Measuring FeNO - The technology behind NIOX VERO?

Fractional exhaled nitric oxide (FeNO) was discovered as a biomarker of airway inflammation in the 1990s.(1) Ever since, FeNO measurements have proved to be a helpful tool in asthma diagnosis and management.(2-4) In this article we will focus on what is important when measuring FeNO levels and how the technology behind NIOX VERO? addresses these needs.

There are various ways to help diagnose asthma, such as spirometry or clinical signs and symptoms. However, although these methods are important, they do not directly reflect the extent of airway inflammation.(5) FeNO testing is accepted as a biomarker of airway inflammation, which is a key characteristic of asthma.(4,6) FeNO testing is a convenient way to assess airway inflammation as it is simple, immediate and non-invasive.(1,2) In addition, performing FeNO testing with NIOX VERO? has been proven not to be an aerosol-generating procedure.(7) In order to achieve the best patient outcomes, it is vital to ensure that the equipment used to perform FeNO testing provides accurate and reproducible results.

Different technologies to help diagnose asthma and other respiratory conditions

In the past few decades, respiratory authorities such as the European Respiratory Society (ERS) and the American Thoracic Society (ATS) have defined guidelines on how to measure and interpret FeNO levels.(8,9)

FeNO devices are equipped with a sensor, a piece of technology which measures the nitric oxide (NO) level in the exhaled breath of the user. An example of the technology that can provide these measurements is chemiluminescence. Unfortunately, chemiluminescence devices can be very expensive and non-portable.(10,11) They may also need frequent calibration and maintenance, which makes these technologies more suitable for research labs or clinical studies.(10,11)

NIOX? trivia: The original NIOX? device was launched in 1998 and was actually the first ever commercially available FeNO device!

In the early 2000s, the company behind the NIOX? brand evolved the technology and launched a new device with an electrochemical sensor, which allowed FeNO devices to go portable for the first time. It is now proven that the NIOX? electrochemical sensor provides equivalent readings to those obtained with chemiluminescence.(6)

Key aspects of electrochemical devices for FeNO measurement

Devices that measure FeNO with electrochemical technology, such as NIOX VERO?, have sensors that convert the gas concentration of exhaled breath into electrical signals. Unlike chemiluminescence technology, they are small devices that are easy to use at the point-of-care.(1) They are also relatively inexpensive to buy and maintain.(14) They usually provide results within a minute or so. FeNO devices are also non-invasive and allow for the measurement of FeNO in children.(1) To guide the patient through the test, most devices have an interface with helpful animations.

Interpreting FeNO test results depends on the device

Many studies have shown a high degree of correlation between the measurements of different devices, although there are discrepancies between device readings, especially for higher levels of inflammation.(12,13,15,16) Studies have concluded that FeNO devices are not interchangeable.(10,11,17)

The ATS/ERS recommendations on the standardisation of the measurement of FeNO are very clear on the need to remove ambient NO from the exhaled breath, to avoid contamination by exogenous NO.(8) High levels of ambient NO can affect FeNO results.(8,18) NIOX VERO? eliminates the impact of environmental NO by using an NO scrubber in the breathing handle. During testing, the patient inhales through the handle and the scrubber filters out NO that is already present in the air. As the exhaled air only contains NO from the patient’s airways, the FeNO value obtained provides an accurate picture of the level of inflammation in the lungs.

The recommended flow rate of a FeNO device is 50mL/s ± 10%, as this was shown to provide a reasonable compromise between measurement sensitivity and patient comfort.(8) It is recommended that, if a patient is unable to maintain this flow rate, the FeNO result should still be recorded with a note highlighting failure to achieve the flow rate criterion.(8) Failure to maintain a steady flow rate may result in inaccurate FeNO values.(8) However, the NIOX VERO? has a specific mechanism called Flow Rate Control? to prevent this.

If you’d like to see NIOX VERO? for yourself, please book a demonstration or contact us for more information at any time.

References:

1. Alving K et al. Validation of a new portable exhaled nitric oxide analyzer, NIOX VERO?: randomized studies in asthma. Pulm Ther. 2017;3:207-218.
2. Menzies-Gow A et al. Clinical utility of fractional exhaled nitric oxide in severe asthma management. Eur Respir J. 2020;55(3):1901633.
3. Ali H et al. The Potential of Fractional Exhaled Nitric Oxide as a Biomarker in Predicting and Optimizing Use of Treatment in Asthma. South East European Journal of Immunology. 2023;6(1):18-23.
4. Busse WW et al. Baseline FeNO as a prognostic biomarker for subsequent severe asthma exacerbations in patients with uncontrolled, moderate-to-severe asthma receiving placebo in the LIBERTY ASTHMA QUEST study: a post-hoc analysis. Lancet Respir Med. 2021;9(10):1165-1173.
5. Hanania NA et al. Measurement of fractional exhaled nitric oxide in real-world clinical practice alters asthma treatment decisions. Ann Allergy Asthma Immunol. 2018;120(4):414-418.
6. Global Initiative for Asthma (GINA). Global strategy for asthma management and prevention, 2023. Available at; https://ginasthma.org/2023-gina-main-report/
7. Sheikh S et al. Are aerosols generated during lung function testing in patients and healthy volunteers? Results from the AERATOR study. Thorax. 2022;77(3):292-4.
8. American Thoracic Society; 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, 2005. Am J Respir Crit Care Med. 2005;171(8):912-30.
9. Dweik RA et al. An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FeNO) for clinical applications. Am J Respir Crit Care Med. 2011;184(5):602-15.
10. Molino A et al. Comparison of three different exhaled nitric oxide analyzers in chronic respiratory disorders. Journal of breath research. 2019;13(2):021002.
11. Maniscalco M et al. Fractional exhaled nitric oxide-measuring devices: technology update. Med Devices (Auckl). 2016;9:151-60.
12. Menzies D et al. Portable exhaled nitric oxide measurement. Chest. 2007;131(2):410-4.
13. Korn S et al. Measurement of fractional exhaled nitric oxide: comparison of three different analysers. Respiration. 2020;99(1):1-8.
14. Hoggins R et al. How to use the fractional exhaled nitric oxide test. Archives of Disease in Childhood-Education and Practice. 2022;107(2):133-40.
15. Huang T et al. Fractional exhaled nitric oxide measurement: Comparison between the Sunvou-CA2122 analyzer and the NIOX VERO analyzer. J Asthma. 2019:1-8.
16. Silkoff PE et al. Clinical precision, accuracy, number and durations of exhalations for a novel electrochemical monitor for exhaled nitric oxide. J Breath Res. 2019;14(1):016011.
17. Kapande KM et al. Comparative repeatability of two handheld fractional exhaled nitric oxide monitors. Pediatr Pulmonol. 2012;47(6):546-50.
18. Corradi M et al. Influence of atmospheric nitric oxide concentration on the measurement of nitric oxide in exhaled air. Thorax. 1998;53(8):673-6.

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