for: Chromatography

A hiccup or hiccough (normally pronounced "HICK-up" IPAEng: ˈhɪkəp), also known as a condition of singulitis, is the spasmodic contraction of the diaphragm that repeats several times per minute. In humans, the abrupt rush of air into the lungs causes the epiglottis to close, creating the "hic" listen noise. In medicine, it is known as synchronous diaphragmatic flutter (SDF), or singultus.

The term "hiccup" is also used to describe a small and unrepeated aberration in an otherwise consistent pattern.

A bout of hiccups generally resolves itself without intervention, although many home remedies claim to shorten the duration, and medical treatment is occasionally necessary.

Causes

While many cases develop spontaneously, hiccups are known to be triggered by specific events, such as lack of water, eating too fast, being hungry for long, taking a cold drink while eating a hot meal, burping, eating very hot or spicy food, laughing vigorously, coughing, drinking alcoholic beverages in excess, crying out loud (sobbing causes air to enter the stomach), some smoking situations where abnormal inhalation can occur (in tobacco or other smoke like cannabis, perhaps triggered by precursors to coughing), electrolyte imbalance, talking too long, clearing the throat, by some of the stronger opiate painkillers such as Heroin, Morphine, and Oxycodone or from lack of vitamins. Hiccups may be caused by pressure to the phrenic nerve by other anatomical structures, or having the sensation that there is food in the esophagus, rarely by tumors and certain kidney disease. The American Cancer Society reports that 30% of chemotherapy patients suffer singultus as a side effect of treatment.

Phylogenetic hypothesis

Christian Straus and co-workers at the Respiratory Research Group, University of Calgary, Canada, propose that the hiccup is an evolutionary remnant of earlier amphibian respiration; amphibians such as frogs gulp air and water via a rather simple motor reflex akin to mammalian hiccuping. In support of this idea, they observe that the motor pathways that enable hiccuping form early during fetal development, before the motor pathways that enable normal lung ventilation form; thus according to recapitulation theory the hiccup is evolutionarily antecedent to modern lung respiration. Additionally, they point out that hiccups and amphibian gulping are inhibited by elevated CO2 and can be completely stopped by the drug Baclofen (a GABAB receptor agonist), illustrating a shared physiology and evolutionary heritage. These proposals would explain why premature infants spend 2.5% of their time hiccuping, indeed they are gulping just like amphibians, as their lungs are not yet fully formed.