|MadSci Network: Medicine|
Dear Catherine, Hiccups are caused by spasms of the diaphragm, the big sheet of muscle at the base of the lungs that separates the thorax from the abdomen. Normally when we breathe this muscle moves smoothly up and down, drawing air in and out of the lungs. However, when we develop hiccups, for some reason this muscle becomes "twitchy" and contracts from time to time in an irregular, jerky way, followed by a sudden closure the vocal cords, (which gives the "hic" sound), and then everything relaxes and works normally until the next spasm.
In most cases there is no obvious cause of hiccups, although sometimes it may be secondary to a condition which irritates the diaphragm or its nerves, such as pneumonia or liver inflammation. It is certainly not caused by air in the blood (I presume you mean air bubbles), which is a very dangerous and potentially fatal condition!
Most minor attacks will clear up without treatment, although various popular remedies, such as drinking cold water upside-down, are often recommended. In rare cases, certain kinds of relaxant drugs can be tried if the hiccups are prolonged and severe. As far as I am aware, the longest recorded attack was suffered by Charles Osborne of Iowa, USA, who started hiccuping in 1922 and was still going strong in 1990!
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