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 Bedfont or your local distributor for more advice.