Four key obstructive sleep apnea (OSA) endotypic traits have been identified, namely: collapsibility, upper airway muscle compensation, arousal threshold and loop gain. However, most methods for extracting these traits require specialized training and equipment not available in a standard sleep clinic, which has hampered the ability to assess the full impact of these traits on OSA outcomes.
This paper aims to provide an overview of current methods for OSA endotyping, focusing on the Endo-Phenotyping Using Polysomnography (PUP) method and its cloud-based extension, PUPpy, which offer scalable and accessible ways to estimate endotypic traits from standard polysomnography.
We employed PUPpy on three large datasets including, MESA, MrOS, and CMUH. The paper is more than just a review paper, but it is also proof that we are able to run these types of analyses at scale.
In summary, it is now attainable to estimate individual differences in the key traits contributing to sleep apnea–collapsibility, compensation, arousal threshold, and loop gain–through analysis of ventilation and ventilatory drive in a routine clinical sleep study, i.e., without invasive measurements or specialized operators.
There are at least four key endotypic traits that contribute to OSA. In the paper, we review current sleep apnea endotyping methodologies and how they can be translated from laboratory research into standard clinical practice. There are three streams of research methods for investigating endotypic traits.
First, the simplest method for trait estimation is to relate direct output parameters from standard polysomnography (PSG) to the underlying sleep apnea pathophysiology [e.g., high apnea index (AI) as an indicator for high upper airway collapsibility]. These methods often require minimal additional calculations but do not take advantage of the wealth of mechanistic information available in PSG studies. Second, in the physiological laboratory, gold standard signals are directly measured to assess ventilation and ventilatory drive, with or without careful experimental procedures to manipulate ventilatory drive. Such studies typically seek to demonstrate physiological differences between patients or effects of therapies. These methods require invasive measurements using specialized equipment and training that are not available in standard sleep clinics.
Finally, in the clinical setting, methods of estimating ventilation and ventilatory drive have been developed, with the goal of translating physiological knowledge from the physiology laboratory to the clinical arena where gold standard recordings are not feasible. Such studies use data collected during a routine sleep study and seek to provide a physiologically-sound means to estimate the underlying pathology of each individual's OSA and predict the likelihood of responding to different interventions.
Guest Blogger: Eysteinn Finnsson
Paper Authors: Finnsson, Eysteinn & Arnardóttir, Eydís & Cheng, Wan-Ju & Alex, Raichel & Sigmarsdóttir, Þóra & Helgason, Snorri & Hang, Liang-Wen & Agustsson, Jon & Wellman, Andrew & Sands, Scott. (2023). Sleep apnea endotypes: from the physiological laboratory to scalable polysomnographic measures. Frontiers in Sleep. 2. 10.3389/frsle.2023.1188052.