Sometimes the respiratory centers go temporarily awry and send extra impulses to the diaphragm. These impulses cause unwanted contractions (hiccups). The same thing happens in unborn children; many pregnant women often feel their babies hiccup. This happens because the respiratory centers of the developing child’s brain are working just like those of an adult even though they are not yet breathing air.

HYPOXIA is the deficiency of oxygen reaching the tissues. Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole (generalized hypoxia) or a region of the body (tissue hypoxia) is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise. A mismatch between oxygen supply and its demand at the cellular level may result in a hypoxic condition.

Hypoxia in which there is complete deprivation of oxygen supply is referred to as anoxia. It may result due to sitting for long hours in a crowded room with poor ventilation. It may also be experienced at high altitudes where the oxygen content of the air is low.