Hiccups Explained: Tadpole Gill Reflexes, Christopher Sands and FIST Straw

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

Hiccups have a folk reputation as a sign that someone is talking about you, a belief found in Slavic, Turkish and Luo traditions, but the medical reality is mechanical. The reflex, called singultus from the Latin for a sob, is a two part event: a sudden involuntary spasm of the diaphragm pulls air in, and about 35 milliseconds later the glottis snaps shut, and that collision makes the hic sound. Everyday triggers include eating fast, spicy food, carbonated drinks and swallowing air, but the same reflex arc can be set off by kidney failure, meningitis, multiple sclerosis, a heart attack, and in one documented case a Plasmodium vivax malaria infection. The common thread is irritation somewhere along the sprawling vagus and phrenic nerves.

The episode weighs two evolutionary explanations. The burping reflex hypothesis says hiccups evolved in suckling mammals to pull swallowed air out of an infant's stomach and make room for milk. The phylogenetic hypothesis traces the reflex to tadpoles, which gulp water across their gills and then close the glottis, and notes that human fetuses develop hiccup pathways before breathing pathways. Medicine classifies hiccups as a bout up to 48 hours, persistent up to a month, and intractable beyond that, most often in adult men and usually on the left side of the diaphragm. British singer Christopher Sands hiccuped for 27 months from February 2007 until surgery in 2009 removed the brain stem tumor pressing on his medulla.

• Charles Osborne began hiccuping in 1922 after slipping while slaughtering a hog and continued until 1990, an estimated 430 million hiccups
• Premature infants in neonatal intensive care spend about 2.5 percent of their time hiccuping
• Raised carbon dioxide and drugs acting on GABA-B receptors stop both tadpole gulping and human hiccups
• A Journal of Internal Medicine case report of intractable hiccups ended by digital rectal massage, alongside implanted vagus nerve stimulators
• The SSMI breathing technique and the FIST device, sold as the HiccAway straw, which over 90 percent of study participants rated above home remedies