Pathogenesis of central and complex sleep apnoea.

Area of Science:

• Sleep Medicine
• Respiratory Physiology
• Cardiorespiratory Control

Background:

• Central sleep apnoea (CSA) presents as periodic breathing or Cheyne-Stokes respiration.
• CSA often involves hypersensitive ventilatory chemoreflexes, leading to elevated loop gain and breathing oscillations.
• Overlap exists between CSA and obstructive sleep apnoea (OSA), with OSA treatments sometimes unmasking CSA.

Purpose of the Study:

• To explore the role of loop gain in central sleep apnoea.
• To understand the mechanisms contributing to breathing instability in CSA.
• To explain the efficacy of CSA treatments through their impact on loop gain.

Main Methods:

• Review of existing evidence on CSA and loop gain.
• Analysis of factors influencing loop gain, including chemosensitivity and circulatory delays.
• Examination of how treatments affect loop gain parameters.

Main Results:

• Elevated loop gain, due to hypersensitive chemoreflexes, is a primary driver of CSA.
• Factors like sleep-wake transitions and pharyngeal muscle activity increase controller gain.
• Conversely, some conditions like congenital central hypoventilation involve low loop gain.
• CSA treatments, such as CPAP and oxygen, modulate loop gain by affecting plant gain or chemosensitivity.

Conclusions:

• Understanding loop gain magnitude and instability mechanisms is crucial for CSA.
• Personalized interventions for CSA can be developed by targeting specific loop gain components.
• Loop gain provides a unifying framework for understanding CSA pathophysiology and treatment efficacy.