Test: Exhaled Nitric Oxide Test

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Background/Purpose

An exhaled nitric oxide test can help with the diagnosis and treatment of asthma. Also known as the fractional exhaled nitric oxide (FeNO) test, this test measures the level of nitric oxide gas in an exhaled sample of your breath.
FEno is a good surrogate marker for eosinophilic airway inflammation. High FEno levels may be used to distinguish eosinophilic from non‐eosinophilic pathologies. This information complements conventional pulmonary function testing in the assessment of patients with nonspecific respiratory symptoms.
There is contradictory evidence regarding the exact function of NO in lung disease. In pathological situations, NO is a proinflammatory mediator with immunomodulatory effects. This appears to predispose to the development of airway hyperresponsiveness (AHR), although this is not a consistent finding.3,4 On the other hand, under physiological conditions NO acts as a weak mediator of smooth muscle relaxation and protects against AHR. In exhaled air, NO appears to originate in the airway epithelium. Although raised levels may occur with a number of airway or lung diseases, the most important context in which the measurement of NO is clinically useful is that of allergic airways disease

Procedure

The subject should discontinue the following items 1 hour prior to the test:
Smoking, Caffeine, Alcohol, Nitrate-rich foods, such as leafy green vegetables and beets.
Subject is seated next to the machine and exhales completely.
Subject places mouthpiece into mouth and breathes in slowly and deeply until their lungs are filled with air.
Clinician instructs subject to exhale slowly and steadily so that the air flows out of their lungs at a steady, even rate.
The results are logged and the test may be repeated to confirm measurements.
Performed: Bilaterally

Dialog

Measurement of exhaled Nitric Oxide gas.

Criteria

• <40 ppb in adults
• <25 ppb in children

Measurement

LOINC Code

Scale/Grading

selection range; grade - LOINC ID
Option - Value option selection range; grade - LOINC IDPass ; Pass - Fail ; Fail -