Hiccups in infants: characteristics and effects on ventilation.

Twenty-seven polygraphic recordings of respiration were obtained on 20 infants, providing data on the frequency, distinguishing features, and medical significance of hiccupping episodes. Eight hiccupping episodes were recorded in seven subjects. The mean duration of the spells was 8.4 +/- 4.2 (SD) minutes. Unintubated subjects, not selected because they were hiccupping, hiccupped 2.5% of the time that they were monitored. Each hiccup was a brief, powerful inspiratory muscle contraction. In unintubated subjects, hiccups were marked by upper airway obstruction, whereas in intubated patients, hiccups were unobstructed inspirations. In unintubated subjects, hiccups were associated with an increase in obstructed eupneic breaths and with decreases in respiratory frequency and minute ventilation; in three subjects hiccups precipitated episodes of mixed apnea. In intubated patients, hiccupping spells were characterized by hyperventilation and respiratory alkalosis. Two types of ECG artifacts were seen with hiccups: high-frequency spikes, mimicking abnormal QRS complexes, and low-frequency waves. From these studies, it appears that hiccups occur frequently in young infants and may affect breathing in clinically significant ways.