Measuring FeNO with the NObreath

Back to Bedfont website

Measuring FeNO with the NObreath®

Methods of Measuring FeNO

The ATS/ERS recommendations 2005 for standardized procedures for the measurement of exhaled nitric oxide (FeNO) testing highlight that whilst evidence shows ambient levels of NO do not affect the result; it is preferable to avoid doubt by removing it from the breath sample1.

This can be done by either:

  1. ‘Partitioning’ the sample; effectively ignoring the potential initial spike caused by ambient NO; or
  2. Inhaling through an NO scrubber prior to exhalation;

NObreath/FeNObreath utilises the first Partitioning method.

What is the Partition Method?

The Partition Method is a method of measuring Fractional Exhaled Nitric Oxide(FeNO) in accordance with the ATS/ERS guidelines1. The Partition Method essentially “parts” the breath sample, and omits the first few seconds to ensure any potential high ambient levels of NO present in the breath is not measured during sampling.

How does the Partition Method work?

When prompted by the NObreath®, patients simply need to exhale through the mouthpiece into the monitor, following the onscreen motivational guide.

As the breath sample enters the NObreath® FeNO monitor, the first few seconds are partitioned and vented through the monitor bypassing the sensor chamber. After the partition period has elapsed, the pump will begin to draw the remaining viable sample into the sensor chamber, where the breath sample will be analysed.

Once the breath sample has been analysed, a result is shown instantly onscreen.

Is the Partition Method effective at measuring FeNO? 

Both methods of FeNO measuring have been subject to the stringent processes of CE, FDA, CFDA & PMDA clearance (to name but a few) as part of their respective product registration and have also been shown in clinical research to result in excellent repeatability, reproducibility and comparability 2,3,4,5,6,7,8.

Additionally, the NObreath® monitor’s electrochemical sensor has been validated against the gold standard, chemiluminescence7 . The NObreath® monitor’s use of the Partition Method has been subject to many clinical studies and case study write-ups proving its accuracy.

Why did we choose the Partition Method?

  1. It’s easy for patients to perform;
  2. It’s accurate;
  3. The patient does not have to inhale through a device that has been used on multiple prior patients as even highly effective BVF filters may not be 100% effective; and
  4. The patient does not have to inhale through an NO scrubber*;

Therefore, the NObreath® FeNO monitor was designed, using the Partition Method, not only to comply to ATS/ERS guidelines for FeNO testing, but to reduce any risk posed to patients, whilst ensuring optimal user-friendly test methods and accuracy.

*NO scrubbing filters typically utilise potassium permanganate (a potentially hazardous substance) which has been referenced in certain conditions, if inhaled, to cause irritation to the nose, throat and lungs causing coughing and/or shortness of breath9,10,11,12. Even though the likelihood of these risks may be low; by avoiding the need for inhalation through the device and/or an NO scrubber, means these risks do not arise and this is another reason why we chose this technique for NObreath/FeNObreath. The NObreath/FeNObreath also utilises an NO scrubber for accuracy but this does not form any part of the breath pathway.

1. American Thoracic Society and European Respiratory Society. ATS/ERS recommendations for standardized procedures for the online and offline measurement of exhaled lower respiratory nitric oxide and nasal nitric oxide. American Journal of Respiratory and Critical Care Medicine. 2005;171(8):912-930.
2. Inoue Y, Sato S, Manabe T, Makita E, Chiyotanda M, Takahashi K, Yamamoto H, Yanagida N, and Ebisawa M. Measurement of exhaled nitric oxide in children: A comparison between NObreath® and NIOX VERO® analyzers. Allergy, asthma and immunology research. 2018;10(5):478-489.
3. Harnan SE, Tappenden P, Essat M, Gomersall T, Minton J, Wong R, Pavord I, Everard M, and Lawson R. Measurement of exhaled nitric oxide concentration in asthma: A Systematic review and economic evaluation of NIOX MINO®, NIOX VERO®, and NObreath®. Health Technology Assessment. 2015;19(82):1-330.
4. Kang SY, Lee SM, and Lee SP. Measurement of fractional exhaled nitric oxide in adults: comparison of two different analysers (NIOX VERO® and NObreath®). Tuberculosis and Respiratory Diseases. 2021;84(3):182-187.
5. National Institute for Health and Care Excellence. Measuring fractional exhaled nitric oxide concentration in asthma: NIOX MINO®, NIOX VERO®, and NObreath®[DG12]. 2014. Available from:
6. Pisi R, Aiello M, Tzani P, Marangio E, Olivieri D, and Chetta A. Measurement of fractional exhaled nitric oxide by a new portable device: comparison with the standard technique. Journal of Asthma. 2010;47(7):805-809.
7. Antus B, Horvath I, and Barta I. Assessment of exhaled nitric oxide by a new hand-held device. Respiratory Medicine. 2010;104(9):1377-1380.
8. Yune S, Lee JY, Choi DC, and Lee BY. Fractional exhaled nitric oxide: Comparison between portable devices and correlation with sputum eosinophils. Allergy, Asthma and Immunology Research. 2015;7(4);404-408.
9. New Jersey Department of Health and Senior Services. Hazardous substance fact sheet. 2002: 1-6.
10. AquaPhoenix Scientific. Safety data sheet potassium permanganate. 2015:1-7. Available from:
11. International Chemical Safety Cards. Potassium permanganate permanganic acid potassium salt. International Labour Organization 2016:1-2. Available from:
12. LabChem. Potassium permanganate safety data sheet. 2014:1-9. Available from: