Sleep Disordered Breathing Associated With Vagal Nerve Stimulation: An Interesting Observation Or Pathologic Condition?

SESSION TITLE: Advances Across the Diagnostic Spectrum in Sleep-Disordered Breathing SESSION TYPE: Original Investigations PRESENTED ON: October 18-21, 2020 PURPOSE: Vagal Nerve Stimulators (VNS) have been associated with sleep disordered breathing (SDB). Previous reports consist of small case series or single case reports, are often limited by non-standard criteria and the clinical relevance of VNS induced SDB is uncertain. The primary purpose of this study is to compare strict AASM definitions with alternative criteria for SDB and to assess outcome variables that may be clinically relevant (i.e. hypoxemia and arousals). METHODS: All patients with a VNS who had undergone comprehensive attended polysomnography (PSG) from 2015 until 2020 were eligible. Electronic medical records were queried for demographics, diagnoses, medications, symptoms, and VNS settings. Sleep studies were initially scored using recommended AASM criteria for SDB. The records were rescored by identifying the change in respiratory pattern during VNS stimulation (i.e. reduced tidal volume and increased respiratory rate), oximetry abnormalities, and arousals. RESULTS: 28 PSGs (21 Diagnostic, 4 CPAP titration and 3 Split-night) were performed on 25 adult patients (13 female). The mean age was 35.2 ± 11.3 and age range 24-67 years; mean BMI 33.0 ± 8.4 and range 20.5-50.0 kg/m2. All patients had VNS placed for refractory seizures. There did not appear to be any predictive clinical risk factors or VNS settings associated with increased AHI. The diagnostic AHI by AASM criteria measured 12.4 ± 12.3/hr and by VNS criteria measured 23.7 ± 11.0/hr. The arousal index during diagnostic studies was low (3.9 ± 2.2/hr). Characteristic VNS respiratory patterns were present in 21/28 (75%) of studies. Mean RR at baseline was 18.0 ± 2.7/min and increased to 22.5 ± 5.4/min with VNS stimulation. CPAP was ineffective or marginally beneficial in attenuating VNS-induced SDB. The AHI by AASM criteria measured 25.1/hr ± 22.7/hr compared to 35.3/hr ± 10.8/hr by VNS criteria. Hypoxemia and desaturations due to VNS related respiratory changes were mild. Characteristic “saw fish” oximetry signals were present in 15/28 (54%) of subjects. CONCLUSIONS: Vagal nerve stimulation frequently results in characteristic respiratory patterns but the degree of aberrant breathing during VNS firing at night is variable and appeared unrelated to specific VNS settings or patient characteristics. The AASM criteria underestimate the frequency of SDB in VNS patients due to oxygen desaturations often being below the 3% threshold. A unique “saw fish” oximetry pattern is seen because of the unique breathing pattern induced by the VNS activation that terminates after VNS firing. CLINICAL IMPLICATIONS: Long term clinical outcomes of VNS-related SDB are difficult to predict but the low arousal indices and minimal hypoxemia suggest that VNS induced SDB may be benign compared to the usual obstructive sleep apnea. Further analysis based upon assessment of hypoxic burden/oxygen resaturation patterns could help predict potential harm. DISCLOSURES: No relevant relationships by Jason Burch, source=Web Response No relevant relationships by Robert Farney, source=Web Response No relevant relationships by Ashley Garrett, source=Web Response Owner/Founder relationship with HypnosCure Please note: $1-$1000 by Krishna Sundar, source=Web Response, value=no money received PI for CPAP vs. Sham CPAP study on cough relationship with Respironics Please note: $1-$1000 by Krishna Sundar, source=Web Response, value=no money received, only CPAP supplies for the study