Fractional exhaled Nitric Oxide (FeNO) level as a predictor of COVID-19 disease severity

The Discrepant Role of Fractional Exhaled Nitric Oxide in SARS-CoV-2 Infection

“…The isolated NO value in this study is not measured; therefore, its involvement without ammonia is unknown. Other studies [3] evaluated only positive COVID-19 patients and demonstrated lower FeNO values in patients with severe disease than in those with mild disease, suggesting that FeNO is a predictor of the severity of COVID-19. The authors also demonstrated that FeNO ≤11.8 ppb is predictive of severe outcomes.…”

“…Inclusion criteria vary widely not only for affected patients (eg, symptomatic respiratory disease [2], mild/severe COVID-19 [3], and critical illness [4]), but also for healthy control groups [5,6]. Moreover, the use of different FeNO measurement devices could also interfere with the results.…”

Fractional Exhaled Nitric Oxide in Normoxic Adult Patients With COVID-19 Infection in the Emergency Department: A Preliminary Observation

“…For instance, Exline et al [ 2 ] reported high FeNO levels in hospitalized, mechanically-ventilated patients with COVID-19 infection. By contrast, Lior et al [ 3 ] showed recently that FeNO levels were decreased in hospitalized patients with severe COVID-19 infection and that admission FeNO < 11.8 ppb heralded adverse outcomes.…”

“…The reason(s) underlying the discrepant reports about FeNO levels in hospitalized patients with COVID-19 infection is uncertain [ 2 , 3 ]. Conceivably, differences in patient characteristics, such as age, sex, race/ethnicity, disease severity, and therapeutic interventions at the time of FeNO testing could account, in part, for these observations.…”

“…Current concepts suggest that local elaboration of nitric oxide (NO) modulates, in part, the intense pro-inflammatory phenomena observed in lungs of patients with certain respiratory viral infections [1]. To that end, fractional exhaled NO (FeNO) monitoring is proposed as simple, portable, noninvasive, costeffective, point-of-care biomarker of pulmonary inflammation in patients with viral-induced acute lung injury [1][2][3]. However, the effects of acute severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (coronavirus disease 2019 (COVID-19)) infection on FeNO levels in human subjects requiring supplemental oxygen therapy is controversial.…”