Exhaled Nitric Oxide test

You may have seen a funny looking egg like device in your asthma clinic or doctors office.  It used for measuring exhaled Nitric Oxide. If you have been toy clinic, this test is somewhat affectionately know as "time with Hilda". The device in my clinics office is connected to monitor that shows a girl named by the RT's as "Hilda" who travels over tropical water from one side of a cliff to another.

Essentially, you have to keep an even exhaled breath that is timed to get Hilda across the water. If your breath is too forceful, she hits the sky or sun, ouch! If your breath is not even enough or if you run out of air, like I have done on occasion. Hilda then falls into the water. Oops! I hope she can swim. This may seem like a complicated example of how to perform an exhaled Nitric Oxide test, however your clinic or doctor will go through how to perform it and why they are recommending that you have one done.  In my circumstance, they wanted another measurement of possible airway inflammation. The very first time I was asked to do this, I had a difficult time but after a bit of practice, it become easy.

Now that I have bored you with a story about a tropical fictional character in a hot air balloon, you may be asking yourself what exactly is this test and what is it thought to indicate.  The test measures the level of nitric gas in an exhaled sample of your breath. The sample is collected by having you breathe into a device that collects the measurements.1 Sometimes it is just a mouth piece, similar to spirometry and you may breathe directly into an egg like device. It looks funny but it goes by quickly. My first time, I breathed into the egg like device that had a dancing cloud that was projected into a mirror. You may have seen this version.

The measurement is thought to detect if you have inflammation in your airways and whether you have good asthma control. This is thought to be especially useful if you are taking steroids to control your asthma.

It is thought that higher than normal ranges of exhaled nitric oxide mean that your airways may be inflamed.

  • Levels under about 20 parts per billion in children and under about 25 parts per billion in adults are considered normal.
  • More than 35 parts per billion in children and 50 parts per billion in adults may signal airway inflammation caused by asthma.3

This test is still being evaluated and as researchers discover more correlations, there will be new information evaluated. My personal experiences is mixed, sometimes my doctors have found a direct correlation, other times not so much.  Since the test in non invasive there are high hopes but more data and analysis is needed.4 It is important to note that test results can vary from patient to patient.  The factors that can affect your test results are as follows:

  • your signs and symptoms
  • previous  nitric oxide results
  • your medication usage
  • 5

I believe that most data can be helpful and since this test is noninvasive it is worth a go.

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