Diagnosis

Question 1

FEV1/FVC results

Answer 1

1. FEV1/FVC < 75% (obstructive)
2. Give SABA
3. FEV1 > 12% after SABA = asthma
   < 12% = COPD

Question 2

Metacholine Challenge

Answer 2

Metacholine binds to muscarinic receptors in the airways and causes them to constrict which in asthma will cause bronchospasm.

Question 3

What are the criteria for an asthma diagnosis?

Answer 3

• An exhaled FeNO of 40 parts per billion or greater
• A post-bronchodilator improvement in lung volume of 200 ml
• A post-bronchodilator improvement in FEV1 of 12% or more
• A peak expiratory flow rate variability of 20% or more
• An FEV1/FVC ratio <70% (it is an obstructive lung disease)

Question 4

Why is fractional exhaled nitric oxide(FeNO) used to diagnose asthma?

Answer 4

One of the types is inducible (iNOS) and levels tend to rise in inflammatory cells, particularly eosinophils. Levels of NO therefore typically correlate with levels of inflammation.

• in adults level of >= 40 parts per billion (ppb) is considered positive
• in children a level of >= 35 parts per billion (ppb) is considered positive