Methodological Implications and Repeatability of Nasal Nitric Oxide: Relevance for Challenge Studies

Area of Science:

• Environmental Health
• Respiratory Medicine
• Biomedical Engineering

Background:

• Nasal nitric oxide (nNO) is an emerging biomarker for upper airway responses.
• Assessing nNO repeatability is crucial for its use as an effect marker.
• Methodological factors can influence nNO measurement reliability.

Purpose of the Study:

• To evaluate the short and long-term repeatability of nasal nitric oxide (nNO) levels.
• To compare nNO measurement methods: breath-holding versus tidal breathing.
• To investigate nNO changes in response to ethyl acrylate exposure in atopic and healthy subjects.

Main Methods:

• A portable electrochemical analyzer was used to measure nNO.
• Subjects (9 atopic, 18 healthy) were exposed to ethyl acrylate (0.05 ppm sham, 5 ppm constant, or 0-10 ppm variable).
• nNO sampling was performed via passive aspiration during breath-holding and calm tidal breathing.

Main Results:

• Breath-holding nNO sampling showed lower intra-session (8.6%) and between-session (13.0%) coefficients of variation compared to tidal breathing (16.4% and 18.5%).
• Atopic subjects exhibited significant nNO increases after constant ethyl acrylate exposure (16% breath-holding, 32% tidal breathing).
• Both methods detected significant group-level changes, but breath-holding offered better individual-level precision.

Conclusions:

• The tidal-breathing method for nNO assessment may be adequate for detecting group-level changes.
• The breath-holding method for nNO measurement demonstrates superior repeatability, advantageous for individual-level analysis.
• Further research is required to validate nNO's utility in assessing irritative, non-allergic upper airway responses.