Spirometry Interpretation Flashcards
What factors should you check to interpret spiro results?
-check age, height, sex and ethnicity is correct on report
-check predicted values used
-is the spiro accurate and repeatable?
-look at the shape of the expiratory flow volume curve
-look at the data
-determine severity
Why is height important for spiro interpretation?
-used to calculate predicted values
-results expressed as % predicted
-over or underestimation of height results in incorrect or predicted values alter interpretation
-restrictive disorders bay be overdiagnosed or missed
-the severity of obstructive disorders will be incorrect
What guidelines do predictedc values have to follow?
ERS/ECCS -1993
-adult 18-70
for paeds predicted values reccommend Rosenthal-1993
GLI 2012
-26 cpuntries
-age 3-95
-ethnicity
-GLI is more accurate and the one followed
When should you discard a spiro test?
-Leak at the mouth
-Obstructed mouthpiece
-Poorly coordinated start to the manoeuvre
-Cough
-Early termination
-Submaximal inspiration
-Poor effort or compliance
How to determine if spiro is normal?
1-check trace and look at curve shapes are they normal?
2-is FEV1/FVC%> LLN or Z score>-1.64
3-is FEV1>LLN?
4-is FVC> LLN?
5-if all are> LLN then spiro is normal
What are the 4 patterns of spiro?
-normal
-obstructed
-restricted
-mixed
What is an obstricted flow in spiro?
-reduction in flow
-narrowed airways
examples- COPD, asthma, bronchiectasis
What is a restriction in spiro?
-reduction in volume
examples-, intistial lung disease, musculoskeletal, neuromuscular,obesity, pregnancy, ascites
How do we interpret spiro?
1-determine whether spiro is normal or abnormal
2-check FEV1/FVC%
3-if FEV1/FVC% is below LLN so a Z score of <-1.64 then there is airways obstruction
What does an obstructed spiro look like?
-becomes more scalloped
-decreased FEV1
-decreased or normal VC
-decreased FEV1/VC%
What does a restricted spiro look like?
-witches hat shape
-decreased FEV1
-decreased VC
Normal or decreased FEV1/VC%
What does a mixed spiro look like?
-all values are down
-looks like a mixture of obstructed and resticted
What does it mean when a flow volume loop is scooped?
-more scooped, more severe the airways obstructed
What are some poor techniques associated with restricted spiro?
-submaximal inspiration
-early termination
What do you have to do if a patient has a mixed defected spiro?
-further testing
-TLC and TLCO to confirm- could be hyperinflation
What are the two stages of classifcation with a severe airflow obstruction?
1-the FEV1/FVC must be below LLN (Z score<-1.64) to be classified obstructive
2-severe grading is then based on the FEV1 Z score
What are the levels of severe obstruction?
<-1.64 mild
<-2 moderate
<-2.5 moderately severe
<-3 severe
<-4 very severe
What is reversibility testing?
-assesses patients response to an inhaled bronchodilator
-either a short acting B2 agonist or an antichollinergic bronchodilator is used
-bronchodilator may be given as a metered dose inhaler or via a nebuliser
-most use salbutamol (ventolin) a short acting B2 agonist to assess reversibility
How do you perform a reversibility test?
1-ensure patient has witheld prescribed bronchodilator therapy prior to test
2-perform baseline spiro
3-administer bronchodilator
4-wait to allow maximal bronchodilation
5-repeat spiro
6-calculate response to bronchodilator in terms of volume increase in FEV1 and FVC and as a % change from baseline
How to calculate bronchodilator results?
- a 12% increase in FEV1 and a 200ml increase in volume is a positive response to bronchodilators
(post BD FEV1- pre BD FEV) /
(Pre BD FEV1) all times 100
What are some key points in spiro interpretation?
-What is the patient’s history? (smoker/non smoker) (SOBOE)
-Is the testing acceptable and repeatable?
-What information can you get from the graphs?
-is it normal / abnormal?
-Is it obstructed / restricted or both?
-Severity?
-Bronchodilator responsiveness?
-Do the numbers confirm our views? What more information do they add? (think alongside predictive values)
