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Three Part Question

In [A patient with Asthma exacerbation in ED], is [Fractional Exhaled Nitric Oxide (FENO) measurement reliable] to [assess the response to the management]?

Clinical Scenario

30 years old male presents to emergency department with SOB and known past medical history of asthma. Recently he was not using his daily puffers as prescribed by his family physician. You start managing him as acute asthma exacerbation, you wonder if there test that will guide your management and assess the patient response to medications given.

Search Strategy

Ovid Medline 1946 to September 2020
[emergency department.mp. or Emergency Service, Hospital/OR ED.mp.OR Emergency room.mp. OR Emergency Service, Hospital/ORER.mp.] AND [Asthma/ or asthma.mp.] AND [exhaled nitric oxide.mp.ORfractional exhaled nitric oxide.mp.]

Search Outcome

76 papers were identified, of which 4 adressed the clinical question in adult and pediatric age group. The table below summarize the included studies.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
karlin et al. 2013 USA	Pediatric	Prospective study	To examine the change of FeNO in pediatric patients after acute exacerbations and at a time of improved asthma control.	Median FeNO value at the time of improved asthma control was 53 ppb (IQR 30e81) in all participants compared with 60 ppb (IQR 49e76) at the time of the preceding acute exacerbation.	- Insufficient power because of the small sample size. - Not assess for atopy, which is associated with elevated FeNO - Follow up was done days later in the clinic without mentioning the exact day. - No FeNO measurement post treatment in ED.
Silverberg et al. 2012 USA	Adult	Prospective study	eNO measurements to determine the effect of ED treatment of acute asthma exacerbations in inner-city adults on changes in eNO and its relation to change in ventilatory status, asthma control parameters, blood leukocyte and IgE levels, and tobacco use.	- Both PEF and eNO were significantly increased after ED treatment of asthma exacerbation. - Change in eNO found to be predictor of ED visit duration. - Improvement of ventilation of previously obstructed and inflamed airways after asthma treatment may allow for better measurement of eNO produced in the entire respiratory tract. - Elevated eNO may have value as an inflammatory biomarker in the acute setting for response to therapy and duration of ED visits.	- Small sample size. - Lack of the follow up and re-measure eNO.
Delclaux et al. 2008 France	Adult	Prospective study	To assess whether FENO time-course predicts subsequent asthma control.	An increase in FENO is observed in almost all patients with acute asthma, and its subsequent increase within 6 hours is associated with a better degree of asthma control in the subsequent week.	- Few patients have been enrolled by each center. - A significant proportion of patients was lost during the follow-up.
Lanz et al. 1999 USA	Pediatric	Prospective study	Determine whether asthmatic children have (1) elevation of exhaled breath nitric oxide (ENO) during acute exacerbations when presenting to the emergency room, (2) reduction of ENO following glucocorticoid treatment, or (3) improvement in spirometry and clinical examination accompanying reduction of ENO levels.	The mean peak ENO level after glucocorticoid therapy was significantly less than that measured before treatment in children with acute asthma exacerbations.	- Small sample size. - The measurement of 2nd ENO was not specified at what time was done in the 5 days following the first ENO level.

Comment(s)

The Studies included were of variable quality. A well-designed clinical trial with larger sample size is required to make better recommendations. On the reviewed studies, Fractional Exhaled Nitric Oxide (FENO) was measured in ED to assess the response to the asthma exacerbation management. Acute asthma exacerbation associated with airways obstruction and limitation of air flow, subsequently will affect the initial measurement of FENO. After administering bronchodilator, the air flow will improve, and the FENO level expected to be higher than the initial value. The post treatment value of FENO can be used as predictor of successful management.

Clinical Bottom Line

FENO can be an effective tool to predict the response to asthma exacerbation management and the asthma control after discharge, in addition to the clinical presentation and exam findings. Further studies need to be done to evaluate this tool.

References

1. Eric Karlin, MD Fractional exhaled nitric oxide change in pediatric patients after emergency department care of asthma exacerbations
2. Jonathan I. Silverberg, M.D., Ph.D Emergency department treatment of adults with acute asthma exacerbations: Effect on exhaled nitric oxide levels
3. Christophe Delclaux Offline Exhaled Nitric Oxide in Emergency Department and Subsequent Acute Asthma Control.
4. Miguel J Lanz, MD Comparison of exhaled nitric oxide to spirometry during emergency treatment of asthma exacerbations with glucocorticoids in children