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Nitric Oxide Icon

nitric oxide

NO is a gas present in small concentrations in the human body and that is considered as an important molecule for biological functions. In the airways, it can take part in inflammatory and immunomodulatory processes (1).

Airway Inflammation and NO production (2-5) 

Asthma is a heterogeneous disease that presents different phenotypes

  • T2 High: T2 high endotype of asthma is the most common endotype that can be found in allergic and non-allergic asthmatics. It is steroid responsive and the Fraction of Exhaled Nitric Oxide (FeNO) is considered a biomarkers for this type of inflammation.
  • T2 Low: Usually people are diagnosed with older ages and it has fewer allergic symptoms. The involved molecules do not contribute to FeNO production.
FeNO in asthma (2)(3)(6) 

The measurement of the FeNO is an easy to implement and perform test, accurate and not expensive that provides instantaneous results on the evaluation of airway inflammation (T2 high) that must be complemented with other exploratory techniques.

Different guidelines have included FeNO on their algorithms. 

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FeNO for... 

Asthma diagnosis

That can be used… in combination with clinical and functional exploration techniques to provide objective information of T2 high airway inflammation (2)(3)(6)

Evolution of ICS responsiveness

That can be used… for predicting the likeliness of having a positive response to ICS if FeNO>50ppb (4)(6)(8)

 ICS Dosing

That can be used… to evaluate objectively the effectiveness of the treatment being also helpful for dose modification decisions (3)(6)

 Monitoring asthma control

That can be used… as a relevant marker of the improvement or loose of control of the disease, that can help to reduce the number of exacerbations, and to assess the treatment compliance (2)(6)(7)


That can be used… to optimize the cost-effectiveness of the treatments (2)(5)


(1) Multiple Roles of Nitric Oxide in the airways. Ricciardolo, F L M. 175-182, s.l. : Thorax, 2003, Vol. 58.

(2) A review of the Uility and Cost Effectiveness of Monitoring Fractional Exhaled Nitric Oxide (FeNO) in asthma management. Renné JG Arnold, Marc Massanari, Todd A.Lee, Elizabeth Brooks. s.l. : Managed Care, 2018.

(3) Measurement of FeNO in asthma: what the hospital doctor needs to know. Hitasha Rupani, Anoop J Chauhan. 2, s.l. : British Journal of Hospital Medicine, 2019, Vol. 80. (4) Airway Inflammation and Inflammatory Biomarkers. Hui Fang Lim, Parameswaran Nair. 1/2018, s.l. : Seminars in Respiratory and Critical Care Medicine, 2018, Vol. 39. (5) Role of Biologics in Asthma. Mary Clare McGregor, James G. Krings, Parameswaran Nair, and Mario Castro. 4, s.l. : Am J Respir Crit Care Med, 2019, Vol. 199.

(6) Clinical Utility Of The Exhaled Nitric Oxide (NO) Measurement With Portable Devices In The Management Of Allergic Inflammation And Asthma. Duong-Quy, Sy. 331-341, s.l. : Journal of Asthma and Allergy, 2019, Vol. 12.

(7) An Official ATS Clinical Practice Guideline: Interpretation of Exhaled Nitric Oxide Levels (FENO) for Clinical Applications. Raed A. Dweik, Peter B. Boggs, Serpil C. Erzurum, Charles G. Irvin, Margaret W. Leigh, Jon O. Lundberg Anna-Carin Olin, Alan L. Plummer, D. Robin Taylor, on behalf of the American Thoracic Society Committee on Interpretation of Exhaled Nitric Oxide Levels. 602-615, s.l. : Am J Respir Crit Care Med, 2011, Vol. 184. DOI: 10.1164/rccm.912011ST.

Airway nflammation characteristics shceme