Spirometry Flashcards
what is spirometry
measures the volume and flow of air during inspiration and expiration; it is an assessment of how effectively the lungs can be emptied and filled. Spirometry uses various measures of inspired and expired air to give an indication of any underlying lung disease.
causes obstructive pattern spirometry
COPD
- Including Alpha1-antitrypsin deficiency
Asthma
Cystic fibrosis
Bronchiectasis
causes restrictive pattern spirometry
Pulmonary fibrosis
Neuromuscular conditions
Heart Failure
Sarcoidosis
Obesity
Spirometry results obstructive lung disease
A reduction in airflow
FEV1 reduced <80% predicted
FVC often normal
FEV1/FVC ratio <70%
“Classical” definition
FEV1/FVC < LLN
LLN – “Lower limit of normal”
A more modern definition
LLN defined by age, gender, weight
if obstructive pattern of lung disease, what is the next step of spirometry testing
bronchodilator reversibility
interpretation of spirometry restrictive disease
reduction in lung capacity
FVC reduced
FEV1 often normal
FEV1/FVC ratio normal or raised
what is reversibility on testing defined as
> 12% AND 200ml increase in FEV1 OR FVC
how is reversibility assessed spirometry
Giving short acting B-agonist (e.g. salbutamol 2-6 puffs via spacer)
Repeat spirometry 10 minutes later
does obstructive spirometry without reversibility guide bronchodilator therapy ?
Failure to respond does not determine the need to prescribe bronchodilators
Many patients with COPD wills till benefit from bronchodilators even if they don’t meet the above criteria
contraindications to spiroemtry
Pneumothorax within the last 6 weeks
Acute coronary syndrome within the last 4 weeks
Haemoptysis within last 48 hours
Thoracic, abdominal or eye surgery (including cataracts) within last 6 weeks
Known thoracic, abdominal or cerebral aneurysm
Known TB or influenza, or other acute illness
describe the process of spirometry to a pt
sit upright
nose clip
take as deep a breath as possible
blow out forcibly into a tube with lips sealted tightly
pt communication before spirometry
Not use bronchodilators on the day of the test
Not smoke on the day of the test
Avoid strenuous exercise on the day of the test
Avoid alcohol on the day of the test
Avoid eating a large meal in the 4 hours before the test
Avoid restrictive clothing
what graphs are used to plot spiroemtry
volume time
flow volume
describe volume time graph of obstructive pattern
slow increase in volume over time (obstructed)
reaches normal volume
describe volume time graph restrictive
sharp increase in volume over time as no obstruction
early plataeu in volume as reduced capacity
