central sleep apnea

If obstructive apnea is a blocked pipe, central sleep apnea (CSA) is a missing instruction. Here the airway is open and unobstructed, but for a stretch of seconds the brain simply does not send the command to breathe, so the chest and diaphragm fall still. There is no struggle against a blockage because there is nothing to struggle against — the drive to inhale has briefly switched off.

The mechanism lies in the brainstem respiratory control center, which normally adjusts breathing to keep carbon dioxide within a narrow range. In CSA this feedback loop becomes unstable: breathing overshoots, blows off too much carbon dioxide, and the level drops below the threshold that triggers a breath, producing a pause until carbon dioxide climbs back up. This instability can cycle, and in heart failure it often takes the form of a waxing-and-waning pattern called Cheyne–Stokes respiration.

Causes include heart failure, stroke and other brainstem injury, high altitude, kidney failure, and opioid medications, which blunt the respiratory center. A particular form, treatment-emergent central apnea, can appear when CPAP is started for obstructive apnea and the underlying control instability is unmasked. Because CSA reflects a control problem rather than a plumbing problem, simply splinting the airway open does not always fix it.

Diagnosis is made on a sleep study by recognizing pauses without accompanying respiratory effort. Treatment targets the underlying cause — optimizing heart failure, reviewing opioids — and may use specialized pressure devices, supplemental oxygen, or carbon dioxide–stabilizing approaches. One honest caveat: some breathing pauses are mixed, beginning as central and ending obstructive, so careful study interpretation matters.