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Background: Vagal nerve stimulators (VNS), which have been approved for management of refractory epilepsy and depression, induce unique disturbances of breathing during sleep (SDB VNS ) that are not captured well using standard criteria. The primary purpose of this retrospective study was to compare AASM definitions with alternative criteria to more accurately measure SDB VNS We also sought to assess outcome variables that may be clinically relevant and response to positive airway pressure therapy., Methods: We analyzed the electronic medical records and comprehensive polysomnography results of all adult subjects with active VNS for epilepsy who were referred to the sleep center for suspected sleep apnea (2015-2020). We compared standard AASM criteria for defining apneas/hypopnea index (AHI AASM ) with three novel scoring criteria for hypopnea according to degree of oxygen desaturation associated with VNS events: AHI VNS0 (none required); AHI VNS2 (2% required); and AHI VNS3 (3% required)., Results: Twenty-six subjects were included in the final analysis with 35 PSGs (14 females/12 males). The mean age was 33.6 years and mean body mass index (BMI) of 32.2 kg/m 2 . AHI AASM measured ≥ 15/hour in 7 (26.9%) subjects versus 21 (80.8%) by AHI VNS0 ; 15 (70.0%) by AHI VNS2 ; and 5 (19.2%) by AHI VNS3 . Clinically significant hypoxemia was not present. The mean time SpO 2 <89% was 7 (20.8) minutes. Oximetry tracings often showed a desaturation pattern that resembled a sawfish rather than sawtooth. Arousals specifically linked to VNS activation were not elevated (2.9/hour). The baseline AHI VNS0 was 27.7/hour with a lowest AHI VNS0 on PAP of 27.9/hr., Conclusions: AASM scoring criteria significantly underestimated the degree of VNS induced respiratory disturbances. VNS events were not associated with increased arousals or significant hypoxemia. PAP therapy was an ineffective treatment in this population. This study adds to the increasing body of evidence of sleep disordered breathing related to VNS and questions the clinical significance of this finding., Competing Interests: Declaration of competing interest None., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Obstructive sleep apnea (OSA) is a highly prevalent disorder that has profound implications on the outcomes of patients with chronic lung disease. The hallmark of OSA is a collapse of the oropharynx resulting in a transient reduction in airflow, large intrathoracic pressure swings, and intermittent hypoxia and hypercapnia. The subsequent cytokine-mediated inflammatory cascade, coupled with tractional lung injury, damages the lungs and may worsen several conditions, including chronic obstructive pulmonary disease, asthma, interstitial lung disease, and pulmonary hypertension. Further complicating this is the sleep fragmentation and deterioration of sleep quality that occurs because of OSA, which can compound the fatigue and physical exhaustion often experienced by patients due to their chronic lung disease. For patients with many pulmonary disorders, the available evidence suggests that the prompt recognition and treatment of sleep-disordered breathing improves their quality of life and may also alter the course of their illness. However, more robust studies are needed to truly understand this relationship and the impacts of confounding comorbidities such as obesity and gastroesophageal reflux disease. Clinicians taking care of patients with chronic pulmonary disease should screen and treat patients for OSA, given the complex bidirectional relationship OSA has with chronic lung disease.