ArticlePDF Available

Why do we hiccup?

Authors:

Abstract

See article on page 590 Considering the fact that almost everyone experiences hiccups at one time or another, remarkably little is known about them. The name itself is onomatopoeic, which is appropriate considering that the only common understanding of the hiccup is of the characteristic sound. Hiccups can be predictably elicited in some individuals by overindulgence of food, alcohol, or both, sometimes providing evidence of such behaviour and making them a common object of humour. There are, however, instances in which hiccups become intractable (singultus) causing insomnia, wasting, exhaustion, and even death, prompting scientific scrutiny of this otherwise harmless curiosity.1In this issue Fass et al (see page 590) present original investigative work on the afferent limb of the hiccup reflex. Fass et al used a barostat to characterise the parameters of oesophageal distention that could elicit hiccups in normal volunteers. They report that rapid phasic distension of the proximal, but not distal, oesophagus could reproducibly induce hiccups in four of 10 subjects. Hiccups occurred during rapid inflation of the barostat bag and immediately resolved with deflation, strongly implicating oesophageal mechanoreceptors as the critical …
Commentary
See article on page 590
Why do we hiccup?
Considering the fact that almost everyone experiences hic-
cups at one time or another, remarkably little is known
about them. The name itself is onomatopoeic, which is
appropriate considering that the only common under-
standing of the hiccup is of the characteristic sound.
Hiccups can be predictably elicited in some individuals by
overindulgence of food, alcohol, or both, sometimes
providing evidence of such behaviour and making them a
common object of humour. There are, however, instances
in which hiccups become intractable (singultus) causing
insomnia, wasting, exhaustion, and even death, prompting
scientific scrutiny of this otherwise harmless curiosity.
1
In
this issue Fass et al (see page 590) present original investi-
gative work on the aVerent limb of the hiccup reflex.
Fass et al used a barostat to characterise the parameters
of oesophageal distention that could elicit hiccups in
normal volunteers. They report that rapid phasic disten-
sion of the proximal, but not distal, oesophagus could
reproducibly induce hiccups in four of 10 subjects.
Hiccups occurred during rapid inflation of the barostat bag
and immediately resolved with deflation, strongly implicat-
ing oesophageal mechanoreceptors as the critical aVerents.
The authors speculatively generalise this observation to the
population as a whole, but in this one needs to be
circumspect, recognising the long list of stimuli that have
been reported to cause prolonged bouts of hiccups. A partial
inventory of hiccup aetiologies encompasses trauma (skull
fracture, closed head trauma, surgery), mass lesions
(aneurysms, tumours, goitres, diverticuli), infections (sub-
diaphragmatic abscess, cholecystitis, pleurisy, meningitis,
encephalitis), irritative stimuli (heartburn, spicy food, gastri-
tis, peptic ulcers, pancreatitis), luminal distension (achalasia,
gastric distension, oesophageal rings and strictures), central
nervous system pathology (multiple sclerosis, cerebrovascu-
lar accidents, psychogenic), and metabolic aberrations
(uraemia, drugs).
2–4
One individual is described in whom a
hair tickling the tympanic membrane was ultimately revealed
to be the cause of singultus. In view of this great diversity of
causative stimuli, defining the aVerent limb of the hiccup
reflex is no simple task and there is reason to suspect
substantial intersubject variability. In the broadest sense, rel-
evant aVerents can course with the vagus or phrenic nerves,
the pharyngeal plexus from C2 to C4, and the sympathetic
chain from T6 to T12.
35
In all likelihood, there is no univer-
sal stimulus for hiccups in adults, but rather, a long list of
potential stimuli in susceptible individuals.
The central elements and eVerent limbs of the hiccup
reflex have been better characterised than the aVerent limb.
The hiccup is an involuntary medullary reflex influenced
by, but independent of, the respiratory centre of the
medulla. In a meticulous investigation, Davis demon-
strated that hiccup frequency could be modulated or com-
pletely suppressed by inhalation of CO
2
(the physiology
behind the remedies of rebreathing into a paper bag and
breath holding).
6
Furthermore, the whole array of inspira-
tory muscles are activated on the eVerent side of the reflex:
the phrenic nerves to the diaphragm, the external intercos-
tal nerves (T1–T11) to the intercostal muscles, and the
scalenus anticus nerve to the scalene muscles which elevate
the clavicles.
46
These inspiratory eVerents are activated far
more vigorously during hiccups than during cyclic respira-
tion. Thirty five milliseconds after inspiratory activation,
the recurrent laryngeal nerve eVects glottic closure, result-
ing in the characteristic “hic” and eliminating any ventila-
tory eVect of the reflex. The large volume changes which
would occur in hiccups were it not for the associated glot-
tal closure is evident in tracheostomised individuals in
whom hiccups can cause severe hyperventilation; Davis
reports such a case in which hiccups resulted in an arterial
pH of 7.58 and a minute ventilation exceeding 20 litres.
6
Thus, although the hiccup reflex results in repetitive,
essentially maximal stimulation of the inspiratory muscula-
ture, it normally serves no respiratory function.
As detailed earlier, the hiccup has minimal impact on
ventilation because of the prompt glottic closure following
the intense inspiratory drive. Thus, speculation regarding
the purpose of the hiccup naturally shifted to the gastroin-
testinal tract because of the numerous gastrointestinal
stimuli observed to elicit them.
6
However, although a spell
of hiccups may interfere with eating, it is not a protective
reflex (despite the speculation presented by Fass et al that
it may prevent the entry of large food boluses into the gas-
trointestinal tract). Whereas vomiting, gagging, and
coughing are eVective (at times life saving) protective
reflexes of the gastrointestinal and respiratory tracts, the
hiccup has no discernible survival value. More likely than
not, spells of hiccups in adults result from activation of a
vestigial reflex that once served some purpose in ontogeny
or phylogeny. Since it is equally diYcult to construe a sce-
nario in which hiccuping is of use to mature beasts, the
more likely candidate would seem to be ontogeny. Hiccup-
ing is observed in utero and the tendency to hiccup contin-
ues after delivery. Fetal hiccuping can be demonstrated
ultrasonographically in utero as large inward and outward
movements of the chest occurring 1–6 times per minute
with spells lasting an average of eight minutes.
7
Premature
infants spend an average of 2.5% of their time hiccuping.
4
Hiccuping spells occur in utero and in premature babies
without any identifiable stimulus for initiation or for cessa-
tion. This suggests that during the perinatal period, when
the respiratory tract needs to mature rapidly, hiccuping
does have a survival value. Perhaps, hiccuping is essentially
a programmed isometric exercise of the inspiratory
muscles which are superfluous in utero, but aVorded no
time for maturation after birth. Beyond the perinatal
period, however, hiccuping is a vestigial reflex, incidentally
elicited by a wide and variable range of autonomic stimuli.
PETER J KAHRILAS
GUOXIANG SHI
Northwestern University Medical School,
Division of Gastroenterology and Hepatology,
Department of Medicine,
Passavant Pavilion, Suite 746,
303 East Superior Street,
Chicago, IL 60611, USA
Correspondence to: Dr Kahrilas.
Gut 1997; 41: 712–713712
1 McFarling DA, Susac JO. Hoquet diabolique: intractable hiccups as a mani-
festation of multiple sclerosis. Neurology 1979; 29: 797–801.
2 Souadjian JV, Cain JC. Intractable hiccup, etiologic factor in 220 cases. Post-
grad Med 1968; 43: 72–7.
3 Nathan MD, Leshner RT, Keller AP. Intractable hiccups (singultus). Laryn-
goscope 1980; 90: 1612–8.
4 Kaufman HJ. Hiccups: causes, mechanism and treatment. Practical
Gastroenterology 1985; 14: 12–20.
5 Salem MR, Baraka A, Rattenborg CC, Holaday DA. Treatment of hiccups
by pharyngeal stimulation in anesthetized and conscious subjects. JAMA
1967; 202: 32–6.
6 Davis JN. An experimental study of hiccup. Brain 1970; 93: 851–72.
7 Patrick J, Campbell K, Carmichael L, Natale R, Richardson B. Patterns of
human fetal breathing during the last 10 weeks of pregnancy. Obstet Gyne-
col 1980; 56: 24–30.
Why do we hiccup? 713
... Any condition that acts on one of these pathways has the potential to induce hiccupping [1, 2,13,14]. The afferent limb is comprised of the vagus nerve, the phrenic nerve, the sympathetic chain from T6 to T12 [1-5, 10, 13, 15], and the pharyngeal plexus from C2 to C4 [5,10]. The CNS or central processing unit likely involves various midbrain and brainstem structures, such as the medulla oblongata and reticular formation, the periaqueductal gray, glossopharyngeal and phrenic nerve nuclei, solitary and ambiguous nuclei, hypothalamus, temporal lobes, and upper spinal cord at levels C3 to 5. [3••] Lastly, the efferent portion of the reflex is composed of the phrenic nerve supplying the diaphragm and the accessory nerves supplying the intercostal muscles. ...
... This includes ischemic or hemorrhagic stroke, meningitis, brain tumors, trauma, epilepsy, Parkinson's disease, multiple sclerosis, and neuromyelitis optica [2,13,14]. It should be noted, however, that hiccups are rarely the single presenting symptom in any of these CNS diseases [5]. ...
Article
Full-text available
Purpose of Review Hiccups and belching are common physiological phenomena that involve air movement in the upper GI tract. Because of their commonplace and often acute nature, the problem of hiccups and belching is often trivialized. As a result, there is a dearth of high-quality original research on these topics. In this review, we will summarize the current understanding of epidemiological data, pathophysiological mechanisms, and therapeutic modalities of intractable hiccups and belching. Recent Findings There has been little advancement in this particular area of gastroenterology beyond case reports and systematic reviews. Hiccups are involuntary contractions of the diaphragm combined with reflexive closure of the glottis. When hiccups last longer than 48 h, they are defined as persistent, and after a month, they become intractable. Hiccups occur when a lesion or irritant triggers the hiccup reflex arc, composed primarily of the midbrain, the phrenic nerve, and the vagus nerve. Non-pharmacological approaches like breath holding can be successful in terminating an acute episode. However, for persistent and intractable hiccups, identifying a specific etiology and initiating pharmacologic treatment, such as a proton pump inhibitor, baclofen, or gabapentin, become essential. Belching is the process of expelling gas from the upper digestive tract into the pharynx. Belching becomes pathological when it impacts usual activities for >3 days per week. It is divided into gastric and supragastric belching. Esophageal manometry with impedance testing is considered the gold standard in its diagnosis. An upper endoscopy is indicated if alarm symptoms are present. Management of belching includes avoiding carbonated beverages, eating slowly, stopping the use of tobacco, avoiding gum chewing, and treating gastroesophageal reflux. Baclofen can also be effective in gastric belching, while supragastric belching is often treated with behavioral modification techniques such as diaphragmatic breathing and speech and cognitive-behavioral therapies. Summary Intractable hiccups and belching are common but poorly studied phenomena. When symptoms become persistent, patients’ quality of life can diminish dramatically. Management hinges on identifying an etiology and, if one is identified, initiating targeted therapy. Otherwise, empiric treatment of GERD is often the first line, followed by baclofen as the second line.
Article
Full-text available
Hiccups result from involuntary contractions of the diaphragm, driven by a complex neuromuscular reflex. Three patients with persistent hiccups underwent esophageal high-resolution manometry during hiccup episodes, revealing a consistent finding: sustained contraction of the esophagogastric junction with intermittent pressure peaks. This pattern, termed the “Hiccup-Induced Esophagogastric Waveform,” shows significant esophageal pressure changes linked to hiccup reflex. It may reflect a compensatory mechanism to expel excess esophageal residue or gas. These findings suggest hiccups could exacerbate symptoms of esophageal disorders, such as dysphagia and chest pain, and highlight the need for targeted therapeutic strategies. Further research is needed to explore these mechanisms.
Article
Full-text available
Background Intractable hiccups, persisting beyond 48 h, pose a clinical challenge, particularly in demyelinating diseases like Neuromyelitis Optica (NMO) and Multiple Sclerosis (MS). Understanding the complex neural pathways of the hiccup reflex and the impact of high-dose steroid therapy is crucial for managing this rare but distressing symptom. The hiccup reflex involves afferents from the vagus, phrenic, and sympathetic nerves, with the reflex center in the anterior horns at the C3 to 5 level and the medulla oblongata. The potential interplay between demyelination and corticosteroid therapy in triggering persistent hiccups requires exploration. Case report This case report details a 21-year-old male with undiagnosed demyelinating disorder, presenting persistent hiccups following high-dose steroid therapy for an acute disease flare. The patient's history included vertigo and progressive neurological symptoms, leading to an MS diagnosis with significant brain and spinal lesions. Persistent hiccups, initiated by steroid administration, were recurrent but responsive to metoclopramide after other measures failed. Discussion The discussion centers on investigating the cause of hiccups in a patient with demyelination following steroid administration. Steroids' impact on neurological systems, including neurotransmitter function, and the potential disruption of neurological pathways due to demyelination may contribute to hiccups. Successful hiccup resolution with metoclopramide suggests a potential pharmacological approach for corticosteroid-induced hiccups in demyelinating diseases. This case emphasizes the need for further research into the intricate relationship between demyelination, steroid therapy, and hiccups to enhance management strategies for this uncommon yet impactful symptom.
Article
Full-text available
Background Hiccups are a common physiologic reflex resulting from intermittent and involuntary spasmodic contraction of the diaphragm and intercostal muscles. While most cases are self-limited, lasting less than 48 hours, rare pathologies may result in prolonged symptoms. Hiccups can be disruptive and uncomfortable, leading many to seek management strategies using common home remedies. Few methods for terminating hiccups have been published in the scientific literature. We report the efficacy of the Hiccup relief using Active Prolonged Inspiration (HAPI) technique, which combines phrenic and vagal nerve stimulation with transient hypercapnia for hiccup relief. Methods Twenty patients with self-limited hiccups and one patient with prolonged hiccups were successful in eliminating hiccups using HAPI. In this method, patients are instructed to inspire maximally. Once at the peak of inspiration, they continue to attempt to inspire with an open glottis for a total of 30 seconds. This is followed by a slow expiration and resumption of normal respiration. Results In all cases, patients reported immediate hiccup relief. Conclusion These findings suggest the HAPI technique is a simple and viable method for hiccup relief. Further studies are needed to validate effectiveness.
Article
Hiccups are a rare but potentially debilitating side effect of opioid treatment, with only a handful of reported cases in the medical literature. The pathophysiological mechanism linking opioids and hiccups is unknown, and a lack of evidence exists concerning the optimal management of the condition. We report on a 64-year-old man diagnosed with advanced renal cancer and painful osteolytic metastases, presenting persistent hiccups while on opioid treatment. Hiccups recurred after multiple challenges with codeine, morphine and hydromorphone on separate occasions. Hiccups ceased only after opioid discontinuation, although various pharmacological treatments were tried to shorten the duration of hiccups. Eventually, fentanyl was introduced and was well tolerated by the patient, without any recurrence of hiccups. The chronological correlation between opioid initiation and the onset of hiccups, as well as opioid discontinuation and the termination of hiccups leads to the conclusion that a causal role of codeine, morphine and hydromorphone in this occurrence is likely. Individual susceptibility probably plays a central role in the development of opioid-related hiccups. Opioid rotation is a promising strategy in the management of opioid-related hiccups, particularly when the mere discontinuation of the opioid is not a viable option, such as in the oncology and palliative care field.
Article
Full-text available
How to cite this article: Goyal A, Pallavi K, Awasthy AK. Persistent Hiccups in Posterior Circulation Stroke as Rare Presentation of Pulmonary Embolism—Don't Jump the Gun. Indian J Crit Care Med 2022;26(9):1058–1059.
Article
Hiccups are experienced by people of all ages. While acute hiccups are benign and self-limited, persistent and intractable hiccups can sometimes signal a serious disease. We present a young previously healthy man who complained of only hiccups for 4 months and later developed a severe headache and projectile vomiting. His systemic examination was within normal limits. Brain imaging revealed a diffuse pontine glioma with mild hydrocephalus.
Article
Full-text available
The possibilities of coronavirus disease 2019 (COVID-19) to present with atypical manifestations have reported. Information of COVID-19 atypical signs and symptoms is still emerging globally. One of these presentations is persistent hiccups. One of the hypotheses is that COVID-19 has been linked to several neurological manifestations and effects. Some observations noticed phrenic nerve paralysis after COVID-19 infection leading to pulmonary failure. We report one case of COVID-19-positive patient where he presented with persistent hiccups. Many predisposing factors might lead to the development of hiccups in COVID-19 infection such as a history of smoking, phrenic and vagus nerve damage or irritation, high inflammatory markers, lower lobe pneumonia, ground-glass-like appearance on x-rays. We hypothesize that hiccups are the first sign of serious deterioration of patients with COVID-19 and such patients are at high risk of developing kidney injury and intubation.
Article
In three patients, intractable hiccups occurred as part of the symptomatology of multiple sclerosis. In one patient intractable hiccups were the presenting complaint, and in another patient exacerbations of symptoms were almost always heralded by intractable hiccups. Intractable hiccups occur in a variety of diseases, including many that affect the brainstem and cervical cord, but have not been reported in multiple sclerosis. The hiccup may be a "primitive" gastrointestinal reflex that is disinhibited by lesions such as multiple sclerosis plaques. Carbamazepine was successful in arresting the hiccups in one of the cases presented.
Article
Hiccup previously was thought to be due to a single disease that produced an abnormal irritation of the phrenic nerve or of the higher centers. A study of 220 cases of intractable hiccup suggests that there may be several exciting causes that one must elucidate in the same patient.
Article
Stimulation of the pharynx with a catheter introduced through the nose appears to be a valuable method for managing hiccups in conscious and anesthetized man. Immediate inhibition of hiccups occurred in 84 of 85 patients treated in this manner, of whom 65 were anesthetized. Hiccups recurred in some patients, but were successfully managed with the same maneuver. The area responding to stimulation is the middle of the pharynx, opposite the body of the second cervical vertebra, which is innervated by the pharyngeal plexus. The suggested mechanism of action is impulses arising in response to pharyngeal stimulation which may block or inhibit afferent impulses being transmitted through the vagi thus interrupting the hiccup reflex. No undesirable effects have been encountered as a result of pharyngeal stimulation.
Article
Continuous measurements of human fetal breathing movements and gross fetal body movements were made with an ultrasonic real-time scanner for periods of 24 houro 31 weeks' gestation, a significant increase in fetal breathing movements occurred during the second and third hours after meals; this pattern apparently followed an increase in maternal plasma glucose concentrations. At 38 to 39 weeks' gestation, fetal breathing movements increased during the second and third hours after breakfast, but the troughs seen before lunch and supper at 30 to 31 weeks' gestation were not present. Fetal breathing movements diminished over the day and reached a minimum between 1900 and 2400 hours. Fetal breathing activity increased in both groups between 0400 and 0700 hours while mothers were asleep; this was not related to an increase in maternal glucose concentrations. Absence of fetal breathing movements was observed for up to 122 minutes in this analysis of 480 hours in 20 patients. These data show that much more information must be obtained on factors that normally influence fetal breathing activity. Only then can research strategies be suggested for clinical evaluation of the usefulness of fetal breathing movements in the assessment of fetal health.
Article
Intractable hiccups (singultus) is an uncommon disorder with various etiologies. The majority of reported studies of intractable hiccups has claimed ipsilateral spasm of the hemidiaphragm based solely on clinical or radiographic evidence. A case of intractable hiccups is presented. Documentation of normal phrenic nerve latencies with bilateral synchronous firing of anterior scalene, intercostal muscles and bilateral hemidiaphragm involvement is presented. This combination of muscle group involvement supports the concept of a “supraspinal hiccup center.” A systematic trial of chemotherapeutic agents described as effective against hiccups was employed. Relief lasting for three to four week periods has been obtained by the intravenous administration of a specially prepared sterile solution of methylphenidate.† The nerve pathways pertinent to hiccup are discussed. The etiology of intractable hiccups and the various treatment modalities are presented.
Hiccups: causes, mechanism and treatment
  • Hj Kaufman
Kaufman HJ. Hiccups: causes, mechanism and treatment. Practical Gastroenterology 1985; 14: 12–20.