As the respiratory muscles relax the air is expelled through the mouth, effectively "burping" the animal.There are a number of characteristics of hiccups that support this theory. The burping of a suckling infant may increase its capacity for milk by more than 15-25%, bringing a significant survival advantage. There is a strong tendency for infants to get hiccups, and although the reflex persists throughout life it decreases in frequency with age. The location of the sensory nerves that trigger the reflex suggests it is a response to a condition in the stomach. The component of the reflex that suppresses peristalsis in the esophagus while the airway is being actively blocked suggests the esophagus is involved. Additionally, hiccups are only described in mammals - the group of animals that share the trait of suckling their young. Phylogenetic hypothesis
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. 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 GABAB receptor agonists, illustrating a possible shared physiology and evolutionary heritage.
The Food and Drug Administration approved the vagus nerve stimulator in 1997 as a way to control seizures in some patients with epilepsy. "Persistent digital rectal massage has also been proven effective in terminating intractable hiccups. Folk remedies
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.Acupressure, either through actual function or placebo effect, may cure hiccups in some people. For example, one technique is to relax the chest and shoulders and find the deepest points of the indentations directly below the protrusions of the collarbones. The index or middle fingers are inserted into the indents and pressed firmly for sixty seconds as long, deep breaths are taken.A simple treatment involves increasing the partial pressure of CO2 and inhibiting diaphragm activity by holding ones breath or rebreathing into a paper bag. Other potential remedies suggested by NHS Choices include pulling the knees up to the chest and leaning forward, sipping ice-cold water and swallowing some granulated sugar.Drinking through a straw with the ears plugged is a folk remedy that can be successful. In 2021 a scientific tool with a similar basis was tested on 249 hiccups subjects; the results were published in the Journal of the American Medical Association (JAMA). This device is named FISST (Forced Inspiratory Suction and Swallow Tool) and branded as "HiccAway".