Synchronous diaphragmatic flutter (SDF) is the medical term for a common, involuntary physiological event that almost every person experiences at some point. While the phrase “synchronous diaphragmatic flutter” might sound like a serious medical diagnosis, the phenomenon is almost always temporary and harmless. The underlying process is a reflex arc involving specific nerves and muscles that govern respiration, causing a sudden disturbance in the body’s breathing reflex.
The Common Name and Mechanism
The common name for synchronous diaphragmatic flutter is “hiccups.” A hiccup is a sudden, involuntary spasm of the diaphragm, which is the large, dome-shaped muscle separating the chest and abdominal cavities. This muscle is responsible for pulling air into the lungs when it contracts. The spasm causes a rapid intake of air that is suddenly interrupted.
Immediately following the diaphragm’s contraction, the glottis—the opening between the vocal cords in the larynx—slams shut. This abrupt closure is what produces the distinctive “hic” sound. The entire event is a reflex arc controlled by the nervous system, not a voluntary action. This involuntary reflex is typically short-lived, with most episodes resolving on their own within a few minutes to a few hours.
Why Hiccups Start
Hiccups begin when something irritates the nerves that control the diaphragm, primarily the vagus and phrenic nerves. The vagus nerve runs from the brainstem down to the abdomen, and the phrenic nerve specifically supplies the diaphragm muscle. Irritation along the pathway of either of these nerves can trigger the involuntary spasms.
A common trigger is rapid expansion of the stomach, often caused by eating too quickly or swallowing too much air. Consuming carbonated beverages, which release gas, can also lead to irritation. Drinking excessive alcohol is another known factor that can prompt the hiccup reflex.
Sudden changes in temperature inside the stomach, such as consuming a very hot beverage immediately followed by a very cold one, are also known to irritate the nerves. Even emotional factors like sudden excitement or intense stress can activate the reflex.
Stopping Hiccups
Remedies for hiccups generally work by either interrupting the reflex arc or stimulating the vagus nerve to reset the diaphragm’s rhythm. One of the most common and effective methods is holding your breath for a short time. This action temporarily increases the level of carbon dioxide in the blood, which can help calm the diaphragm’s spasms.
Another technique involves stimulating the vagus nerve, often by drinking a glass of cold water quickly or gargling with cold water. Some people find relief by swallowing a teaspoon of granulated sugar, which may provide a strong, distracting input to the nerve endings in the throat. These simple maneuvers aim to override the nervous system’s signal that is causing the flutter.
Hiccups that last longer than 48 hours are termed persistent, while those lasting over a month are called intractable. Both conditions can signal a more serious underlying health issue. Medical attention is warranted if the episode lasts more than two days, as prolonged hiccups can be a sign of nerve damage, a central nervous system disorder, or a metabolic issue.