The diaphragm is a dome-shaped sheet of muscle situated at the base of the chest, separating the thoracic cavity, which contains the heart and lungs, from the abdomen. As the primary muscle of respiration, its function is to contract and flatten during inhalation, increasing the chest cavity’s volume to draw air into the lungs. When this muscle involuntarily contracts, it is known as a diaphragm spasm, with the most common manifestation being the hiccup.
The Mechanical Action of a Spasm
A diaphragm spasm begins with an irritation along the nerve pathways that control its movement, particularly the phrenic nerve. This nerve originates in the neck and extends down to the diaphragm, acting as the primary signaling route for respiration. When this pathway is stimulated, it triggers a sudden contraction of the muscle.
This spasm pulls air rapidly into the lungs, but the phrenic nerve’s signal simultaneously causes the glottis—the opening between the vocal cords—to close abruptly. The sudden intake of air being instantly blocked by the closed glottis is what creates the characteristic “hic” sound. The entire sequence is a reflex arc that bypasses conscious control and repeats until the irritation subsides.
Everyday Causes of Diaphragm Spasms
The vast majority of diaphragm spasms, or hiccups, are temporary and triggered by simple actions that irritate the phrenic nerve. These common triggers often involve the stomach distending and physically pressing against the diaphragm muscle. Eating or drinking too quickly can cause a person to swallow excess air, a condition known as aerophagia, which leads to stomach inflation. Similarly, consuming carbonated beverages or alcohol causes a rapid buildup of gas in the stomach, physically irritating the diaphragm from below.
Sudden changes in temperature, such as drinking a cold beverage immediately after eating hot soup, can also shock the nerves and trigger a spasm. Emotional factors, including sudden excitement, stress, or nervousness, can disrupt the normal rhythm of the breathing reflex. Another common source of irritation is acid reflux, or gastroesophageal reflux disease (GERD), where stomach acid splashes back up into the esophagus. Since the esophagus passes directly through an opening in the diaphragm, this acid acts as a local irritant to the nearby nerves.
Underlying Health Conditions as Causes
While most spasms are temporary, chronic or persistent hiccups—those lasting longer than 48 hours—may point to an underlying health issue. Intractable hiccups can be caused by conditions that irritate or damage the nerves controlling the diaphragm, primarily the phrenic and vagus nerves. Damage to these nerves can result from neck or chest trauma, or from irritation caused by a tumor or cyst pressing on the nerve pathway.
Certain systemic health conditions, such as stroke, multiple sclerosis, or kidney failure, can also disrupt the central nervous system’s control over the hiccup reflex. A hiatal hernia, where a portion of the stomach pushes up through the diaphragm’s opening, is another structural cause of chronic irritation. If spasms persist for more than two days, or if they are severe enough to interfere with eating or sleeping, it is important to seek medical attention to rule out a more serious cause.
Techniques to Stop a Spasm
To interrupt the hiccup reflex, techniques aim to disrupt the phrenic nerve signal or stimulate the vagus nerve. One common approach involves intentionally increasing the level of carbon dioxide in the blood, which may help relax the diaphragm and reset the breathing pattern. This can be achieved by holding one’s breath for a short period or by breathing into a small paper bag.
Another effective strategy is to engage the vagus nerve, which influences the diaphragm’s function and runs through the throat and chest. Simple actions that stimulate the back of the throat can override the hiccup signal. This includes gargling with ice water, quickly drinking a glass of water, or swallowing a teaspoon of granulated sugar, which activates sensory receptors in the back of the mouth and throat. The Valsalva maneuver, which involves exhaling forcefully against a closed airway, also works by stimulating the vagus nerve and overriding the involuntary spasm.