Review of Hypoxemia Quantification Methods for Assessing the Severity of Obstructive Sleep Apnea

Purpose of Review Obstructive sleep apnea (OSA) is a common nocturnal breathing disorder characterized by recurrent upper airway obstruction during sleep, leading to sleep fragmentation and intermittent hypoxemia. The apnea-hypopnea index (AHI) is the most widely used clinical metric to assess OSA severity; however, the AHI fails to capture the full physiological burden caused by recurrent oxygen desaturations. Consequently, quantifying hypoxemia, the cumulative burden of oxygen desaturations, has become crucial for assessing the physiological impact of OSA more comprehensively. Furthermore, studies have illustrated that hypoxemia is associated with cardiovascular morbidity, metabolic dysfunction, and neurocognitive impairment in OSA patients. Recent Findings This narrative review aims to explore various methods used to quantify nocturnal hypoxemia from sleep recordings and discuss the different approaches, and their association with OSA-related comorbidities. The discussed metrics include traditional measures and newer parameters that provide a more detailed quantification of oxygen desaturation, including separate characterization of desaturation and re-saturation dynamics as well as integrated measures of the overall hypoxic load. Additionally, this review discusses how these more detailed metrics have provided further insight into the associations between OSA-related hypoxemia and clinically relevant outcomes, including cardiometabolic comorbidities and impaired daytime functioning. Summary This narrative review emphasizes the need for diagnostic modifications and advocates for the integration of metrics quantifying hypoxemia into routine clinical practice to enable early recognition of the health risks associated with OSA.