Spirometry Flashcards
(24 cards)
What is FEV1?
Forced Expiratory Volume in one second. Reduced in both OLD and RLD
What is vital capacity?
Maximal amount of air breathed out steadily from full inspiration to maximal expiration (not time dependant). In a normal pt the VC should be greater than LLN. Reduced below LLN suggests restrictive disease of severe OLD
What is FVC?
Forced vital capacity, maximum volume blown out as hard as possible from maximal inspiration to maximal expiration. Reduced below LLN in restrictive and possibly in severe OLD
What does a FEV1/VC ration <LLN suggest?
Airflow obstruction
What can the %predicted FEV1 used for?
Grading the severity of airflow obstruction.
Mild >79%
Moderate 50-79%
Severe 30-49%
Very severe <30%
What is PEF?
Peak expiratory flow (L/min) - maximum speed of forced expiration, following inspiration to total lung capacity. Limited clinical use alone, but can be useful in monitoring serial asthma
What does the flow volume graph show?
It can identify type and distribution of airway obstruction. Often seen in asthma and COPD as a scooping in the expiratory section of the loop
The degree of reversibility to β2 agonist
Technique can be seen in real time
What are reference values?
Lung health predictors are based on patient age, gender, height and ethnicity. Results are typically displayed as a percentage of the predicted value.
What are SRs/Z-scores?
They define whether results are within ‘normal range’
What are some databases for reference values?
European Community for Coal and Steel (ECCS)
Global Lung Initiative (GLI)
What are pros/cons of GLI and ECCS?
ECCS equations are based on male coal miners 23-65, mostly caucasian, cohort not screened for non smokers, no spirometry guidelines, performed in 1960s so change in data and technology
GLI is global and multi-ethnic reference equations for spirometry that span all ages
What disease patterns can spirometry identify?
Obstruction and restriction
What can cause airflow obstruction?
Inflammation
Bronchospasm
Mucus
Loss of elastic support to the airways
What are the spirometry results for airflow obstruction?
FEV1 low
FVC -
FEV1/VC low
What is airflow obstruction?
Narrowing of the airways causing flow to be limited during forced expiration
What is airflow restriction?
Reduced volume in lungs due to inability of lungs to expand
What can cause airflow restriction?
Intrapulmonary diseases:
Pulmonary fibrosis
Pulmonary oedema
Collapse/consolidation of the lung
Extra-pulmonary conditions:
Large pleural effusion
Rib cage / spinal deformity (scoliosis)
Respiratory muscle weakness
Obesity
What spirometry values would you find with airway restriction?
Low FEV1
Low FVC
High FEV1/VC ratio
What values would you find with mixed obstruction and restriction on spirometry?
FEV1 low
FVC low
FEV1/VC low
What does FEV1/VC ratio reduced below LLN indicate?
Airflow obstruction
In the presence of obstruction, what does FEV1 % predicted indicate?
Severity of obstruction
What does VC less than LLN suggest
Restrictive defect
What is the pathway for spirometry interpretation?
Check FEV1/VC ratio. Is it less than LLN (SR -1.64)
Yes
Is VC less than LLN?
No -> obstructive -> categorise severity using FEV1 % predicted
Yes -> Combined
No
Is VC less than LLN?
Yes -> restrictive
No -> Normal
