Background: Nasal nitric oxide (nNO) is decreased in patients with primary ciliary dyskinesia (PCD) as compared to healthy subjects (HS). nNO measurement has been proposed as a screening tool for PCD, but NO analyzers are not widely available and reference values are lacking.
Objectives: to determine the normal values of nNO in adults using a widely-used hand-held NO analyzer, and explore correlations with ambient NO, age, gender, weight, height, body mass index (BMI), and time of measurements.
Methods: in a pilot phase, 25 adult HS had nNO sampled during breath hold (BH), tidal mouth breathing through a fixed resistance (straw, TB-S) and tidal breathing through a continuous positive airway pressure apparatus (TB-CPAP). TB-S was the most reproducible and comfortable sampling technique and was chosen to measure nNO in 200 adult HS of both genders aged 20 to 80 years, and in 7 adults with PCD.
Results: In HS, mean nNO adjusted for ambient NO was 517 ± 226 ppb and was negatively correlated with age (! = -3.76, p = 10-4). No correlation was found with gender, weight, height, BMI, month of the year, and time of the day. The lower limit of normal nNO (2.5th centile) decreased from 201 ppb at age 20 to 46 ppb at age 80. 6 out of 7 PCD patients had nNO below lower limit of normal.
Conclusions: nNO values significantly decrease with age in adult HS. Reference values are available to use a handheld nNO analyzer as a screening tool for PCD in adults.