Mode of vagus nerve stimulation differentially affects sleep related breathing in patients with epilepsy

PURPOSE We describe the influence of vagus nerve stimulation (VNS) with standard mode and rapid cycling mode on sleep related breathing in two patients with epilepsy. METHODS Two VNS treated patients underwent digital video-polysomnography for three nights (night 1: rapid cycling mode; night 2: standard mode; night 3: off mode). RESULTS In patient 1, on off mode, apnea-hypopnea index (AHI) was 11.1/h, respiratory effort-related arousal index (RERAI) 0.9/h, flow limitation index (FLI) 0.9/h and oxygen desaturation index (ODI) 10.2/h. On standard mode, AHI was 5.5/h, RERAI 1.7/h, FLI 4.1/h and ODI 5.5/h. On rapid cycling mode, AHI was 10.4/h, RERAI 7.9/h, FLI 17.3/h and ODI 10.3/h. In patient 2, on off mode, AHI was 1.6/h, RERAI 0.8/h, FLI 2.2/h and ODI 0/h. On standard mode, AHI was 2.9/h, RERAI 2.4/h, FLI 2.6/h and ODI 2.9/h. On rapid cycling mode, AHI was 0.7/h, RERAI increased to 15.4/h, FLI to 52.0/h and ODI was 0.7/h. CONCLUSIONS The number of RERAs as well as the number of flow limitations were higher with the rapid cycling mode compared to standard mode and stimulation off and might be related to the higher impulse frequency.