Intermittent Hypoxia Associated with Sleep Apnea Disrupts Microvascular Hemodynamics and Oxygen Delivery.

Obstructive sleep apnea (OSA) is characterized by recurrent episodes of intermittent hypoxia (IH). In this study, we investigated how cyclic IH (21%/10% O₂) acutely alters systemic hemodynamics and microvascular vascular tone, hemodynamics, and oxygen transport compared to the control (21%/21% O₂). Using a dorsal window chamber model on unanesthetized Golden Syrian hamsters, we applied 30-second oxygen cycling for 60 minutes. Microvascular oxygen saturation was continuously monitored using hyperspectral imaging (HSI), and vessel diameter, red blood cell velocity, functional capillary density (FCD), and vascular resistance were quantified through intravital microscopy. Animals exposed to IH exhibited significant reductions in mean arterial pressure and arterial oxygen saturation, along with increased heart rate and blood lactate. Microvascular SO₂ declined rapidly in the microcirculation and stabilized after 8 mins. Arteriolar blood flow decreased, and FCD was significantly reduced relative to both baseline and control. Despite a decrease in vascular resistance, vasodilatory compensation was insufficient and resulted in decreased oxygen delivery (DO₂) and oxygen extraction (VO₂) to tissues. The oxygen extraction ratio increased, suggesting a limited capacity to offset hypoxic stress. These findings demonstrate that cyclic IH significantly disrupts peripheral microcirculatory flow and oxygenation, highlighting the relevance of IH models in assessing oxygen transport during OSA.