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Breath Nitrogen Test

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The breath nitrogen test is used to measure the amount of dead space in the lungs and the presence of any airway closure. Continue reading to learn more.

Written byDr. Asna Fatma

Medically reviewed byDr. Kaushal Bhavsar

Published At May 9, 2023
Reviewed AtDecember 29, 2023

Introduction:

The nitrogen breath test is a simple procedure used to measure the anatomic dead space in the lungs during a respiratory cycle. This test also measures certain parameters of airway obstruction. During this test, the patient inhales through a mouthpiece connected to a source of 100 percent oxygen while one-way valves direct the exhaled gas into a collection bag. Normal patients may complete this test in three to four minutes, but people with severe obstructive airway disease may need more time, up to 15 minutes.

What Is Breath Nitrogen Test?

The breath nitrogen test, nitrogen washout, or Fowler’s method is a pulmonary function test that measures the anatomic dead space in the lungs during one respiratory cycle. Moreover, it also measures certain parameters associated with airway closure. In other words, the functional residual capacity of the lungs and airflow is measured by the breath nitrogen test. The purpose of this test is to locate the dead space, or air that is not actively participating in the exchange of gasses, in the tiny air sacs of the lungs. This typically occurs due to a capillary that is linked to the air sacs that are not functioning, preventing the air sacs from receiving oxygen or releasing carbon dioxide. Large amounts of dead space within the lungs contribute to decreased efficacy and poor lung function.

Why Is Breath Nitrogen Test Done?

A breath nitrogen test is used to determine the amount of dead space within the lungs and any airway closure. The basis of the nitrogen washout method is that the patient inhales 100 percent oxygen, exhales into a spirometer, and monitoring of this exhaled nitrogen is done until it is washed out. The test typically takes about 15 minutes to be carried out.

How to Prepare for Breath Nitrogen Test?

The breath nitrogen test usually requires no prior preparations. In most cases, the patient can carry on with their regular schedule. However, there are certain factors to be considered to ensure accurate results. These factors include the following:

  • Smoking should be avoided before the test.

  • Wearing tight-fitted clothes should be avoided.

  • A heavy meal should not be consumed two hours before the test.

  • Alcohol should not be consumed four hours before the test.

  • For a few hours before the test, strenuous activity and exercises should be avoided.

  • If the patient uses inhalers, they should be instructed to bring that along.

  • The doctor's instructions should be followed for the use of inhaled breathing medications or other medications before the test.

Certain medicines should be avoided before lung function tests. These include;

  • Salbutamol and Terbutaline, four hours before the test.

  • Ipratropium bromide, eight hours before the test.

  • Salmeterol, Budesonide, or Fluticasone, 12 hours before the test.

  • Tiotropium bromide, 24 hours before the test.

How Is Breath Nitrogen Test Done?

A breath nitrogen test can be done with single or multiple nitrogen breaths. The multiple-breath test more precisely measures absolute lung volumes. However, both tests employ identical equipment and can determine functional residual capacity and the degree of non-uniformity of gas distribution in the lungs. A breath nitrogen test is performed in the following ways:

  • First, the patient will be asked to breathe through a machine providing 100 percent oxygen. There will not be any additional gases in the air.

  • The patient will then exhale as long as possible into a one-way valve, which will then measure how much nitrogen is in the breath.

  • Nitrogen remains in the lungs until it is breathed since it is not exchanged in the lungs. However, it is difficult to exhale if the breath is excessively shallow due to respiratory inflammation.

  • Due to the nitrogen present in the earth's atmosphere, the air humans typically breathe contains about 78 percent nitrogen. Therefore, if just oxygen is inhaled, one will exhale any residual nitrogen present in the lungs. The percentage of nitrogen above 78 percent, which is considered to be normal, will show how much residual gas is present in the lungs.

  • The test is finished, and the amount of nitrogen collected is measured when the exhaled nitrogen concentration drops below two percent.

  • Additionally, the patient may be instructed to breathe normally for a short period of time while still receiving pure oxygen inhalation. This often calculates the length of time it takes people to remove nitrogen from their lungs.

What Are the Risks Involved With Breath Nitrogen Test?

The test is not carried out if the patient had the following:

  • Recently had a heart attack or other heart issues because it involves some physical activity.

  • Angina pain that is unstable.

  • Pneumothorax (entrapment of air within the chest wall).

  • Heart attack or stroke.

  • Recent eye surgery.

  • Recent abdominal surgery.

  • Recently coughed up blood due to unknown causes.

Conclusion:

The nitrogen washout test is one of many procedures to evaluate how well the lungs work. The test is usually performed on individuals who have compromised lung functioning. Within seven minutes, most people with a normal distribution of airway resistance will experience a decrease in their expired nitrogen concentrations. It may take longer than seven minutes for people with strong airway resistance to expel all of the nitrogen from their lungs completely.

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Frequently Asked Questions

The breath nitrogen test detects early symptoms of small airway disease (SAD), particularly in people who have smoked cigarettes and helps to identify COPD risk and progression. It distinguishes between smokers and nonsmokers, as well as symptomatic and asymptomatic patients, although with lesser sensitivity than spirometry. Recent research has shown its utility in assessing the effects of inhaled medications on small airways in asthma and COPD, contributing to disease management and prognosis.

A breath nitrogen test can reveal disorders that impair nitrogen metabolism and protein breakdown, such as liver dysfunction, kidney disease, and wasting syndromes. Elevated breath nitrogen levels can suggest issues with protein digestion and absorption. Low breath nitrogen levels may indicate malnutrition or insufficient protein intake.

The breath nitrogen test is not a standard diagnostic practice. It is mostly used in studies that assess protein metabolism. The test requires specialized equipment to analyze breath samples, so it is typically only administered in larger hospitals or academic medical centers with access to gas chromatography machines. Overall, the application of breath nitrogen testing is limited due to equipment price and availability.

During the breath nitrogen test, the subject breathes through a mouthpiece connected to oxygen and exhales into an oxygen-flushed bag to eliminate nitrogen. The collected nitrogen volume determines functional residual capacity (FRC), often 80 % of lung gas, measured instantly by advanced microprocessors. This process lasts three to four minutes in healthy subjects but may be prolonged for those with severe airway obstruction.

Yes, medications and dietary patterns can influence breath nitrogen test results. Medications that affect protein digestion or nitrogen metabolism, like antibiotics or steroids, may alter breath nitrogen levels. High-protein diets and recent protein intake before the test can increase breath nitrogen. Low-protein diets and fasting can substantially lower breath nitrogen outputs.

In cases where accurate assessment of functional residual capacity (FRC) is critical, such as evaluating lung function in people with respiratory diseases like asthma or COPD or assessing response to treatment, the test may be recommended on a regular basis, usually as part of routine pulmonary function testing. However, healthcare providers select the specific frequency of testing based on the patient's condition and treatment plan.

Individuals of all demographics and ages are typical candidates for a breath nitrogen test, particularly those with suspected or diagnosed respiratory disorders such as asthma, chronic obstructive pulmonary disease (COPD), or cystic fibrosis. Individuals with symptoms suggestive of small airway disease, as well as those at risk due to a smoking history, may benefit from this test for early detection and monitoring. While there is no age limit, it is often used in both pediatric and adult populations, depending on clinical indications and medical history.

The breath nitrogen test is primarily used to measure lung function and small airway physiology rather than to evaluate metabolic health or aid in weight management. While changes in lung function may indirectly influence metabolic processes, the test itself does not provide direct insights into metabolic health or weight management.

The breath nitrogen test does not directly examine digestive health; instead, it evaluates lung function and small airway physiology. However, the breath nitrogen test may play an indirect role in some cases, such as when testing for gastroesophageal reflux disease (GERD).

The breath nitrogen test differs from other diagnostic procedures for similar situations, such as spirometry or bronchial provocation tests, because it focuses on examining small airway function and measuring functional residual capacity (FRC). While spirometry assesses overall lung function, the breath nitrogen test focuses on small airways, offering additional information. Furthermore, unlike bronchial provocation tests, which evaluate airway hyperresponsiveness, the breath nitrogen test primarily assesses gas exchange dynamics and lung volumes, providing unique insights into respiratory physiology.

The breath nitrogen test cannot detect food intolerances or allergies because it focuses on lung function and small airway physiology. However, in rare situations, people with food intolerances or allergies may have respiratory symptoms like wheezing or shortness of breath, which could have an indirect impact on the test results.

Yes, there are specialized variants of breath nitrogen tests designed for specific purposes. One type, known as the multiple breath nitrogen washout test, measures ventilation inhomogeneity and small airway function in diseases such as cystic fibrosis. Another type, known as the single-breath nitrogen test, assesses lung volumes and gas exchange dynamics, particularly in those with respiratory illnesses such as asthma or chronic obstructive pulmonary disease (COPD).

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Dr. Kaushal Bhavsar from iCliniq
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)

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