Related Experiment Video
Updated: Jan 22, 2026

5/6th Nephrectomy in Combination with High Salt Diet and Nitric Oxide Synthase Inhibition to Induce Chronic Kidney Disease in the Lewis Rat
Published on: July 3, 2013
Exhaled nitric oxide in chronic cough: A good tool in a multi-step approach
T Lamon1, A Didier2, D Brouquières1
1Department of respiratory medicine, Larrey Hospital, University hospital centre of Toulouse, 31059 Toulouse, France.
Introduction:
The impact of fractional exhaled nitric oxide (FENO) on the management of chronic cough (CC) is still inconclusive. The aim of the present study was to assess whether FENO is a good tool to predict the response to inhaled corticosteroids (ICS) in patients with CC.
Methods:
Patients, referred for investigation of CC, had a FENO measurement determined as part of their first-line assessment. A methacholine test was performed as part of a second-line assessement. Patients were assigned to two groups according to their FENO values: a high FENO level group (Ⱕ25 ppb) and a normal FENO level group (<25 ppb).
Results:
One hundred patients were included in the study. High FENO levels were found in 25 patients (25%). The proportion of patients who responded to ICS was significantly greater in the high FENO group compared to the normal FENO level group (86.4% vs 46.3%, P<0.05). FENO is a good tool to predict ICS response in patients with high FENO levels but a response to ICS cannot be ruled out in patients with normal FENO levels. In patients with normal FENO values, a methacholine test could be an interesting tool for a second-line assessment. Among the 13 patients with a positive methacholine test result, 11 responded to ICS whilst 2 did not. Of the patients with a negative methacholine test result, 3 responded to ICS whilst 13 did not.
Conclusion:
FENO may be a more reliable predictor of ICS response when used as part of a multi-step assessment procedure.
Related Concept Videos
Nitric Oxide Signaling Pathway
Multi-Step Reactions
Pulmonary Cycle: Exhalation
Rate-Determining Steps
In a multistep reaction mechanism, one of the elementary steps progresses significantly slower than the others. This slowest step is called the rate-limiting step (or rate-determining step). A reaction cannot proceed faster than its slowest step, and hence, the rate-determining step limits the overall reaction rate.
The concept of rate-determining step can be understood from the analogy of a 4-lane freeway with a short-stretch of traffic-bottleneck caused due to...
Oxidation Numbers
Pyruvate Oxidation
First, the enzyme pyruvate dehydrogenase removes the carboxyl group from pyruvate and releases it as carbon dioxide. The stripped molecule is then oxidized and releases electrons, which are then picked up by NAD+...

