Gibson’s team think they have the answer with a tiny sensor that can be swallowed like a medical pill. As it passes through the body, the capsule samples the gases at regular intervals and relays them to a tablet computer; it will also measure things like the ambient temperature and acidity, which can provide further information about its position in the gut. This is particularly important at the end of its voyage. “You want to know if it’s passed out of the backside, but you wouldn’t know because it’s just part of the stool” says Gibson. The temperature sensor, however, could offer an instant warning. “When the temperature falls, that’s when it’s gone outside.”

In this way, a doctor can collect real-time data at each stage of the pill’s journey. So far, the team have tested an early prototype on a couple of pigs, and they hope to begin human trials within the next few months.

Once the sensor has proven itself to be safe and effective, he plans to build up a library profiling the gases associated with different diseases and lifestyles. From there, it may be possible to see the direct effects of different treatments for some of the related ailments.

Since methane is thought to be linked to constipation Gibson hopes to understand where and when it is produced. “What you’d like is something that reduces methanogenesis – a simple dietary change or drug that improves constipation, which is a major problem across the world,” he says. “But we can’t know until we measure it.”

Gibson certainly can’t be faulted for his enthusiasm on this subject. “It’s very exciting – the more we get into [the subject] the more we see the potential,” he says. Let’s just hope his probe delivers on that promise, and that the excitement doesn’t just turn out to be a load of hot air.

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David Robson is BBC Future’s feature writer. He is @d_a_robson on twitter. Olivia Howitt is BBC Future’s picture editor. She is @oliviahowitt on Twitter.

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