--- title: What can affect repeatability/reproducibility of readings on NObreath? description: To ensure good repeatability/reproducibility of FeNO testing, the NObreath has a built-in flow meter to ensure patients provide a test at a constant a flow rate --- [Skip to content](https://support.bedfont.com/en/knowledge/what-can-affect-repeatability/reproducibility-of-readings-on-nobreath#main-content) English Show submenu for translations [Customer portal](https://support.bedfont.com/ticket-portal?hsLang=en) ![Bedfont logo-high resolution png-2](https://support.bedfont.com/hs-fs/hubfs/Bedfont%20logo-high%20resolution%20png-2.webp?width=120&height=122&name=Bedfont%20logo-high%20resolution%20png-2.webp) - [Raise a Support Ticket](https://ticket.bedfont.com/) Open main navigation Close main navigation - [Raise a Support Ticket](https://ticket.bedfont.com/) - English Show submenu for translations - [Customer portal](https://support.bedfont.com/ticket-portal) - Go to www.bedfont.com Go to www.bedfont.com Hello. How can we help you? - There are no suggestions because the search field is empty. 1. [Help Centre](https://support.bedfont.com/en/knowledge?hsLang=en) 2. [NObreath](https://support.bedfont.com/en/knowledge/nobreath?hsLang=en) 3. [FAQ](https://support.bedfont.com/en/knowledge/nobreath?hsLang=en#faq) # What can affect repeatability/reproducibility of readings on NObreath? ## To ensure good repeatability/reproducibility of FeNO testing, the NObreath has a built-in flow meter to ensure patients provide a test at a constant a flow rate As a healthcare practitioner, you may wish to take multiple Fractional exhaled Nitric Oxide (FeNO) tests to ensure you are happy with the result before making a decision on patient care. There are many factors that can influence a FeNO result, as detailed in the patient preparation, and therefore verifying the repeatability/reproducibility of a FeNO breath test may be necessary. In this instance, at least two breath tests should be performed with results that are within ±5ppb or 10% of each other (whichever is greater), and the exhaled nitric oxide (NO) is then calculated as the mean of two values. To ensure good repeatability/reproducibility of FeNO testing, the NObreath has a built-in flow meter to ensure patients provide a test at a constant a flow rate, as recommended by ATS/ERS Guidelines (50ml/s for the full test period). This, alongside the built-in test verification, ensures you will always know when a FeNO breath test has been successful, and minimises the need to repeat breath testing. On the rare occasion that repeatability/reproducibility of FeNO results should fall outside of the of the specified range (±5ppb or 10%) there are some troubleshooting steps that can be followed to help rectify this issue: - **Did the user ensure to perform FeNO tests before any other respiratory tests?** It is important to ensure the FeNO test is taken before other respiratory tests such as spirometry, because forced breathing manoeuvres might influence FENO values. - **How many tests have been performed and has the patient been given adequate rest time between readings?** ATS/ERS recommend at least 30 seconds of relaxed tidal breathing between tests. - **Are the tests being carried out on the same test mode each time** Adult and Child should not be used interchangeably. - **Is the mouthpiece’s connector O’ring present?** It is important that the O’ring has not been removed or dislodged so that there is a firm seal when taking the breath test to ensure the full breath sample is analysed. - **Is the mouthpiece fully inserted into the device?** It is important that the mouthpiece is fully inserted into the NObreath device so that there is a firm seal when taking the breath test to ensure the full breath sample is analysed. - **Has the device been used with or near any strong cleaning products containing alcohol?** Cleaning solutions containing alcohol used on or near the device emit strong VOC’s that can affect the sensor’s reading capabilities. Please let the device settle in a clean environment free from VOCs for 24 hours before resuming breath testing. - **When was the device last serviced/calibrated?** If the NObreath has missed a service/calibration, it is possible that the sensor may have drifted. It is important that routine service and maintenance is performed to keep your device reading within specification. Please perform the necessary service/calibration before resuming breath testing. - **Is the rear exhaust blocked?** Please check all exhaust ports are free from obstruction when performing a breath test; if obstructed, this can increase back pressure and impact results. - **Does the device have the most recent firmware version?** It is best practice to ensure the NObreath device is always updated to the latest firmware version; any firmware updates may contain bug fixes and enhancements to the performance of the device. - **Has the battery been left to go completely flat for several weeks?** This could mean the sensor has not yet stabilised/biased. Please fully charge the NObreath and allow \>24 hours for the sensor to stabilise.  If all of the above factors have been tried/considered and the device is still showing reproducibility issues, please contact your local distributor for more information. 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