Measuring Loop Gain via Home Sleep Testing in Patients with Obstructive Sleep Apnea

To the Editor:Nonanatomical traits contribute to obstructive sleep apnea (OSA) in certain individuals (1) and can predict response to therapies beyond continuous positive airway pressure (CPAP) (2, 3).Unstable ventilatory control (high loop gain) is one such trait that is useful for personalizing treatment (4).Measuring loop gain has traditionally required the use of specialized equipment and laborintensive techniques (5); however, recently developed methods can determine loop gain from polysomnography (PSG) using a modelfitting technique (6).Because clinical testing for OSA is shifting to home sleep testing (HST), our aim in this study was to determine whether we could estimate loop gain using this limited dataset, which might facilitate personalized OSA treatment in clinical practice.Subjects with untreated OSA (apnea-hypopnea index [AHI] > 5/h) who underwent both PSG and HST within a 3-month period were included in the study.The research was approved by the institutional review board (#141272 and #150465), and the subjects provided written informed consent.The exclusion criteria were use of sedatives, hypnotics, or narcotics, ongoing OSA treatment, and/or prior airway surgery.In-laboratory attended PSG was performed in the standard fashion with the subjects supine.HST was performed with a type III device (ApneaLink Plus/Air; ResMed).Results were scored using American Academy of Sleep Medicine Chicago criteria (3% desaturation) by a technologist blinded to outcomes.