A reliable protocol for the measurement of nitric oxide in the nose and paranasal sinuses

Abstract

Objectives: Nitric oxide (NO) is known to play an important role in the pathophysiology of the paranasal sinuses. Despite of the existence of a vast array of publications on NO, standard protocols for its measurement do not exist. As part of a larger study to assess the role of NO in the paranasal sinuses, pilot work was undertaken to establish how NO measurements could be reliably and reproducibly obtained. Materials and Methods: 6 different measuring methods were assessed on 54 nasal cavities. NO measurements were taken from the nasal cavities in the natural and decongested state. Cavity and maxillary sinus measurements were also obtained with mouth breathing and breath holding techniques. Results: Despite training, 22% of subjects failed to stop NO leakage into the oropharynx during mouth breathing. Not all patients could breath hold for long periods. Peak levels in the nasal cavity could be reliably assessed after 15 seconds of breath holding and peak levels in the maxillary sinus were found to be best assessed in the decongested state early during a breath hold. Using 'NO accumulation coefficients', we were able to show intra- subject variation was predictable and consistent. Conclusions: Measurement of NO in the nose cannot be reliably achieved during mouth breathing. Nasal decongestion reduces data error. With adequate data analysis equipment, peak levels within the nasal cavity and maxillary sinus can be optimally assessed after decongestion and during breath holding. We commend these two protocols for reliable and reproducible NO measurement in nasal research.