This simple breathing test measures nitric oxide levels in exhaled breath.
A feno test helps doctors identify and monitor certain types of asthma. It's especially useful for detecting eosinophilic asthma, a specific form of the condition.
The test takes just a few minutes and provides results right away.
Many patients find feno tests easier than other asthma tests. There's no need for exercise or medication challenges.
You simply breathe into a machine. The feno test adds another tool for managing respiratory health.
Feno Test Fundamentals
The Feno test measures nitric oxide levels in exhaled breath. This quick and non-invasive procedure helps assess airway inflammation in patients with respiratory conditions.
Definition and Importance
A Feno test, or fractional exhaled nitric oxide test, checks the amount of nitric oxide in a person's breath. Nitric oxide is a gas produced in the lungs and airways. Higher levels often mean there is inflammation in the airways.
The test is easy to do. A person breathes into a small handheld device. It takes just a few minutes and doesn't hurt. The results come back quickly, usually within minutes.
Feno tests are important because they can:
- Help diagnose asthma
- Show how well asthma treatments are working
- Guide decisions about medication doses
- Predict asthma flare-ups
Clinical Applications
Doctors use Feno tests in several ways. They can help figure out if someone has asthma, especially when other tests aren't clear.
For people already diagnosed with asthma, the test shows if their treatment plan is working well.
Feno results may lead to changes in medication. If levels are high, it might mean more medicine is needed. Low levels could mean less medicine is okay.
The test is useful for many types of patients:
- Children who have trouble with other breathing tests
- Adults with unexplained coughing or wheezing
- People who might have work-related asthma
Doctors often use Feno tests along with other tools to get a full picture of a person's lung health.
Procedure and Techniques
The feno test involves specific steps for preparation and execution. These procedures ensure accurate measurement of exhaled nitric oxide levels in the breath.
Preparation for Feno Test
Patients should avoid eating, drinking, smoking, and exercise for at least 1 hour before the test. These activities can affect nitric oxide levels in breath. Medications like inhaled steroids may also impact results.
Patients should inform their doctor about any medicines they take.
The testing room needs proper ventilation. This prevents ambient nitric oxide from skewing results.
The feno device requires calibration before use. Technicians check that all parts work correctly.
Patients receive clear instructions on how to perform the test. They learn the proper breathing technique.
Understanding the process helps reduce anxiety and improves test accuracy.
Execution Protocol
The patient sits upright and places a mouthpiece between their lips. A nose clip prevents nasal breathing during the test.
The technician guides the patient through the breathing process.
The patient takes a deep breath in. They then exhale slowly and steadily into the device. The exhale should last for about 10 seconds.
The machine measures nitric oxide levels during this time.
Most feno tests require at least two valid measurements. The results should be within 10% of each other. If not, more attempts may be needed.
The entire process usually takes 15-20 minutes.
The device displays the results immediately after the test.
Doctors interpret these results based on established guidelines. They consider factors like age, height, and medical history.
Interpreting Test Results
FeNO test results provide important information about airway inflammation. Proper interpretation helps guide diagnosis and treatment decisions.
Normal vs. Abnormal Values
FeNO levels below 25 parts per billion (ppb) in adults are considered normal. Levels between 25-50 ppb suggest mild inflammation. Readings above 50 ppb indicate significant airway inflammation.
For children under 12, normal is under 20 ppb. Levels of 20-35 ppb are borderline. Over 35 ppb suggests inflammation.
Doctors compare results to these ranges. They also look at changes over time. A big jump in FeNO levels may signal worsening asthma control.
Factors Influencing Results
Several factors can affect FeNO test results. Recent use of steroid medications may lower levels.
Smoking can also reduce FeNO readings.
Eating nitrate-rich foods before the test might raise levels. These include leafy greens and cured meats.
Respiratory infections can cause temporary spikes.
Age and height impact normal ranges. Allergies and eczema may lead to higher baseline levels.