Hiccup

• Swallowing air excessively[3]
• Gastroesophageal reflux[4]
• Hiatal hernia[5]
• Rapid eating[6]
• Carbonated beverages, alcohol, dry breads, and some spicy foods[7]
• Opiate drug use[8]
• Laughing[9]

Hiccups may be triggered by a number of common human conditions. In rare cases, they can be a sign of serious medical problems.

• Kidney failure[10]

• Stroke[10]
• Multiple sclerosis[11]
• Meningitis[10]

• Damage to the vagus nerve after surgery[5]

• Although no clear pathophysiological mechanism has been described, hiccups is known to have been the initial symptom of Plasmodium vivax malaria in at least one documented case.[12]

One suggestion is that hiccups may have evolved along with other reflexes developed in mammals that allow them to coordinate suckling milk and breathing.[6] Hiccups are only found in mammals, and are most common in infants, becoming rarer as mammals age. This may suggest that they evolved to allow air trapped in the stomach of suckling infants to escape, allowing more milk to be ingested. The hypothesis suggests that the air bubble in the stomach stimulates the sensory limb of the reflex at receptors in the stomach, esophagus and along the diaphragm. This triggers the hiccup, which creates suction in the chest, pulling air from the stomach up and out through the mouth, effectively burping the animal. This theory is supported by the strong tendency for infants to get hiccups, the component of the reflex that suppresses peristalsis in the esophagus, and the existence of hiccups only in milk-drinking mammals.

An international respiratory research group composed of members from Canada, France, and Japan proposed that the hiccup is an evolutionary remnant of earlier amphibian respiration.[13] Amphibians such as tadpoles gulp air and water across their gills via a rather simple motor reflex akin to mammalian hiccuping. The motor pathways that enable hiccuping form early during fetal development, before the motor pathways that enable normal lung ventilation form. Thus, the hiccup is evolutionarily antecedent to modern lung respiration.

Additionally, this group (C. Straus et al.) points out that hiccups and amphibian gulping are inhibited by elevated CO₂ and may be stopped by GABA_B receptor agonists, illustrating a possible shared physiology and evolutionary heritage. These proposals may explain why premature infants spend 2.5% of their time hiccuping, possibly gulping like amphibians, as their lungs are not yet fully formed.[14]

Fetal intrauterine hiccups are of two types. The physiological type occurs prior to twenty-eight weeks after conception and tend to last five to ten minutes. These hiccups are part of fetal development and are associated with the myelination of the phrenic nerve, which primarily controls the thoracic diaphragm.

The phylogeny hypothesis explains how the hiccup reflex might have evolved, and if there is not an explanation it may explain hiccups as an evolutionary remnant, held over from our amphibious ancestors.[15] This hypothesis has been questioned because of the existence of the afferent loop of the reflex, the fact that it does not explain the reason for glottic closure, and because the very short contraction of the hiccup is unlikely to have a significant strengthening effect on the slow-twitch muscles of respiration.

There are many superstitious and folk remedies for hiccups, including headstanding, drinking a glass of water upside-down, being frightened by someone, breathing into a bag, eating a large spoonful of peanut butter and placing sugar on or under the tongue.[20][21]

A simple treatment involves increasing the partial pressure of CO₂ and inhibiting diaphragm activity by holding one’s breath or rebreathing into a paper bag.[22] Other potential remedies suggested by NHS Choices include pulling your knees up to your chest and leaning forward, sipping ice-cold water and swallowing some granulated sugar.[23]