What does FEno level measure in exhaled breath?

FEno level measures the concentration of nitric oxide in exhaled breath. Nitric oxide is a biomarker that reflects airway inflammation, particularly in conditions like asthma. Elevated levels of FEno can indicate underlying inflammation of the airways, which can be particularly useful in monitoring patients with asthma or evaluating the effectiveness of anti-inflammatory treatment.

Oxygen concentration pertains to how much oxygen is in the blood and is typically measured through pulse oximetry or arterial blood gas analysis, not through exhaled breath. Carbon dioxide levels are indicative of respiratory exchange efficiency and are also measured via different methods, such as capnography. Hydrogen levels are not a standard measure in respiratory assessment; instead, they can sometimes be indicative of certain metabolic processes but are not relevant for the context of FEno measurement.

Thus, FEno specifically targets nitric oxide as a key indicator of respiratory health, particularly concerning inflammation and asthma management.