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FeNO stands for fractional exhaled nitric oxide and is used to measure airway inflammation, a key characteristic of asthma. FeNO testing is safe and easy to perform, even in young children or when lung function is severely reduced. The ability to test and obtain results at the point-of-care means FeNO is the most convenient biomarker of airway inflammation for more accurate diagnosis and better asthma management. Ensuring ideal performance of your FeNO testing device is therefore critical too.
A low level of NO in the breath is normal. The problem is, NO is not just an endogenous gas in the airways, it’s part of the air we breathe. How then do we ensure that the NO we detect in the exhaled breath during a FeNO test is truly reflective of any abnormal levels in the patient’s lungs? The key of course is to make sure only exhaled breath from the patient’s lungs is tested.
FeNO devices usually detect exhaled NO levels up to 300 parts per billion (ppb). However, ambient NO levels can vary greatly – from 2 to 500 ppb – and are higher in urban areas and during daylight.1 Many studies have shown that high levels of ambient NO significantly affect FeNO values.2-4 These findings led the American Thoracic Society (ATS) and the European Respiratory Society (ERS) to suggest that “standardised techniques must prevent the contamination of biological samples with ambient NO” and that “the use of NO-free air (containing <5 ppb) for inhalation is preferable”.5
The accuracy of NIOX VERO® is maintained through unique technology that eliminates the impact of environmental NO, irrespective of the surroundings. NIOX VERO® is the only portable FeNO device outside China to include inhalation through the breathing handle as part of the FeNO measurement process. The NIOX® breathing handle contains a scrubber that removes NO from the ambient air as it passes through, using potassium permanganate for filtration. The device itself includes a zero scrubber, which removes ambient NO from aspired air to create the zero against which the breath sample is analysed.
New breathing handle scrubber (L) and used (R).
Over time and with use, the potassium permanganate will deplete and lose the ability to remove ambient NO – its superpower! This will obviously impact the accuracy of any FeNO measurements when the main goal is to keep your results at their most reliable so it’s important to ensure all the parts of your FeNO testing device are safe.
Like all FeNO devices, NIOX® technology is impeded by alcohol. Firstly, the scrubber can be subject to external exposures. A reaction with alcohol could degrade the critical potassium permanganate, possibly causing irreversible damage.
Secondly, to achieve its impressive levels of accuracy, NIOX® uses sealed tubing to maintain the exhaled breath at 100% relative humidity throughout the analysis. However, the seal means the tubing can provide a reservoir for alcohol vapour, which could temporarily impact the sensor and lead to erroneous results.
Thirdly, the electrochemical sensor used in FeNO devices is sensitive to chemicals. Alcohol vapour has the potential to harm the electrodes in the sensor, which could then produce incorrect results.
Simply put, any alcohol on or near FeNO testing technology can impair its ability to provide accurate and reliable FeNO values. The good news is, protecting your NIOX VERO® is simple and some small but significant precautions will help you get the best from your experience of FeNO for asthma.
NIOX® publishes a regularly updated guide on the best way to clean your device, click here to read the guide. There’s also a list of alcohol-free disinfecting wipes that are approved for use with NIOX® products which can be found by clicking here or you can buy suitable wipes directly from your local NIOX® team .
If you’d like to discuss anything you’ve read, please contact us.
To learn more about FeNO testing, visit NIOX.com
Learn more about the gold standard FeNO device.
1. Clapp LJ, Jenkin ME. Analysis of the relationship between ambient levels of O3, NO2 and NO as a function of NOx in the UK. Atmos Environ. 2001;35(36):6391-6405.
2. Corradi M et al. Influence of atmospheric nitric oxide concentration on the measurement of nitric oxide in exhaled air. Thorax. 1998; 53(8):673–676.
3. Dotsch J et al. Airway nitric oxide in asthmatic children and patients with cystic fibrosis. Eur Respir J. 1996;9(12) :2537-2540.
4. Baraldi E et al. Effect of atmospheric nitric oxide (NO) on measurements of exhaled NO in asthmatic children. Pediatr Pulmonol. 1998;26:30-34.
5. 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):912-930.