Abstracts

Rationale: Generalized convulsive seizures (GCS) can be associated with profound hypoxemia and hypercapnia and, in the most severe cases, can result in terminal apnea related to sudden unexpected death in epilepsy (SUDEP). Abnormal breathing patterns may contribute to insufficient ventilation. However, apart from post-convulsive central apnea (PCCA), no other types of abnormal breathing patterns have been studied in the postictal period. Our study aims to identify and characterize postictal breathing patterns to gain a better understanding of how abnormal patterns may impact ventilation and potentially contribute to adverse outcomes in patients with GCS.

Methods: Subjects included adult epilepsy patients aged > 18 years-old with GCS admitted to the epilepsy monitoring unit (EMU) at the University of Iowa. Subjects were fitted with respiratory monitoring equipment including respiratory inductance plethysmography (RIP) chest and abdominal belts, nasal pressure transducer (NPT), pulse oximetry, transcutaneous CO2 (TcCO2) monitoring, and audiovisual video recording.

Results: 59 subjects with 106 GCS were analyzed. Of these, 33 GCS (23 subjects) had accurate TcCO2 and/or oximetry data along with interpretable RIP belt (n = 30) and/or NPT (n = 14) data. These subjects had evidence of reduced ventilation with mean peak TcCO2 of 56.6 ± 9.2 mmHg (n = 21) and oxygen saturation nadir of 59.1 ± 18.3% (n = 24). Most seizures (n = 32/33, 97.0%) had alterations of breathing patterns compared to their interictal baseline. We classified the breathing patterns into 4 overlapping categories: 1) Irregular rhythmicity (n = 16/33, 48.5%) (Figure 1), 2) shallow breathing (n = 12/33, 36.4%), 3) thoracoabdominal asynchrony (TAA), in which the chest and abdomen move in an uncoordinated or opposing manner (n = 25/30, 83.3%) (Figure 2), and 4) upper airway obstruction, including inspiratory NPT flattening (n = 14/14, 100%), inspiratory and/or expiratory vibration on NPT (n = 4/14, 28.6%), and upper airway inspiratory and/or expiratory noises (n = 22/33, 66.7%). Most subjects had two or more abnormal patterns after each seizure, and often had consistent combinations of breathing patterns when individual subjects had more than one seizure.


Conclusions: This study is significant as it is the first detailed analysis of postictal breathing patterns comprised of extensive monitoring of respiratory parameters. Based on animal models, we hypothesize disruption of serotonergic neurons in the brainstem may lead to depressed respiratory drive, arousal, and upper airway tone which may affect breathing patterns. These patterns may lead to reduced ventilation leading to critical hypercapnia and hypoxemia and may help in understanding the chain of events leading to terminal apnea in SUDEP.

Funding: NIH: R38 HL150208-04
NIH: U01 NS090414
NIH: R01 NS113764-01