An abnormal pattern of breathing that is characterized by a waxing and waning depth and sometimes frequency of breaths. It may include periods of absent or shallow breaths (apnea or hypopnea) followed by increasingly large breaths that plateau and then diminish in volume until periods of shallow breathing recur. This crescendo-descrescendo breathing pattern is sometimes referred to as "periodic breathing". The cycles may last from 60-90 seconds and typically resolve during rapid eye movement (REM) sleep.
This variability in breathing is due to carbon dioxide fluctuations. It may be associated with heart failure, strokes, traumatic brain injury, carbon monoxide poisoning, imminent death, or in healthy people sleeping at high altitudes. It can also occur in central sleep apnea and may be treated with the use of bilevel therapy.