Original Article

Medullar impairment resolves hiccups

Toshiro Obuchi, Jun-ichi Wakahara, Naoyuki Fujimura, Akinori Iwasaki


Background: In a previous article we reported the time that hiccups stop as the instant when CO2 levels in both expiratory gas (EtCO2) and inspiratory gas (InspCO2) reach approximately 50 mmHg. To support our findings, in this article we aim to clarify the precise values of the CO2 level in arterial blood (PaCO2) and venous blood (PvCO2) during plastic bag rebreathing.
Methods: A healthy male volunteer was asked to perform a rebreathing experiment using a 20 L air-filled plastic bag. During the experiment, his blood oxygen saturation level (SpO2), EtCO2 and InspCO2 were measured until the volunteer gave up. PaCO2 and PvCO2 were measured at the following four points: P0, when the rebreathing started; P1, when both EtCO2 and InspCO2 indicated the same value; P2, when both reached 50 mmHg; and P3, when SpO2 dropped to 90%.
Results: InspCO2 increased from the beginning and showed the same value as EtCO2 at P1. PaCO2 at P1 was almost the same value as both InspCO2 and EtCO2. After P1, InspCO2, EtCO2 and PaCO2 increased at the same rate, and at P2, they reached the level of PvCO2. After P2, all four markers continued to show the same value as they gradually increased.
Conclusions: Creating conditions inside the body in which PaCO2 increases to the same level as PvCO2 will stop hiccups consistently. Although other physiological pathways to stop hiccups may exist, for a successful outcome it is important that the balance of power between the cerebellum and the medulla is drastically altered.

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