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New study shows FeNO testing with NIOX VERO® is not an aerosol-generating procedure (AGP)

Pulmonary assessments are fundamental to the diagnosis and monitoring of respiratory disease. However, there has been some uncertainty about whether the procedures generate potentially infectious aerosols. Concern about transmitting COVID-19 in this way has seen some diagnostic services delayed or even cancelled during the pandemic. Fortunately, work has been carried out to pinpoint the levels of aerosol generated by each procedure so respiratory care can continue safely. One of the techniques that went under the microscope was FeNO testing with NIOX VERO®, where it was reported that researchers were unable to elicit any aerosol emission at all.

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Testing fractional exhaled nitric oxide (FeNO) is not listed as an aerosol-generating procedure (AGP) in any published documents, including those from Public Health England and the US Centers for Disease Control and Prevention (CDC)1-6. The Association for Respiratory Technology and Physiology (ARTP) classifies FeNO as a low-risk procedure thanks to the low potential for cough and the low expiratory flow it requires7. The British Thoracic Society also supports this conclusion8. In addition, there have been no spontaneous reports of cough using the NIOX VERO® and no coughing-related adverse events during NIOX VERO® clinical trials9.

Using a NIOX VERO® is safe, easy and non-invasive. Every volunteer or patient taking a FeNO test with a NIOX VERO® receives a fresh, single-use mouth filter in a sealed package that is unwrapped and attached to the device’s breathing handle. The patient completely closes their lips around the mouth filter before inhaling and exhaling steadily through the breathing handle.

NIOX VERO® is designed to filter out pathogens, including COVID-19, and its filters have exceptionally high efficiencies: ≥99.99% bacterial filtration efficiency and ≥99.97% viral filtration efficiency9. The airflow rate required during a FeNO test with NIOX VERO® is 50ml/s, meaning only gentle exhalation is needed to successfully obtain a result. Used in this way, FeNO testing with NIOX VERO® has been proven not to produce any significant level of aerosol or droplets.

A patient taking a FeNO test with a DR and a NIOX VERO®

A doctor explaining how the NIOX VERO® works before a test

Which new studies have been conducted?

A study published in November 2021 looked at the risk of aerosol generation from common test procedures (spirometry, peak flow and FeNO). During testing with NIOX VERO®, the investigators found that “FeNO measurement produced negligible aerosols” and that they “could not elicit any aerosol emission from the FeNO device”. They concluded that FeNO testing “does not generate significant aerosol concentrations compared with coughs in healthy volunteers and patients with lung disease”, supporting the removal or omission of FeNO from lists of AGPs.10

Another 2021 paper, which also excludes FeNO from the list of tests to avoid during the COVID-19 outbreak, said: “FeNO measurements do not cause significant risk of aerosolization and may be permissible. FeNO may be used when available as the risk of transmission is lower.”11 The authors cited a letter that notes FeNO “does not require forced manoeuvres and reduces the potential for coughing and droplet formation, [and] could represent a possible first functional approach to diagnosis and assessment of patients with asthma.”12

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A December 2020 review examining potential alternatives to pulmonary function testing during the pandemic stated: “Institutions familiar with FeNO testing may therefore consider using this technology as a potentially safer, ie less likely to generate aerosols, method in inpatient and outpatient settings for diagnosing and following patients with asthma characterised by Type 2 airway inflammation.”13

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1. Public Health England. Guidance 6. COVID-19 infection prevention and control guidance: aerosol generating procedures. Updated 14 April 2021. (last accessed 26 April 2021).
2. Centers for Disease Control and Prevention. Clinical Question about COVID-19: Questions and Answers. Which procedures are considered aerosol generating procedures in healthcare settings? Updated 4 March 2021. (last accessed 26 April 2021).
3. Tran K, et al. Aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review. PLoS One. 2012; 7(4): e35797.
4. Association for Respiratory Technology and Physiology. ARTP COVID19 Update - 9 April 2020. (last accessed 29 March 2021).
5. Pasnick S, et al. SARS-CoV-2 transmission and the risk of aerosol generating procedures. Am J Respir Crit Care Med. 2020 June 30. doi:10.1164/rccm.2020C11.
6. Jackson T, et al. Classification of aerosol-generating procedures: a rapid systematic review. BMJ Open Respir Res. 2020 Oct; 7(1): e000730.
7. Association for Respiratory Technology and Physiology. Guidelines for recommencing physiological services during the Coronavirus Disease 2019 (COVID-19) endemic phase. Version 5.1 (August 2020 update). (last accessed 29 March 2021).
8. British Thoracic Society. COVID-19: information for the respiratory community. Advice for those conducting lung function tests. Last update 26/5/2020. (last accessed 12 April 2021).
9. Circassia. Data on file.
10. Sheikh S, et al. Are aerosols generated during lung function testing in patients and healthy volunteers? Results from the AERATOR study. Thorax Published Online First: 02 November 2021. doi: 10.1136/thoraxjnl-2021-217671.
11. Christopher DJ, et al. Pulmonary function testing during the COVID-19 pandemic. Lung India. 2021 Mar;38 (Suppl 1):S91-6. Doi: 10.4103/lungindia.lungindia_738_20.
12. Lombardi C, et al. Rethinking respiratory function laboratories in the era of coronavirus disease 2019, Considerations for today and the day after. Ann Allergy Asthma Immunol. 2020 Aug;125(2):210-1. doi: 10.1016/j.anai.2020.05.021.
13. Kouri A, et al. Addressing reduced laboratory-based pulmonary function testing during a pandemic. Chest. 2020; 158(6): 2502-10.