Revolutionizing asthma diagnosis through simple breath analysis
Simple breath test
Within seconds
Objective inflammation data
Imagine if diagnosing a complex condition like asthma could be as simple as blowing into a tube. For millions of people worldwide, this is becoming a reality thanks to a remarkable medical breakthrough: Fractional Exhaled Nitric Oxide (FeNO) testing.
This non-invasive technology transforms a single breath into a precise measurement of airway inflammation, revolutionizing how we diagnose and manage asthma.
FeNO testing represents a paradigm shift in respiratory medicine, moving beyond symptom-based diagnosis to objective biological evidence. As global asthma rates continue to pose significant health challenges, this innovative approach offers healthcare providers a window into the invisible inflammatory processes occurring deep within patients' airways.
FeNO testing provides immediate, quantifiable data that helps personalize treatment plans, potentially reducing hospitalizations and improving quality of life for asthma sufferers.
Fractional Exhaled Nitric Oxide (FeNO) measures the concentration of nitric oxide gas in parts per billion (ppb) in exhaled breath. Nitric oxide, a signaling molecule produced naturally in the body, plays a crucial role in respiratory health.
In the lungs, it's primarily generated by the airway epithelial cells when certain inflammatory pathways are activated 3 .
The connection between nitric oxide and asthma revolves around a specific type of inflammation called Type 2 inflammation. This inflammatory pattern triggers the release of specific cytokines (IL-4 and IL-13) that upregulate an enzyme called inducible nitric oxide synthase (iNOS) 3 .
This enzyme dramatically increases nitric oxide production in the airways, making elevated FeNO levels a reliable marker of this treatable form of asthma.
Traditional asthma diagnostics like peak flow meters and spirometry measure lung function—what your lungs can do physically. FeNO testing goes a step further by revealing what's happening at a biological level inside your airways.
Patients avoid eating, drinking (except water), and smoking for at least an hour before the test to prevent interference with measurements.
A handheld FeNO device such as NIOX VERO or NObreath® is prepared with a new disposable mouthpiece to ensure hygiene and accuracy.
The patient takes a deep breath to total lung capacity, then exhales steadily into the device at a constant flow rate.
Electrochemical sensors analyze the exhaled air and calculate the nitric oxide concentration within seconds.
| Population | Low FeNO (ppb) | Intermediate FeNO (ppb) | High FeNO (ppb) |
|---|---|---|---|
| Adults | < 25 | 25 - 50 | > 50 |
| Children | < 20 | 20 - 35 | > 35 |
Source: Adapted from American Thoracic Society and NICE/BTS/SIGN guidelines 4 7
| Clinical Scenario | Typical FeNO Pattern | Clinical Interpretation |
|---|---|---|
| Treatment-naïve symptomatic asthma | High (>50 ppb adults, >35 ppb children) | High likelihood of ICS response |
| 4-8 weeks after starting ICS | >40% decrease from baseline | Confirms treatment adherence and effectiveness |
| Stable on ICS maintenance | Within normal range | Supports current treatment plan |
| Symptomatic despite ICS treatment | Persistently elevated | Suggests poor adherence or need for dose adjustment |
FeNO levels don't exist in a vacuum—they're influenced by various factors that clinicians must consider when interpreting results. The clinical context is essential for accurate interpretation.
| Factor | Effect on FeNO | Clinical Considerations |
|---|---|---|
| Allergen Exposure | Increases | Recent exposure may temporarily elevate levels |
| Smoking | Decreases | Can suppress FeNO, requiring adjusted interpretation |
| Age and Sex | Varies | Slightly higher in males and with increasing age |
| Time of Day | Fluctuates | Diurnal variation—often higher in afternoon |
| Respiratory Infections | Increases | Recent infection may elevate levels temporarily |
The 2025 GINA guidelines specify that in patients with typical asthma symptoms but normal lung function tests, FeNO values ≥50 ppb for adults and ≥35 ppb for children support diagnosing Type 2 asthma 2 .
The 2024 NICE/BTS/SIGN guidelines position FeNO as a first-line test in asthma diagnosis for both adults and children 4 .
Low FeNO levels do not rule out asthma completely, as some patients have non-eosinophilic asthma that doesn't elevate nitric oxide production 2 .
Elevated FeNO can occasionally occur in other conditions like eosinophilic bronchitis or allergic rhinitis.
FeNO is most valuable when interpreted as part of a comprehensive clinical assessment.
The advancement and application of FeNO technology rely on specialized tools and biological reagents. Here's a look at the essential components driving this field forward:
Function: Portable devices using electrochemical sensors to measure nitric oxide concentration in exhaled breath 3 .
Examples: NIOX MINO, NObreath®, VeroFunction: Research tools to detect and quantify iNOS expression in airway epithelial cells 3 .
Validation ToolFunction: Key signaling molecules (IL-4 and IL-13) that stimulate iNOS expression in airway epithelium 3 .
Experimental ModelsFunction: The core technology in FeNO devices that specifically detects nitric oxide molecules 1 .
Core TechnologyFunction: Precision gas mixtures with known nitric oxide concentrations used to calibrate FeNO analyzers 3 .
StandardizationFunction: Single-use mouthpieces and bacterial filters that maintain hygiene during testing 3 .
Hygiene & ProtectionA groundbreaking 2025 study explored FeNO levels in breast cancer detection. Researchers measured FeNO in 192 women—both with breast cancer and malignancy-free controls—using the same handheld devices developed for asthma monitoring.
The study found that FeNO levels were lower in breast cancer patients compared to controls, with the lowest levels observed in women with HER2-expressing tumors .
This intriguing discovery suggests that the relationship between nitric oxide and disease processes may be more complex than previously understood. While airway inflammation increases FeNO, systemic conditions like breast cancer might alter nitric oxide metabolism differently.
The FeNO testing landscape is rapidly advancing, with several trends shaping its future:
Integration of artificial intelligence to enhance pattern recognition and predictive capabilities 1
Home-based FeNO devices that enable continuous inflammation tracking between clinical visits 1
Devices that measure FeNO alongside other volatile organic compounds for comprehensive breath analysis
Development of smaller, more affordable devices to increase accessibility 5
These innovations promise to further establish breath analysis as a cornerstone of precision medicine for respiratory conditions and beyond.
Fractional Exhaled Nitric Oxide testing represents a remarkable convergence of biology, technology, and clinical medicine. By harnessing the information contained in a single breath, FeNO provides a unique window into airway inflammation that has transformed asthma management from symptom control to targeted biological treatment.
As research continues to unveil new applications and technologies make testing increasingly accessible, FeNO stands as a powerful example of how understanding basic biological processes can lead to diagnostic breakthroughs that directly improve patient care.
"Breath analysis is a novelty in medicine and has the potential to reshape clinical diagnosis due to its non-invasiveness, painlessness, safety, ready acceptance by patients, and nearly unlimited access to samples" .
As this field advances, the simple act of breathing may become one of our most valuable diagnostic tools.