Figure 10.

Upper airway transition model for obstructive sleep apnea (OSA). In OSA, the upper airway alternates between states of flow limitation during sleep, and non-flow-limited breathing during wakefulness. During sleep, a flow limited upper airway caps ventilatory supply, which dissociates from ventilatory drive (see dashed line). When ventilatory supply does not meet demand, differences (Δ) are detected by mechanical and chemical receptors and respiratory control centers, leading to increases in ventilatory drive. Increases in ventilatory drive during periods of flow limitation trigger arousal from sleep with restoration of upper airway patency.