Endobronchial tumour
Foreign body
Restrictive diseases
PAINT P - pleural A - alveolar I - interstitial N - neuromuscular T - thoracic cage
Define RV
Volume left in lungs after max expiration
What are lung volumes
Measurements which cannot be measured by simple spirometry as contain RV which cannot be expired
How to measure RV?
Use tracer gas (helium) to mix with air in lung but doesn’t diffuse out
Check amount that tracer gas has diluted as it mixes with air to determine volume
How to measure gas transfer?
Indirectly measure oxygen transfer using CO
TLCO
TLCO/VA = KCO (measure of how good each alveoli is at gas transfer)
2 loops in Flow Volume Loop
Larger = Maximal Flow Volume Loop Smaller = Exercise Tidal Flow Volume Loop
VT, EELV, EILV, ERV, IRV, IC on flow volume loop?
VT = tidal volume EELV = end expiratory lung volume EILV = end inspiratory lung volume ERV = expiratory reserve volume IRV = inspiratory reserve volume IC = inspiratory capacity
What does an asthma flow volume loop look like?
Notched
Volume dependent
Reduced FEV1
What does severe emphysema look like on a flow volume loop?
Bigger notch than asthma
L shape
FEV1 even less
Pressure dependent
What does tracheal stenosis look like on a flow volume loop?
Rigid obstruction
Reduced width/volume
Box shape
Lost notch pattern
Difference between extrathoracic tracheal obstruction and intrathoracic large airway obstruction on a flow volume loop?
Extra = flow mostly above 0, insp flat, exp normal Intra = flow mostly below 0, exp flat, insp normal
Normal FEV1 and FVC
Normal FEV1/FVC ratio
80-120%
Ratio = 70%
