Opinion from somebody who searched for an explanation of the bizarre term: Surely the term ″periodic breathing″ became established within some very limited pathological context which neglects that breathing is normally periodic -- and should be deflected to some sort of disambiguation, e.g. ″Aperiodic breathing″ or some such.
Periodic breathing is a normal variation of breathing found in premature and full term infants. It occurs when the infant has pauses in breathing for no more than 10 seconds at a time followed by a series of rapid, shallow breaths. Then the breathing returns to normal without any stimulation or intervention. These pauses in breathing may be accompanied by minor oxygen desaturation and bradycardia. It usually occurs when the infant is sleeping deeply, but may occur with light sleep or even when awake. Studies have shown that 78% of healthy full-term infants experience episodes of periodic breathing in the first two weeks of life, which typically resolves in the first six months of life.
This is not the same as apnea, which is a cessation of breathing for greater than 20 seconds associated with limpness and cyanotic color change.