In the 13C urea breath test in the diagnosis of Helicobacter pylori infection, Isotopically labelled CO2 is normally detected in breath using various methods. My question is will the CO2 also diffuse into the air inside the stomach? If I insert a CO2 sensor into the stomach through an endoscope, will I also detect Isotopically labelled CO2 there?
The honest answer is I do not for certain. However, based on observations made with 13C breath tests using 13C-labelled bicarbonate as tracer chances are there will be some gaseous CO2 present within the stomach.
That being said, what kind of CO2 sensor are you planning to use? In which IR band does this sensor operate? Are you sure this sensor has the resolution required to distinguish between 12CO2 and 13CO2 absorption lines?
Furthermore, what will the advantage be of inserting a CO2 sensor via an endoscope as compared to analysing 13CO2 in exhaled breath using a laser based stable isotope analyzer (IRIS)? The whole point of 13CO2 breath tests is to avoid invasive (surgical or quasi-surgical) procedures such as endoscopy. If you are planning to use an endoscope anyway you might as well sample the lining of the stomach, do a culture and check this for presence of H. pylori.
What will the advantage be of inserting a CO2 sensor via an endoscope as compared to analysing 13CO2 in exhaled breath ?
The 13C urea breath test (UBT) is widely used for determination of H pylori infection.
The whole point of 13CO2 breath tests is to avoid invasive (quasi-surgical) procedures such as endoscopy. I agree you might as well sample the lining of the stomach, do a culture and check this for presence of H. pylori.
Hi Wolfram and Issam ,
Thank you for your answers and interests. I am developing a fiber coupled photoacoustic sensor for gas detection, which is small enough to be inserted into an endoscope. My idea here is if the CO2 produced by H. pylori will also present in the volume of the stomach, then my sensor has the potential to localize the H.pylori colonies in-vivo, because I expect larger CO2 concentrations above the colonies. I thought the information of H.pylori colonies' location and scale could help doctors to evaluate the diseases related somehow.
I was not intended to differentiate 13C labeled CO2 from 12C CO2, but only measure the 12C CO2 increase on top of the base level after drinking normal urea. The laser source I am using is a tunable L band laser. The sensitivity reached by now is around 60 ppm for CO2.
Hi Sheng Zou, usually I am not in the habit of discourageing young enthusiastic scientists. However, in this instance I would advise caution.
(1) Due its invasive nature alone to my mind your proposed test offers no advantage over the 13CO3 UBT.
(2) I suspect your test will not have the levels of specificity and sensitivity required for a reliable diagnostic test.
Since you will only detect CO2 rather than 13CO2 specifically released by H pylori after 13C-urea administration, your test is prone to suffer from artefacts. By this I mean you may detect the presence of CO2 the origin of which is unrelated to H pylori. It is not even necessary for reactions in the stomach to produce CO2. Even intestinal gas formation and gas build up may lead to CO2 being present in the stomach.
Your proposed test will not be able to distinguish between background CO2 and H pylori generated CO2. Apart from its non-invasive nature this however is the chief advantage of the UBT, actually of any 13CO2 breath test. Breath 13CO2 abundance measurements post administration of the 13C-tracer are corrected for each patient's individual 13CO2 background.
Hi Wolfram,
I get your point. Indeed, if the background CO2 concentration is already very high, the CO2 released by H. pylori may not be detectable.
I will do more study and find other potential applications that my small sensor can play a role.
Thank you again for your help!
It is a minimum amount produced and can be easily liberated by the breath
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