Methods of measuring FeNO
Fractional exhaled Nitric Oxide (FeNO) measurement plays a crucial role in the diagnosis and management of airway inflammation. FeNO testing is recommended in the joint guidelines from the National Institute for Health and Care Excellence (NICE), the British Thoracic Society (BTS), and the Scottish Intercollegiate Guidelines Network (SIGN) for the diagnosis and management of asthma1.
In 2005 the American Thoracic Society (ATS) and the European Respiratory Society (ERS) published recommendations for standardised procedures of FeNO testing highlighting that whilst evidence shows ambient levels of nitric oxide (NO) do not affect the result; it is preferable to avoid doubt by removing it from the breath sample2.
NObreath® uses a sampling method, effectively omitting the initial spike caused by ambient NO, ensuring that the FeNO reading accurately reflects lower airway NO. This article explores this method, how it works, and why Bedfont® Scientific Limited selected this method for the NObreath® device.
NObreath® TrueFlo™ Technology2
TrueFlo™ Technology refers to the precise control and measurement techniques used during FeNO testing to ensure accurate, repeatable, and clinically meaningful readings that meet the ATS/ERS recommendations for standardised procedure.
1.Controlled exhalation flow
ATS/ERS guidelines recommend a standardised exhalation flow rate to ensure consistent and comparable FeNO measurements
The NObreath® maintains this controlled flow using precise engineering, which ensures repeatable readings across tests. With multiple flow incentives built into the device to ensure exhalation at 50mls per second.
2.Preventing NO contamination
During FeNO testing, the soft palate (velum) must close to prevent nasal NO from affecting results. The guidelines recommend techniques to ensure the measurement reflects lower airway NO.
NObreath® mouthpieces incorporate a built-in valve that provides the correct pressure to ensure velum closure during exhalation, in line with guideline recommendations.
3.Measuring the exhaled nitric oxide plateau
FeNO values should be recorded during the stable plateau phase of exhalation to capture steady NO levels.
The NObreath® omits the first few seconds of exhaled breath, ensuring only the plateau phase of the breath is measured. With the environmental NO influence removed the NObreath® falls in the line with the ATS/ERS standard.
4.Managing ambient NO
Whilst the guidelines recognise conflicting evidence regarding the effect of ambient NO on FeNO results, they highlight the importance of managing environmental NO to ensure reliable readings. Different technological approaches may be used to address ambient NO during testing.
The NObreath® sampling and flow control technology effectively minimise ambient NO influence, supporting highly accurate FeNO measurements even in variable environments.
How a FeNO test is performed with the NObreath®
When performing a breath test with the NObreath®, the user will be prompted to take a deep breath and then instructed to blow gently into the mouthpiece with an onscreen flow meter to guide the patient on their exhalation rate.
The NObreath® offers two test modes:
- A 12-second test mode,
- 10-second test mode for those up to 10 years old who cannot complete the 12-second test mode.
As the breath sample enters the NObreath® device, the first few seconds are omitted and vented through the device bypassing the sensor chamber. After the first few seconds has elapsed, the pump will draw the remaining viable sample into the sensor chamber, where the breath sample will be analysed. When the patient completes a breath test using the NObreath® a green tick will appear on the screen to indicate a successful test, and the patient’s results will be shown onscreen in parts per billion (ppb) instantly.
Advantages of the NObreath® TrueFlo™ Technology
The TrueFlo™ Technology is a user-friendly method designed to measure airway inflammation, providing instant results, and eliminating wait times for both patients and healthcare professionals. The patient does not have to inhale through a device that has been used on multiple prior patients, as even highly effective bacterial viral filters may not be 100% effective, and the patient does not have to inhale through an NO scrubber*. Avoiding inhalation means these risks do not arise and this is another reason why Bedfont® chose this technique for NObreath®. The NObreath® also utilises an NO scrubber for accuracy but this does not form any part of the breath pathway.
To learn more about the NObreath® utilising TrueFlo® Technology, please visit https://www.nobreathfeno.com/measuring-feno-with-the-nobreath/
The clinical value of FeNO testing
The use of FeNO testing, combined with a comprehensive clinical history and additional examinations, enhances the efficiency of asthma diagnosis and improves patient care. This allows for effective monitoring of patients’ responses to asthma interventions. Bedfont® are world leaders in breath analysis, with nearly 50 years of experience. Bedfont® has been manufacturing the NObreath® portable FeNO device for over 15 years. Used by healthcare professionals to measure airway inflammation to aid in the diagnosis and management of asthma, taking a minimal amount of valuable consultation time with the ability to monitor airway inflammation in both adult and child patients. With annual servicing and minimal consumables, the NObreath® can be used as a functional device for years**.
Visit https://www.nobreathfeno.com to learn how to support your patients with FeNO monitoring using the NObreath® from Bedfont® Scientific Limited.
*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 breath3,4,5,6.
**The NObreath® has been validated for up to 29,000 tests when used as instructed and properly maintained and serviced. The number of tests can be periodically checked within the settings of the device; when 29,000 tests are reached a service is recommended. Contact your local service centre.
References:
- Asthma pathway (BTS, NICE, SIGN) [Internet]. National Institute for Health and Care Excellence. 2024. Available from: https://www.nice.org.uk/guidance/ng244
- 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.
- Hazardous substance fact sheet [Internet]. New Jersey Department of Health and Senior Services. 2002. Available from: https://nj.gov/health/eoh/rtkweb/documents/fs/1578.pdf
- Safety data sheet potassium permanganate [Internet]. AquaPhoenix Scientific. 2015. Available from: https://beta-static.fishersci.com/content/dam/fishersci/en_US/documents/programs/education/regulatory-documents/sds/chemicals/chemicals-p/S25497.pdf
- Potassium permanganate permanganic acid potassium salt [Internet]. Safety International Chemical Cards. 2016. Available from: https://www.ilo.org/dyn/icsc/showcard.display?p_lang=en&p_card_id=0672&p_version=2
- Potassium permanganate safety data sheet [Internet]. LabChem. 2014. Available from: https://palsusa.com/wp-content/uploads/sites/6/2024/08/POTASSIUM-PERMANGANATE.pdf
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