CO2 retention: The key to stopping hiccups.

BACKGROUND: While investigating the mechanisms behind hiccups, our team discovered what could be the sufficient physiological conditions for terminating even persistent cases. METHODS: To investigate the role of CO2 retention, a healthy male volunteer was asked to perform three kinds of rebreathing experiments using different materials: (I) a 20 L air-filled plastic bag, (II) a 20 L air-filled plastic bag with a 1.5 × 1.5 cm hole and (III) a 20 L oxygen-filled plastic bag. During each experiment, CO2 level upon expiration (EtCO2 ) and inspiration (InspCO2 ) were measured until the volunteer gave up. Once the safety of this manoeuvre was demonstrated with the volunteer, we performed the technique using the materials from experiment (I) on two actual patients with persistent hiccups. RESULTS: In experiments (I) and (III), InspCO2 increased from the beginning and reached almost the same level as EtCO2 after 90 seconds. Both levels continued simultaneously increasing, finally reaching 56 mm Hg in (I) and 79 mm Hg in (III), respectively. In (II), both increased; however, after 120 seconds, EtCO2 plateaued at 47 mm Hg and InspCO2 at 37 mm Hg. In the actual patients, both CO2 levels reached the same value of 35.9 mm Hg at 60 seconds and 37.0 mm Hg at 90 seconds, and hiccups stopped at 195 seconds and at 359 seconds when EtCO2 reached 50 mm Hg and 53 mm Hg, respectively. CONCLUSION: The study determined that to successfully obstruct the mechanisms causing hiccups, it is necessary that the level of InspCO2 not only increases at the same level as EtCO2 , but also reaches approximately 50 mm Hg.

Hiccups: a new explanation for the mysterious reflex.

The hiccup may have evolved to remove swallowed air from the stomach, which may help suckling mammals to consume more milk.

The hiccup reflex arc and persistent hiccups with high-dose anabolic steroids: is the brainstem the steroid-responsive locus?

Hiccups have been classified as a neurologic reaction triggered by a multitude of factors. There are only a few reports of persistent hiccups associated with oral and intravenous corticosteroid use in the medical literature. It has been proposed that corticosteroids lower the threshold for synaptic transmission in the midbrain and directly stimulate the hiccup reflex arc. There is a recent report of progesterone-induced hiccups, which were thought to occur secondary to the glucocorticoid-like effects of progesterone on the brainstem. We report the first case of anabolic steroid-induced hiccups occurring in an elite power lifter. The hiccups occurred within 12 hours of the individual increasing his doses of oral anabolic steroids and persisted for 12 consecutive hours until medical attention was sought. In this report the pathophysiology of anabolic steroid-induced hiccups is discussed, and the postulated relationships of steroids and the hiccup reflex arc reviewed.